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  • 301.
    Stomby, Andreas
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine. Region Jönköping County, Jönköping, Sweden.
    Boraxbekk, Carl-Johan
    Umeå University, Faculty of Social Sciences, Centre for Demographic and Ageing Research (CEDAR). Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Lundquist, Anders
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Nordin Adolfsson, Annelie
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    Nilsson, Lars-Göran
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Department of Psychology, Stockholm University, Stockholm, Sweden.
    Adolfsson, Rolf
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Olsson, Tommy
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Higher diurnal salivary cortisol levels are related to smaller prefrontal cortex surface area in elderly men and women2016In: European Journal of Endocrinology, ISSN 0804-4643, E-ISSN 1479-683X, Vol. 175, no 2, p. 117-126Article in journal (Refereed)
    Abstract [en]

    Objective: Elevated cortisol levels with aging have been associated with atrophy of the hippocampus and prefrontal cortex (PFC), as well as with impaired cognitive functions in men. However, coexisting diseases have confounded many studies examining these relationships. Studies in women are lacking. Our objective was to test whether salivary cortisol levels were related to morphology of the hippocampus and the PFC, and to cognitive performance. Design: A cross-sectional study including 200 elderly (55-80 years old) men and women. Method: We used magnetic resonance imaging, tests of episodic-, semantic-, and working memory, visuospatial ability, and cortisol levels in four saliva samples collected during 1 day. Results: Area under the curve (AUC) for cortisol levels was negatively related to cortical surface area of the left anterior cingulate gyrus (caudal P < 0.001; rostral P = 0.006), right lateral orbitofrontal cortex (P = 0.004), and right rostral middle frontal gyrus (P = 0.003). In women, there was also a negative relationship with cortical surface area in the left rostral middle frontal gyrus (P = 0.006). No relationship was found between cortisol levels and hippocampal volume. Conclusion: This study suggests that the structure of the medial PFC is related to cortisol levels in both elderly women and men.

  • 302.
    Stomby, Andreas
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine. Jönköping County Hospital, Region Jönköping County, Jönköping, Sweden.
    Otten, Julia
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Ryberg, Mats
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Olsson, Tommy
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Boraxbekk, Carl-Johan
    Umeå University, Faculty of Social Sciences, Centre for Demographic and Ageing Research (CEDAR). Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital, Hvidovre, Denmark.
    A Paleolithic Diet with and without Combined Aerobic and Resistance Exercise Increases Functional Brain Responses and Hippocampal Volume in Subjects with Type 2 Diabetes2017In: Frontiers in Aging Neuroscience, ISSN 1663-4365, E-ISSN 1663-4365, Vol. 9, article id 391Article in journal (Refereed)
  • 303.
    Sundström, Anna
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology. Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Bergdahl, Jan
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS). Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Bergdahl, Maud
    Institute of Clinical Dentistry, University of Tromsø, Tromsø, Norway.
    Nilsson, Lars-Göran
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Stressful negative life events and amalgam-related complaints2011In: Community Dentistry and Oral Epidemiology, ISSN 0301-5661, E-ISSN 1600-0528, Vol. 39, no 1, p. 12-18Article in journal (Refereed)
    Abstract [en]

    Objectives:  The role of stressful life events in the onset of self-reported amalgam-related complaints is unclear. The aim of this study was to examine the relationship between life events and amalgam-related complaints.

    Method:  The participants were selected from a longitudinal population-based study. One-to-one matching of 337 participants with amalgam-related complaints to 337 participants without such complaints was performed. For 81 of the participants with amalgam-related complaints and their matched controls, data was also available approximately 5 years before the onset of complaints, making longitudinal analysis possible. All participants completed questionnaires assessing the occurrence of 55 life events.

    Results:  The results showed that many participants with amalgam-related complaints experienced negative life events before and at the onset of amalgam-related complaints. They also reported more unexpected and uncontrollable events difficult to adjust to in comparison with controls. The groups did not differ on positive or neutral life events. Somatic illness or surgical operation was the most common life event. Death of a very close family member and a major change in financial situation were also commonly reported.

    Conclusions:  This study indicates that adverse negative life events could play a vital role in understanding and explaining amalgam-related complaints.

  • 304.
    Sundström, Anna
    et al.
    Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Nilsson, Lars-Göran
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Cognitive performance before and after mild head injury.2002In: Journal of cognitive neuroscience, ISSN 0898-929X, E-ISSN 1530-8898, Vol. Suppl, no B77, p. 60-Article in journal (Refereed)
  • 305.
    Sundström, Anna
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    APOE influences in neuropsychological function after mild head injury: Within-person comparisons - Reply2004In: Neurology, ISSN 0028-3878, E-ISSN 1526-632X, Vol. 63, p. 2460-Article in journal (Refereed)
  • 306.
    Sundström, Torbjörn
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Larsson, Anne
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Riklund, Katrine
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Influences of age and length of education on rCBF-SPECT in healthy elderly: diagnostic implications for dementia2011In: International Journal of Clinical Medicine, ISSN 2158-284X, Vol. 2, no 2, p. 143-157Article in journal (Refereed)
    Abstract [en]

    Background: Few previous studies have described other than age- and gender related changes in regional cerebral blood flow (rCBF) in healthy elderly. What is the influence of other common clinically relevant variables such as ache, education, MMSE, and smoking history?

    Purpose: To study rCBF in Swedish healthy elderly by single-photon emission computed tomography (SPECT) and evaluate the influence on rCBF of age, gender, education, MMSE, ache, and smoking with a focus on education in relation to the ‘cognitive reserve’.

    Methods: Healthy subjects (n = 45, 50 -75 y), sampled from a large longitudinal aging study took part in an extensive examination of health and memory, including cognitive testing and socio-economic survey. After injection of 99 mTc-hexamethylpropylene amine oxime (HMPAO) followed by SPECT the rCBF-SPECT images were analyzed using statistical parametric mapping (SPM).

    Results: Age-related decreases in uptake were seen in interhemispheric and interlobar regions. There was a positive rCBF correlation with education in the inferior frontal lobe and a higher uptake in the left temporal lobe in an age-gender-matched high education subgroup.

    Conclusion: The localization of the age related findings except for the medial temporal lobe differs markedly from typical dementia related findings. A reduction close to interhemispheric or interlobar space should always be related to chronological age. Education seems to have an influence on basal brain function at a resting-state condition. Knowledge of normal rCBF variations for variables such as age and education should be considered when making clinical diagnosis. The findings could be interpreted as further support for the theory of cognitive reserve.

  • 307.
    Säfström, Daniel
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Edin, Benoni B
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Acquiring and adapting a novel audiomotor map in human grasping.2006In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 173, no 3, p. 487-497Article in journal (Refereed)
    Abstract [en]

    For sensorimotor transformations to be executed accurately, there must be mechanisms that can both establish and modify mappings between sensory and motor coordinates. Such mechanisms were investigated in normal subjects using a reach-to-grasp task. First, we replaced the normal input of visual information about object size with auditory information, i.e., we attempted to establish an 'audiomotor map'. The size of the object was log linearly related to the frequency of the sound, and we measured the maximum grip aperture (MGA) during the reaching phase to determine if the subjects had learned the relationship. Second, we changed the frequency-object size relationship to study adaptation in the newly acquired map. Our results demonstrate that learning of an audiomotor map consisted of three distinct phases: during the first stage (approximately 10-15 trials) subjects simply used MGAs large enough to grasp any reasonably sized object and there were no overt signs of learning. During the second stage, there was a period of fast learning where the slope of the relationship between MGA and object size became steeper until the third stage where the slope was constant. In contrast, when sensorimotor adaptation was studied in the established audiomotor map, there was rapid learning from the start of a size perturbation. We conclude that different learning strategies are employed when sensorimotor transformations are established compared to when existing transformations are modified.

  • 308.
    Säfström, Daniel
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Edin, Benoni B
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Prediction of object contact during grasping.2008In: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale, ISSN 1432-1106, Vol. 190, no 3, p. 265-77Article in journal (Refereed)
    Abstract [en]

    The maximum grip aperture (MGA) during prehension is linearly related to the size of objects to be grasped and is adapted to the haptically sensed object size when there is a discrepancy between visual and haptic information. We have investigated what information is used to drive this adaptation process and how the onset of fingertip forces on the object is triggered. Subjects performed a reach-to-grasp task, where the object seen and the object grasped physically never were the same. We measured the movements of the index finger and the thumb and the contact forces between each fingertip and the object. The subjects' adaptation of the MGA was unrelated both to different fingertip velocities at the moment of object contact, or the fingertip forces. Instead, the 'timing' of contact between the fingers and the object was most consistently influenced by introducing a size discrepancy. Specifically, if the object was larger than expected, the moment of contact occurred earlier, and if the object was decreased in size, then the contact occurred later. During adaptation, these timing differences were markedly reduced. Also, the motor command for applying forces on the object seemed to be released in anticipation of the predicted moment of contact. We therefore conclude that the CNS dynamically predicts when contact between the fingertips and objects occur and that aperture adaptation is primarily driven by timing prediction errors.

  • 309.
    Säfström, Daniel
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Edin, Benoni B
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Short-term plasticity of the visuomotor map during grasping movements in humans.2005In: Learning & memory (Cold Spring Harbor, N.Y.), ISSN 1072-0502, E-ISSN 1549-5485, Vol. 12, no 1, p. 67-74Article in journal (Refereed)
    Abstract [en]

    During visually guided grasping movements, visual information is transformed into motor commands. This transformation is known as the "visuomotor map." To investigate limitations in the short-term plasticity of the visuomotor map in normal humans, we studied the maximum grip aperture (MGA) during the reaching phase while subjects grasped objects of various sizes. The objects seen and the objects grasped were physically never the same. When a discrepancy had been introduced between the size of the visual and the grasped objects, and the subjects were fully adapted to it, they all readily interpolated and extrapolated the MGA to objects not included in training trials. In contrast, when the subjects were exposed to discrepancies that required a slope change in the visuomotor map, they were unable to adapt adequately. They instead retained a subject-specific slope of the relationship between the visual size and MGA. We conclude from these results that during reaching for grasping, normal subjects are unable to abandon a straight linear function determining the relationship between visual object size and MGA. Moreover, the plasticity of the visuomotor map is, at least in short term, constrained to allow only offset changes, that is, only "rigid shifts" are possible between the visual and motor coordinate systems.

  • 310.
    Säfström, Daniel
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Edin, Benoni B
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Task requirements influence sensory integration during grasping in humans.2004In: Learning & memory (Cold Spring Harbor, N.Y.), ISSN 1072-0502, E-ISSN 1549-5485, Vol. 11, no 3, p. 356-363Article in journal (Refereed)
    Abstract [en]

    The sensorimotor transformations necessary for generating appropriate motor commands depend on both current and previously acquired sensory information. To investigate the relative impact (or weighting) of visual and haptic information about object size during grasping movements, we let normal subjects perform a task in which, unbeknownst to the subjects, the object seen (visual object) and the object grasped (haptic object) were never the same physically. When the haptic object abruptly became larger or smaller than the visual object, subjects in the following trials automatically adapted their maximum grip aperture when reaching for the object. This adaptation was not dependent on conscious processes. We analyzed how visual and haptic information were weighted during the course of sensorimotor adaptation. The adaptation process was quicker and relied more on haptic information when the haptic objects increased in size than when they decreased in size. As such, sensory weighting seemed to be molded to avoid prehension error. We conclude from these results that the impact of a specific source of sensory information on the sensorimotor transformation is regulated to satisfy task requirements.

  • 311.
    Säfström, Daniel
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Flanagan, J Randall
    Department of Psychology and Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Skill learning involves optimizing the linking of action phases2013In: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 110, no 6, p. 1291-1300Article in journal (Refereed)
    Abstract [en]

    Many manual tasks involve object manipulation and are achieved by an evolving series of actions, or action phases, recruited to achieve task subgoals. The ability to effectively link action phases is an important component of manual dexterity. However, our understanding of how the effective linking of sequential action phases develops with skill learning is limited. Here, we addressed this issue using a task in which participants applied forces to a handle to move a cursor on a computer screen to successively acquire visual targets. Target acquisition required actively holding the cursor within the target zone (hold phase) for a required duration, before moving to the next target (transport phase). If the transport phase was initiated prematurely, before the end of the required hold duration, participants had to return to the target to acquire it. The goal was to acquire targets as quickly as possible. Distinct visual and auditory sensory events marked goal completion of each action phase. During initial task performance, the transport phase was reactively triggered by sensory events signaling hold phase completion. However, with practice, participants learned to initiate the transport phase based on a prediction of the time of hold phase completion. Simulations revealed that participants learned to near-optimally compensate for temporal uncertainty, presumably related to estimation of time intervals and execution of motor commands, so as to reduce the average latency between the end of the required hold phase duration and the start of the transport phase, while avoiding an excess of premature exits.

  • 312.
    Säfström, Daniel
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Flanagan, J Randall
    Department of Psychology and Centre for Neuroscience Studies, Queen’s University, Kingston, Ontario, Canada.
    Gaze behavior when learning to link sequential action phases in a manual task2014In: Journal of Vision, ISSN 1534-7362, E-ISSN 1534-7362, Vol. 14, no 4Article in journal (Refereed)
    Abstract [en]

    Most manual tasks comprise a sequence of action phases. Skill acquisition in such tasks involves a transition from reactive control, whereby motor commands for the next phase are triggered by sensory events signaling completion of the current phase, to predictive control, whereby commands for the next phase are launched in anticipation of these events. Here we investigated gaze behavior associated with such learning. Participants moved a cursor to successively acquire visual targets, as quickly as possible, by actively keeping the cursor within the target zone (hold phase) for a required duration, before moving to the next target (transport phase). Distinct visual and auditory events marked completion of each phase and, with learning, the launching of the transport phase shifted from being reactively to predictively controlled. Initially, gaze was directed to the current target throughout the hold phase, allowing visual feedback control of the cursor position, and shifted to the next target in synchrony with the cursor. However, with learning, two distinct gaze behaviors emerged. Gaze either shifted to the next target well before the end of the hold phase, facilitating planning of the forthcoming cursor movement, or shifted to the next target after the cursor, enabling cursor exits to be monitored in central vision. These results suggest that, with learning, gaze behavior changes to support evolving task demands, and that people distribute different gaze behaviors across repetitions of the task.

  • 313.
    Söderlund, H
    et al.
    Department of Psychology, Stockholm University, Stockholm, Sweden / Rotman Research Institute, Baycrest Centre, Toronto, Ontario, Canada.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nilsson, L-G
    Department of Psychology, Stockholm University, Stockholm, Sweden.
    Cerebral atrophy as predictor of cognitive function in old, community-dwelling individuals2004In: Acta Neurologica Scandinavica, ISSN 0001-6314, E-ISSN 1600-0404, Vol. 109, no 6, p. 398-406Article in journal (Refereed)
    Abstract [en]

    Objectives: The impact of cortical and subcortical atrophy on cognitive function was examined in a sample of older community-dwelling men and women.

    Material and methods: Magnetic resonance imaging was performed on a sample of 129 individuals [age: 68.4 ± 3.6 years (mean ± SD), range 64–74 years, 64 women and 65 men, Mini-Mental State Examination scores above 23] to assess cortical and subcortical atrophy. Participants also performed a number of cognitive tasks, and the measures of atrophy were used to predict performance in these tasks.

    Results: In men, frontal cortical atrophy predicted worse performance in word fluency and the Stroop test, and occipital cortical atrophy was associated with poor performance in motor speed. In women, poor performance in motor speed was associated with subcortical atrophy at the level of the caudate nucleus.

    Conclusion: Atrophy in certain areas was associated with poor performance in specific cognitive tasks, although the amount of explained variance was rather limited in this quite homogenous sample.

  • 314.
    Terao, Yasuo
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Andersson, N E Micael
    Flanagan, J Randall
    Queen's University, Kingston, Ontario.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Engagement of gaze in capturing targets for future sequential manual actions.2002In: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 88, no 4, p. 1716-25Article in journal (Refereed)
    Abstract [en]

    We investigated the role of saccadic gaze fixations in encoding target locations for planning a future manual task consisting of a sequence of discrete target-oriented actions. We hypothesized that fixations of the individual targets are necessary for accurate encoding of target locations and that there is a transfer of sequence information from visual encoding to manual recall. Subjects viewed four targets presented at random positions on a screen. After various delays following target extinction, the subjects marked the remembered target locations on the screen with the tip of a hand-held stick. When the targets were presented simultaneously among distracting elements, the overall accuracy of marking increased with presentation time and total number of targets fixated because the subjects had to serially fixate the individual targets to locate them. Without distractors, the marking accuracy was similarly high regardless of duration of target presentation (0.25-8 s) and number of targets fixated; it was comparable to that with distractors when all four targets had been fixated. This indicates parallel encoding of target locations largely based on peripheral vision. Location memory was stable in these tasks over the delay periods investigated (0.5-8 s). With parallel encoding there was a "shrinkage" in the visuomotor transformation, i.e., the distances between the markings were systematically smaller than the corresponding inter-target distances. When the targets were presented sequentially without distractors, marking accuracy improved with the total number of targets fixated and shrinkage in the visuomotor transformation occurred only with parallel encoding, i.e., when subjects did not fixate the targets. In all experimental conditions for trials in which targets were fixated during encoding, there was little correspondence between the marking sequence and the sequence in which the targets were fixated. We conclude that subjects benefit from fixating targets for subsequent target-oriented manual actions when the targets are presented among distractors and when presented sequentially; when distinct targets are presented simultaneously against a blank background, they are efficiently encoded in parallel largely by peripheral vision.

  • 315.
    Theorin, Anna
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
    To select one hand while using both: neural mechanisms supporting flexible hand dominance in bimanual object manipulation2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In daily activities, the brain regularly assigns different roles to the hands dependingon task and context. Yet, little is known about the underlying neural processes. Thiscertainly applies to how the brain, where each hemisphere primarily controls onehand, manages the between-hand coordination required in bimanual objectmanipulation. By using behavioral, neurophysiological and functional magneticresonance imaging techniques, the present thesis examines neural mechanisms thatsupport hand coordination during tasks where the two hands apply spatiotemporallycoupled but opposing forces for goal attainment, e.g., as when removing the cap froma bottle. Although the two hands seem to operate symmetrically in such tasks, Study Ishowed that one hand primarily acts while the other assists. Moreover, this roledifferentiation was found to be flexible with the brain appointing either hand asprime actor depending on the spatial congruency between hand forces and desiredmovement consequences. Accordingly, when we remove a cap from a bottle, the handthat grasps the cap, be it left or right depending on overall task constraints, isappointed as prime actor because the twist forces it generates are aligned with thegoal to remove the cap, while the other hand, holding the bottle, applies stabilizingforces in the opposite direction. Changes in hand assignments are caused by amidline shift of lateralized activity throughout the motor system, from distal handmuscles to corticospinal pathways and primary sensorimotor and cerebellar corticalareas (Study I). Although the bimanual actions examined involved both within- andbetween-hand coordination, Study II failed to reveal additional brain activity duringbimanual as compared to matching unimanual actions, except for the primarysensorimotor areas where subpopulations of neurons were preferentially engagedduring either bimanual or unimanual actions. Thus, dedicated neurons in the motorcortices might support critical bimanual coordinative operations. While imagingresults indicated that a mainly left-lateralized parietal-premotor network managedthe task irrespective of prime actor, premotor areas presumably established handassignment by allocating the lead either to the left or the right primary sensorimotorareas (Study I and II). Regarding the process of prime actor selection and hence thecontrol of these premotor networks, imaging results indicate a transitory involvementof prefrontal cortical areas (Study III). The detected areas belong to a networkconsidered critical for cognitive operations such as judgment and decision-making,and for evaluation of utility of actions, including conflict detection. The implicitselection of prime actor during bimanual tasks thus seems to be supported by corticalareas traditionally associated primarily with complex cognitive challenges.

  • 316.
    Theorin, Anna
    et al.
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
    Johansson, Roland
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
    Selection of prime actor in bimanual object manipulationManuscript (preprint) (Other academic)
  • 317.
    Theorin, Anna
    et al.
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
    Johansson, Roland
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
    Zones of bimanual and unimanual preference within human primary sensorimotor cortex during object manipulation2007In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 36, no Suppl 2, p. T2-T15Article in journal (Refereed)
    Abstract [en]

    We asked which brain areas are engaged in the coordination of our hands in dexterous object manipulations where they cooperate for achieving a common goal. Well-trained right-handers steered a cursor on a screen to hit successively displayed targets by applying isometric forces and torques to a rigid tool. In two bimanual conditions, the object was held freely in the air and the hands thus generated coupled opposing forces. Yet, depending on the mapping rule linking hand forces and cursor movements, all subjects selected either the left or the right hand as prime actor. In two unimanual conditions, the subjects performed the same task with either the left or the right hand operating on a fixed tool. Functional magnetic resonance imaging revealed common activation across all four conditions in a dorsal fronto-parietal network biased to the left hemisphere and in bilateral occipitotemporal cortex. Contrary to the notion that medial wall premotor areas are especially active in complex bimanual actions, their activation depended on acting hand (left, right) rather than on grip type (bimanual, unimanual). We observed effects of grip type only in the primary sensorimotor cortex (SMC). In particular, with either hand as prime actor, bimanual actions preferentially activated subregions of the SMC contralateral to the acting hand. A sizeable subregion with preference for unimanual activity was found only in the left SMC in our right-handed subjects. Collectively, these results indicate a hemispheric asymmetry for the SMC and that partially different neural populations support the control of bimanual versus unimanual object manipulations.

  • 318.
    Theorin, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Selection of prime actor in humans during bimanual object manipulation2010In: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 30, no 31, p. 10448-10459Article in journal (Refereed)
    Abstract [en]

    In bimanual object manipulation tasks, people flexibly assign one hand as a prime actor while the other assists. Little is known, however, about the neural mechanisms deciding the role assignment. We addressed this issue in a task in which participants moved a cursor to hit targets on a screen by applying precisely coupled symmetrical opposing linear and twist forces on a tool held freely between the hands. In trials presented in an unpredictable order, the action of either the left or the right hand was spatially congruent with the cursor movements, which automatically rendered the left or right hand the dominant actor, respectively. Functional magnetic resonance imaging indicated that the hand-selection process engaged prefrontal cortical areas belonging to an executive control network presumed critical for judgment and decision-making and to a salience network attributed to evaluation of utility of actions. Task initiation, which involved switching between task sets, had a superordinate role with reference to hand selection. Behavioral and brain imaging data indicated that participants initially expressed two competing action representations, matching either mapping rule, before selecting the appropriate one based on the consequences of the initial manual actions. We conclude that implicit processes engaging the prefrontal cortex reconcile selections among action representations that compete for the establishment of a dominant actor in bimanual object manipulation tasks. The representation selected is the one that optimizes performance by relying on the superior capacity of the brain to process spatial congruent, as opposed to noncongruent, mappings between manual actions and desired movement goals.

  • 319. Thomas, C K
    et al.
    Johansson, Roland
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Bigland-Ritchie, B
    EMG changes in human thenar motor units with force potentiation and fatigue.2006In: Journal of Neurophysiology, ISSN 0022-3077, Vol. 95, no 3, p. 1518-26Article in journal (Refereed)
    Abstract [en]

    Few studies have analyzed activity-induced changes in EMG activity in individual human motor units. We studied the changes in human thenar motor unit EMG that accompany the potentiation of twitch force and fatigue of tetanic force. Single motor unit EMG and force were recorded in healthy subjects in response to selective stimulation of their motor axons within the median nerve just above the elbow. Twitches were recorded before and after a series of pulse trains delivered at frequencies that varied between 5 and 100 Hz. This stimulation induced significant increases in EMG amplitude, duration, and area. However, in relative terms, all of these EMG changes were substantially smaller than the potentiation of twitch force. Another 2 min of stimulation (13 pulses at 40 Hz each second) induced additional potentiation of EMG amplitude, duration, and area, but the tetanic force from every unit declined. Thus activity-induced changes in human thenar motor unit EMG do not indicate the alterations in force or vice versa. These data suggest that different processes underlie the changes in EMG and force that occur during human thenar motor unit activity.

  • 320.
    Thomas, Christine K
    et al.
    University of Miami School of Medicine.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Bigland-Ritchie, Brenda
    Yale University Medical School, New Haven, Connecticut.
    Incidence of F waves in single human thenar motor units.2002In: Muscle and Nerve, ISSN 0148-639X, E-ISSN 1097-4598, Vol. 25, no 1, p. 77-82Article in journal (Refereed)
    Abstract [en]

    F-wave generation, axon conduction velocities, and contractile properties were compared in 44 healthy individual human thenar motor units. Force and muscle action potentials were recorded when single motor axons were stimulated intraneurally about 10 cm proximal to the elbow. Each stimulus usually evoked only one electromyographic (EMG) potential. However, in seven units (16%), a single stimulus elicited an F wave in response to 1.7 +/- 1.6% (mean +/- SD) of the stimuli applied. Axon conduction velocity proximal to the site of stimulation was faster than distal conduction velocity (72.7 +/- 8.0 m/s versus 64.2 +/- 10.5 m/s). Distal conduction velocities, twitch forces, and contraction times were similar for units that did and did not generate F waves. Thus, no obvious subset of thenar motor units generated F waves. These results provide valuable baseline information on F waves that can be used to assess changes in axon conduction, motor unit contractile properties, and motoneuron excitability in disease.

  • 321.
    Trulsson, M
    et al.
    Karolinska Institute.
    Francis, S T
    University of Nottingham.
    Kelly, E F
    University of North Carolina.
    Westling, Göran
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Bowtell, R
    University of Nottingham.
    McGlone, F
    Port Sunlight Laboratory, Unilever Research, Wirral, University of Wales, Bangor, United Kingdom, .
    Cortical responses to single mechanoreceptive afferent microstimulation revealed with fMRI2001In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 13, no 4, p. 613-622Article in journal (Refereed)
    Abstract [en]

    The technique of intraneural microneurography/microstimulation has been used extensively to study contributions of single, physiologically characterized mechanoreceptive afferents (MRAs) to properties of somatosensory experience in awake human subjects. Its power as a tool for sensory neurophysiology can be greatly enhanced, however, by combining it with functional neuroimaging techniques that permit simultaneous measurement of the associated CNS responses. Here we report its successful adaptation to the environment of a high-field MR scanner. Eight median-nerve MRAs were isolated and characterized in three subjects and microstimulated in conjunction with fMRI at 3.0 T. Hemodynamic responses were observed in every case, and these responses were robust, focal, and physiologically orderly. The combination of fMRI with microstimulation will enable more detailed studies of the representation of the body surface in human somatosensory cortex and further studies of the relationship of that organization to short-term plasticity in the human SI cortical response to natural tactile stimuli. It can also be used to study many additional topics in sensory neurophysiology, such as CNS responses to additional classes of afferents and the effects of stimulus patterning and unimodal/crossmodal attentional manipulations. Finally, it presents unique opportunities to investigate the basic physiology of the BOLD effect and to compare the operating characteristics of fMRI and EEG as human functional neuroimaging modalities in an unusually specific and well-characterized neurophysiological setting.

  • 322.
    Trulsson, Mats
    et al.
    Karolinska Institutet.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Orofacial mechanoreceptors in humans: encoding characteristics and responses during natural orofacial behaviors.2002In: Behavioural Brain Research, ISSN 0166-4328, E-ISSN 1872-7549, Vol. 135, no 1-2, p. 27-33Article in journal (Refereed)
    Abstract [en]

    We used microneurography to characterize stimulus-encoding properties of low-threshold mechanoreceptive afferents in human orofacial tissues. Signals were recorded from single afferents in the infraorbital, lingual and inferior alveolar nerves while localized, controlled, mechanical stimuli were delivered to the facial skin, lips, oral mucosa and teeth. We likewise analyzed activity in these afferents during orofacial behaviors such as speech, chewing and biting. The afferents in the soft tissues functionally resemble four types described in the human hand: hair follicle afferents, slowly adapting (SA) type I and type II afferents and fast adapting (FA) type I afferents. Afferents in the facial skin, lips and buccal mucosa respond not only to contact with environmental objects, but also to contact between the lips, changes in air pressure generated for speech sounds, and to facial skin and mucosa deformations that accompany lip and jaw movements associated with chewing and swallowing. Hence, in addition to exteroceptive information, these afferents provide proprioceptive information. In contrast, afferents terminating superficially in the tongue do not signal proprioceptive information about tongue movements in this manner. They only respond when the receptive field is brought into contact with other intraoral structures or objects, e.g. the teeth or food. All human periodontal afferents adapt slowly to maintained tooth loads. Populations of periodontal afferents encode information about both which teeth are loaded and the direction of forces applied to individual teeth. Most afferents exhibit a markedly curved relationship between discharge rate and force amplitude, featuring the highest sensitivity to changes in tooth load at low forces (below 1 N). Accordingly, periodontal afferents efficiently encode tooth load when subjects first contact, hold, and gently manipulate food by the teeth. In contrast, only a minority of the afferents encodes the rapid and strong force increase generated when biting through food. We conclude, that humans use periodontal afferent signals to control jaw actions associated with intraoral manipulation of food rather than exertion of jaw power actions.

  • 323.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Does testing enhance memory by influencing subsequent restudy?2012Conference paper (Refereed)
  • 324.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB). Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Testing alters brain activity during subsequent restudy: Evidence for test-potentiated encoding2014In: Trends in Neuroscience and Education, ISSN 2211-9493, Vol. 3, no 2, p. 69-80Article in journal (Refereed)
    Abstract [en]

    Mixed testing/studying lead to better memory retention compared to repeated study only. A potentiating influence of tests on encoding, particularly during restudy of non-retrieved items, may contribute to this effect. This study investigated whether and how testing affects brain activity during subsequent restudy of Swahili–Swedish word pairs after a cued-recall test. Item-events during fMRI were categorized according to history (tested/studied only) and recall outcome at prescan and postscan tests. Activity was higher for tested compared to studied-only items in anterior insula, orbital parts of inferior frontal gyrus and hippocampus, and lower in regions implicated in the default network, such as precuneus, supramarginal gyrus and the posterior middle cingulate. Findings are discussed in terms of top-down biasing of attention to tested items with concomitant deactivation of regions in the default network. Increased/focused attention to tested items during restudy may lead to test-potentiated encoding via deeper semantic processing and increased associative binding.

  • 325.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Test-potentiated encoding of paired associates as revealed by functional magnetic resonance imaging2013In: Journal of cognitive neuroscience, ISSN 0898-929X, E-ISSN 1530-8898, Vol. 25, no Suppl., p. S113-S114Article in journal (Other academic)
  • 326.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Test-potentiated encoding revealed by fMRI: Viewing an old phenomenon with new glasses2013Conference paper (Other academic)
  • 327.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Social Sciences, Department of applied educational science.
    Rönnlund, Michael
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University and Stockholm Brain Institute, Sweden.
    Development of the cognitive dysfunction questionnaire (CDQ) in a population based sample2011In: Scandinavian Journal of Psychology, ISSN 0036-5564, E-ISSN 1467-9450, Vol. 52, no 3, p. 218-228Article in journal (Refereed)
    Abstract [en]

    The study reports on the development of a questionnaire for assessment of adult cognitive dysfunction (CDQ). Participants in a population-based sample(65 ± 15 years, N = 370) responded to a 90-item pilot version covering multiple aspects of memory/cognition. Based on exploratory principal components analyses and correlations with criterion measures of cognitive functioning (MMSE, Block Design, semantic/episodic memory), 20 items loading on 6 components were selected for the final version of the questionnaire. Cronbach’s a for the total score was 0.90. There was evidence of construct validity as judged by correlations between CDQ scores, objective cognitive measures, and a subjective memory measure (PRMQ). Discriminant validity was demonstrated by a low and non-significant correlation with depressive symptoms. Further evidence of construct validity was provided by correlations with age and educational attainment. In conclusion, the CDQ is promising as a self-rating screening tool for cognitive dysfunction, and will be the subject of further development and validation.

  • 328.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Social Sciences, Department of applied educational science, Departement of Educational Measurement.
    Rönnlund, Michael
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University and Stockholm Brain Institute, Sweden.
    Multigroup confirmatory factor analysis of the cognitive dysfunction questionnaire: instrument refinement and measurement invariance across age and sex2012In: Scandinavian Journal of Psychology, ISSN 0036-5564, E-ISSN 1467-9450, Vol. 53, no 5, p. 390-400Article in journal (Refereed)
    Abstract [en]

    The study adopted CFA to investigate the factorial structure and reduce the number of items of the Cognitive Dysfunction Questionnaire (CDQ; Vestergren, Rönnlund, Nyberg, & Nilsson, 2011). The analyses were based on data for a total of 1115 participants from population based samples (mean age: 63.0 ± 14.5 years, range: 25 - 95) randomly split into a refinement (n = 569) and a cross-validation (n = 546) sample. Equivalence of the measurement and structural portions of the refined model was demonstrated across the refinement and cross-validation samples. Among competing models the best fitting and parsimonious model had a hierarchical factor structure with five first-order and one second-order general factor. The final version of the CDQ consisted of 20 items in five domains (Procedural actions, Semantic word knowledge, Face recognition, Temporal orientation and Spatial navigation). Internal consistency reliabilities were adequate for the total scale and for the subscales. Multigroup CFAs were performed and the results indicate measurement invariance across age and sex up to the scalar level. Finally, higher levels of cognitive dysfunction as reflected by CDQ scores were observed with advancing age and with deficits in general cognitive functioning as reflected by scores on the Mini-Mental State Examination. In conclusion, adoption of the final version of the CDQ appears to be a way of measuring cognitive dysfunction without administering formal cognitive tests. Future studies should apply it among clinical groups to further test its usefulness.

  • 329. Vidal-Pineiro, Didac
    et al.
    Sneve, Markus H.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Mowinckel, Athanasia M.
    Sederevicius, Donatas
    Walhovd, Kristine B.
    Fjell, Anders M.
    Maintained Frontal Activity Underlies High Memory Function Over 8 Years in Aging2019In: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 29, no 7, p. 3111-3123Article in journal (Refereed)
    Abstract [en]

    Aging is characterized by substantial average decline in memory performance. Yet contradictory explanations have been given for how the brains of high-performing older adults work: either by engagement of compensatory processes such as recruitment of additional networks or by maintaining young adults' patterns of activity. Distinguishing these components requires large experimental samples and longitudinal follow-up. Here, we investigate which features are key to high memory in aging, directly testing these hypotheses by studying a large sample of adult participants (n > 300) with fMRI during an episodic memory experiment where item-context relationships were implicitly encoded. The analyses revealed that low levels of activity in frontal networks-known to be involved in memory encoding-were associated with low memory performance in the older adults only. Importantly, older participants with low memory performance and low frontal activity exhibited a strong longitudinal memory decline in an independent verbal episodic memory task spanning 8 years back (n = 52). These participants were also characterized by lower hippocampal volumes and steeper rates of cortical atrophy. Altogether, maintenance of frontal brain function during encoding seems to be a primary characteristic of preservation of memory function in aging, likely reflecting intact ability to integrate information.

  • 330.
    Von Helversen, Bettina
    et al.
    University of Basel, Department of Psychology, Switzerland.
    Karlsson, Linnea
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Mata, Rui
    Max Planck Institute for Human Development, Berlin, Germany.
    Wilke, Andreas
    Clarkson University, Department of Psychology, USA.
    Why does cue polarity information provide benefits in inference problems?: The role of strategy selection and knowledge of cue importance2013In: Acta Psychologica, ISSN 0001-6918, E-ISSN 1873-6297, Vol. 144, no 1, p. 73-82Article in journal (Refereed)
    Abstract [en]

    Knowledge about cue polarity (i.e., the sign of a cue–criterion relation) seems to boost performance in a wide range of inference tasks. Knowledge about cue polarity information may enhance performance by increasing (1) the reliance on rule- relative to similarity-based strategies, and (2) explicit knowledge about the relative importance of cues. We investigated the relative contribution of these two mechanisms in a multiple-cue judgment task and a categorization task, which typically differ in the inference strategies they elicit and potentially the explicit task knowledge available to participants. In both tasks participants preferred rule-based relative to similarity-based strategies and had more knowledge about cue importance when cue polarity information was provided. Strategy selection was not related to increases in performance in the categorization task and could only partly explain increases in performance in the judgment task. In contrast, explicit knowledge about the importance of cues was related to better performance in both categorization and judgment independently of the strategy used. In sum, our results suggest that the benefits of receiving cue polarity information may span across tasks, such multiple-cue judgment and categorization, primarily by enhancing knowledge of relative cue importance.

  • 331.
    Westberg, Karl-Gunnar
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Kolta, Arlette
    Faculté de médecine dentaire, and Groupe de Recherche sur le Système Nerveux Central du FRSQ, Université de Montréal C.P. 6128, succursale Centre-villeMontréal (Qc), Canada.
    The trigeminal circuits responsible for chewing2011In: Translating mechanisms of orofacial neurological disorder: from the peripheral nervous system to the cerebral cortex / [ed] Masayuki Kobayashi, Noriaki Koshikawa, Koichi Iwata och John Waddington, London ; Waltham, MA: Academic Press, 2011, Vol. 97, p. 77-98Chapter in book (Refereed)
    Abstract [en]

    Mastication is a vital function that ensures that ingested food is broken down into pieces and prepared for digestion. This review outlines the masticatory behavior in terms of the muscle activation patterns and jawmovements and gives an overview of the organization and function of the trigeminal neuronal circuits that are known to take part in the generation and control of oro-facial motor functions. The basic pattern of rhythmic jaw movements produced during mastication is generated by a Central Pattern Generator (CPG) located in the pons and medulla. Neurons within the CPG have intrinsic properties that produce a rhythmic activity, but the output of these neurons is modified by inputs that descend from the higher centers of the brain, and by feedback from sensory receptors, in order to constantly adapt the movement to the food properties.

  • 332.
    Westberg, Karl-Gunnar
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    McFarland, David
    Kolta, Arlette
    Stohler, Christian
    Feine, Jocelyne
    Woda, Alain
    From movement to pain: a tribute to professor James P. Lund2008In: Journal of Orofacial Pain, ISSN 1064-6655, E-ISSN 1945-3396, Vol. 22, no 4, p. 297-306Article in journal (Refereed)
    Abstract [en]

    This tribute article to Professor James P. Lund stems from 6 of the presentations delivered at the July 1, 2008, symposium that honored 3 "giants" in orofacial neuroscience: B. J. Sessle, A. G. Hannam, and J. P. Lund. It was noted that soon after his training as a dentist in Australia, Jim Lund became interested in research. At the time he decided to do a PhD, there was a lot of discussion about how rhythmic movements were programmed. The early belief, based on Sherrington's studies of motor systems, was that these movements were simply an alternating series of reflexes. In the late 1960s and early 1970s, some still shared this belief, whereas others favored Graham Brown's hypothesis that repetitive movements were centrally programmed and did not depend on reflexes triggered by sensory inputs. There was no strong evidence then for either scenario except for the rhythmic movements of respiration. Lund's pioneering work during his PhD proved the existence of a central pattern generator (CPG) for mastication in the brainstem. Since then he has been interested in understanding how CPGs function and how sensory feedback works to adjust the motor patterns that they produce. Sections in this tribute article to Lund are written by some of his close collaborators and reflect the evolution of his work throughout the years. The first 4 presentations in this article (by K.-G. Westberg, D. McFarland, A. Kolta, and C. Stohler) highlight various aspects of these interests, and the final 2 presentations (by J. Feine and A. Woda) focus especially on clinical aspects of Lund's interests. The last section of this article is a final commentary from Professor Lund.

  • 333.
    Westberg, Karl-Gunnar
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Scott, G
    Université de Montréal, McGill University, Montréal.
    Olsson, Kurt
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Lund, J P
    Université de Montréal, McGill University, Montréal.
    Discharge patterns of neurons in the medial pontobulbar reticular formation during fictive mastication in the rabbit2001In: European Journal of Neuroscience, ISSN 0953-816X, E-ISSN 1460-9568, Vol. 14, no 10, p. 1709-1718Article in journal (Refereed)
    Abstract [en]

    In this study, we describe functional characteristics of neurons forming networks generating oral ingestive motor behaviours. Neurons in medial reticular nuclei on the right side of the brainstem between the trigeminal and hypoglossal motor nuclei were recorded in anaesthetized and paralysed rabbits during two types of masticatory-like motor patterns induced by electrical stimulation of the left (contralateral) or right (ipsilateral) cortical masticatory areas. Sixty-seven neurons in nucleus reticularis pontis caudalis (nPontc), nucleus reticularis parvocellularis (nParv), and nucleus reticularis gigantocellularis (Rgc) were studied. These were classified as phasic or tonic depending on their firing pattern during the fictive jaw movement cycle. Phasic neurons located in the dorsal part of nPontc were active during the jaw opening phase, whilst those in dorsal nParv tended to fire during the closing phase. In most neurons, burst duration and firing frequency changed between the two motor patterns, but there was little change in phase of firing. Tonic units were mainly recorded in the ventral half of nPontc, and at the junction between Rgc and caudal nParv. Cortical inputs with short latency from the contralateral masticatory area were more frequent in phasic (82%) than tonic (44%) neurons, whilst inputs from the ipsilateral cortex were equal in the two subgroups (57% and 56%). Phasic neurons had significantly shorter mean contralateral than ipsilateral cortical latencies, whilst there was no difference among tonic neurons. Intra- and perioral primary afferent inputs activated both types of neurons at oligo-synaptic latencies. Our results show that subpopulations of neurons in medial reticular nuclei extending from the caudal part of the trigeminal motor nucleus to the rostral third of the hypoglossal motor nucleus are active during the fictive masticatory motor behaviour. Unlike masticatory neurons in the lateral tegmentum, the medial subpopulations are spatially organized according to discharge pattern.

  • 334. Wettels, N
    et al.
    Popovic, D
    Santos, VJ
    Johansson, Roland
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Loeb, GE
    Biomimetic tactile sensor for control of grip2007In: 2007 IEEE 10th International Conference on Rehabilitation Robotics, ICORR'07, 2007, p. 923-932Conference paper (Refereed)
  • 335. Wettels, Nicholas
    et al.
    Santos, Veronica J
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Loeb, Gerald E
    Biomimetic Tactile Sensor Array2008In: Advanced Robotics, ISSN 0169-1864, E-ISSN 1568-5535, no 22, p. 829-849Article in journal (Refereed)
    Abstract [en]

    The performance of robotic and prosthetic hands in unstructured environments is severely limited by their having little or no tactile information compared to the rich tactile feedback of the human hand. We are developing a novel, robust tactile sensor array that mimics the mechanical properties and distributed touch receptors of the human fingertip. It consists of a rigid core surrounded by a weakly conductive fluid contained within an elastomeric skin. The sensor uses the deformable properties of the finger pad as part of the transduction process. Multiple electrodes are mounted on the surface of the rigid core and connected to impedance-measuring circuitry safely embedded within the core. External forces deform the fluid path around the electrodes, resulting in a distributed pattern of impedance changes containing information about those forces and the objects that applied them. Here we describe means to optimize the dynamic range of individual electrode sensors by texturing the inner surface of the silicone skin. Forces ranging from 0.1 to 30N produced impedances ranging from 5 to 1000 kΩ. Spatial resolution (below 2mm) and frequency response (above 50Hz) appeared to be limited only by the viscoelastic properties of the silicone elastomeric skin.

  • 336.
    Wikgren, Mikael
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    Karlsson, Thomas
    Linköping University, Department of Behavioral Sciences and Learning.
    Nilbrink, Therese
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    Nordfjäll, Katarina
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Hultdin, Johan
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry.
    Sleegers, Kristel
    VIB, Department of Molecular Genetics.
    Van Broeckhoven, Christine
    VIB, Department of Molecular Genetics.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Roos, Göran
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Nilsson, Lars-Göran
    Stockholm University, Department of Psychology.
    Adolfsson, Rolf
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    Norrback, Karl-Fredrik
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    APOE ε4 is associated with longer telomeres, and longer telomeres among ε4 carriers predicts worse episodic memory2012In: Neurobiology of Aging, ISSN 0197-4580, E-ISSN 1558-1497, Vol. 33, no 2, p. 335-344Article in journal (Refereed)
    Abstract [en]

    Both leukocyte telomere length and the apolipoprotein epsilon4 allele have been associated with mortality, cardiovascular disease, cognition, and dementia. The authors investigated whether leukocyte telomere length was associated with APOE genotype or cognitive abilities in the context of APOE genotype. The setting for this cross-sectional study was 427 nondemented individuals aged 41-81 yr. The authors found that epsilon4 carriers overall exhibited significantly longer telomeres compared with non-carriers (difference of 268 bp, p = 0.001). This difference was greatest at the lower limit of the age span and nonsignificant at the upper limit, which translated into a significantly higher telomere attrition rate (p = 0.049) among epsilon4 carriers (37 bp/years) compared with non-carriers (21 bp/year). Further, longer telomeres among epsilon4 carriers significantly predicted worse performance on episodic memory tasks. No significant associations were found on tasks tapping semantic and visuospatial ability, or among epsilon3/epsilon3 carriers. In conclusion, APOE epsilon4 carriers had longer telomeres compared with non-carriers, but higher rate of attrition. Among them, longer telomeres predicted worse performance on episodic memory tasks. These observations suggest that the epsilon4 allele is associated with abnormal cell turnover of functional and possibly clinical significance.

  • 337.
    Wiklund-Hörnkvist, Carola
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Karlsson, Linnea
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Eriksson, Johan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Jonsson, Bert
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    The neural mechanisms underlying test-enhanced learning: An event-related functional magnetic resonance imaging study2012In: Earli-SIG 22: Neuroscience and Education" 24th-26th May 2012, Institute of Education, London, 2012, p. 9-9Conference paper (Refereed)
    Abstract [en]

    Considerable research in cognitive psychology has demonstrated that testing improves the performance on later retention tests, a phenomenon called the testing-effect. However, the neural mechanisms of test-enhanced learning are not well understood. The current study examined changes in functional brain networks in relation to repeated retrieval (i.e. test-enhanced learning).

    Participants (n=20) first studied 60 Swahili-Swedish word-pairs. Subsequently, they underwent functional magnetic resonance imaging while being tested on each study item three times.

    Successful repeated retrieval was characterized by decreased activity in prefrontal and premotor regions and in the right caudate, compared to items not successfully retrieved at consecutive tests. Successful repeated retrieval was also characterized by increased activity in right middle temporal cortex (BA 37 & 21).

    Tentatively, these results imply that the benefits of test-enhanced learning in part is due to decreased need for executive processing along with strengthening of semantic representations.

    The current results generate novel information on the effectiveness of testing as a learning method and thus contribute to bridge the current gap between cognitive neuroscience and educational research.

  • 338.
    Wiklund-Hörnqvist, Carola
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Karlsson, Linnea
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Eriksson, Johan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Andersson, Micael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Jonsson, Bert
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Activity in left temporal-parietal regions characterizes long-term retention after repeated testing2013In: Journal of cognitive neuroscience, ISSN 0898-929X, E-ISSN 1530-8898, Vol. 25, no Suppl., p. S114-S114Article in journal (Other academic)
  • 339.
    Wirell, Staffan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Binding of radiographic contrast media to serum proteins: a clinical and experimental investigation of their adverse effects through influence on active steroid hormone levels1982Doctoral thesis, comprehensive summary (Other academic)
  • 340.
    Yelhekar, Tushar D.
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Druzin, Michael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Karlsson, Urban
    Blomqvist, Erii
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Johansson, Staffan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    How to Properly Measure a Current-Voltage Relation? -Interpolation vs. Ramp Methods Applied to Studies of GABA(A) Receptors2016In: Frontiers in Cellular Neuroscience, ISSN 1662-5102, E-ISSN 1662-5102, Vol. 10, article id 10Article in journal (Refereed)
    Abstract [en]

    The relation between current and voltage, I-V relation, is central to functional analysis of membrane ion channels. A commonly used method, since the introduction of the voltage-clamp technique, to establish the I-V relation depends on the interpolation of current amplitudes recorded at different steady voltages. By a theoretical computational approach as well as by experimental recordings from GABA(A) receptor mediated currents in mammalian central neurons, we here show that this interpolation method may give reversal potentials and conductances that do not reflect the properties of the channels studied under conditions when ion flux may give rise to concentration changes. Therefore, changes in ion concentrations may remain undetected and conclusions on changes in conductance, such as during desensitization, may be mistaken. In contrast, an alternative experimental approach, using rapid voltage ramps, enable I-V relations that much better reflect the properties of the studied ion channels.

  • 341.
    Yelhekar, Tushar
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Kuznetsova, Tatiana
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Malinina, Evgenya
    Ponimaskin, Evgeni
    Dityatev, Alexander
    Druzin, Michael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Johansson, Staffan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Extracellular Matrix Regulates Neuronal Chloride Concentration via K+-Cl--cotransporter 2Manuscript (preprint) (Other academic)
  • 342.
    Åberg, Maria
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Ljungberg, Christina
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Edin, Ellenor
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Millqvist, Helena
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Nordh, Erik
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neurophysiology.
    Theorin, Anna
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Terenghi, Giorgio
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Wiberg, Mikael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy. Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Clinical evaluation of a resorbable wrap-around implant as an alternative to nerve repair: A prospective, assessor-blinded, randomised clinical study of sensory, motor and functional recovery after peripheral nerve repair.2009In: Journal of plastic, reconstructive & aesthetic surgery : JPRAS, ISSN 1748-6815, Vol. 62, no 11, p. 1503-1509Article in journal (Refereed)
    Abstract [en]

    Peripheral nerve injures are common and often result in impaired functional recovery. The majority of injuries involve the arm and/or the hand. The traditional treatment for peripheral nerve injuries is repair by using microsurgical techniques, either by primary nerve suture or nerve graft, but research to find more successful methods that could improve recovery is ongoing. Tubulisation has been investigated by several authors and is suggested as an alternative to microsurgical techniques. The resorbable poly[(R)-3-hydroxybutyrate] (PHB) is one of the materials that has been previously tested experimentally. In this prospective, randomised, assessor-blinded clinical study, PHB was investigated as an alternative to epineural suturing in the treatment of peripheral nerve injuries at the wrist/forearm level of the arm. Twelve patients, with a complete, common, sharp injury of the median and/or ulnar nerve at the wrist/forearm level, were treated by either using PHB or microsurgical epineural end-to-end suturing. All patients were assessed using a battery of tests, including evaluation of functional, sensory and motor recovery by means of clinical, neurophysiological, morphological and physiological evaluations at 2 weeks and 3, 6, 9, 12 and 18 months after surgery. No adverse events or complications considered as product related were reported, and thus PHB can be regarded as a safe alternative for microsurgical epineural suturing. The majority of the methods in the test battery showed no significant differences between the treatment groups, but one should consider that the study involved a limited number of patients and a high variability was reported for the evaluating techniques. However, sensory recovery, according to the British Medical Research Council score and parts of the manual muscle test, suggested that treating with PHB may be advantageous as compared to epineural suturing. This, however, should be confirmed by large-scale efficacy studies.

  • 343.
    Öhberg, Fredrik
    et al.
    Umeå University, Faculty of Medicine, Radiation Sciences.
    Johansson, H
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
    Bergenheim, M
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
    Pedersen, J
    Djupsjöbacka, M
    A neural network appoach to real-time spike discrimination during simultaneous recording from several multi-unit nerve filaments1996In: Journal of Neuroscience Methods, ISSN 0165-0270, E-ISSN 1872-678X, Vol. 64, no 2, p. 181-187Article in journal (Refereed)
    Abstract [en]

    A multi-channel, real-time, unsupervised spike discriminator was developed in order to reconstruct single spike trains from several simultaneously recorded multi-unit nerve filaments. The program uses a Self Organising Map (SOM) algorithm for the classification of the spikes. In contrast to previous similar techniques, the described method is made for use on a PC, and the method may thus be implemented at relatively low cost. In order to test the accuracy of the program, a robustness test was performed, where noise with different RMS levels was superimposed on the spikes. Furthermore, the maximal classification rate was determined. The program is easy to use, since the only manual inputs needed are the voltage threshold for spike detection, and the number of units present in each recorded nerve filament.

4567 301 - 343 of 343
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