From the Department of Physiology, Baghiyatollah University of Medical Sciences, Tehran
Abstract: (4181 Views)
The second somatosensory area (SlI) has been studied both by electrical
evoked potentials24 and magnetoencephalography (MEG)5 Magnetic evoked
fields of contralateral primary somatosensory and ipsilateral second somatosensory
cortices of 12 normal subjects were recorded in response to median nerve electrical
stimulation by means of a single magnetometer. We detected. in addition to the
usual contralateral SI responses, ipsilateral second somatosensory evoked fields
(sSEF's) in 4 subjects at a latency of 35-45 ms over the dominant hemisphere for
handedness, i.e., right hemisphere in left handed subjects and vice versa. On no
occasion were ipsilateral somatosensory fields recorded from the non-dominant
hemisphere whichever median nerve was stimulated. There were no consistent
responses at 90-150 ms. We concluded that the ipsilateral responses were from the
SlI area.
Our observations indicate the following: a) despite the known bilateral
representation of SII, there is hemispheric dominance, b) we could not confirm the
long latency (>95 ms) signals reported by Hari et al. in any of our subjects.5.6