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"Seeing" invisible motion: responses of area V5 neurons in the awake-behaving macaque

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons84091

Moutoussis,  K
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84068

Maier,  A
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84063

Logothetis,  NK
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Moutoussis, K., Maier, A., Zeki, S., & Logothetis, N. (2006). "Seeing" invisible motion: responses of area V5 neurons in the awake-behaving macaque. Poster presented at AREADNE 2006: Research in Encoding and Decoding of Neural Ensembles, Santorini, Greece.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-D145-6
Abstract
We studied the relationship between brain activity and conscious visual experience of motion in area V5, the activity of which correlates directly with perceived motion in monkey and man. We used flash-suppression to dissociate the constant stimulus from the varying percept and showed that neurons in V5 modulate their firing rate according to whether a random-dot motion stimulus is perceived or not. In all cases, these changes reflect the ones produced under physical stimulus alternations, i.e. are higher for the motion compared to the static checkerboard stimulus and also increase in strength with increases in the directional coherence of the perceived dot movies. Over half of these perceptually-modulating neurons showed a further modulation when the strength of the suppressed motion stimulus was varied. These modulations also reflected the ones observed under physical stimulation - an increase in firing rate with an increase in the coherence of the motion stimulus. V5 neurons were thus shown not only to modulate their responses with respect to perceptual modulations under constant stimulation conditions, but also with respect to physical stimulus modulations under constant perceptual conditions. Therefore, characterizing neurons as‘perceptually modulating‘ or ‘stimulus modulating‘ is not straightforward. Furthermore, activity in V5, which correlates with the perceived motion, also modulates in response to changes in the physical stimulus that never reach perceptual awareness. Our results suggest that there is no clear distinction between purely ‘processing‘ and purely ‘perceptual‘ neurons or areas in the brain. It is rather the activation of the same neuronal assemblies, responsible for the processing of a certain visual feature, that can also lead to its perception.