Hippocampal lesions and inhibition of avoidance behavior.

Ontogeny of two‐way avoidance in male and female rats

“…These observations are in agreement with the suggestion that responses elicited by the US are important for avoidance acquisition (Bolles, 1970). Greater avoidance of 21-and 90-day-old animals with a niore intense CS may be due to disruption of these inappropriate defense responses (Bauer, 1971,) or to increased discriminability of the CS (D'Amato et al, 1968).…”

“…A 10-cm speaker was centered 40 cm above the grid floor and provided white noise conditioned stimulus (CS) at 75 dB (8 dB above background, as measured by a model 1551-B General Radio Corporation sound level meter). Footshock, the unconditioned stimulus (US), of approximately 1.5 mA, was delivered to the floor and aluminum walls by a circuit described elsewhere (Lovely, Grossen, Moot, Bauer, & Peterson, 1971). Briefly, a 916-V d.c. source and 8 General Electric NE-2 neon bulbs were connected in parallcl with the grid bars and walls.…”

An automated maze task for assessing hippocampus-sensitive memory in mice

“…This potentially contrasts with other effects of hippocampal manipulations which have been described in terms of an inability to withhold or inhibit inappropriate responses (e.g. approach/avoidance behaviours on ethological, unconditioned tests of anxiety such as the elevated plus maze) [26], passive avoidance [27], differential reinforcement of low rates of responding (DRL) operant task [28], spatial discrimination in the watermaze [29]. This suggests that hippocampal lesions could impair performance on cognitive tasks for different reasons, although it is important to be cautious and not to over-interpret these latency data.…”

The Hippocampus as a Cognitive Map

“…This increased rate of inter-trial responding could be responsible for the facilitation seen after lesions. Thus, Schlosberg et al (1969) have shown that hippocampal rats have an abnormally strong tendency to run in response to unsignalled shocks, while Lovely et al (1971) have shown that hippocampal rats run more to stimuli which predict shock, even in the absence of an avoidance contingency. The latter authors conclude that the 'facilitated CAR performance is simply a consequence of this altered responsivity to electric shock' (p. 349).…”

“…This, of course, partly accounts for the well-known difficulty associated with extinction of avoidance behaviours. Lovely et al (1971) have shown how this can affect extinction rates in hippocampal rats trained on a two-way avoidance task. They found an extinction deficit in their lesioned rats when one considered the number of trials on which a response was made after shock had been made contingent upon response; this is consistent with what we have already seen concerning the learning of this task.…”