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  • 1.
    Bergström, Fredrik
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Faculty of Psychology and Educational Sciences, University of Coimbra, Portugal.
    Eriksson, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Neural evidence for non-conscious working memory2018Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 28, nr 9, s. 3217-3228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent studies have found that non-consciously perceived information can be retained for several seconds, a feat that has been attributed to non-conscious working memory processes. However, these studies have mainly relied on subjective measures of visual experience, and the neural processes responsible for non-conscious short-term retention remains unclear. Here we used continuous flash suppression to render stimuli non-conscious in a delayed match-to-sample task together with fMRI to investigate the neural correlates of non-conscious short-term (5-15 s) retention. The participants' behavioral performance was at chance level when they reported no visual experience of the sample stimulus. Critically, multivariate pattern analyses of BOLD signal during the delay phase could classify presence versus absence of sample stimuli based on signal patterns in frontal cortex, and its spatial position based on signal patterns in occipital cortex. In addition, univariate analyses revealed increased BOLD signal change in prefrontal regions during memory recognition. Thus, our findings demonstrate short-term maintenance of information presented non-consciously, defined by chance performance behaviorally. This non-consciously retained information seems to rely on persistent neural activity in frontal and occipital cortex, and may engage further cognitive control processes during memory recognition.

  • 2.
    Eriksson, Johan
    et al.
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Larsson, Anne
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Riklund Åhlström, Katrine
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Similar frontal and distinct posterior cortical regions mediate visual and auditory perceptual awareness2007Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 17, nr 4, s. 760-765Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Activity in ventral visual cortex is a consistent neural correlate of visual consciousness. However, activity in this area seems insufficient to produce awareness without additional involvement of frontoparietal regions. To test the generality of the frontoparietal response, neural correlates of auditory awareness were investigated in a paradigm that previously has revealed frontoparietal activity during conscious visual perception. A within-experiment comparison showed that frontal regions were related to both visual and auditory awareness, whereas parietal activity was correlated with visual awareness and superior temporal activity with auditory awareness. These results indicate that frontal regions interact with specific posterior regions to produce awareness in different sensory modalities.

  • 3. Guitart-Masip, Marc
    et al.
    Salami, Alireza
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Aging Research Center, Karolinska Institute, Stockholm, Sweden .
    Garrett, Douglas
    Rieckmann, Anna
    Center for Brain Science, Harvard University, Cambridge, USA.
    Lindenberger, Ulman
    Bäckman, Lars
    BOLD Variability is Related to Dopaminergic Neurotransmission and Cognitive Aging2016Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 26, nr 5, s. 2074-2083Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dopamine (DA) losses are associated with various aging-related cognitive deficits. Typically, higher moment-to-moment brain signal variability in large-scale patterns of voxels in neocortical regions is linked to better cognitive performance and younger adult age, yet the physiological mechanisms regulating brain signal variability are unknown. We explored the relationship among adult age, DA availability, and blood oxygen level-dependent (BOLD) signal variability, while younger and older participants performed a spatial working memory (SWM) task. We quantified striatal and extrastriatal DA D1 receptor density with [(11)C]SCH23390 and positron emission tomography in all participants. We found that BOLD variability in a neocortical region was negatively related to age and positively related to SWM performance. In contrast, BOLD variability in subcortical regions and bilateral hippocampus was positively related to age and slower responses, and negatively related to D1 density in caudate and dorsolateral prefrontal cortex. Furthermore, BOLD variability in neocortical regions was positively associated with task-related disengagement of the default-mode network, a network whose activation needs to be suppressed for efficient SWM processing. Our results show that age-related DA losses contribute to changes in brain signal variability in subcortical regions and suggest a potential mechanism, by which neocortical BOLD variability supports cognitive performance.

  • 4. Habib, Reza
    et al.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Neural Correlates of Availability and Accessibility in Memory2008Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 8, nr 7, s. 1720-1726Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Failure to remember can be due to not having information available in memory or to an inability to access information that is available. We used functional magnetic resonance imaging to examine brain responses during encoding and successive cued recall and associative recognition tests of paired associates. Items were classified into 3 categories based on performance on the 2 retrieval tests: 1) successfully remembered (both recalled and recognized), 2) inaccessible (not recalled but later recognized), and 3) forgotten (neither recalled nor recognized). During cued recall, availability in memory was signaled in a network of regions including bilateral medial temporal lobe, left middle temporal cortex, and the parietal cortex. Memory access resulted in heightened activity in these regions as well as in left inferior frontal cortex. Encoding-related activity in hippocampus and inferior temporal cortex predicted subsequent availability and left inferior frontal activity predicted subsequent access. These results suggest that failure to access information that is available in memory may reflect weaker memory representations.

  • 5. Hedden, Trey
    et al.
    Schultz, Aaron P
    Rieckmann, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Mormino, Elizabeth C
    Johnson, Keith A
    Sperling, Reisa A
    Buckner, Randy L
    Multiple Brain Markers are Linked to Age-Related Variation in Cognition2016Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 26, nr 4, s. 1388-1400Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Age-related alterations in brain structure and function have been challenging to link to cognition due to potential overlapping influences of multiple neurobiological cascades. We examined multiple brain markers associated with age-related variation in cognition. Clinically normal older humans aged 65-90 from the Harvard Aging Brain Study (N = 186) were characterized on a priori magnetic resonance imaging markers of gray matter thickness and volume, white matter hyperintensities, fractional anisotropy (FA), resting-state functional connectivity, positron emission tomography markers of glucose metabolism and amyloid burden, and cognitive factors of processing speed, executive function, and episodic memory. Partial correlation and mediation analyses estimated age-related variance in cognition shared with individual brain markers and unique to each marker. The largest relationships linked FA and striatum volume to processing speed and executive function, and hippocampal volume to episodic memory. Of the age-related variance in cognition, 70-80% was accounted for by combining all brain markers (but only ∼20% of total variance). Age had significant indirect effects on cognition via brain markers, with significant markers varying across cognitive domains. These results suggest that most age-related variation in cognition is shared among multiple brain markers, but potential specificity between some brain markers and cognitive domains motivates additional study of age-related markers of neural health.

  • 6. Iurilli, Giuliano
    et al.
    Benfenati, Fabio
    Medini, Paolo
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Loss of Visually Driven Synaptic Responses in Layer 4 Regular-Spiking Neurons of Rat Visual Cortex in Absence of Competing Inputs2012Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 22, nr 9, s. 2171-2181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Monocular deprivation (MD) during development shifts the ocular preference of primary visual cortex (V1) neurons by depressing closed-eye responses and potentiating open-eye responses. As these 2 processes are temporally and mechanistically distinct, we tested whether loss of responsiveness occurs also in absence of competing inputs. We thus compared the effects of long-term MD in layer 4 regular-spiking pyramidal neurons (L4Ns) of binocular and monocular V1 (bV1 and mV1) with whole-cell recordings. In bV1, input depression was larger than potentiation, and the ocular dominance shift was larger for spike outputs. MD-but not retinal inactivation with tetrodotoxin-caused a comparable loss of synaptic and spike responsiveness in mV1, which is innervated only by the deprived eye. Conversely, brief MD depressed synaptic responses only in bV1. MD-driven depression in mV1 was accompanied by a proportional reduction of visual thalamic inputs, as assessed upon pharmacological silencing of intracortical transmission. Finally, sub- and suprathreshold responsiveness was similarly degraded in L4Ns of bV1 upon complete deprivation of patterned vision through a binocular deprivation period of comparable length. Thus, loss of synaptic inputs from the deprived eye occurs also in absence of competition in the main thalamorecipient lamina, albeit at a slower pace.

  • 7. Kalpouzos, Gregoria
    et al.
    Garzon, Benjamin
    Sitnikov, Rouslan
    Heiland, Carmel
    Salami, Alireza
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Aging Research Center (ARC), Karolinska Institutet and Stockholm University, Stockholm, Sweden; .
    Persson, Jonas
    Backman, Lars
    Higher Striatal Iron Concentration is Linked to Frontostriatal Underactivation and Poorer Memory in Normal Aging2017Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 27, nr 6, s. 3427-3436Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the brain, intracellular iron is essential for cellular metabolism. However, an overload of free iron is toxic, inducing oxidative stress and cell death. Although an increase of striatal iron has been related to atrophy and impaired cognitive performance, the link between elevated iron and altered brain activity in aging remains unexplored. In a sample of 37 younger and older adults, we examined whether higher striatal iron concentration could underlie age-related differences in frontostriatal activity induced by mental imagery of motor and non-motor scenes, and poorer recall of the scenes. Higher striatal iron concentration was linked to underrecruitment of frontostriatal regions regardless of age and striatal volume, the iron-activity association in right putamen being primarily driven by the older adults. In older age, higher striatal iron was related to poorer memory. Altered astrocytic functions could account for the link between brain iron and brain activity, as astrocytes are involved in iron buffering, neurovascular coupling, and synaptic activity. Our preliminary findings, which need to be replicated in a larger sample, suggest a potential frontostriatal target for intervention to counteract negative effects of iron accumulation on brain function and cognition.

  • 8.
    Lindgren, Lenita
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för omvårdnad. Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Bergdahl, Jan
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi. Department of Clinical Dentistry, Faculty of Health Sciences, UIT - The Arctic University of Norway, Tromsø, Norway.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Longitudinal Evidence for Smaller Hippocampus Volume as a Vulnerability Factor for Perceived Stress2016Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 26, nr 8, s. 3527-3533Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hippocampal volume has been found to be smaller in individuals with stress-related disorders, but it remains unclear whether smaller volume is a consequence of stress or rather a vulnerability factor. Here, we examined this issue by relating stress levels to hippocampal volumes in healthy participants examined every 5 years in a longitudinal population-based study. Based on scores of 25- to 60-year-old participants on the perceived stress questionnaire, we defined moderately to high (n = 35) and low (n = 76) stress groups. The groups were re-examined after 5 years (at the 6th study wave). Historical data on subjective stress were available up to 10 years prior to Wave 5. At the first MRI session, the moderately to high stress group had a significantly smaller hippocampal volume, as measured by FreeSurfer (version 5.3), compared with the low-stress group. At follow-up, group differences in stress levels and hippocampal volume remained unchanged. In retrospective analyses of subjective stress, the observed group difference in stress was found to be stable. The long-term stability of group differences in perceived stress and hippocampal volume suggests that a small hippocampal volume may be a vulnerability factor for stress-related disorders.

  • 9. Lövdén, Martin
    et al.
    Karalija, Nina
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Andersson, Micael
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Wåhlin, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Axelsson, Jan
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Köhncke, Ylva
    Jonasson, Lars S.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Samhällsvetenskapliga fakulteten, Enheten för demografi och åldrandeforskning (CEDAR).
    Rieckmann, Anna
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Papenberg, Goran
    Garrett, Douglas D.
    Guitart-Masip, Marc
    Salami, Alireza
    Riklund, Katrine
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Bäckman, Lars
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Lindenberger, Ulman
    Latent-profile analysis reveals behavioral and brain correlates of dopamine-cognition associations2018Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 28, nr 11, s. 3894-3907Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Evidence suggests that associations between the neurotransmitter dopamine and cognition are nonmonotonic and open to modulation by various other factors. The functional implications of a given level of dopamine may therefore differ from person to person. By applying latent-profile analysis to a large (n = 181) sample of adults aged 64-68 years, we probabilistically identified 3 subgroups that explain the multivariate associations between dopamine D2/3R availability (probed with C-11-raclopride-PET, in cortical, striatal, and hippocampal regions) and cognitive performance (episodic memory, working memory, and perceptual speed). Generally, greater receptor availability was associated with better cognitive performance. However, we discovered a subgroup of individuals for which high availability, particularly in striatum, was associated with poor performance, especially for working memory. Relative to the rest of the sample, this subgroup also had lower education, higher body-mass index, and lower resting-state connectivity between caudate nucleus and dorsolateral prefrontal cortex. We conclude that a smaller subset of individuals induces a multivariate non-linear association between dopamine D2/3R availability and cognitive performance in this group of older adults, and discuss potential reasons for these differences that await further empirical scrutiny.

  • 10.
    Persson, Jonas
    et al.
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Nyberg, Lars
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Lind, Johanna
    MR Research Center, Karolinska Hospital, S-171 76 Stockholm, Sweden.
    Larsson, Anne
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University, S-106 91 Stockholm, Sweden.
    Ingvar, Martin
    MR Research Center, Karolinska Hospital, S-171 76 Stockholm, Sweden.
    Buckner, Randy L
    Departments of Psychology, Radiology, and Anatomy & Neurobiology, Howard Hughes Medical Institute at Washington University, St Louis, MO 63130, USA.
    Structure-function correlates of cognitive decline in aging2006Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 16, nr 7, s. 907-915Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To explore neural correlates of cognitive decline in aging, we used longitudinal behavioral data to identify two groups of older adults (n = 40) that differed with regard to whether their performance on tests of episodic memory remained stable or declined over a decade. Analysis of structural and diffusion tensor imaging (DTI) revealed a heterogeneous set of differences associated with cognitive decline. Manual tracing of hippocampal volume showed significant reduction in those older adults with a declining memory performance as did DTI-measured fractional anisotropy in the anterior corpus callosum. Functional magnetic resonance imaging during incidental episodic encoding revealed increased activation in left prefrontal cortex for both groups and additional right prefrontal activation for the elderly subjects with the greatest decline in memory performance. Moreover, mean DTI measures in the anterior corpus callosum correlated negatively with activation in right prefrontal cortex. These results demonstrate that cognitive decline is associated with differences in the structure as well as function of the aging brain, and suggest that increased activation is either caused by structural disruption or is a compensatory response to such disruption.

  • 11.
    Persson, Jonas
    et al.
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Pudas, Sara
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Lind, Johanna
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Kauppi, Karolina
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nilsson, Lars-Göran
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Longitudinal structure-function correlates in elderly reveal MTL dysfunction with cognitive decline2012Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 22, nr 10, s. 2297-2304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By integrating behavioral measures and imaging data, previous investigations have explored the relationship between biological markers of aging and cognitive functions. Evidence from functional and structural neuroimaging has revealed that hippocampal volume and activation patterns in the medial temporal lobe (MTL) may predict cognitive performance in old age. Most past demonstrations of age-related differences in brain structure-function were based on cross-sectional comparisons. Here, the relationship between 6-year intraindividual change in functional magnetic resonance imaging (fMRI) signal and change in memory performance over 2 decades was examined. Correlations between intraindividual change in fMRI signal during episodic encoding and change in memory performance measured outside of scanning were used as an estimate for relating brain-behavior changes. The results revealed a positive relationship between activation change in the hippocampus (HC) and change in memory performance, reflecting reduced hippocampal activation in participants with declining performance. Using a similar analytic approach as for the functional data, we found that individuals with declining performance had reduced HC volume compared with individuals with intact performance. These observations provide a strong link between cognitive change in older adults and MTL structure and function and thus provide insights into brain correlates of individual variability in aging trajectories.

  • 12.
    Pudas, Sara
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
    Josefsson, Maria
    Umeå universitet, Samhällsvetenskapliga fakulteten, Enheten för demografi och åldrandeforskning (CEDAR).
    Rieckmann, Anna
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
    Longitudinal evidence for increased functional response in frontal cortex for older adults with hippocampal atrophy and memory decline2018Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 28, nr 3, s. 936-948Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The functional organization of the frontal cortex is dynamic. Age-related increases in frontal functional responses have been shown during various cognitive tasks, but the cross-sectional nature of most past studies makes it unclear whether these increases reflect reorganization or stable individual differences. Here, we followed 130 older individuals' cognitive trajectories over 20-25 years with repeated neuropsychological assessments every 5th year, and identified individuals with stable or declining episodic memory. Both groups displayed significant gray matter atrophy over 2 successive magnetic resonance imaging sessions 4 years apart, but the decline group also had a smaller volume of the right hippocampus. Only individuals with declining memory demonstrated increased prefrontal functional responses during memory encoding and retrieval over the 4-year interval. Regions with increased functional recruitment were located outside, or on the borders of core task-related networks, indicating an expansion of these over time. These longitudinal findings offer novel insight into the mechanisms behind age-associated memory loss, and are consistent with a theoretical model in which hippocampus atrophy, past a critical threshold, induces episodic-memory decline and altered prefrontal functional organization.

  • 13.
    Rieckmann, Anna
    et al.
    Aging Research Center, Department of Neurobiology, Care Sciences & Society, Karolinska Institute, SE-113 30 Stockholm, Sweden.
    Karlsson, Sari
    Aging Research Center, Department of Neurobiology, Care Sciences & Society, Karolinska Institute, SE-113 30 Stockholm, Sweden.
    Karlsson, Per
    Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, SE-171 76 Stockholm, Sweden.
    Brehmer, Yvonne
    Aging Research Center, Department of Neurobiology, Care Sciences & Society, Karolinska Institute, SE-113 30 Stockholm, Sweden.
    Fischer, Håkan
    Aging Research Center, Department of Neurobiology, Care Sciences & Society, Karolinska Institute, SE-113 30 Stockholm, Sweden.
    Farde, Lars
    Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, SE-171 76 Stockholm, Sweden.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Bäckman, Lars
    Aging Research Center, Department of Neurobiology, Care Sciences & Society, Karolinska Institute, SE-113 30 Stockholm, Sweden.
    Dopamine D1 receptor associations within and between dopaminergic pathways in younger and elderly adults: links to cognitive performance2011Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 21, nr 9, s. 2023-2032Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Age-related dopamine (DA) losses have been extensively demonstrated for the D2 receptor subtype. Comparatively little is known about adult age changes regarding D1 receptors. In this study, we demonstrate marked age-related D1 receptor losses in striatal, limbic, and cortical areas using positron emission tomography and the radioligand [(11)C]SCH23390 in humans. Interregional correlations of binding potential (BP) values were high for areas within DA pathways in younger and elderly adults alike. Furthermore, interregional correlations in D1 BP between DA pathways were uniformly high in younger adults, indicating that D1 receptor densities in striatal, limbic, and cortical areas are not regulated independently, despite dopaminergic innervation from different midbrain areas. For elderly adults, between-pathway correlations of D1 receptor densities were preserved only between mesolimbic and mesocortical areas, whereas striatal BPs were weakly related to those in limbic and neocortical regions. Importantly, weak between-pathway correlations in elderly adults were found only for the slower half of the sample when BP was estimated during a cognitive interference task. These results suggest that D1 receptor densities in different pathways are not regulated independently in younger adults, but segregate in older age, and that this segregation of D1 receptor systems may be related to age-related cognitive slowing.

  • 14.
    Salami, Alireza
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden.
    Rieckmann, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Karalija, Nina
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Avelar-Pereira, Bárbara
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden.
    Andersson, Micael
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Wåhlin, Anders
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Papenberg, Goran
    Garrett, Douglas D.
    Riklund, Katrine
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Lövdén, Martin
    Lindenberger, Ulman
    Bäckman, Lars
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
    Neurocognitive Profiles of Older Adults with Working-Memory Dysfunction2018Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 28, nr 7, s. 2525-2539Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Individuals differ in how they perceive, remember, and think. There is evidence for the existence of distinct subgroups that differ in cognitive performance within the older population. However, it is less clear how individual differences in cognition in old age are linked to differences in brain-based measures. We used latent-profile analysis on n-back working-memory (WM) performance to identify subgroups in a large sample of older adults (n = 181; age = 64-68 years). Our analysis identified one larger normal subgroup with higher performance (n = 113; 63%), and a second smaller subgroup (n = 55; 31%) with lower performance. The low-performing subgroup showed weaker load-dependent BOLD modulation and lower connectivity within the fronto-parietal network (FPN) as well as between FPN and striatum during n-back, along with lower FPN connectivity at rest. This group also exhibited lower FPN structural integrity, lower frontal dopamine D2 binding potential, inferior performance on offline WM tests, and a trend-level genetic predisposition for lower dopamine-system efficiency. By contrast, this group exhibited relatively intact episodic memory and associated brain measures (i.e., hippocampal volume, structural, and functional connectivity within the default-mode network). Collectively, these data provide converging evidence for the existence of a group of older adults with impaired WM functioning characterized by reduced cortico-striatal coupling and aberrant cortico-cortical integrity within FPN.

  • 15.
    Salami, Alireza
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Aging Research Center, Karolinska Institutet and Stockholm University, SE-113 30, Stockholm, Sweden.
    Wåhlin, Anders
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Kaboodvand, Neda
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Aging Research Center, Karolinska Institutet and Stockholm University, SE-113 30, Stockholm, Sweden.
    Lundquist, Anders
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Longitudinal Evidence for Dissociation of Anterior and Posterior MTL Resting-State Connectivity in Aging: Links to Perfusion and Memory2016Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 26, nr 10, s. 3953-3963Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neuroimaging studies of spontaneous signal fluctuations as measured by resting-state functional magnetic resonance imaging have revealed age-related alterations in the functional architecture of brain networks. One such network is located in the medial temporal lobe (MTL), showing structural and functional variations along the anterior-posterior axis. Past cross-sectional studies of MTL functional connectivity (FC) have yielded discrepant findings, likely reflecting the fact that specific MTL subregions are differentially affected in aging. Here, using longitudinal resting-state data from 198 participants, we investigated 5-year changes in FC of the anterior and posterior MTL. We found an opposite pattern, such that the degree of FC within the anterior MTL declined after age 60, whereas elevated FC within the posterior MTL was observed along with attenuated posterior MTL-cortical connectivity. A significant negative change-change relation was observed between episodic-memory decline and elevated FC in the posterior MTL. Additional analyses revealed age-related cerebral blood flow (CBF) increases in posterior MTL at the follow-up session, along with a positive relation of elevated FC and CBF, suggesting that elevated FC is a metabolically demanding alteration. Collectively, our findings indicate that elevated FC in posterior MTL along with increased local perfusion is a sign of brain aging that underlie episodic-memory decline.

  • 16. Vidal-Pineiro, Didac
    et al.
    Sneve, Markus H.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Mowinckel, Athanasia M.
    Sederevicius, Donatas
    Walhovd, Kristine B.
    Fjell, Anders M.
    Maintained Frontal Activity Underlies High Memory Function Over 8 Years in Aging2019Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 29, nr 7, s. 3111-3123Artikkel i tidsskrift (Fagfellevurdert)
    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.

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