Chu Yun Wen, Chinta Suma, Keri Hayagreev V S, Beri Shreya, Pluta Scott R
Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America.
PLoS Biol. 2025 Mar 31;23(3):e3003057. doi: 10.1371/journal.pbio.3003057. eCollection 2025 Mar.
A fundamental trait of intelligent behavior is the ability to respond selectively to stimuli with higher value. Where along the neural hierarchy does somatosensory processing transition from a map of stimulus location to a map of stimulus value? To address this question, we recorded single-unit activity from populations of neurons in somatosensory cortex (S1) and midbrain superior colliculus (SC) in mice conditioned to respond to a positive-valued stimulus and withhold responses to an adjacent, negative-valued stimulus. The stimulus preference of the S1 population was equally weighted towards either stimulus, in line with a somatotopic map. Surprisingly, we discovered a large population of SC neurons that were disproportionately biased towards the positive stimulus. This disproportionate bias was largely driven by enhanced spike suppression for the negative stimulus. Removing the opportunity for mice to behaviorally select the positive stimulus reduced positive stimulus bias and spontaneous firing rates in SC but not S1, suggesting that neural selectivity was augmented by task readiness. Similarly, the spontaneous firing rates of SC but not S1 neurons predicted reaction times, suggesting that SC neurons played a persistent role in perceptual decision-making. Taken together, these data indicate that the somatotopic map in S1 is transformed into a value-based map in SC that encodes stimulus priority.
智能行为的一个基本特征是能够对具有更高价值的刺激做出选择性反应。体感处理在神经层级的哪个位置从刺激位置图转变为刺激价值图？为了解决这个问题，我们记录了小鼠体感皮层（S1）和中脑上丘（SC）中神经元群体的单单元活动，这些小鼠经过训练，对正价值刺激做出反应，而对相邻的负价值刺激不做反应。S1群体的刺激偏好对两种刺激的权重相同，这与躯体定位图一致。令人惊讶的是，我们发现大量的SC神经元对正刺激存在不成比例的偏向。这种不成比例的偏向在很大程度上是由对负刺激增强的尖峰抑制驱动的。去除小鼠行为选择正刺激的机会会降低SC中对正刺激的偏向和自发放电率，但不会影响S1，这表明神经选择性因任务准备而增强。同样，SC而非S1神经元的自发放电率预测了反应时间，这表明SC神经元在感知决策中发挥了持续作用。综上所述，这些数据表明，S1中的躯体定位图在SC中转变为基于价值的图，该图编码刺激优先级。
