HIPPOCAMPAL-FORMATION IS INVOLVED IN MOVEMENT SELECTION - EVIDENCE FROM MEDIAL SEPTAL CHOLINERGIC MODULATION AND CONCURRENT SLOW-WAVE (THETA-RHYTHM) RECORDING

Hippocampal rhythmical slow-wave field activity which occurs in respon se to sensory stimulation is predominantly cholinergic (atropine-sensi tive theta rhythm), can precede movement initiation, and co-occurs dur ing non-cholinergic theta rhythm associated with ongoing movement (atr opine-resistant). This relationship suggests that theta rhythm plays s ome role in movement control. The present naturalistic experiments tes ted the idea that atropine-sensitive theta rhythm plays a role in sens ory integration and planning required for initiating appropriate movem ents. One of a pair of hungry rats, the victim, implanted with hippoca mpal field recording electrodes, a septal injection cannula, and a pos terior hypothalamic stimulating electrode, was given food which the ot her, the robber, tries to steal. Since the victim dodges from the robb er with a latency, distance, and velocity dependent upon the size of t he food, elapsed eating time, and proximity of the robber, the movemen t requires sensory integration and planning. Although eating behavior seemed normal, atropine-sensitive theta rhythm and dodging were disrup ted by an infusion of a cholinergic antagonist into the medial septum. When the victim in turn attempted to steal the food back, Type 1 thet a rhythm was present and robbery attempts seemed normal. Prior to chol inergic blockade, posterior hypothalamic stimulation produced theta rh ythm and dodges, even in the absence of the robber, but following inje ctions, atropine-sensitive theta rhythm and dodging were absent as the animals dropped the food and ran. The results provide the first evide nce to link atropine-sensitive theta rhythm and hippocampal structures to a role in sensory integration and planning for the initiation of m ovement. (C) 1997 Elsevier Science B.V.