Working memory neurons in pigeons.

Working memory, the ability to temporarily store and manipulate currently relevant information, is required for most cognitive faculties. In humans and other mammals, the prefrontal cortex (PFC) provides the underlying neural network for these processes. Within the PFC, working memory neurons display sustained elevated activity while holding active an internal representation of the relevant stimulus during its physical absence or retaining a motor plan for the forthcoming response. Working memory, however, is not a hallmark of higher vertebrates endowed with a neocortex. Birds also master complex cognitive problems invoking working memory, but they lack a laminated neocortex. Behavioral studies in pigeons show that the neostriatum caudolaterale (NCL) plays a central role in executive functions, such as working memory and response control. For neurons in the NCL of pigeons, we show activity changes during the delay of a working memory task, which were similar to those observed in PFC neurons and were related to the successful holding of information in memory and to the subsequent behavior. Thus, although the anatomical and morphological structure of the neuronal substrate in birds is radically different from the mammalian neocortical architecture, the neuronal mechanisms evolved to master equivalent cognitive demands seem to be very similar.