A bird-brain view of episodic memory

Abstract

In humans, the hippocampus plays a critical role in the formation of episodic memories. Although non-human animals are unable to report whether they also re-experience past events, at least some birds and mammals exhibit ‘episodic-like’ memory characterized by an ability to recall what happened where and when. In mammals, the hippocampus interacts closely with virtually the entire neocortex to form episodic-like memories. The hippocampus receives highly processed information from high-order association areas, and thereby the rest of the neocortex. Distinct neurophysiological hippocampal rhythms (theta and sharp-wave ripples) coordinate activity between the hippocampus and high-order association areas during the encoding and retrieval of information contributing to episodic-like memories. Although recent studies have demonstrated that food hoarding birds are able to remember what food they hid where and when, neuroanatomical and neurophysiological studies suggest that there may be a fundamental difference between episodic-like memory in birds and mammals. In contrast to the mammalian hippocampus, the avian hippocampus only receives visual and olfactory input; most high-order association areas in the avian brain involved in performing functions similar to those performed by neocortical association areas do not project to the hippocampus or structures providing it with direct input. Consistent with this neuroanatomical difference, mammalian-like rhythms involved in communicating between the hippocampus and neocortical high-order association areas have not been found in birds. Collectively, this suggests that information contributing to episodic-like memory is more limited and processed in a different manner in birds when compared to mammals.