Specific changes in somatosensory evoked magnetic fields during recovery from sensorimotor stroke

We studied recovery‐induced changes in the responsiveness of the primary somatosensory cortex in stroke patients with sensory and/or motor symptoms. Somatosensory evoked magnetic fields, in response to median nerve stimulation, were recorded in 14 patients with their first symptomatic unilateral stroke 1 to 15 days from the first symptoms and again 2 to 3 months later. Neuronal activity at the contralateral primary somatosensory cortex was modeled with equivalent current dipoles at the peak latencies of the first two cortical deflections at about 20 msec (N1m) and at 28 to 91 msec (P1m). Twenty‐three age‐matched healthy volunteers, 9 of whom were tested also in serial recordings, served as control subjects. At follow‐up, 6 patients showed a significant increase of P1m amplitude, whereas N1m increased only in 1. Clinical improvement of two‐point discrimination ability, but not of other basic somatosensory skills, was significantly correlated with the increase of P1m. We conclude that the recovery of discriminative touch after stroke is paralleled by the growth of the P1m somatosensory evoked magnetic field deflection, and we propose that this may reflect re‐establishment of lateral inhibitory functions at the primary somatosensory cortex. Ann Neurol 2000;47:353–360

[1]  C Xerri,et al.  Plasticity of primary somatosensory cortex paralleling sensorimotor skill recovery from stroke in adult monkeys. , 1998, Journal of neurophysiology.

[2]  K. Nakashima,et al.  Somatosensory evoked potentials over the non-affected hemisphere in patients with unilateral cerebrovascular lesions , 1985, Journal of the Neurological Sciences.

[3]  T. Neumann-Haefelin,et al.  Increased long‐term potentiation in the surround of experimentally induced focal cortical infarction , 1998, Annals of neurology.

[4]  D. Prince,et al.  Frequency‐dependent depression of inhibition in guinea‐pig neocortex in vitro by GABAB receptor feed‐back on GABA release. , 1989, The Journal of physiology.

[5]  L. Parkkonen,et al.  122-channel squid instrument for investigating the magnetic signals from the human brain , 1993 .

[6]  B. Rosen,et al.  A functional MRI study of subjects recovered from hemiparetic stroke. , 1997, Stroke.

[7]  R. Dykes,et al.  Functional role of GABA in cat primary somatosensory cortex: shaping receptive fields of cortical neurons. , 1984, Journal of neurophysiology.

[8]  R. Ilmoniemi,et al.  Magnetoencephalography-theory, instrumentation, and applications to noninvasive studies of the working human brain , 1993 .

[9]  Karl J. Friston,et al.  Functional reorganization of the brain in recovery from striatocapsular infarction in man , 1992, Annals of neurology.

[10]  O. Creutzfeldt,et al.  Extracellular and intracellular recordings from cat's cortical whisker projection area: thalamocortical response transformation. , 1977, Journal of neurophysiology.

[11]  O. Creutzfeldt,et al.  [POSTSYNAPTIC POTENTIALS OF NERVE CELLS OF THE MOTOR CORTEX AFTER ELECTRIC STIMULATION OF SPECIFIC AND NONSPECIFIC THALAMIC NUCLEI]. , 1964, Pflugers Archiv fur die gesamte Physiologie des Menschen und der Tiere.

[12]  M Hämäläinen,et al.  Early deflections of cerebral magnetic responses to median nerve stimulation. , 1989, Electroencephalography and clinical neurophysiology.

[13]  C. Robinson,et al.  Organization of the S II Parietal Cortex , 1981 .

[14]  B. Rockstroh,et al.  Increased Cortical Representation of the Fingers of the Left Hand in String Players , 1995, Science.

[15]  W. Lytton,et al.  Receptive field changes after strokelike cortical ablation: a role for activation dynamics. , 1997, Journal of neurophysiology.

[16]  Mark Hallett,et al.  Mechanisms of Deafferentation-Induced Plasticity in Human Motor Cortex , 1998, The Journal of Neuroscience.

[17]  R. Caselli,et al.  Ventrolateral and dorsomedial somatosensory association cortex damage produces distinct somesthetic syndromes in humans , 1993, Neurology.

[18]  M. Merzenich,et al.  Reorganization of neocortical representations after brain injury: a neurophysiological model of the bases of recovery from stroke. , 1987, Progress in brain research.

[19]  T. Allison,et al.  Functional magnetic resonance imaging of sensory and motor cortex: comparison with electrophysiological localization. , 1995, Journal of neurosurgery.

[20]  M. D. Egger,et al.  Formation of New Connexions in Adult Rat Brains after Partial Deafferentation , 1971, Nature.

[21]  Oili Salonen,et al.  Somatosensory evoked magnetic fields from the primary somatosensory cortex (SI) in acute stroke , 1999, Clinical Neurophysiology.

[22]  R. Ilmoniemi,et al.  Effects of interstimulus interval on somatosensory evoked magnetic fields (SEFs): a hypothesis concerning SEF generation at the primary sensorimotor cortex. , 1996, Electroencephalography and clinical neurophysiology.

[23]  P M Field,et al.  A quantitative investigation of the development of collateral reinnervation after partial deafferentation of the septal nuclei. , 1973, Brain research.

[24]  R. Ilmoniemi,et al.  Somatosensory evoked magnetic fields to median nerve stimulation: interhemispheric differences in a normal population. , 1997, Electroencephalography and clinical neurophysiology.

[25]  G. Donnan,et al.  Serial changes in somatosensory evoked potentials following cerebral infarction. , 1991, Electroencephalography and clinical neurophysiology.

[26]  Yue Cao,et al.  Pilot study of functional MRI to assess cerebral activation of motor function after poststroke hemiparesis. , 1998, Stroke.

[27]  O. Witte,et al.  Extended brain disinhibition following small photothrombotic lesions in rat frontal cortex , 1997, Neuroreport.

[28]  C C Wood,et al.  Electrical sources in human somatosensory cortex: identification by combined magnetic and potential recordings. , 1985, Science.

[29]  C. C. Wood,et al.  Human cortical potentials evoked by stimulation of the median nerve. I. Cytoarchitectonic areas generating short-latency activity. , 1989, Journal of neurophysiology.

[30]  R. Dykes,et al.  An electrophysiological laminar analysis of single somatosensory neurons in partially deafferented rat hindlimb granular cortex subsequent to transection of the sciatic nerve , 1988, Brain Research.

[31]  J. Kaas.  The functional organization of somatosensory cortex in primates. , 1993, Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft.

[32]  V. Ramachandran,et al.  Behavioral and magnetoencephalographic correlates of plasticity in the adult human brain. , 1993, Proceedings of the National Academy of Sciences of the United States of America.