Neurons in the crow nidopallium caudolaterale encode varying durations of visual working memory periods.

Adaptive sequential behaviors rely on the bridging and integration of temporally separate information for the realization of prospective goals. Corvids' remarkable behavioral flexibility is thought to depend on the workings of the nidopallium caudolaterale (NCL), a high-level avian associative forebrain area. We trained carrion crows to remember visual items for three alternating delay durations in a delayed match-to-sample task and recorded single-unit activity from the NCL. Sample-selective delay activity, a correlate of visual working memory, was maintained throughout different working memory durations. Delay responses remained selective for the same preferred sample item across blocks with different delay durations. However, selectivity strength decreased with increasing delay durations, mirroring worsened behavioral performance with longer memory delays. Behavioral relevance of delay activity was further evidenced by reduced encoding of the preferred sample item during error trials. In addition, NCL neurons adapted their time-dependent discharges to blocks of different memory durations, so that delay duration could be successfully classified based on population activity a few trials after the delay duration switched. Therefore, NCL neurons not only maintain information from individual trials, but also keep track of the duration for which this information is needed in the context of the task. These results strengthen the role of corvid NCL in maintaining working memory for flexible control of temporally extended goal-directed behavior.