Escape and approach induced by brain stimulation: a parametric analysis.

Abstract

The study reported pursued two general aims: (a) to find out whether a brain-stimulation-induced escape response results from the bringing into play of similar mechanisms irrespective of whether the stimulation is applied to a site located in the mesencephalic central gray (CG), in the medial hypothalamus (MH) or in the lateral hypothalamus (LH); and (b) to verify whether escape and approach that can be induced by stimulating one and the same hypothalamic site result from a combined activation of two distinct neuronal systems, by means of specifying some of their functional characteristics that would possibly allow differentiation between them. Three experiments were carried out using a situation (shuttle-box) that allowed the measurement, for each given brain site, of both the time for which the rat underwent the stimulation before interrupting it (stimulation time, st., corresponding to an escape latency) and the time for which the animal remained non-stimulated before eventually restarting the stimulation himself (non-stimulation time, nst, corresponding to an approach latency). The following stimulation parameters were varied: the pulse duration (D), the stimulation intensity (I) and the interpulse interval (IPI = 1/stimulation frequency), i.e. the time interval that separated the beginning of a stimulating pulse from the beginning of the next one. The results obtained suggest the following. (1) Some of the mechanisms implicated in the elaboration of an escape response are similar irrespective of whether escape is induced by stimulating a site located in the CG, in the MH or in the LH.