Exploring variation in learning using zebra finches : developmental and proximate factors

Abstract

The experiences an organism go through during early life can shape who they become as adults via glucocorticoid hormones which have negative impacts on learning abilities. Previous work has examined very early life or crossed key developmental boundaries leaving final scale comparisons difficult. I aimed to refine this by restricting corticosterone administration to two precise developmental periods using a standardised manipulation paradigm to 1) examine the sensitivity of discrete developmental stages to corticosterone; 2) explore sensitivity later in development; and 3) increase the comparability of the experiments. I first examine a diverse learning suit within animal to see how developmental corticosterone affects multiple abilities concurrently. I then relate this to an individual’s response to change to explore potential behavioural syndromes, tying learning to the wider phenotype.

My take home findings were that: developmental corticosterone can affect performance on learning tests variably depending on specific cue/paradigm, stage of test, and developmental timing of corticosterone; novel measures pertaining to learning matter in addition to simple trials to pass a test; timing of developmental corticosterone affects how individuals vary in their behavioural responses to disturbance and novelty when comparing between social contexts; and timing of developmental corticosterone alters how individuals respond to changing social conditions by measure of body mass. Overall, it is important to consider when and why we time our manipulations, to include descriptive measures of what animals do during tests, and to consider what happens to animals when we set up them for tests. These factors will improve studies into learning, boldness, and developmental CORT.