Distributed coding of stimulus magnitude in rodent prefrontal cortex

Abstract

As we interact with the external world, we judge magnitudes from sensory information. The estimation of magnitudes has been characterized in primates, yet it is largely unexplored in non-primate species. Here, we show that gerbils that solve a time-interval reproduction task display primate-like magnitude estimation characteristics, most prominently a systematic overestimation of small stimuli and an underestimation of large stimuli, often referred to as regression effect. We investigated the underlying neural mechanisms by recording from medial prefrontal cortex and show that the majority of neurons respond either during the measurement or the reproduction of a time-interval. Cells that are active during both phases display distinct response patterns. We categorize the neural responses into multiple types and demonstrate that only populations with mixed responses can encode the bias of the regression effect. These results reveal the organizing neural principles of magnitude estimation a process important to higher cognitive functions.