Anatomical specificity of septal projctions in active and passive avoidance behavior in rats.

Abstract

Lesions were placed in pathways anatomically associated with some septal projections to assess their individual contributions to the enhanced active avoidance performance and passive avoidance deficit found after large septal lesions. Septal and stria medullaris-habenular lesions impaired performance on a food-reinforced passive avoidance task, while fornix lesions had little effect. Septal, stria medullaris-habenular, and fornix lesions all enhanced two-way shuttle-box avoidance performance and led to greater resistance to extinction of this task with massed trials. The results do not support a unitary conceptualization of septal function; instead, they suggest that the various behavioral effects associated with septal lesions are mediated over different projections.

Habenular lesions and avoidance learning deficits in albino rats

“…Previous studies which support this contention include the findings that rats with habenular lesions extinguish a conditioned emotional response (CER) faster than controls (Brady & Nauta, 1955), ambulate more in an open field , and are less likely to attempt to escape from a step-down platform (Davis et al, 1966). Reduced fearfulness can also be invoked to account for the apparently .contradictory findings that rats with habenular lesions are better at shuttlebox avoidance (Van Hoesen et al, 1969) but worse at avoidance learning in a T-maze , since in the former task fear of returning to the compartment in which shock has been experienced is presumed to retard the learning rate of controls. Moreover, Reinert (1964) has described the effects of habenular stimulation in cats as producing a behavioral pattern which resembles fear rather than rage or aggression.…”

“…A generalized learning deficit is not supported by the present data, however, since rats with habenular lesions performed as well as controls in the passive avoidance tests. There are other indications that these rats are not simply poor learners: since they can learn operant discriminations with ease (Eaton, Rausch, Rausch, & Long, 1972 ;Rausch, Rausch, & Long, 1971) and in some paradigms learn avoidance responses at a rate faster than do controls (Davis et al, 1966;Van Hoesen et al, 1969). The following discussion proposes that the effects of habenular lesions are best explained by positing reduced fearfulness, possibly accompanied by some impairment in the initiation of new behaviors.…”

“…Davis et al (1966), using a step-down task, found that rats with lesions were better at passively avoiding shock than were controls (i.e., they stayed on the platform longer). However, Van Hoesen et al (1969) and Wilson et al (1972) reported impairment in passive avoidance of shock paired with food consumption (l.e., rats with habenular lesions continued to eat after being shocked while eating). The inhibition hypothesis can account for both find ings on the basis of a tendency to continue ongoing behavior, although one must specify which of the two incompatible responses (stepping down or staying on the platform ; eating or not eating) is to be considered as prepotent or ongoing in each situation.…”

“…On the other hand , Van Hoesen and his coworkers (Van Hoesen, MacDougall, & Mitchell , 1969 ;Wilson, Mitchell, & Van Hoesen, 1972) reported that habenular lesions impaired food-related passive avoidance , while enhancing two-way shuttle box avoidance perform ance. Large medial thalamic lesions, which included damage to the habenula, have been found to severely impair one-way active avoidance acquisition (Delacour, ' 1971 ;Vanderwolf, 1967Vanderwolf, , 1971, although Delacour (1971) stated that lesions limited to the habenular complex did not result in impairment in this task.…”

Impairment of one-way active avoidance in rats with habenular or dorsomedial thalamic lesions

“…For example, rats with habenular lesions are deficient in passive avoidance performance but superior to normal animals in two-way active avoidance (Van Hoesen, MacDougall, & Mitchell, 1969); they extinguish a postoperatively learned CER more rapidly than normal (Brady & Nauta, 1955); they are hyperactive in a brightly illuminated open field and are deficient in one-way active avoidance (Nielson & McIver, 1966). However, this last task was somewhat complex and, conseq uen tly, difficult to compare to other one-way active avoidance findings.…”