Speaker：
Dr. Chung-Chuan Lo 羅中泉
Institute of Systems Neuroscience
National Tsing Hua University

Topic:
The control of speed and accuracy in perceptual decision - A dual-mechanism hypothesis and spiking neural circuit model

Time:
14:00-16:00 10/14/2014 (Tuesday)

Location:
1st Conference Room, Auditorium and Activity Center, NYMU
(陽明大學活動中心第一會議室)

Abstract:
A hallmark of flexible decision-making is the brains ability to dynamically adjust behavior, e.g., to slow down in order to achieve a better decision or to reach a quick judgment when time is at a premium. Such speed-accuracy tradeoff can take place based on learning, task instruction, the environment or our own will. Whereas much work has been devoted to the psychometrics and mathematical theories of the speed-accuracy tradeoff, the underlying neurobiological mechanisms remain poorly studied. Based on a previously proposed non-linear attractor neural network model of perceptual decision, we hypothesize that there are two distinct mechanisms underlying performance tuning in perceptual decision: a reward-dependent mechanism through the basal ganglia pathway and a reward-independent mechanism through the prefrontal top-down pathway.
The basal ganglia mechanism takes place when the behavioral outcome (receiving a reward or not) is fed back to the neural network through dopamine modulated plasticity. This mechanism does not change the dynamical properties of the circuit but only shift the decision threshold which gradually leads the subject to the optimal decision state. The prefrontal mechanism acts when the subject applies a top-down control with balanced synaptic excitation and inhibition to the decision neural circuit. We found that the mechanism alters the energy landscape of the system and makes it less likely to be trapped by the wrong attractor (wrong decision).
This dual-mechanism hypothesis not only provides biologically plausible explanation for several recent observations in neurophysiological studies, but also provides a fresh aspect in the theory of perceptual decision.