Conditioning of hippocampal cells: its acceleration and long-term facilitation by post-trial reticular stimulation.
Neuronal activity, recorded in the dorsal hippocampus (CA3) during classical conditioning, was studied in rats receiving mild post-trial stimulation of the mesencephalic reticular formation. Hippocampal multi-unit activity increased in response to an auditory signal (conditioned stimulus) after pairing of the signal with a footshock (unconditioned stimulus), while the auditory signal alone, presented before conditioning, did not change the rate of hippocampal cell discharges. Trial-by-trial analysis of hippocampal multi-unit responses to the conditioned stimulus, both during acquisition and during a test of long-term retention, indicated that post-trial mesencephalic reticular stimulation hastened the onset of cellular conditioning and facilitated conversion to long-term storage. A study of evoked potentials recorded in the hippocampal formation to stimulation of the perforant path in awake rats, suggested that these effects could be mediated through a modulation of synaptic efficiency within hippocampal neuronal networks. These data are discussed in relation to the concept of neural perseveration in memory consolidation.
D000818:Animals; D003214:Conditioning, Classical / Q000502:physiology*; D004558:Electric Stimulation; D005071:Evoked Potentials; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D008636:Mesencephalon / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology; D051381:Rats; D012153:Retention, Psychology / Q000502:physiology; D012154:Reticular Formation / Q000502:physiology*; D009435:Synaptic Transmission