Environment-specific conditioning produced by electrical stimulation of the lateral hypothalamus

Rats received noncontingent electrical stimulation of the lateral hypothalamus on one side of a place preference apparatus and no stimulation on the other side. Subsequently, when allowed access to both sides, the rats spent more time on the side associated with stimulation. This change in preference was only found in rats receiving stimulation in the side least preferred prior to conditioning trials. It was further shown that the place preference conditioning procedure produces increased locomotor activity. Thus, the place preference obtained was not an artifact produced by a conditioned freezing response. These data suggest that both the reinforcing and activating effects of lateral hypothalamic stimulation may be conditioned to a specific environment. Some methodological problems of the place preference paradigm are discussed.