Strain differences in retrieval of unilateral and bilateral engrams

Abstract

Abstract Acquisition and retrieval of an active avoidance reaction (shuttle between two elevated retractable platforms) was compared in albino and hooded rats. Under control conditions both strains showed no difference either in learning or in retrieval of the habit. When retention of the bilaterally acquired reaction was tested during unilateral cortical spreading depression (CSD) no savings was seen in the hooded rats, while the albino rats required about three times more trials to criterion than during the original learning. This result was not changed much by reducing the acquisition-retrieval interval from 24 hr to 10 or 60 min or by allowing 1 hr adaptation to the conditions of functional hemidecortication. Also, the avoidance learing was impaired by unilateral CSD more in albino rats than in hooded rats. When retention of the unilaterally acquired reaction was tested with the intact brain, significant savings were found in the hooded but not in the albino rats. Transfer of information from the normal to the hemidecorticated state and vice versa is discussed. It is suggested that the difference between albino and hooded rats is due to a higher percentage of uncrossed fibers in the visual pathway of the hooded animals.