Text

theses

Both humans and songbirds learn to vocalize by imitating conspecific tutors heard during development. Through imitation, juvenile male zebra finches develop a copy of their tutor’s song. However, these copies are imperfect; each male produces a slightly different song that is unique and therefore useful for individual recognition. Although zebra finches can no longer learn to produce new vocal signals in adulthood, they remain able to show behavioral recognition of new songs they hear in social interactions that may involve reinforcement. Furthermore, neural memories of specific songs can be detected in the size and rate of adaptation of electrophysiological responses recorded in two auditory processing areas in the songbird brain, the caudomedial mesopallium (CMM) and caudomedial nidopallium (NCM), which may be analogous to a secondary auditory cortex. The current experiment tests the effects of auditory discrimination training in a GO/NoGO operant paradigm on auditory responses in these areas, which can serve as models for neural representations of socially learned auditory objects. To do this, adult male and female zebra finches (n=16) were trained to peck in response to one of two stimuli (GO) and to withhold responding from the other (NoGO). Prior to this conditioning, female subjects had cohabited with a male, heard his song in that social context, and produced a brood of offspring. After performance reached criterion, multi- and single-unit neural responses to operantly-trained, socially-relevant and novel song stimuli were obtained from multiple electrodes inserted bilaterally into NCM and CMM of awake, restrained birds. The results show that both male and female subjects exhibited neural memories for operantly-trained auditory objects in forebrain auditory areas. The magnitude of neural responses and the rates of response adaptation for operantly-trained stimuli differed from those evoked by novel stimuli and also showed a different pattern of effects in NCM and CMM. In addition, when subjects were grouped by the number of days required to reach criterion during training, fast learners showed higher absolute responses and faster neuronal adaptation in CMM than slow learners, while, in NCM, fast learners showed absolute responses that were more strongly left-lateralized than slow learners. When females were also tested for neural memories of their mate’s songs, the effects of operant and social conditioning on auditory responses were in different directions. Therefore, although both social exposure and operant conditioning induced neural memories for song in adult zebra finches, operant discrimination learning is not an appropriate model for studying the process by which individuals acquire the ability to recognize each other through song in social contexts.

ETD_5037

M.S.

Includes bibliographical references

by Brittany Alicia Bell

doi:10.7282/T3TT4NZR

ETD graduate

The author owns the copyright to this work.