Role of the calcarine cortex (V1) in perception of visual cues for saccades.
OBJECTIVE
To determine the initial level at which the pathways for cue perception, saccades and antisaccades diverge.


METHODS
Two procedures: single pulse transcranial magnetic stimulation (sTMS) over posterior occiput and backward masking were used. A visual cue directed saccades to the left or right, either a pro-saccade (to the side of the cue but beyond it) or an antisaccade, i.e., contraversive saccade. No visual target was presented.


RESULTS
Latencies of the two types of saccades did not differ. Focal sTMS applied unilaterally over V1 suppressed both perception of a cue flashed 80-90ms earlier contralaterally (but not ipsilaterally) and the appropriate saccade. Masking at a delay of 100ms abolished the appropriate saccade and cue perception.


CONCLUSIONS
V1 is essential for the perception of a flashed cue and for executing appropriate pro- and contraversive saccades. Masking may occur beyond V1, where the pathways for perception and for saccades at least to the next visual processing level start separating.


CONCLUSIONS
VI is needed for rapid, accurate perceptual and motor responses to the crudest (left versus right) cues. It is unlikely that the "where" system can have a major direct input bypassing V1.
Lalli
S
S
Department of Neurology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA.
Hussain
Z
Z
Ayub
A
A
Cracco
R Q
RQ
Bodis-Wollner
I
I
Amassian
V E
VE
D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D003463:Cues; D004596:Electroretinography / Q000379:methods; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*