Human frontal eye field and eyelid motor area revisited with electrical cortical stimulation and electrode co-registration

Abstract We investigated the anatomical localization of the frontal eye field (FEF) and its relationship to the eyelid motor area (EMA) and precentral motor cortex. We performed functional mapping using electrical cortical stimulation (ECS) and correlated electrode position by non-linear co-registration techniques using postoperative MRI. We studied 22 patients who underwent chronic implantation of subdural electrodes for epilepsy surgery. Eye movements were elicited at 52 electrodes overall. The majority of the movements were conjugated, saccadic eye deviation contralateral to the side of ECS. Head turning and non-saccadic eye deviation more frequently occurred in the vicinity of the precentral sulcus. Anatomically, FEF was located at Brodmann’s area 6 in the most-caudal region of the middle frontal gyrus and in the adjacent part of the superior frontal sulcus and precentral sulcus. Functionally, FEF was situated at the level of the hand motor area, more dorsal than was described in Penfield’s motor homunculus. The FEF is situated anteriorly from the precentral motor cortex. The EMA was situated within the precentral motor cortex, partially overlapping with but distinctly ventral and caudal to FEF, and dorsal to the lower face motor area. A standardized map of the FEF and precentral motor homunculus is provided as a reference for human system neuroscience research. Competing Interest Statement Tomoyuki Fumuro is a visiting researcher of the Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan. This department is the Industry-Academia Collaboration Courses, supported by Eisai Co., Ltd., Nihon Kohden Corporation, Otsuka Pharmaceutical Co., and UCB Japan Co., Ltd., while this study was conducted. Other authors have no conflict of interest to disclose. Footnotes ↵† Deceased author: Died June 9, 2022. Abbreviations - ANOVA - analysis of variance - BA - Brodmann’s area - ECoG - electrocorticogram - ECS - electrical cortical stimulation - EMA - eyelid motor area - FEF - frontal eye field - FSL - FMRIB Software Library - HT - head turning - LE - lower extremity - MANOVA - multivariate analysis of variance - MFG - middle frontal gyrus - MNI - Montreal Neurological Institute - PrCG - precentral gyrus - PrCS - precentral sulcus - SEEG - stereotactic-electroencephalography - SFS - superior frontal sulcus