Steven Brauth - US grants

The present research plan examines the neuroanatomical basis for complex learning in the budgerigar. Much is already known about basic neuroethological processes in this species from studies of vocalizations, hearing, and the ethology and physiology of reproductive behavior and the neuroanatomy of the CNS. For this reason the budgerigar offers a unique model for examining the interaction of basic biological factors in learning. Three related sets of experiments are proposed. First, neuroanatomical and pathway tracing techniques will be used to extend a study of the pathways involved in the processing of acoustic information in the central nervous system of the budgerigar - work that was initiated and is currently funded with a small grant from NIMH. Second, an operant conditioning procedure already proven successful in this species will be modified to allow the application of sophisticated multidimensinal scaling tecniques to examine, for the first time, perceptual learning of natural acoustic and visual stimuli. Third, guided by the knowledge gained from the above pathway tracing, operant conditioning, and multidimensional scaling experiments, these techniques will be combined to examine the effect of lesioning selected brain areas and pathways on learning. This blend of techniques provides a unique opportunity to explore the neural basis of the integration or intermodal association of auditory and visual information during learning. By addressing general biological issues, the present research plan will offer some penetrating insights into the basic biological foundations of learning common to all complex vertebrates including humans.

The present proposal describes a series of behavioral, anatomical and neurohistochemical experiments designed to evaluate the neural systems underlying the control of movement in the reptile, Caiman crocodilus. Caiman crocodilus was selected as an animal model because the motor system of reptiles is simpler than that of mammals. No direct equivalent of the mammalian motor cortex is present in reptiles, yet precision movement and coordination are nevertheless part of the behavioral repertoire of these species. Pilot work indicates that two neural systems, both derived from the paleostriatum, or basal ganglia, are involved in the control of complex movement in this species. The first of these is derived from the globus pallidus and expresses motor functions largely via the optic tectum. The other is derived from neurons in the ventral pallidum and projects upon portions of the reticular formation afferent to motor neuron pools such as the trigeminal motor nucleus. A new theory of motor behavior in reptiles is advanced which holds that pallidofugal pathways control orientation and tectally mediated behaviors, while the pathways derived from the ventral pallidum control precision movement, particularly of the jaws and mouth region. These systems are anatomically and chemically distinct. Pallidofugal neurons utilize LANT6 and GABA as neurotransmitters while the ventral pallidal region contains many cholinergic neurons. Experiments are proposed to test hypotheses and to further evaluate the chemical, anatomical and behavioral correlates of both systems.

This research program aims to examine the neuroanatomical foundations of vocal learning in budgerigars as a model for studying the neural basis of interactions between innate, constitutional factors and experiential learning during postnatal development. Previous results have shown that vocal learning spends upon both innate factors and experiential learning in this species since the acquisition of a normal vocal repertoire requires exposure to an appropriate external model during postnatal development. Neuroanatomical experiments are proposed to further study the pathways by which sensory feedback can influence vocal motor centers as well as the pathways by which vocal motor centers can cue the sensory systems. Behavioral experiments using multidimensional scaling and assessment of vocal plasticity will pinpoint the role of these anatomical pathways in guiding and shaping learned vocal responses by evaluating the effects of lesions in these pathways at different points during postnatal development.

LAY ABSTRACT -
IBN 9816061 - "Neural Pathways for Auditory-Vocal Learning"

PI - Steven E. Brauth

The investigator will use a novel laboratory animal preparation, the budgerigar (M. undulatus) to investigate the neural basis of auditory-vocal learning. Auditory-vocal learning is a fundamentally
important learning process in which individuals acquire communication sounds in a social context from other members of their species and is necessary for normal human speech acquisition.
Budgerigars are used in these experiments because, as in humans, specialized brain pathways have evolved which interconnect auditory and vocal areas of the forebrain. In order to understand how these neural systems acquire and utilize learned communication sounds in a social context, the investigator will use a strategy which combines neuroanatomical techniques, which map out brain circuits, with powerful new methods which map expression of immediate early gene
proteins. There is now overwhelming evidence that long term changes in neuronal function, such as those underlying learning and memory, depend on the expression of immediate early gene proteins. In this application, the investigator will first identify neurons which both process auditory feedback for vocal learning and also express the zenk immediate early gene protein (also called zif268, egr1, NGFIA, Krox 24). Zenk is believed to be closely related to the plasticity processes associated with vocal learning. The investigator will then assess the effects of dysfunction of these neurons on both vocal learning as well as on long term zenk expression by neurons in other portions of the auditory and vocal control systems.