The effect of a lesion of the habenula on passive avoidance learning

Habenular lesions and avoidance learning deficits in albino rats

“…While these findings indicate that rats with habenular lesions are capable of acquiring adaptive behavior in aversive situations, they are inconsistent with previous research which has found either impairment (VanHoesen etal, 1969 ;Wilson etal, 1972) or enhancement (Davis et al, 1966) of passive avoidance behavior in animals with habenular lesions. However, the present negative results may be a function of differential active avoidance experience, since the independent variable for producing passive avoidance was the shock received during active avoidance training, which was different for the two groups.…”

“…Lowered emotional reactivity would be expected to reduce the animal's response to shock and hence to result in less motivation to learn the one-way active avoidance task in the present study. 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.…”

“…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.…”

“…The Davis-Van Hoesen controversy is also susceptible to solution by relating it to motor inhibition. 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).…”

“…Nielson and his associates (Davis, Stevenson , McIver, & Nielson, 1966 ; found that rats with habenular lesions learned a step-down passive avoidance response faster than did controls, but were impaired in the acquisition of a conditioned active avoidance response to shock in a T-maze. 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.…”