Why whisking? One of the major functions of the brain is to use information from the environment to guide behavior. Much of this information is acquired actively, using movements of sense organs such as the eyes or the tips of the fingers, which continually scan the environment. How are the movements of these mobile sensors controlled by the brain? How is the information they obtain processed by peripheral and central neurons? How is this information used to control the movements of the sensors themselves? How do animals and humans develop the ability to control sensor movements in time and space; i.e., to generate appropriate scanning patterns, and to process and utilize the information acquired in this way? Such questions are central to the research program of H. Philip Zeigler, Distinguished Professor of Psychology and Biology at The Graduate Center and Hunter College. The line of study may be approached experimentally by identifying a model system: i.e., an animal which (a) generates behaviors displaying all the essential features of the types of movement one is trying to explain, and in which (b) the behaviors are accessible to experimental control and analysis. Professor Zeigler's group is using the rat's whisking as a model system for the study of how the brain controls mobile sensors and how these sensors are used to acquire sensory information and use it to guide behavior.
Rats spend much of their time in the dark, and their whiskers are an important sense system. A specialized set of whiskers are arranged in a Row X Column grid on the sides of the animal's snout and moved by special sets of muscles. Just as humans can close their eyes and use their fingers to explore objects in their environment, the rat can use its whiskers to discriminate between different objects, and to build up a brain map of the environment through which it moves. It has been shown that the rat obtains the information it needs by controlling the pattern of whisker movements (whisking rate, whisking amplitude) in specific ways, related to the characteristics of environmental objects. Each whisker is a sensory hair, embedded in a capsule, moved by a single muscle at the base of the capsule. The capsule contains a variety of sense organs sensitive to movement of the whisker hair. Information about these movements is conveyed to the brain by a sensory nerve. Each individual whisker is represented by groups of nerve cells, themselves arranged in a grid-like fashion, forming maps of the whiskers at various brain levels. A specific group of brain cells is activated by movements of the whisker which it represents, transmitting information about whisker movements to various brain cells. This one-to-one arrangement makes it feasible to study the anatomy and physiology of this system, since manipulation of a single hair produces predictable changes in the central maps. Computer-controlled optical (laser) systems enable Dr. Zeigler's group to monitor and control whisker movements in awake animals and record from brain cells during whisking. The data helps scientists to understand how the brain processes sensory input from the body and uses it to control movements.
After 39 years of support by the National Institute of Mental Health, Dr. Zeigler's research is currently supported by a grant from the National Institute of Neurological Disorders and Stroke.
* Adapted from 2002 Research Foundation Report