Locating the human frontal eye fields with transcranial magnetic stimulation.
The variability in the location and function of the human frontal eye fields (FEFs) was assessed using transcranial magnetic stimulation (TMS). Ten subjects performed a saccadic eye movement task previously shown to be influenced by TMS of the FEFs. A sequence of points over the prefrontal cortex was stimulated until an effective site of the TMS was found that induced contralateral saccade delays. In 7 out of the 10 subjects, we were able to localize a region in the prefrontal cortex that when stimulated produced delays in the execution of contralateral saccadic eye movements. The location of this functionally defined FEF region across these subjects was approximately 1.5 cm anterior to the motor hand area, although there was considerable variability in this measure. In the remaining 3 subjects, no site within our circumscribed probing was found that when disrupted with TMS produced delays in contralateral saccadic eye movements. The inter-individual differences in the location and function of the FEFs highlights the importance of using functional as well as anatomical landmarks when attempting to localize brain structures.
Ro
Tony
T
Department of Psychology, Rice University, Houston, TX 77005-1892, USA. tro@rice.edu
Farnè
Alessandro
A
Chang
Erik
E
D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation; D055590:Electromagnetic Phenomena; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*