Gary Rose

RESEARCH:

Information processing in the auditory and electrosensory systems

We study animal behavior at both 'proximate' and 'ultimate' levels. At the proximate level, we investigate how neural circuits in fish and anuran amphibians control natural behaviors. At the ultimate level, we study the adaptive significance and evolution of these behaviors. Our research methodology, therefore, ranges from neurophysiological analysis of single neuron function to behavioral studies in the lab and field. Behavioral studies allow us to generate testable hypotheses concerning neural control. Conversely, neurophysiological experiments provide clues as to the evolution of behaviors. This 'neuroethological' approach is evident in the specific research projects described below.

Neural control and evolution of electrosensory behaviors in electric fish:

In many animal behaviors, information about the environment is detected by sensory receptors and then transmitted to the central nervous system where stimulus patterns of relevance must be discriminated. Often, sensory signals are then translated into motor commands. The cellular mechanisms by which these operations are performed are poorly understood. Electric fish are particularly suitable for studying these questions. Behaviors such as the 'jamming avoidance responses' remain intact in neurophysiological preparations, permitting analysis of the entire neural circuit for generating these behaviors. Presently, we are using newly-developed methods for making intracellular recordings in vivo (see ref. below) to investigate how particular computations are performed. Recently we have found that short-term synaptic plasticity mechanisms are important in generating neural filters of temporal information.

Comparative neurophysiological studies of the electrosensory system of closely related species that lack jamming avoidance responses are also in progress. These studies should shed light on how neural circuits change during evolution to generate new behaviors.

Neural mechanisms of audition in anurans:

Acoustic communication plays an important role in the reproductive behavior of anuran amphibians (frogs and toads). Much of the information in these vocalizations is encoded in the temporal structure (e.g. pulse repetition rate). The anuran auditory system, therefore, is well suited for investigating how the temporal structure of sound is represented at various stages in the auditory nervous system. We are particularly interested in understanding the mechanisms that underlie transformations in these representations. For example, the periodic modulations in the amplitude of sound are coded in the peripheral auditory system by the periodic fluctuations in the discharge rate of these neurons. At the midbrain, however, this 'periodicity' coding is replaced by a 'temporal filter' coding scheme wherein individual neurons selectively respond to particular rates of amplitude modulation. The mechanisms that underlie this transformation are unknown. Recent neurophysiological and behavioral studies indicate that integration and recovery processes play critical roles in generating the temporal tuning properties of midbrain neurons. We are now using intracellular recording methods to examine the mechanisms that underlie these processes.

Song learning in songbirds:

In collaboration with Franz Goller's lab, we are studying how songbirds learn their songs. Songbirds must hear song early in life in order to later develop a good copy of the song of their local dialect; they are not innately able to produce a correct song. During song development, birds compare what they produce to the memorized representation (template) of the song(s) that they heard during their 'sensitive period' early in life. We are currently studying song learning in the species of white-crowned sparrows that is found in our local mountains. Our work is directed at exploring the nature of the 'template', how experience shapes it, and how it is used to guide song development. Recent advances in digital signal processing now enable us to track the developmental paths that these birds take in producing complete song.

Social control of sex, behavior and coloration in wrasses:

Wrasses are coral-reef fishes that exhibit highly plastic reproductive behavior and life histories. Individuals begin life in an 'initial phase', wherein males and females are similarly cryptically colored. Later in life, particular individuals may undergo a transformation, becoming more brilliantly colored and, if genetically female, switch sex. These 'supermales' maintain control over a harem of females. We are currently studying the social factors that govern the decision to undergo this transformation. Eventually, we hope to understand the physiological processes that underlie this change.

My Bibliography: