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Behavioral/Systems/Cognitive Neural Activity in Macaque Parietal Cortex Reflects
 

Summary: Behavioral/Systems/Cognitive
Neural Activity in Macaque Parietal Cortex Reflects
Temporal Integration of Visual Motion Signals during
Perceptual Decision Making
Alexander C. Huk1 and Michael N. Shadlen2
1Section of Neurobiology, Center for Perceptual Systems, and Department of Psychology, University of Texas at Austin, Austin, Texas 78712, and 2Howard
Hughes Medical Institute, Department of Physiology and Biophysics and National Primate Research Center, University of Washington, Seattle, Washington
98195
Decision-making often requires the accumulation and maintenance of evidence over time. Although the neural signals underlying
sensory processing have been studied extensively, little is known about how the brain accrues and holds these sensory signals to guide
later actions. Previous work has suggested that neural activity in the lateral intraparietal area (LIP) of the monkey brain reflects the
formation of perceptual decisions in a random dot direction-discrimination task in which monkeys communicate their decisions with
eye-movement responses. We tested the hypothesis that decision-related neural activity in LIP represents the time integral of the
momentary motion "evidence." By briefly perturbing the strength of the visual motion stimulus during the formation of perceptual
decisions,wetestedwhetherthisLIPactivityreflectedapersistent,integrated"memory"ofthesebriefsensoryevents.Wefoundthatthe
responsesofLIPneuronsreflectedsubstantialtemporalintegration.Briefpulseshadpersistenteffectsonboththemonkeys'choicesand
the responses of neurons in LIP, lasting up to 800 ms after appearance. These results demonstrate that LIP is involved in neural time
integrationunderlyingtheaccumulationofevidenceinthistask.Additionalanalysessuggestthatdecision-relatedLIPresponses,aswell
as behavioral choices and reaction times, can be explained by near-perfect time integration that stops when a criterion amount of
evidencehasbeenaccumulated.Temporalintegrationmaybeafundamentalcomputationunderlyinghighercognitivefunctionsthatare

  

Source: Andrzejak, Ralph Gregor - Departament de Tecnologia, Universitat Pompeu Fabra
Huk, Alex - Institute for Neuroscience & Department of Psychology, University of Texas at Austin
Shadlen, Michael - Department of Physiology and Biophysics, University of Washington at Seattle

 

Collections: Biology and Medicine; Computer Technologies and Information Sciences