Asymmetries in classically conditioned head movements and cingulate cortex slow potentials in cats.

Presuming that conditioned head movements in the cat indicate a preference for a specific direction, asymmetries were also expected to be found in bilaterally recorded cingulate cortex slow potentials to a symmetrical tone stimulus during discriminative conditioning. Conditioned stimuli (CS, 1000 and 2500 Hz tones) were delivered through two miniature loudspeakers fitted to the head in front of both ears. The unconditioned stimulus (US) was an electrical stimulation of either the left or right lateral hypothalamus yielding, in addition to its rewarding effects, an unconditioned head turning response (UR) either to the left, right, forwards or upwards. Discrimination learning appeared as more extended and more rapid headturns and greater negativity in the cingulate cortex to the CS+ than to the CS-. The preferred conditioned behavioral response (CR) was a headturn to the left in 11 of 12 cats accompanying increased negativity in evoked slow potentials in the right cingulate cortex during the 128-324 ms period after the CS onset. No differences in the movements and in the cingulate potentials were found between the left versus right US stimulations. The results showed that regardless of the direction of the original unconditioned head movement, the direction of the CR was at the end of the training period to the left in 11 out of the 12 cats. Larger evoked slow potentials observed in the right cingulate cortex which were not present in the baseline measurements suggest a population bias between the hemispheres.