History information emerges in the cortex during learning

Abstract

We learn from our experience but the underlying neuronal mechanisms incorporating past information to facilitate learning is relatively unknown. Specifically, which cortical areas encode history-related information and how is this information modulated across learning? To study the relationship between history and learning, we continuously imaged cortex-wide calcium dynamics as mice learn to use their whiskers to discriminate between two different textures. We mainly focused on comparing the same trial type with different history information, i.e., a different preceding trial. We found history information in barrel cortex (BC) during stimulus presentation. Importantly, history information in BC emerged only as the mouse learned the task. Next, we also found learning-dependent history information in rostrolateral (RL) association cortex that emerges before stimulus presentation, preceding activity in BC. History information was also found in other cortical areas and was not related to differences in body movements. Interestingly, a binary classifier could discriminate history information at the single trial level just as well as current information both in BC and RL. These findings suggest that past experience emerges in the cortex around the time of learning, starting from higher-order association area RL and propagating down (i.e., top-down projection) to lower-order BC where it can be integrated with incoming sensory information. This integration between the past and present may facilitate learning.

Reward history cues focal attention in whisker somatosensory cortex

“…History signals in mouse cortex have not previously been described for attention, but have been identified in posterior parietal cortex (PPC) and orbitofrontal cortex (OFC) during decision making [66][67][68] and in reversal learning [69][70][71][72] . S1 receives instructional signals from OFC that are necessary for reversal learning 71 , but whether this pathway plays a role in reward history-cued attention is unknown.…”

“…History signals in mouse cortex have not previously been described in the context of attention but have been studied in the context of choice biases during decision making [76][77][78] and in reversal learning [79][80][81][82] . Higher order cortical areas including posterior parietal cortex (PPC) 54 and orbitofrontal cortex (OFC) 81 of mice these history signals were found to have a causal role in the representation and use of these forms of history information.…”