Daphne Soares - US grants

How does one find a friend in a crowd? The way in which brains perform scene analysis is still unknown and it turns out to be a difficult problem for scientists to crack. There are many features of the environment that need to be differentially encoded by the nervous system to lead to an appropriate behavior. Crocodilian brains face the same problem as any other animal: localizing a source of interest in a busy background. But for them, the task is perhaps easier and understanding how they do it gives scientists a peak into the general rules of computation that brains use to carry out scene analysis. Crocodilians often hunt in complete darkness, waiting half-submerged for prey to disturb the water interface. All crocodilians have evolved specialized sensory organs (DPRs) that can detect small disruptions of the water. These are dome-like in shape and are linked to a dedicated neural pathway. DPRs provide an array of sensors that are tuned to a two-dimensional surface wave front. DPRs are therefore an excellent model system to study stimulus source location and feature detection because the scene is relatively simple and the stimulus easily reproducible. This project investigates the psychophysical basis of DPR sensitivity and general processing rules by examining the anatomical substrate that allows for the transmission of information, and by using electrophysiology to determine the codes used by the nervous system. The results will provide insights into understanding the ways in which animals take the environment apart and put it back together again in their brains. The study of a non-traditional animal species can be advantageous when introducing science to the general public, through general public talks and filming and consultation. The program of study integrates these public outreach opportunities with the research. This project provides educational opportunities to high school students, undergraduate and graduate students as well as a postdoctoral fellow. The behavioral setup is simple, and easy to operate. Thus, it is particularly attractive for relatively inexperienced researchers such as undergraduates and high school students.

Project Title: EAGER: Cavefishes of the Guangzi Karst Region in China
Investigator: Soares, Daphne
Project Number: IOS 1048820

This research plan investigates how animals adapt to new environments. Specifically, the proposal examines how evolution has changed the sensory modalities that allow vertebrates to thrive in the perpetual world of darkness found in caves. Do species adapt in their own way or there are rules that they must follow? Is there interplay between sensory modalities during evolution? How are nervous systems constrained by their environment? These questions are especially interesting in caves because the harsh quality of the environment provide unique insights into the malleability of nervous systems over time. This proposal compares the behavior, neuroanatomy and genes of many species of cavefishes. These animals have a diverse phylogeny and various completely unrelated species have independently colonized caves all over the world. Examining unrelated animals can point towards general rules of evolution and comparative studies create an intellectual framework for the study of adaptation. China contains the majority of reported cavefishes in the literature and this project funds preliminary work between the University of Maryland and the Shanghai Ocean University. Researchers and students will be examining rare, unique and often undescribed species of cavefish in the Guangxi autonomous region. Aside from studying the organisms themselves results are likely to uncover conservational issues that may impact the long term survival of these animals. This proposal not only addresses unique biological questions in possibly endangered species, establishes a new international collaboration, but also creates a venue for undergraduate students to learn essential aspects of Biology.

Summary Neuronal reorganization is a critical step in the recovery of function, whether after injury or as in response to disease. In our research training program, we will use a new animal model to address neural reorganization in the visual circuit. The fish Astyanax mexicanus provides a particularly novel window into network remodeling because it is extant in two readily available forms: a visual river-dwelling (surface fish) form and a cave-dwelling form (cavefish). It is closely related to zebrafish, and all techniques use in this zebrafish can be used in Astyanax. Adult cavefish lack eyes and the corresponding visual neural structures are severely reduced. Eye development is nevertheless initiated during embryogenesis, but later arrests with the lens undergoing programmed cell death and the rest of the eye degenerating and sinking into the orbit. However, it is possible to rescue the eye, and the corresponding visual circuits, by transplanting an embryonic surface fish lens into a degenerating cavefish eye. We will use neuroanatomy, behavior and calcium imaging to measure the changes that occur in the brains of blind cavefishes after developmental manipulation. Our central hypothesis is that the developing optic tectum circuitry in the cavefish is robust and receptive to coherent visual information, so that homeostatic mechanisms will allow for the emergence of visual codes. Our specific objective is to test the malleability of the optic tectum circuitry in response to visual input during development. To accomplish this, we will train two undergraduate students, one master's student and a PhD student as well as high school volunteers from a charter school in Newark, NJ.