Wednesday 12th October 2011
B10 Seminar Room,
Alexandra House, 17 Queen Square, London, WC1N 3AR
Optimal integration of evidence for decision-making in the rat
Gradual accumulation of evidence over time is thought to be a fundamental component of decision-making, but the mechanisms and properties of the accumulation remain unclear. Although most models assume a noisy evidence accumulation process, the properties of this noise have never been isolated and measured. We developed a novel decision-making task that is particularly amenable to quantitative analyses that reveal properties of the decision process. The task allowed us to measure, for the first time, the magnitude of noise in the evidence accumulator process, separately from the magnitude of noise in sensory processes. Remarkably, we found that accumulator noise magnitude was zero. In addition, we found that the accumulator had very long ( ~ 1 sec ) time constants. Our results show that rats have near-optimal graded evidence accumulators, characterized by long, noiseless memories.