Uneven interhemispheric connections between left and right primary sensori-motor areas

• Published in: Human brain mapping 2012-01, Vol.33 (1), p.14-26
• Main Authors: Terada, Kiyohito, Umeoka, Shuichi, Usui, Naotaka, Baba, Koichi, Usui, Keiko, Fujitani, Shigeru, Matsuda, Kazumi, Tottori, Takayasu, Nakamura, Fumihiro, Inoue, Yushi
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Biological and medical sciences; Brain Mapping; Cognition. Intelligence; corpus callosum; Corpus Callosum - physiology; Electric Stimulation; Electrodes, Implanted; Electroencephalography; epilepsy; Epilepsy - physiopathology; evoked potentials; Evoked Potentials, Motor - physiology; Evoked Potentials, Somatosensory - physiology; Female; Functional Laterality - physiology; functional mapping; Fundamental and applied biological sciences. Psychology; human brain; Humans; intracranial recording; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Mental imagery. Mental representation; Motor Cortex - physiology; Nerve Net - physiology; Nervous system; neural networks; primary motor cortex; primary sensory cortex; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Somatosensory Cortex - physiology; subdural electrode
• ISSN: 1065-9471; 1097-0193
• DOI: 10.1002/hbm.21189

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. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.