Research Interests

We study sensory function in aquatic animals by measuring behaviorally relevant psychophysical and physiological indices of stimulus detection. The questions we ask can all be paraphrased: what information does this sense provide the nervous system? Or in other words, what do animals know about their world, and how do they know it? Our approach is to compare measures of sensory function (detection, discrimination, filter properties, etc.) in species that differ in structural, behavioral or ecological detail. We also make parallel comparisons between sensory modalities that are responsive to overlapping sets of stimuli.

---

Individual Research Projects

Our current investigations focus on the senses fish use to detect moving and sound-producing objects. We want to know what some fish can hear that others can not. Fishes have multiple sensory systems that respond to these kinds of sources, what can some modalities detect that others can not? We are also applying our comparative approach to the neural control of an active sense, the electrogenic and electrosensory system of gymnotiform fishes. These fascinating fishes produce and sense weak electric fields and use this electricity to communicate and to actively form images of the electrical properties (e.g. conductance) of the objects nearby. Some species produce these fields at a variable rate and appear to change their output in rapid response to immediate events. Other species only change their outputs in more subtle ways, over daily or seasonal periods. This has a direct impact on the performance of their electric imaging and is also a behavioral readout of specific neural circuit differences. Do species differences reflect different ecological needs or cost-benefit tradeoffs? Can we use the diversity in behaviors to examine the function of individual bits of neural circuitry?

Current projects in my lab include:

Multisensory integration in the perception of moving or vibrating objects: All fishes have a wealth of senses involved in the detection of vibrating objects. These include hearing and related senses, and the less-commonly known lateral line system. Each of these senses is responsive to different aspects of the physical disturbances caused by vibratory motion. Do these multiple senses each contribute to different behaviors, or only in certain contexts? Or does each modality make a partial contribution to a single percept of an object with multiple properties? We use anatomical, physiological, and behavioral techniques in combination with surgical or pharmacological manipulation of the sensory periphery, to determine which senses are absolutely necessary for detection and what each individual sense contributes to perception. We are currently focused on the interactions between audition, motion detection, and the lateral line in the perception of the spatial location of vibrating objects.

Evolution of communication systems in South American Electric Fishes: A large group of South American fishes, the Gymnotiformes, have the unusual ability to both produce and sense very weak electric fields. They use this ability to detect the tiny currents produced by their prey or other animals, and they use this sense to form an electric image of their surroundings (like a kind of radar). Interestingly, these fish also use this ability to communicate with each other by sending tiny pulses in specific patterns. The pattern of pulse spacing seems to be particularly important for communication, but less is known of the significance of pulse structure. We are looking at the structure of the pulse itself, how it differs in different species, and particularly how and why it varies within certain species, but not in others. We have conducted geographic surveys of this variability in Brazil, and we are currently determining if each regional population has a different ‘accent.’ If pulse structure is species-specific, as is thought, it can prevent different species in the same habitat from interbreeding, but if different populations of the same species begin to vary due to geographic barriers, small differences could easily lead to the evolution of new species. So we are comparing the diversity of pulse type to the genetic structure of several populations to determine if animals with different signals are interbreeding. We are also looking at how individuals of the same species, but from different populations, interpret each other’s electric discharge. Can they judge the sender’s species? Sex? Reproductive desirability? All of these questions are important for understanding how this ‘language’ evolves, and for understanding how this may lead to the birth of new species. This research is in collaboration with researchers at the Instituto Nacional de Pesquisas da Amazonas (Brazil -- INPA) and Yale University.

Photos from the first Hunter College-INPA expedition to the middle Rio Negro (webpage under construction)

Lab Contact Information

Braun Lab of Hydroacoustic Research and Discovery
Department of Psychology
Room 606 North Building
Hunter College
695 Park Avenue
New York, NY 10021
Phone: 212-772-5554
Fax: 212-650-3018
Email Dr. Braun