Heterotopic stimuli-related potential gradients in a small volume of the medullary reticular formation in the cat.

In anaesthetized cats the role of the medullary reticular formation in discriminative functions was studied. We analysed (1). variability of collective reactions of the reticular neurons (extracellular potential gradients recorded bipolarly in three directions by a tetrad of micropipettes with closely-positioned tips in a small volume of the reticular formation) to the same stimulus, and (2). reactions to heterotopic stimuli. The pattern of the potential gradients generated by the stimulation (electrical, natural) of the same spot on the body surface was constant during the time periods studied (up to 30 min). Responses evoked from reciprocally remote receptor areas were manifestly different, at least in one of the depth profiles investigated. It can be concluded that the reticular formation, through its reactions, can differentiate heterotopic stimuli; in this respect it does not operate as a 'nonspecific' system.