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Science. 2015 Jul 10;349(6244):184-7. doi: 10.1126/science.aaa4056.

NEURONAL MODELING. Single-trial spike trains in parietal cortex reveal discrete steps during decision-making.

Author information

1
Center for Perceptual Systems, The University of Texas at Austin, Austin, TX 78712, USA. Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA.
2
Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA. Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
3
Center for Perceptual Systems, The University of Texas at Austin, Austin, TX 78712, USA. Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA. Department of Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA. Department of Psychology, The University of Texas at Austin, Austin, TX 78712, USA.
4
Center for Perceptual Systems, The University of Texas at Austin, Austin, TX 78712, USA. Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA. Department of Psychology, The University of Texas at Austin, Austin, TX 78712, USA. Princeton Neuroscience Institute and Department of Psychology, Princeton University, Princeton, NJ 08544, USA. pillow@princeton.edu.

Abstract

Neurons in the macaque lateral intraparietal (LIP) area exhibit firing rates that appear to ramp upward or downward during decision-making. These ramps are commonly assumed to reflect the gradual accumulation of evidence toward a decision threshold. However, the ramping in trial-averaged responses could instead arise from instantaneous jumps at different times on different trials. We examined single-trial responses in LIP using statistical methods for fitting and comparing latent dynamical spike-train models. We compared models with latent spike rates governed by either continuous diffusion-to-bound dynamics or discrete "stepping" dynamics. Roughly three-quarters of the choice-selective neurons we recorded were better described by the stepping model. Moreover, the inferred steps carried more information about the animal's choice than spike counts.

PMID:
26160947
PMCID:
PMC4799998
DOI:
10.1126/science.aaa4056
[Indexed for MEDLINE]
Free PMC Article

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