Passive avoidance deficit with septal lesions: Disturbance of response inhibition or response acquisition?

Interference with septal function by injection of a local anaesthetic (lidocaine hydrochloride) bilaterally into the lateral septal area of male rats impaired acquisition of a passive avoidance response to an electrified water spout. This effect does not appear to be due to an impairment of performance since injections of lidocaine into the lateral septum of rats which had previously acquired the passive avoidance tendency did not impair avoidance behaviour. In another experiment, injections of lidocaine during passive avoidance training did attenuate the tendency of rats to avoid the spout 24 hr later even though tere was no impairment of septal function at the time of testing. These results are interpreted as indicating that the septal area is involved in learning, and specifically in the establishment of inhibitory processes responsible for preventing a previously dominant response tendency from expressing itself behaviourally.