The Effects of Neuronal Growth and Social Experience on the Development of Behavioral Plasticity

Abstract

The nervous system of a young animal experiences three kinds of plasticity as it grows: developmental changes, changes resulting from learning and memory, and experience-dependent changes in behavioral state. The first two are familiar and intertwined: neurons grow in size and complexity as sensory, motor and cognitive experience refine the synaptic organization of the brain during certain critical periods. At the same time, processes of learning and memory occur in and around synapses to enable sensory and motor experiences to be abstracted, categorized, and stored for later recall. Changes related to behavioral state are less studied at the level of neural mechanisms, but are also the subject of common experience. The behavior of all social animals is strongly conditioned by their social experience: their size and skill relative to their siblings and peers, or the social rank of their parents determines how they behave in the group. Moreover, sudden shifts in experience can lead to equally sudden changes in social behavior that may be short-lived or last a lifetime: the injury, disappearance or death of a dominant rival, or the appearance of a new, larger rival, can instantly and persistently change an animal’s behavior.