Microstimulation of area V4 has little effect on spatial attention and on perception of phosphenes evoked in area V1.
Previous transcranial magnetic stimulation (TMS) studies suggested that feedback from higher to lower areas of the visual cortex is important for the access of visual information to awareness. However, the influence of cortico-cortical feedback on awareness and the nature of the feedback effects are not yet completely understood. In the present study, we used electrical microstimulation in the visual cortex of monkeys to test the hypothesis that cortico-cortical feedback plays a role in visual awareness. We investigated the interactions between the primary visual cortex (V1) and area V4 by applying microstimulation in both cortical areas at various delays. We report that the monkeys detected the phosphenes produced by V1 microstimulation but subthreshold V4 microstimulation did not influence V1 phosphene detection thresholds. A second experiment examined the influence of V4 microstimulation on the monkeys' ability to detect the dimming of one of three peripheral visual stimuli. Again, microstimulation of a group of V4 neurons failed to modulate the monkeys' perception of a stimulus in their receptive field. We conclude that conditions exist where microstimulation of area V4 has only a limited influence on visual perception.
Department of Vision and Cognition, Netherlands Institute for Neuroscience (an institute of the Royal Academy of Arts and Sciences of the Netherlands), Amsterdam, The Netherlands;
Bruno
B
Dagnino
Department of Vision and Cognition, Netherlands Institute for Neuroscience (an institute of the Royal Academy of Arts and Sciences of the Netherlands), Amsterdam, The Netherlands;
Marie-Alice
MA
Gariel-Mathis
Department of Vision and Cognition, Netherlands Institute for Neuroscience (an institute of the Royal Academy of Arts and Sciences of the Netherlands), Amsterdam, The Netherlands; Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands; and Psychiatry Department, Academic Medical Center, Amsterdam, The Netherlands p.roelfsema@nin.knaw.nl.
Pieter R
PR
Roelfsema
D000818:Animals; D001288:Attention; D025461:Feedback, Physiological; D000882:Haplorhini; D008297:Male; D009474:Neurons / Q000378:metabolism; D010719:Phosphenes; D013028:Space Perception; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*
area V1; area V4; cortico-cortical feedback; phosphenes; visual awareness; visual cortex