Response to novel environment following septal lesions or cholinergic blockage in rats.

Abstract

Rates of habituation of an exploratory head-poke response were compared for control rats vs. rats with septal lesions or scopolamine-hydrobromide injections. Controls exhibited decreasing response rates and increasing durations per response within sessions. Response-contingent light presentation attenuated both effects; the major influence of light presentation was an activating rather than a direct reinforcing effect. Both the scopolamine-hydrobromide-injected rats and rats with septal lesions showed decreasing response rates similar to controls; however, neither increased their durations per response, suggesting a more profound impairment of habituation. Both reacted to response-contingent light presentation similarly to controls but in a more exaggerated fashion, indicating that an increased responsivity to responseproduced stimulus feedback caused the habituation deficit.

The effects of septal lesions or scopolamine injections on retention of habituation to a novel environment

“…The rate and mean duration of exploratory responding of the control rats during Phase 1 was consistent with the previous results of Feigley and Hamilton (1971) and Feigley et al (1972).…”

“…The Combined Cons had an increasing poke duration across intervals, whereas the other two groups' response duration remained at a low level and were not significantly different from each other (see Figure IB). Thus, as in previous experiments (Feigley & Hamilton, 1971), both scopolamine and septal lesions resulted in a disruption of the normal pattern of exploratory habituation.…”

“…The effect of both medial septal lesions and scopolamine injections resulted in no change from control animals in the number of exploratory responses during the test period, but changes were found in response duration. Response duration of control rats increased with increased exposure to the novel situation, while the response duration of the septal and scopolamine groups remained constant and unchanging over time as if no habituation was occurring (Feigley & Hamilton, 1971).…”

“…Three identical Plexiglas chambers (20 x 21 x 21 em) with wire mesh floors were used (see Feigley & Hamilton, 1971 for details). A single tube (12 x 5 cm diam) centered 5.5 cm above the floor contained an infrared light beam which operated an electronic switch when it was interrupted.…”

“…In this task, normal adult rats initially show high rates of performing a discrete exploratory response (head-poking into a tube) which gradually decreases with continued exposure to the novel situation. while the mean duration per response increases (Feigley & Hamilton, 1971;Feigley, Parson, Hamilton. & Spear, 1972).…”