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Flight behaviour elicited by electrical stimulation of the hypothalamus and midbrain in rats : Escape and avoidance properties Clarke, Robert John

Abstract

Emotional, motivational, or species-specific behaviour can be elicited by intracranial electrical stimulation (ICS) in unanesthetized and unrestrained animals with chronically implanted electrodes. The purpose of this investigation was to describe and quantify, using an escape and avoidance task, a behaviour called flight, using rats as the experimental animal. An enclosed test box was used that had a hole in one wall covered by a moveable clear plastic plate. With the interior light on and exterior lights off, the hole represented the only opening in the box. Flight was then operationally defined as plate-pushing in response to ICS (escape response). It was found that only 25% of rats which showed manifestations of flight on pre-test screening would perform the escape response. After establishing reliable escape, the rats were given the opportunity to avoid ICS, at the threshold voltage for escape, by responding to a signal (bell, light or click) predicting the occurrence of ICS. In over 200 trials there were at most only 10% avoidances and no tendency for faster responding. A current explanation for this, proposed by W. W. Roberts, was tested by allowing these rats to press a bar for brief ICS at the voltage used in avoidance. Only 40% of the subjects would self-stimulate. These, and other results from the literature suggest that rewarding onset of ICS, as in the Roberts hypothesis, is insufficient to explain the lack of avoidance. The electrode sites producing escape were found to be in the central gray of the midbrain, and in both the medial and lateral divisions of the middle to posterior hypothalamus near the fornix. The sites producing similar behavioural manifestations but not escape were found to be in the same regions of the hypothalamus and midbrain.

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