David Bodznick - US grants

Electrophysiological and behavioral studies are described to examine the neuronal basis for spatial analysis of electrosensory information in the optic tectum of the skate as related to production of a simple behavior. In a wide range of vertebrates the tectum has been found to organize spatial features of multisensory inputs and to direct oriented motor output. Local bioelectric fields associated with prey animals are sufficient alone to direct the close-range orientation and attack by skates on their prey. Such unconditioned orientation responses can be elicited by dipole E fields produced to simulate the bioelectric signals. The tectum in the little skate, Raja erinacea, receives a large input from ascending electrosensory fibers. Multiple and single unit studies will examine the organization of electrosensory information in the skate tectum and its relationship to other sensory modalities represented. The existence of spatial mapping of electrosensory as well as visual information will be examined and the relationship of such maps for different modalities determined. Quantitative measurements of such spatial representations will determine if space is represented uniformly in each modality. The receptive field properties of single cells will be studied along with the selectivity for specific sensory features (e.g. stimulus size, movement and direction). Finally, the responses of tectal cells to stimuli in more than one sensory modality will be measured. Behavioral studies of animals with partial or complete tectal abltaions will be used to assess the role of the tectum in the orienting responses to the E fields. The studies may provide insight into general principles of neuronal processing of spatial information by the vertebrate brain which have relevance for understanding the disruption of these processes in disease states. The evidence from many vertebrate classes indicates that the function of the optic tectum in organizing spatial information and directing orienting behavior is conserved throughout the vertebrates. The results of the studies proposed should, therefore, have relevance for understanding the tectum (superior colliculus) in humans.

A major problem for sensory processing is the separation of "signal" from "noise." Self-generated activity stimulates sensory receptors, yet must be distinguished from externally produced sensory stimulation. An excellent model system for testing possible mechanisms is electrosensory processing by certain fish. Several fish species have well-developed electro- receptor systems that are exquisitely sensitive to the tiny electrical potentials produced by other animals. Among elasmo- branchs (sharks, skates, and rays), electroreception is used for prey detection. The medulla of the brainstem is a major site for neural processing of this information. This project will examine how physiological mechanisms eliminate sensory responses to the intense self-stimulation caused by ventilation movements of the gill chambers. Preliminary data suggest this mechanism relies on the primciple of "common-mode rejection," as central circuits compare inputs from different parts of the body and by subtraction eliminate the signals that all receive simultaneously. Similar processing by the same circuits may enhance sensitivity to differential signals of natural electric fields. These experiments will determine the cellular mechanisms involved, examining the anatomy and physiology of the circuits involving the brainstem and parts of the cerebellum. This approach is a novel one with an excellent model system, and results will be important for understanding the fundamental sensory problem of signal and noise separation, and for understanding the evolution of electrosense and sensory processing in this vertebrate class with such an ancient history.

Elasmobranch fishes (sharks, skates and rays) have an extremely sensitive and specialized sensory system that is critical for the detection of weak electric fields in their marine environments. This sense is used in finding prey and in orientation. A significant problem is that the fish's own activities such as swimming and respiration, stimulate these electroreceptors. Therefore, mechanisms must exist within the brain for separating responses to important external electric fields as distinct from this self-generated "noise". Previous experiments from this laboratory have shown that such a process is accomplished in the first stages of sensory information-processing in the hindbrain region. A series of physiological and anatomical studies are being conducted to better understand the mechanisms responsible for this noise- reduction process. In general, separating signal information from noise is a problem that has broad significance for understanding how all vertebrate sensory systems operate. Therefore, the results obtained from these experiments are relevant for other sensory systems in all vertebrates species, including humans.

The objective of this renovation project is to enable Wesleyan University to comply with the USDA Welfare Act and DHHS policies related to the care and use of laboratory animals. Wesleyan University currently is consolidating and upgrading its animal facilities on the fourth floor of Shanklin Laboratory in three phases. Phase I, consisting of a five-room surgical suite was completed in April 1992. Phase II, this proposal, will create an adjacent clean/dirty wash room supplied with modern equipment for the sanitation of racks and cages, aerosol control of soiled bedding and animal drinking water quality protection. For reasons of cost effectiveness and availability of rooftop space, the scope of the mechanical and electrical work of Phase II anticipates the needs of Phase III, five newly renovated animal rooms equipped with an HVAC system providing 15 changes of air per room per hour. Finally, funds are requested here for purchase of 2 large seawater aquaria to provide' adequate space for maintaining small elasmobranch fishes in healthy condition.

There are numerous mathematical challenges surrounding the theory and practice of medical imaging. Images obtained with the various imaging modalities typically suffer from imperfections such as low resolution, low contrast, high noise level, modality-specific artifacts and geometric deformations. Furthermore, given the vast amount of data collected in these images, automated tools are needed that aid in analyzing the data.

These challenges are ripe for mathematical exploration. The PIs will spend the academic year 2010/11 at the Dartmouth Medical School and the Dartmouth Hitchcock Medical Center immersed in the study and application of medical imaging under the guidance of Dr.John B. Weaver. In addition to Professor Weaver, there is an active and accomplished cohort of faculty with imaging expertise both at the Thayer School of Engineering at Dartmouth and in the Radiology Department at the Medical School with whom the PIs will interact. The PIs will focus mostly on the segmentation problem and the registration problem as applied to digital tomosynthesis, although they intend to gain knowledge in all areas of medical image analysis during their immersion year. The PIs plan to use this experience to open and sustain a new avenue of research in their research profiles.

The PIs will use this experience to broaden the curricular offerings available to Wesleyan students in future years. They will offer a suite of classes at the advanced undergraduate/graduate level in areas such as the mathematics of imaging, data analysis, and medical imaging. They expect that this activity will lead to a significant evolution of course offerings in their department. With ongoing research in medical imaging we would also hope to be able to attract some graduate students into this important field.