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  • 1.
    Birznieks, Ingvars
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Jenmalm, Per
    Goodwin, A. W.
    Johansson, Roland S
    Directional encoding of fingertip force by human tactile afferents2001In: Journal of Neuroscience, ISSN 0270-6474, Vol. 21, no 8222-8237, p. 8222-8237Article in journal (Refereed)
  • 2.
    Birznieks, Ingvars
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Jenmalm, Per
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Goodwin, Antony W
    University of Melbourne, Victoria.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Encoding of direction of fingertip forces by human tactile afferents2001In: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 21, no 20, p. 8222-8237Article in journal (Refereed)
    Abstract [en]

    In most manipulations, we use our fingertips to apply time-varying forces to the target object in controlled directions. Here we used microneurography to assess how single tactile afferents encode the direction of fingertip forces at magnitudes, rates, and directions comparable to those arising in everyday manipulations. Using a flat stimulus surface, we applied forces to a standard site on the fingertip while recording impulse activity in 196 tactile afferents with receptive fields distributed over the entire terminal phalanx. Forces were applied in one of five directions: normal force and forces at a 20 degrees angle from the normal in the radial, distal, ulnar, or proximal directions. Nearly all afferents responded, and the responses in most slowly adapting (SA)-I, SA-II, and fast adapting (FA)-I afferents were broadly tuned to a preferred direction of force. Among afferents of each type, the preferred directions were distributed in all angular directions with reference to the stimulation site, but not uniformly. The SA-I population was biased for tangential force components in the distal direction, the SA-II population was biased in the proximal direction, and the FA-I population was biased in the proximal and radial directions. Anisotropic mechanical properties of the fingertip and the spatial relationship between the receptive field center of the afferent and the stimulus site appeared to influence the preferred direction in a manner dependent on afferent type. We conclude that tactile afferents from the whole terminal phalanx potentially contribute to the encoding of direction of fingertip forces similar to those that occur when subjects manipulate objects under natural conditions.

  • 3.
    Jenmalm, Per
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Birznieks, Ingvars
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Goodwin, A. W.
    Johansson, Roland S
    Influences of object shape on responses in human tactile afferents under conditions characteristic for manipulationManuscript (Other academic)
  • 4.
    Jenmalm, Per
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Schmitz, Christina
    Neuropediatric Unit, Department of Women and Child Health, Karolinska Institutet, Stockholm, Sweden / Centre National de la Recherche Scientifique–Groupe Développement et Pathologie de l’Action, Marseilles, France.
    Forssberg, Hans
    Neuropediatric Unit, Department of Women and Child Health, Karolinska Institutet, Stockholm, Sweden.
    Ehrsson, H. Henrik
    Neuropediatric Unit, Department of Women and Child Health, Karolinska Institutet, Stockholm, Sweden / Wellcome Department of Imaging Neuroscience, Institute of Neurology, London, United Kingdom.
    Lighter or heavier than predicted: neural correlates of corrective mechanisms during erroneously programmed lifts2006In: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 26, no 35, p. 9015-9021Article in journal (Refereed)
    Abstract [en]

    A central concept in neuroscience is that the CNS signals the sensory discrepancy between the predicted and actual sensory consequences of action. It has been proposed that the cerebellum and parietal cortex are involved in this process. A discrepancy will trigger preprogrammed corrective responses and update the engaged sensorimotor memories. Here we use functional magnetic resonance imaging with an event-related design to investigate the neuronal correlates of such discrepancies. Healthy adults repeatedly lifted an object between their right index fingers and thumbs, and on some lifting trials, the weight of the object was unpredictably changed between light (230 g) and heavy (830 g). Regardless of whether the weight was heavier or lighter than predicted, activity was found in the right inferior parietal cortex (supramarginal gyrus). This suggests that this region is involved in the comparison of the predicted and actual sensory input and the updating of the sensorimotor memories. When the object was lighter or heavier than predicted, two different types of preprogrammed force corrections occurred. There was a slow force increase when the weight of the object was heavier than predicted. This corrective response was associated with activity in the left primary motor and somatosensory cortices. The fast termination of the excessive force when the object was lighter than predicted activated the right cerebellum. These findings show how the parietal cortex, cerebellum, and motor cortex are involved in the signaling of the discrepancy between predicated and actual sensory feedback and the associated corrective mechanisms.

  • 5. Schmitz, Christina
    et al.
    Jenmalm, Per
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Ehrsson, H Henrik
    Forssberg, Hans
    Brain activity during predictable and unpredictable weight changes when lifting objects.2005In: Journal of Neurophysiology, ISSN 0022-3077, Vol. 93, no 3, p. 1498-509Article in journal (Refereed)
    Abstract [en]

    When humans repetitively lift the same object, the fingertip forces are targeted to the weight of the object. The anticipatory programming of the forces depends on sensorimotor memory representations that provide information on the object weight. In the present study, we investigate the neural substrates of these sensorimotor memory systems by recording the neural activity during predictable or unpredictable changes in the weight of an object in a lifting task. An unpredictable change in weight leads to erroneous programming of the fingertip forces. This triggers corrective mechanisms and an update of the sensorimotor memories. In the present fMRI study, healthy right-handed subjects repetitively lifted an object between right index finger and thumb. In the constant condition, which served as a control, the weight of the object remained constant (either 230 or 830 g). The weight alternated between 230 and 830 g during the regular condition and was irregularly changed between the two weights during the irregular condition. When we contrasted regular minus constant and irregular minus constant, we found activations in the right inferior frontal gyrus pars opercularis (area 44), the left parietal operculum and the right supramarginal gyrus. Furthermore, irregular was associated with stronger activation in the right inferior frontal cortex as compared with regular. Taken together, these results suggest that the updating of sensorimotor memory representations and the corrective reactions that occur when we manipulate different objects correspond to changes in synaptic activity in these fronto-parietal circuits.

  • 6.
    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, E
    Jenmalm, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Millqvist, H
    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.
    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.
    Considerations in evaluating new treatment alternatives following peripheral nerve injuries: a prospective clinical study of methods used to investigate sensory, motor and functional recovery.2007In: J Plast Reconstr Aesthet Surg, ISSN 1748-6815, Vol. 60, no 2, p. 103-13Article in journal (Refereed)
    Abstract [en]

    The current problem finding reliable and objective methods for evaluating results after peripheral nerve repair is a challenge when introducing new clinical techniques. The aim of this study was to obtain reference material and to evaluate the applicability of different tests used for clinical assessment after peripheral nerve injuries. Fifteen patients with a history of complete median nerve transsection and repair, and 15 healthy volunteers were included. Each subject was investigated using a battery of conventional and new tests for functional, sensory and motor recovery including questionnaires, clinical evaluations, neurophysiological and physiological findings. The results were statistically analysed and comparisons were made within the patient group and between patients and healthy volunteers using a 'per protocol' and an 'intention to treat' approach. Criteria for success were stipulated in order to be able to judge the usefulness of each method. The results showed that 19 of 34 variables, representing six of 16 methods, were not able to fulfil the criteria and were thus questionable for the evaluations of nerve repair in a clinical trial setting. However, 2pd, sensory recovery according to the non-modified British Medical Research Council, sensory neurography, manual muscle test, electromyography, questionnaires (i.e. DASH and the 4 question form) and performance tests (i.e. AMPS and Sollerman's subtests 4 and 8) did fulfil the criteria defined for being useful.

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