Hippocampal lesions and activity

Abstract

Rats with hippocampal damage, neocortical damage, and unoperated controls were given three tests of spontaneous activity. Hippocampal destruction was produced either by aspiration or electrolytic fulguration. Both hippocampally damaged groups spontaneously alternated at only "chance rates." Both were more active in exploration, but the aspiration group failed to display the normal decrements over time. The electrolytic hippocampals ran more in the exercise wheel, while the aspiration hippocampals ran less. IntroductionThe present experiment was undertaken to expand investigations of the role of the hippocampus in "spontaneous" (un rewarded) activity. Three different measures were used: spontaneous alternation in a T maze, exploration of a strange cage, and running in the exercise wheel. Reports on the effects of hippocampal lesions on activity in these situations already exist in the literature, but there is great variability between the studies in the location, type, and extent of leSions, as well as in general procedures. In the present study all animals were used in every task, and two methods of hippocampal destruction were employed. Apparatus Spontaneous alternation. An enclosed Tmazeoftheusual size and contruction was used, with illumination provided by a 7 1/2 w light placed over the choice point. Activity cages. Three wire mesh cages measuring 11 x 18 in and 11 in high were bisected on their longer axis by a photocell beam, interruptions of which were continuously recorded. The cages were used simultaneously in a darkened room. Exercise wheels. 'Three exercise wheels of 12 1/2-indiameter with 5 1/2-in wide tracks were used in a dark room. Each wheel turn was automatically recorded. McthodSubjects.

Effects of hippocampal damage on reward threshold and response rate during self-stimulation of the ventral tegmental area in the rat

“…These animals also consistently exhibited higher maximal response rates during self-stimulation tests. Collectively, these novel results extend previous demonstrations of the involvement of the hippocampal formation in motor output and rewarded behavior [5,9,17,24,48,49] by demonstrating that lesions of this structure can dramatically alter behaviors traditionally ascribed to the mesoaccumbens DA system [2,13,14,29,[43][44][45].…”

“…First, maximal response rates for ICSS are usually considered to be a measure of motor performance [33]. Rats with hippocampal damage, produced by a variety of different methods, have been reported to display increased motor output in response to activating situations, food reward, and following drug administration [5,8,9,17,24,38,48,49,59,60]. These results may thus be another example of the enhancement in motor output resulting from hippocampal damage.…”

“…This modulatory influence has been consistently demonstrated in many studies of spontaneous and drug-induced locomotion. Thus, it has been shown that extensive lesions of the hippocampal formation produce increases in spontaneous locomotion [9,24] and result in heightened locomotor responses to psychostimulants and dopamine agonists [5,38,47,59,60]. This enhancement in drug-induced activity following extensive hippocampal damage: (i) occurs as a direct function of increased locomotion and not indirectly, from reductions in competing behaviors [59]; (ii) is dependent on the integrity of the mesolimbic dopamine (DA) projection, as 6-OHDA lesions of the NACC block this effect [59]; (iii) occurs specifically in response to pharmacological stimulation of dopamine D2 receptors, which is consistent with the possibility of underlying receptorbased changes [38]; and (iv) corresponds to increases in amphetamine stimulated DA release in the NACC [60].…”

Approach and inhibitory reactions in rats after bilateral hippocampal damage.

“…However# this possibility seems unlikely since Douglas & Isaacson (1964) In this respect, the relatively homogeneous nature of the flashing lights might be more analagous to the conditions which ! originally showed no differences in habituation in the movement…”

The effect of physostigmine on spontaneous alternation in infant rabbits

“…Apparently this is a rather ubiquitous aspect of mammalian Ii fe , but it has been most extensively studied in the rat (see Douglas, 1966). Under various experimental conditions, the resuIts of the utilization of this tendency as a behavioral task have provided insights into some of the neural mechanisms underlying this response; for example, it is eliminated by bilateral destruction of the hippocampus (Douglas & Isaacson, 1964). After such alesion, responses to the two goalbox locations drop to chance level.…”