A method for measuring locomotor behavior in rodents: contrast-sensitive computer-controlled video tracking activity assessment in rats.
A newer locomotor activity system for rodents is described. The system consists of a black, ventilated test chamber, internally lighted with a ceiling mounted video camera. The camera's image is transmitted to a contrast-sensitive tracker which maps the point of highest contrast and relays the digitalized coordinates to a PC. Dedicated software stores the information and simultaneously displays a map of the tracked subject. To illustrate the system's utility, results from an experiment are presented using an established behavioral teratogen, phenytoin. Pregnant Sprague-Dawley CD rats were exposed to 0 or 200 mg/kg of phenytoin by gavage on embryonic days 7-18 and the offspring tested in the videotracker activity monitoring device. Phenytoin is known to induce hyperactivity and circling behavior in the offspring. The system revealed that phenytoin-exposed offspring that exhibit neurological impairment were hyperactive compared to controls and the effect was predominantly seen in females. These animals exhibited more section transitions and more central and peripheral activity. When peripheral activity was subdivided into that occurring along corners versus sides, it was found that corner activity represented only a small component of the group differences whereas the side component represented most of the effect. Moreover, phenytoin offspring exhibiting the circling defect were found to display a qualitatively different pattern than noncirclers or controls. Videotracking represents a different approach to the analysis of locomotor activity patterns in experimental animals compared to older methods. Two advantages of this method are higher spatial resolution and not having to pre-specify data capture intervals. Other features are detailed regional movement information and qualitative mapping of ambulatory patterns.