The effects of social isolation on the physical and neural development of zebra finches

Acute stress causes rapid release of adrenal steroids, such as corticosterone, allowing organisms to respond to life-threatening situations. However, chronic stress has detrimental effects, such as decreased neurogenesis, impaired memory and suppressed immune function. For this reason, it is important to understand how stress affects different species at different life stages. In our study we raised a highly sociable species, the zebra finch (Taeniopygia guttata), in social isolation, which delays the development of adult plumage. No physiological mechanism for this phenomenon has been identified. We hypothesize this delay is a result of chronically-elevated corticosterone in isolated birds. We further hypothesize that the stress of isolation would affect neural development associated with song learning. We tested our hypotheses with three experimental groups: isolated birds with naturally high corticosterone, birds given exogenous corticosterone raised in isolation or in a social colony, and finally a control group raised in a social colony. In zebra finch, brain areas associated with song learning and production normally increase in size during puberty. Groups will be compared based on changes in the size of these brain regions. Preliminary data confirm the finding that isolated birds delay molt, and furthermore, that this effect can be replicated by delivering exogenous corticosterone. We expect that isolated birds and birds treated with exogenous corticosterone will not show the normal neuronal development associated with song learning. These results will be discussed. This study contributes to how we understand stress in terms of early development and its effects on vertebrate neural and physical development.