Interhemispheric Connection of Motor Areas in Humans

Abstract

We attempted to clarify functional interhemispheric connections of motor cortex (MC) by investigating cortico-cortical evoked potentials from human brains in vivo. Three patients with intractable epilepsy who underwent invasive EEG monitoring with subdural electrodes as presurgical evaluation were studied. Electric pulse stimuli were delivered in a bipolar fashion to two adjacent electrodes on and around MC. Cortico-cortical evoked potentials were recorded by averaging electrocorticograms from the contralateral hemisphere. An initial positive triphasic or an initial negative biphasic wave was recorded when the contralateral MCs were stimulated. When the non-MC electrodes were stimulated, no response was recorded. The latencies ranged from 9.2 to 23.8 ms for the initial positive peak, and 25.4 to 39.4 ms for the initial or the second negative peak. The cortico-cortical evoked potentials responses were maximal around the homonymous electrodes with the stimulated electrodes. Our results directly demonstrate the presence of the functional interhemispheric connections originating in MC. The interhemispheric transit time is indicated. The homotopic distribution of the responses indicates that motor coordination of the bilateral bodies is, at least partially, controlled within MC.

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

“…Consistent with our previous report [Terada et al, 2008], CCEP responses were recorded from the contralateral hemisphere in the current study. Compared with the previous study, this study investigated a larger number of patients, and furthermore succeeded to stimulate not only f-MA but also nf-MA and SA.…”

“…Previously, we recorded CCEP responses from the contralateral hemisphere by stimulating facial motor area (f-MA) in three epilepsy patients [Terada et al, 2008]. Our result demonstrated that most of these interhemispheric CCEP responses showed initial positive triphasic waveforms (P1-N1-P2).…”

“…As transcallosal CCEP responses were well recognized at the contralateral homologous area in the previous study [Terada et al, 2008], the homonymous electrodes and their contiguous electrodes were mainly selected as recording sites. Because of time pressure, not all pairs could be examined.…”

“…For CCEP recording, we conducted stimulation by applying the same parameters as in the previous reports [Terada et al, 2008;Umeoka et al, 2009]. Briefly, the electrical stimulation consisted of a constant-current square pulse at a duration of 0.3 ms with a frequency of 1 Hz in alternating polarity (SEN-3301/SSI04J, Nihon Koden Corp., Tokyo).…”

“…Electrophysiologically, these connections may also be examined by cortico-cortical evoked potential (CCEP) studies [Brugge et al, 2003;Greenlee et al, 2004;Matsumoto et al, 2004Matsumoto et al, , 2005Matsumoto et al, , 2007Rutecki et al, 1989;Terada et al, 2008;Umeoka et al, 2009;Wilson et al, 1990Wilson et al, , 1991.…”