Institute of Physiological Psychology I, Heinrich-Heine-University of Düsseldorf, Düsseldorf, Germany
The analysis of behavioral asymmetries plays an important role for the experimental analysis of behavior in relation to functions of the brain. Out of the repertory of presently available measures, turning behavior (circling, rotation) of rodents is probably the one which has been examined the most. Turning has usually been measured using mechanical devices (roto-meters) where the animal's movement is detected by a wire fixed to a harness around the animal's chest which transmits rotation to a microswitch or photocell system. Such rotometer techniques have contributed substantially to the study of behavioral asymmetries, including measurement of spontaneous or conditioned turning of intact animals in relation to specific brain mechanisms, or investigation of the effects of brain lesions or pharmacological treatments. In the unilateral 6-OHDA lesion model, for example, it has become a standard behavioral method to screen the functional effects of potential treatments (drugs, grafts) against Parkinson's disease. The wide dissemination of this method is certainly determined by the fact that rotometers are relatively simple, easy to use, and usually inexpensive; furthermore, they produce quantitative data and allow time-dependent analyses. However, they have some drawbacks which limit their application, particularly when qualitative aspects of behavior are of importance. Thus, the animal's behavior is reduced to 'turns' of a wire which may lead to a loss of important behavioral information or even to a misinterpretation of data. Even more, rotometers cannot discriminate between rotation and other possible behavioral asymmetries, especially those in thigmotactic scanning. Thus, if a differential and qualitative analysis of behavioral asymmetries is intended, other methods have to be considered.
The most obvious way to measure the 'actual' behavior is provided either by skilled human observation or by video monitoring of behavior in combination with sophisticated computer systems. Here, the video image analyzing system "VIAS" (Schwarting et al., J. Neurosci. Meth. 49:199-210, 1993) will be presented, which allows measurement of different kinds of turning, thigmotactic scanning and locomotion; this system will be discussed in comparison to other techniques, and its possible applications to analyze spontaneous, conditioned and drugged behavior in the rodent will be indicated using examples from intact animals and those with central or peripheral unilateral interventions.