title: Integration of direction cues is invariant to the temporal gap between them.
abstract: Many decisions involve integration of evidence conferred by discrete cues over time. However, the neural mechanism of this integration is poorly understood. Several decision-making models suggest that integration of evidence is implemented by a dynamic system whose state evolves toward a stable point representing the decision outcome. The internal dynamics of such point attractor models render them sensitive to the temporal gaps between cues because their internal forces push the state forward once it is dislodged from the initial stable point. We asked whether human subjects are as sensitive to such temporal gaps. Subjects reported the net direction of stochastic random dot motion, which was presented in one or two brief observation windows (pulses). Pulse strength and interpulse interval varied randomly from trial to trial. We found that subjects' performance was largely invariant to the interpulse intervals up to at least 1 s. The findings question the implementation of the integration process via mechanisms that rely on autonomous changes of network state. The mechanism should be capable of freezing the state of the network at a variety of firing rate levels during temporal gaps between the cues, compatible with a line of stable attractor states.
authors.affiliation: Center for Neural Science, New York University, New York, New York 10003, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, Howard Hughes Medical Institute, Kavli Institute and Department of Neuroscience, Columbia University, New York, New York 10038, and Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195.
authors.forename: Roozbeh
authors.initials: R
authors.lastname: Kiani
authors.forename: Anne K
authors.initials: AK
authors.lastname: Churchland
authors.forename: Michael N
authors.initials: MN
authors.lastname: Shadlen
mesh_terms: D000328:Adult; D003463:Cues; D003657:Decision Making / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008959:Models, Neurological; D009039:Motion Perception / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors