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Neuron. 2015 Feb 18;85(4):861-73. doi: 10.1016/j.neuron.2015.01.007. Epub 2015 Feb 5.

A neural implementation of Wald's sequential probability ratio test.

Author information

1
Neurobiology & Behavior Program, University of Washington, Seattle, WA 98195, USA; Department of Neuroscience, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
2
Institute of Neuroscience, Key Laboratory of Primate Neurobiology, CAS Center for Excellence in Brain Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
3
Department of Neuroscience, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA; Kavli Institute of Brain Science, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA. Electronic address: shadlen@columbia.edu.

Abstract

Difficult decisions often require evaluation of samples of evidence acquired sequentially. A sensible strategy is to accumulate evidence, weighted by its reliability, until sufficient support is attained. An optimal statistical approach would accumulate evidence in units of logarithms of likelihood ratios (logLR) to a desired level. Studies of perceptual decisions suggest that the brain approximates an analogous procedure, but a direct test of accumulation, in units of logLR, to a threshold in units of cumulative logLR is lacking. We trained rhesus monkeys to make decisions based on a sequence of evanescent, visual cues assigned different logLR, hence different reliability. Firing rates of neurons in the lateral intraparietal area (LIP) reflected the accumulation of logLR and reached a stereotyped level before the monkeys committed to a decision. The monkeys' choices and reaction times, including their variability, were explained by LIP activity in the context of accumulation of logLR to a threshold.

PMID:
25661183
PMCID:
PMC4365451
DOI:
10.1016/j.neuron.2015.01.007
[Indexed for MEDLINE]
Free PMC Article

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