title: Pre-SMA actively engages in conflict processing in human: a combined study of epicortical ERPs and direct cortical stimulation.
abstract: Previous non-invasive studies have proposed that the deeply seated region of the medial frontal cortex engages in conflict processing in humans, but its core region has remained to be elucidated. By means of direct cortical stimulation, which excels other techniques in temporal and spatial resolutions and in the capacity of producing transient, functional impairment even in the deeply located cortices, we attempted to obtain direct evidence that the pre-supplementary motor area (pre-SMA) actively engages in conflict processing. Subject was a patient with right frontal lobe epilepsy who underwent invasive presurgical evaluation with subdural electrodes placed on the medial and lateral frontal cortices. During a conflict task--modified Eriksen flanker task, direct cortical stimulation was delivered time-locked to the task at the inferior part of the medial superior frontal gyrus (inferior medial SFG), the superior part of the medial SFG, and the middle frontal gyrus. By adopting the session of sham stimulation that was employed as a within-block control, event-related potentials (ERPs) were recorded from the medial and lateral frontal cortices. The inferior medial SFG showed a significant ERP difference between trials with more and less conflict, while the other frontal cortices did not. Among the three stimulus sites, only stimulation of the inferior medial SFG significantly prolonged reaction time in trials with more conflict. Anatomically, the inferior medial SFG corresponded with the pre-SMA (Brodmann area 8). It was located 1-2 cm rostral to the vertical anterior commissure line where cortical stimulation elicited arrest of motion (the supplementary negative motor area). Functionally, this area corresponded to the dorso-rostral portion of the activation loci in previous neuroimaging studies focusing on conflict processing. By combining epicortical ERP recording and direct cortical stimulation in a human brain, this study, for the first time, presented one direct piece of evidence that the pre-SMA actively participates in conflict processing.
authors: Department of Neurology, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
authors: Kiyohide
authors: K
authors: Usami
authors: Riki
authors: R
authors: Matsumoto
authors: Takeharu
authors: T
authors: Kunieda
authors: Akihiro
authors: A
authors: Shimotake
authors: Masao
authors: M
authors: Matsuhashi
authors: Susumu
authors: S
authors: Miyamoto
authors: Hidenao
authors: H
authors: Fukuyama
authors: Ryosuke
authors: R
authors: Takahashi
authors: Akio
authors: A
authors: Ikeda
mesh_terms: D000328:Adult; D001931:Brain Mapping; D003220:Conflict, Psychological; D004558:Electric Stimulation; D004566:Electrodes; D004569:Electroencephalography; D017034:Epilepsy, Frontal Lobe / Q000473:pathology*; D005071:Evoked Potentials / Q000502:physiology*; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000098:blood supply / Q000503:physiopathology*; D010100:Oxygen; D010775:Photic Stimulation; D011930:Reaction Time
chemical_list: D010100:Oxygen