Extraretinal saccadic signals in human LGN and early retinotopic cortex.
In the human LGN and V1, saccades in darkness lead to enhanced activity while saccades made during strong visual stimulation suppress activity [Sylvester, R., Haynes, J.D., and Rees, G., 2005. Saccades differentially modulate human LGN and V1 responses in the presence and absence of visual stimulation. Curr. Biol. 15, 37-41]. Here, we explored this differential modulation further using graded changes in the strength of visual stimulation by changing the mean luminance of a flickering visual stimulus. We replicate the finding of differential modulation of activity in human LGN and V1, and show that this relationship also holds in retinotopic areas V2 and V3. Suppression of visually evoked activity during saccades was detectable during strong visual stimulation, but not during weaker stimulation. This suggests that the activation of visual cortex by saccades in darkness represents a signal that persists irrespective of the state of visual stimulation, masking suppressive effects of saccades when visual stimulation is weak. Such a signal may represent a motor signal in a sensory area. We discuss the possible role of oculomotor corollary discharge in changes in visual perception that occur peri-saccadically, which contribute to the successful negation of the disruptive effects of saccades on our seamless visual experience of the world.
Sylvester
Richard
R
Wellcome Department of Imaging Neuroscience, Institute of Neurology, University College London, 12 Queen Square, London WC1N 3BG, UK. r.sylvester@fil.ion.ucl.ac.uk
Rees
Geraint
G
D000328:Adult; D001931:Brain Mapping; D003623:Dark Adaptation / Q000502:physiology*; D004569:Electroencephalography; D004585:Electrooculography; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D005425:Flicker Fusion / Q000502:physiology*; D005829:Geniculate Bodies / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009802:Oculomotor Nerve / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013223:Statistics as Topic; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology
D010100:Oxygen