Professor Gerald Pollack

Research Interests:

Sensory signals provide animals with crucial information about the availability of food, the approach of a predator, the location and desirability of a potential mate, etc. To make use of this information, the nervous system must extract the pertinent bits and pieces from the vast amount of sensory input to which it is exposed, much of which may be uninformative or irrelevant. This is a formidable computational task. We are interested in learning which features of signals are meaningful to their recipients, and how these features are analyzed by nerve cells and neural circuits. We study acoustic communication in crickets as a model system in which we can address the general problem of sensory signal processing at the cellular level.

Crickets use acoustic signals (cricket songs) to communicate with other members of their species. Only males sing; they do so to attract potential mates, to entice them to copulate, and in aggressive encounters with other males. The songs consist of series' of discrete sound pulses that are produced with species-specific pitch and temporal pattern. The graph below shows a sonogram of the calling song of the species Teleogryllus oceanicus.

The ordinate represents sound frequency, and the abscissa is time. Each black mark represents a single sound pulse. Click on the graph to hear the song. A striking feature of the song (indeed of all cricket songs) is its rhythm. Behavior experiments have shown that this is a crucial cue to the species identity of the singer.

Another type of acoustic signal of that is important to crickets are the echolocation cries of insectivorous bats, which hunt flying insects by broadcasting ultrasonic probes and analyzing any resulting echoes. Crickets, like many other insects that fly at night, detect these ultrasonic signals and, when they do, they take evasive action. Bat sounds differ from cricket songs both in pitch and in rhythm. The graph below is a sonogram of the sounds produced by one species of bat.

We are interested in how the cricket's nervous system analyzes these signals. Our studies focus on how important aspects of the signals such as their pitch, rhythm, and direction of origin are analyzed by the nervous system. We study behavioral responses (phonotaxis or mounting during courtship), as well as the anatomy and physiology of individual, uniquely identified nerve cells.

This figure shows two of the neurons we study, named AN2 (red) and ON1 (green):

The techniques that we use include behavioral observations, extracellular and intracellular neurophysiological recordings, intracellular dye injection and confocal microscopy, and computer-based modeling of neurons and neural circuits.

Last update: Apr. 28, 2010