title: Uneven interhemispheric connections between left and right primary sensori-motor areas.
abstract: To clarify the characteristics of interhemispheric connections, we investigated cortico-cortical evoked potentials (CCEP) in human. Fourteen patients with temporal lobe epilepsy who underwent invasive EEG monitoring with bilaterally implanted subdural electrodes were studied. Electric pulse stimuli were given in a bipolar fashion at two adjacent electrodes on and around the motor area (MA) or sensory area (SA), and CCEP responses were recorded by averaging electrocorticograms from the contralateral hemisphere. Seventy-two pairs of electrodes were stimulated, and 468 recordings were analyzed. Fifty-one of 468 recordings demonstrated CCEP responses. Of 51 responses, 16 consisted of an initial positive triphasic wave (Type 1), 27 had an initial negative biphasic wave (Type 2), and 8 showed an initial positive biphasic wave (type 3). The mean latencies of the earliest peaks were 13.1, 28.9, and 29.4 ms in Types 1, 2, and 3 responses, respectively. The responses were more frequently evoked by stimulating facial MA (f-MA) and nonfacial MA (nf-MA) than by stimulating SA or noneloquent area. In both f-MA and nf-MA stimulation, the responses were more frequently recorded at the contralateral f-MA than at the contralateral nf-MA or other areas. SA stimulation never evoked CCEP responses at the contralateral MA or SA. The amplitudes were maximal when f-MA was stimulated and responses recorded at the contralateral f-MA. These findings suggest that the interhemispheric connections are uneven. Both f-MA and nf-MA send dense interhemispheric connections to the contralateral f-MA. SA may have no or only rare direct connection with the contralateral MA or SA.
authors.affiliation: Department of Neurology, National Epilepsy Center, Shizuoka Institute of Epilepsy and Neurological Disorders, Aoi-ku, Shizuoka 420-8688, Japan. kyht-terada@umin.net
authors.forename: Kiyohito
authors.initials: K
authors.lastname: Terada
authors.forename: Shuichi
authors.initials: S
authors.lastname: Umeoka
authors.forename: Naotaka
authors.initials: N
authors.lastname: Usui
authors.forename: Koichi
authors.initials: K
authors.lastname: Baba
authors.forename: Keiko
authors.initials: K
authors.lastname: Usui
authors.forename: Shigeru
authors.initials: S
authors.lastname: Fujitani
authors.forename: Kazumi
authors.initials: K
authors.lastname: Matsuda
authors.forename: Takayasu
authors.initials: T
authors.lastname: Tottori
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Nakamura
authors.forename: Yushi
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D003337:Corpus Callosum / Q000502:physiology*; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology; D019054:Evoked Potentials, Motor / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*