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Behavioral/Systems/Cognitive Bounded Integration in Parietal Cortex Underlies Decisions
 

Summary: Behavioral/Systems/Cognitive
Bounded Integration in Parietal Cortex Underlies Decisions
Even When Viewing Duration Is Dictated by the
Environment
Roozbeh Kiani, Timothy D. Hanks, and Michael N. Shadlen
Howard Hughes Medical Institute, National Primate Research Center, and Department of Physiology and Biophysics, University of Washington, Seattle,
Washington 98195
Decisions about sensory stimuli are often based on an accumulation of evidence in time. When subjects control stimulus duration, the
decisionterminateswhentheaccumulatedevidencereachesacriterionlevel.Undermanynaturalcircumstancesandinmanylaboratory
settings, the environment, rather than the subject, controls the stimulus duration. In these settings, it is generally assumed that subjects
commit to a choice at the end of the stimulus stream. Indeed, failure to benefit from the full stream of information is interpreted as a sign
ofimperfectaccumulationormemoryleak.Contrarytotheseassumptions,weshowthatmonkeysperformingadirectiondiscrimination
task commit to a choice when the accumulated evidence reaches a threshold level (or bound), sometimes long before the end of stimulus.
Thisboundedaccumulationofevidenceisreflectedintheactivityofneuronsinthelateralintraparietalcortex.Thus,thereadoutofvisual
cortex embraces a termination rule to limit processing even when potentially useful information is available.
Key words: lateral intraparietal area; LIP; perceptual decision; bounded accumulation; leaky accumulation; direction discrimination;
electrophysiology; psychophysics; vision
Introduction
A hallmark of cognition is the ability to choose among alter-
natives based on evidence bearing on the state of the world and

  

Source: Andrzejak, Ralph Gregor - Departament de Tecnologia, Universitat Pompeu Fabra
Wagner, Anthony - Department of Psychology, Stanford University

 

Collections: Biology and Medicine; Computer Technologies and Information Sciences