Morcos Ari S, Harvey Christopher D
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.
Nat Neurosci. 2016 Dec;19(12):1672-1681. doi: 10.1038/nn.4403. Epub 2016 Oct 3.
We studied how the posterior parietal cortex combines new information with ongoing activity dynamics as mice accumulate evidence during a virtual navigation task. Using new methods to analyze population activity on single trials, we found that activity transitioned rapidly between different sets of active neurons. Each event in a trial, whether an evidence cue or a behavioral choice, caused seconds-long modifications to the probabilities that govern how one activity pattern transitions to the next, forming a short-term memory. A sequence of evidence cues triggered a chain of these modifications resulting in a signal for accumulated evidence. Multiple distinguishable activity patterns were possible for the same accumulated evidence because representations of ongoing events were influenced by previous within- and across-trial events. Therefore, evidence accumulation need not require the explicit competition between groups of neurons, as in winner-take-all models, but could instead emerge implicitly from general dynamical properties that instantiate short-term memory.
我们研究了在虚拟导航任务中，当小鼠积累证据时，后顶叶皮层如何将新信息与正在进行的活动动态相结合。使用新方法分析单试次中的群体活动，我们发现活动在不同的活跃神经元组之间快速转变。试次中的每个事件，无论是证据线索还是行为选择，都会对控制一种活动模式如何转变为下一种活动模式的概率产生长达数秒的改变，从而形成短期记忆。一系列证据线索触发了这些改变的连锁反应，产生了一个积累证据的信号。对于相同的积累证据，可能存在多种可区分的活动模式，因为正在进行的事件的表征受到先前试次内和跨试次事件的影响。因此，证据积累不一定需要像赢家通吃模型那样，神经元组之间进行明确的竞争，而是可以从实例化短期记忆的一般动态特性中隐含地出现。
