Frederic E. Theunissen
Neural Basis of Vocal Learning in Songbirds. Auditory Physiology
Our long-term goal is to understand the neural mechanisms underlying complex sound recognition, the formation of perceptual acoustical memories and the role of these memories in guiding vocal learning. In order to achieve our goal, we are studying neural processing in the auditory forebrain areas of songbirds in the context of their song learning behavior. Songbirds learn to produce their complex songs by comparing the auditory feedback from their own vocalizations with a memorized version of a tutors song. This memory based vocal learning is reminiscent of some aspects of speech learning in humans and very rare in non-avian animals. In addition, songbirds have a set of specialized brain structures, called the song system, that have been shown to be essential for vocal production and learning.
Auditory neurons in the song system have very selective response properties characterized by a strong response to the sounds of the birds own song and much weaker responses to other complex sounds. This neural selectivity emerges in development during vocal learning. We are studying auditory processing in forebrain areas that are pre-synaptic to the song system, starting from the avian brain area that is homologous to the primary auditory cortex in mammals. To characterize the nature of the acoustical features that are being selectively encoded at each level along this auditory circuitry, we are using an innovative approach that will combine the use of large ensembles of complex sound stimuli with sophisticated analytical techniques. We expect to find that some of the selectivity measured in the auditory neurons of the song system is in part due to the acoustical processing and selectivity in the pre-synaptic auditory areas. We are also investigating the effect of early sensory experience on this acoustical processing. From such experiments, we will be able to assess the role of these auditory areas in the formation of a memory for the familiar sounds of the tutor song and of the birds own song. We will also investigate the role of the selective auditory responses found in the song system and in the high level auditory areas in guiding vocal learning. Our results may provide insight into the mechanisms underlying complex sound recognition and production in humans, in particular as they relate to speech comprehension and learning.