The human frontal oculomotor cortical areas contribute asymmetrically to motor planning in a gap saccade task.
BACKGROUND
Saccadic eye movements are used to rapidly align the fovea with the image of objects of interest in peripheral vision. We have recently shown that in children there is a high preponderance of quick latency but poorly planned saccades that consistently fall short of the target goal. The characteristics of these multiple saccades are consistent with a lack of proper inhibitory control of cortical oculomotor areas on the brainstem saccade generation circuitry.


RESULTS
In the present paper, we directly tested this assumption by using single pulse transcranial magnetic stimulation (TMS) to transiently disrupt neuronal activity in the frontal eye fields (FEF) and supplementary eye fields (SEF) in adults performing a gap saccade task. The results showed that the incidence of multiple saccades was increased for ispiversive but not contraversive directions for the right and left FEF, the left SEF, but not for the right SEF. Moreover, this disruption was most substantial during the approximately 50 ms period around the appearance of the peripheral target. A control condition in which the dorsal motor cortex was stimulated demonstrated that this was not due to any non-specific effects of the TMS influencing the spatial distribution of attention.


CONCLUSIONS
Taken together, the results are consistent with a direction-dependent role of the FEF and left SEF in delaying the release of saccadic eye movements until they have been fully planned.
van Donkelaar
Paul
P
Department of Human Physiology and Institute of Neuroscience, University of Oregon, Eugene, Oregon, United States of America. paulvd@uoregon.edu
Lin
Yu
Y
Hewlett
David
D
D000328:Adult; D001288:Attention; D001933:Brain Stem / Q000378:metabolism; D004525:Efferent Pathways; D005133:Eye Movements; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D006801:Humans; D008297:Male; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D014785:Vision, Ocular / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology; D014796:Visual Perception / Q000502:physiology