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Topography of somatosensory processing: Cerebral lateralization and focused attention

Published online by Cambridge University Press:  16 May 2002

K.J. MEADOR
Affiliation:
Department of Neurology, Medical College of Georgia, Augusta
J.D. ALLISON
Affiliation:
Department of Radiology, Medical College of Georgia, Augusta
D.W. LORING
Affiliation:
Department of Neurology, Medical College of Georgia, Augusta
T.B. LAVIN
Affiliation:
Department of Radiology, Medical College of Georgia, Augusta
J.J. PILLAI
Affiliation:
Department of Radiology, Medical College of Georgia, Augusta
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Abstract

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Healthy dextrals underwent fMRI during a task of graphesthesia requiring detection of any number written consecutively from an otherwise random number sequence. Test conditions included (1) focus on unilateral right hand stimuli, (2) focus on unilateral left hand stimuli, (3) focus on right hand only during bilateral hand stimulation, (4) focus on left hand only during bilateral hand stimulation, and (5) rest. Attention to unilateral hand stimulation produced bihemispheric activation with minimal or no activation of ipsilateral primary sensorimotor region. Attention to unilateral left hand stimuli resulted in more activation than attention to unilateral right hand stimuli. Stimulation of the nonattended hand activated the contralateral somatosensory area, but to a lesser spatial extent than attended stimuli. Comparing focused attention to the left versus right side during identical sensory inputs (i.e., bilateral hand stimulation), focused attention to the right hand increased activation in the left somatosensory region, but focused attention to the left hand increased activation in both cerebral hemispheres. Thus, focused attention to unilateral somatosensory stimuli produces bilateral cerebral activation, but the increase in blood flow is greater in the contralateral hemisphere. Unattended stimuli activate the contralateral primary somatosensory area. Left/right asymmetries were demonstrated consistent with cerebral lateralization. (JINS, 2002, 8, 349–359.)

Type
Research Article
Copyright
© 2002 The International Neuropsychological Society