Publications
Text queries can be conducted by Author, Title, or Keyword.
Successive discrimination performance improves with increasing
numbers of stimulus preexposures in septal rats
Source: Behavioral and Neural Biology 1982 Feb;34(2):141-151.
Author: Burton HA, Toga AW.
PubMed ID: 7082260
Abstract:
ABSTRACT: Rats with damage to the lateral septum in a successive discrimination task improve their performance with increasing amounts of preexposure to a previously meaningless stimulus. Septal operates receiving 270 nonreinforced tone preexposures perform at a level superior to that of controls. In normal rats, increasing the amount of preexposure to a meaningless stimulus serves to further retard sebsequent learning with that stimulus. This effect has been termed latent septum result in a direct positive relationship between the number of preexposures and performance on a successive discrimination task. Damage to the lateral nucleus of the septum appears to sensitize rats to available stimuli. The present results demonstrate that the degree of sensitization can be varied by manipulation of the number of preexposures. METHOD: The subjects used in this study were 24 naive 90-day-old female Sprague-Dawley rats. The rats were reduced to 80% of their free feeding weight during a 1-week period immediately prior to the start of the experiment. Sujects were trained and tested in either of 2 clear plastic lever boxes, each contained in a sound-proof chamber. A lever was horizontally centered on an endpanel of each box and was 10 cm from the base of the box. A food magazine and stimulus light were located to the left of the lever on the same endpanel. Auditory stimuli were presented by a 7.5 cm diameter speaker mounted behind the front panel. Each subject's participation in the experiment consisted of seven phases: (1) magazine training; (2) lever press training; (3) discrete trial training; (4) successive discrimination training signaled by the cue light; (5) surgery; (6)preexposure to tone; (7) successive discrimination training signaled by tone. Briefy, the first 2 phases served to habituate and train the subjects to bar press for food. In the discrete trial training phase, a bar press resulted in food reward only during illumination of both the house and cue lights. After being given free access to food for 2 days, the rats were divided into the septal-operate group and the sham-operate group. Each septal-operate rat was anesthetized and septal lesions were made stereotactically using a stereotaxic apparatus. RESULTS: In all septal operates, the lateral septum was damaged at least unilaterally. In none of the sham operates was there destruction ventral to the corpus callosum. DISCUSSION: Septal lesions appear to be the critical factor in the production of improved discrimination performance, because an effect in the opposite direction was shown by sham operates. Septal lesions appear to have a disruptive effect upon the occurrence of latent inhibition. The lesion-preexposure compound appears to result in enhancement of stimulus saliency such as that performance in a successive discrimination task can be improved, and even made superior to that of controls. Pretrial conditions may thus be of considerable importance in a wide variety of situations, and careful attention to them is critical in understanding subsequent stimulus-response relationships.
Source: Behavioral and Neural Biology 1982 Feb;34(2):141-151.
Author: Burton HA, Toga AW.
PubMed ID: 7082260
Abstract:
ABSTRACT: Rats with damage to the lateral septum in a successive discrimination task improve their performance with increasing amounts of preexposure to a previously meaningless stimulus. Septal operates receiving 270 nonreinforced tone preexposures perform at a level superior to that of controls. In normal rats, increasing the amount of preexposure to a meaningless stimulus serves to further retard sebsequent learning with that stimulus. This effect has been termed latent septum result in a direct positive relationship between the number of preexposures and performance on a successive discrimination task. Damage to the lateral nucleus of the septum appears to sensitize rats to available stimuli. The present results demonstrate that the degree of sensitization can be varied by manipulation of the number of preexposures. METHOD: The subjects used in this study were 24 naive 90-day-old female Sprague-Dawley rats. The rats were reduced to 80% of their free feeding weight during a 1-week period immediately prior to the start of the experiment. Sujects were trained and tested in either of 2 clear plastic lever boxes, each contained in a sound-proof chamber. A lever was horizontally centered on an endpanel of each box and was 10 cm from the base of the box. A food magazine and stimulus light were located to the left of the lever on the same endpanel. Auditory stimuli were presented by a 7.5 cm diameter speaker mounted behind the front panel. Each subject's participation in the experiment consisted of seven phases: (1) magazine training; (2) lever press training; (3) discrete trial training; (4) successive discrimination training signaled by the cue light; (5) surgery; (6)preexposure to tone; (7) successive discrimination training signaled by tone. Briefy, the first 2 phases served to habituate and train the subjects to bar press for food. In the discrete trial training phase, a bar press resulted in food reward only during illumination of both the house and cue lights. After being given free access to food for 2 days, the rats were divided into the septal-operate group and the sham-operate group. Each septal-operate rat was anesthetized and septal lesions were made stereotactically using a stereotaxic apparatus. RESULTS: In all septal operates, the lateral septum was damaged at least unilaterally. In none of the sham operates was there destruction ventral to the corpus callosum. DISCUSSION: Septal lesions appear to be the critical factor in the production of improved discrimination performance, because an effect in the opposite direction was shown by sham operates. Septal lesions appear to have a disruptive effect upon the occurrence of latent inhibition. The lesion-preexposure compound appears to result in enhancement of stimulus saliency such as that performance in a successive discrimination task can be improved, and even made superior to that of controls. Pretrial conditions may thus be of considerable importance in a wide variety of situations, and careful attention to them is critical in understanding subsequent stimulus-response relationships.