Alterations in the generalisation of visual stimuli induced by lysergic acid diethylamide in cats

Summary

Cats were trained to carry out avoidance behaviour on the presentation of a visual stimulus. The effect of lysergic acid diethylamide and amphetamine were then tested on the rate of extincition of the conditioned response and responses evoked through generalisation by other visual stimuli which had not been used previously in the training procedure and which differed from the conditioned stimulus only in intensity. LSD-25 in doses of 10 and 20 μg/kg i.p. produced a significant increase in the number of generalised and conditioned responses without effecting the gradient of generalisation. A smaller dose of 5 μg/kg increased the number of generalised responses without modifying that of the conditioned response. At all three dose levels LSD-25 increased the amount of generalisation, that is the total number of visual stimuli capable of eliciting responses, either by producing upward displacement of the graph of generalisation of extinction or in the lower dose ranges by altering the gradient of the graph.

Amphetamine produced an increase in the number of conditioned responses and a relatively smaller rise in the number of responses evoked through generalisation. At each dose level there was a change in the gradient of generalisation but only after 1.0 mg/kg i.p. did the amount of generalisation alter significantly.