Filial Imprinting: Behaviour and Neurobiology

Research on filial imprinting has yielded insights into a range of behavioural and neurobiological phenomena, and these insights have in turn fed back to elucidate behavioural development. This review will summarize important stages in this progression, with emphasis on the neural mechanisms underlying visual filial imprinting in the domestic chick. Imprinting entails recognition of stimuli, in terms of both form and certain abstract features. A striking property of imprinting is the development of a preference for a stimulus slightly different from one that has become familiar, a property having profound implications for survival. Compelling evidence indicates that the intermediate and medial mesopallium (IMM) in the chick forebrain is a site of memory encoding for imprinting. In addition, processes within the IMM are intimately associated with learning capacity in the absence of specific experience (a predisposition). Electrophysiological, neuroanatomical, pharmacological, biochemical and ablation studies have implicated the IMM in the recognition of individual conspecifics, and recent research has elucidated the underlying neurobiological mechanisms at the cellular and sub-cellular levels. Results from studies of imprinting in chicks have led to the discovery of analogous processes in humans and promise to yield insights into cognitive development in both species.