Unilateral and bilateral lesions of the anteromedial cortex increase perseverative head movements of the rat.
Lesions of the anteromedial cortex were made in rats trained to orient their heads to 9 positions located laterally and centrally in upper, middle and lower regions of space. The water-deprived subjects were tested in sessions of 20 trials in each of which all positions were baited once with a small amount of water. Training continued until no position was consistently missed and the number of returns to positions already selected on that trial (perseverative responses) was low and stable. In Expt. 1, rats with unilateral anteromedial lesions tested with 3 days recovery did not miss any position or significantly change the order in which correct positions were selected but they made more perseverative responses to all positions. Bilateral anteromedial lesions moderately increased misses but markedly increased perseverations. Visual cortex lesions comparable in size produced no changes. In Expt. 2, unilateral anteromedial lesions tested with 7 days' recovery did not increase misses and only slightly increased perseverations. In Expt. 3, unilateral anteromedial lesions tested within 1 day increased perseverations more than lesions tested with 6 days' recovery. Neither group increased misses or changed selection order. The perseverations appeared on a trial after 6 of the 9 correct selections and were directed to both recently and remotely selected positions. Lesions of the anteromedial cortex appear to produce a deficit in the suppressive control of head orienting.
Sinnamon
H M
HM
Laboratory of Neuropsychology, Wesleyan University, Middletown, CT 06457.
Charman
C S
CS
D000818:Animals; D005625:Frontal Lobe / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006257:Head / Q000502:physiology*; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D014793:Visual Cortex / Q000502:physiology