2015年7月14日火曜日

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

Kenneth W. Latimer, Jacob L. Yates, Miriam L. R. Meister, Alexander C. Huk, Jonathan W. Pillow
Science 10 July 2015: Vol. 349 no. 6244 pp. 184-187

知覚的意思決定において、LIPニューロンの活動は「連続的に徐々に蓄積される情報を反映している」とされていたが、むしろ「情報の蓄積に対して離散的(情報が蓄積するとジャンプが起きる)に反応する」ことが分かった。

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.

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