| Abstract: | In 2 experiments, a treatment phase of septal stimulation preceded the acquisition of free operant leverpressing on a random-interval 64-sec reinforcement schedule. 32 male Sprague-Dawley rats were chronically implanted with a bilateral septal stimulating electrode and a unilateral bipolar hippocampal recording electrode. Ss received (a) low-frequency (7.7 Hz) stimulation, which drove the hippocampal theta rhythm; (b) random-pulse stimulation (average frequency 7.7 Hz), which produced only nonregular waveforms in the hippocampus; or (c) no stimulation. After 12 days of leverpress acquisition, Ss were presented while leverpressing with an auditory signal associated with a particular schedule of shock delivery: In Exp I, shocks occurred despite the S's response strategy; in Exp II, shocks were delivered only if the S pressed the lever. In both experiments, leverpressing was suppressed by the auditory stimulus. Theta-driving but not random-pulse septal stimulation proactively increased behavioral tolerance to the effects of electric shock. Results support the idea that proactive behavioral effects of septal stimulation are a consequence of the production of the hippocampal theta rhythm. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
