Delay activity in the Wulst of pigeons (Columba livia) represents correlates of both sample and reward information.

The avian Wulst is the pallial (analogous to mammalian cortex) termination point of the thalamofugal pathway, one of two main visual pathways in birds, and is considered to be equivalent to primate striate cortex. We recorded neuronal activity from the Wulst in pigeons during two versions of a delayed matching-to-sample procedure. Two birds were trained on a common outcomes (CO) procedure, in which correct responses following both the skateboarder and the flower stimuli were associated with reward. Two other birds were trained on a differential outcomes (DO) procedure in which correct responses following only the skateboarder stimulus were associated with reward, while correct responses following the flower stimulus were not rewarded. In line with previous studies, under CO conditions, and for both excitatory and inhibitory neurons, delay activity in the Wulst was significantly different from baseline activity following both sample stimuli, which may indicate that Wulst delay activity is a neural correlate of working memory for the sample stimulus. On the other hand, under DO conditions, Wulst delay activity appeared to more likely be a neural correlate of the upcoming reward. We argue that Wulst neurons display flexibility in their encoding in that Wulst neurons can encode both sample and reward information, but may default to one type of coding over the other based on the demands of the current task. The current study provides the first evidence that delay activity in the Wulst represents both a neural correlate for sample information as well as reward information.