Masashi Kawasaki - US grants

The broad, long-term objective of this proposal is to understand neuronal mechanisms by which animals process sensory information and accordingly generate adaptive behavior. Of particular interest is how animals generate diverse behaviors using limited sets of motor circuits. The proposed study is designed to elucidate the neuronal mechanisms underlying a variety of electrical behaviors performed by an electric fish, Hypopomus, during courtship and aggression. It was recently discovered that a variety of behaviors can be induced in a curarized preparation of this electric fish by microiontophoresis of L-glutamate into a small region in the diencephalon, the prepacemaker nucleus. The first two specific aims are to understand how different behaviors are organized in this small brain structure. Physiological recordings and anatomical labeling will be performed in in vivo preparations. The prepacemaker nucleus projects to the final motor nucleus, the pacemaker nucleus, and modulates its regular oscillation to generate electrical behaviors. The following two specific aims are to understand how the pacemaker nucleus generates complex motor outputs. Despite its very simple organization and the rigid electrical coupling between constituent neurons, the pacemaker nucleus is capable of generating a variety of outputs under the modulatory inputs from the prepacemaker nucleus. In vivo preparations will also be used for intracellular penetration of pacemaker neurons while behaviors are induced by stimulation of the prepacemaker nucleus. The results of these experiments will contribute to the understanding of how the central nervous system regulates different types of behavior at the single-neuron level and how seemingly rigid networks can be modulated to generate different patterns of vertebrate behavior.

This is a request for a Research Scientist Development Award. The broad, long-term objective of this proposal is to understand neuronal mechanisms by which animals process sensory information and accordingly generate adaptive behaviors. Of particular interest is to identify the neuronal mechanisms for sensory processing and motor generation for the jamming avoidance response in an African electric fish, Gymnarchus. My recent behavioral studies demonstrated that the spatial and temporal patterns of two sensory cues, differential phase modulation and amplitude modulation are essential for this behavior. In the proposed project I plan to investigate neuronal mechanisms for detection of these two parameters and the promotor mechanisms which generate the behavioral output. Specifically, I prepose to (1) identify the neuronal mechanisms that process differential phase information (2) determine the precise morphology and topography of amplitude coding system, and (3) determine the final motor output mechanisms for this behavior. I will use intracellular recording and labeling techniques as well as extracellular recording techniques and electron microscopy to reveal morphology and function of neuronal elements. I will also take a comparative approach. The findings made in the proposed project will be compared with the already known neuronal mechanisms for the same behavior in an electric fish species which evolved independently from Gymnarchus. This comparison will allow us to obtain insights into general significance of the findings. I plan to learn electron microscopic techniques and field techniques to enhance my research career. The expected results will contribute to the understanding of basic principles of information processing by the brain for vertebrate behaviors.

Certain fish known as weakly electric fish produce motor commands that do not activate muscles, but produce a regularly repeated discharge from small electric organs in the body, and they have electroreceptor cells in the skin that detect these electric waveforms. The electric field produced around the body can be used for navigation (as with echolocation by sound) and for communication between animals. Mechanisms in the brain detect the timing and spatial distortions of the electrosensory waveform with a very high precision. When two animals with similar discharge rates approach each other, the one with the slightly higher frequency shifts its own discharge higher, and the lower one shifts still lower, and this response is known as the 'jamming avoidance response' by analogy to the way two radio stations keep their signals separate to avoid having one signal interfere, or 'jam', with the other. The electrosensory pathways in the brain of some electric fish have been well studied, and provide an excellent simpler model for more advanced and complex central sensory systems such as vision or audition. This project carries the analysis to the cellular level with sophisticated methodology for recording and identifying the structure of single cells, to examine how the separate inputs of spatial and temporal information are detected and combined within single nerve cells in the brain.
Results will provide a sophisticated cellular analysis of how timing and spatial information are integrated in a sensory pathway in the brain, and so contribute to understanding basic principles of information processing in the brain for particular behaviors.

In the brain, the process of sensory-motor integration produces behavioral outputs that are generated as a result of sensory computation and orchestration of motor commands. In animals with complex brains, this process can involve enormously complex neuronal circuits. Although large-scale morphological units for sensory motor integration are known, little is known about the precise neuronal circuits mediating sensory-motor integration in vertebrate species including humans. There are fish species known as 'weakly electric fish' that emit weak electrical signals into their surrounding environment and use them for navigation and communication. These fish provide models for the vertebrate brain in which relatively simple sensory and motor systems can be studied together, because rather precise sensory processes and their neuronal substrates are already known, and motor behaviors and their immediate controlling circuits are also now known. This project is aimed at understanding how individual behavioral acts are organized in the brain of a species of weakly electric fish. Electrophysiological and neuroanatomical techniques are used to investigate activity of nerve cells in the brain that are involved in well-defined electrical behaviors of the fish. Results will clarify the exact location, morphology and function of neurons that mediate specific behaviors.
The expected results from the proposed study will have an impact on our understanding of both sensory and motor principles underlying behavioral organization within the brain. The project also involves work spanning the scales from subcellular to behavioral, and so provides valuable training for graduate and undergraduate students.

The broad, long-term objective of this project is to understand neuronal mechanisms by which animals process sensory information and accordingly generate adaptive behaviors. An electrical behavior of electric fishes provides an excellent model system in which neural mechanisms can be analyzed in great detail. The current focus of the laboratory is to elucidate neural mechanisms that deal with temporal information in electric fishes. Temporal processing is often involved in sensory and communicatory abilities of animals and humans, and is one of the most important aspects of information processing by the brain. This project will deal with neuronal computation of temporal information in two time scales, milliseconds to seconds and microseconds. The temporal pattern of sensory signals on the order on milliseconds to seconds are important in auditory communication signals such as human languages and birdsongs. Temporal signals on the order of microseconds are important for sound localization capabilities. Physiological and anatomical properties of neuronal circuits for temporal processing in electric fishes have been described by the primary investigator. The primary investigator is currently identyfying the specific neurons that receive timed input signals and examining their temporal patterns. The project aims to identify neurotransmitters used by the synapses at these temporal pattern detector neurons. Electrophysiological recording will be made from these neurons while various neurotransmitter specific blockers will be applied locally. After the candidates for the neurotransmitters are identified pharmacologically, immunohistochemistry will be performed to localize where these activities occur within component neurons of the temporal circuit. The results will contribute to the future study of the system in which the ultimate cellular (membrane and channel) properties of temporal processing will be discovered. The project will also involve integration of the research into undergraduate/graduate education.

Leading researchers in the field of Neuroethology from around the world meet at the International Congress of Neuroethology to share their research findings and forge research collaborations that are critical in moving the discipline forward. Research in neuroethology is at the cutting edge of neuroscience and behavioral research with basic biological and health related implications. For U.S. researchers to remain current, it is essential that they exchange ideas directly with their international colleagues. The Congress will emphasis comparative evolutionary approaches which meets the biodiversity initiatives of NSF as well as fostering development of scientists that may be involved in the Brain Initiative. The exchange of information among scientists during oral and poster presentations is of great value, but equally important are the personal exchanges and resulting collaborations established in the hallways between sessions and during the numerous topic-based workshops and symposia scheduled throughout the congress.

Funds provided by NSF will help support the attendance of future leaders of in neuroethology and behavioral neuroscience. Specifically, recipients will be at an early stage in their careers (e.g., graduate students, post-doctoral fellows, and beginning investigators) and will be from U.S. institutions. The selection committee will also strive to support individuals from groups that are historically underrepresented. Assistance of such scientists will help forge new, international collaborations, thereby creating long-term benefits for all involved.