Age-related changes in working and reference memory performance and locomotor activity in the Wistar rat

Wistar rats of three age groups were tested in an automated tunnel-maze system of variable geometry to investigate whether changes in spontaneous locomotor activity and in learning and memory develop differentially or in a correlated fashion as a function of age. Senescent (30 months) as well as mature-adult (17 months) rats showed an age-correlated decline of locomotor activity as compared to the mature-young (5 months) group. Both working-memory (measured as within-trial arm discrimination performance) and reference-memory (measured as avoidance of "blind alley" visits) were severely affected in the senescent group, whereas the middle-aged animals suffered only from a working-memory deficit. The findings provide evidence that locomotor deficits do not necessarily interfere in the assessment of age-related changes in cognitive performance. Furthermore the results support the hypothesis that working and reference memory have different underlying physiological correlates and that these neuronal systems are differentially affected by the aging process.     

Strength of scopolamine-induced amnesia as a function of time between training and testing

Variations in the strength of scopolamine-induced amnesia as a function of age of the habit were studied in Swiss Webster mice. Animals were trained in an active avoidance task to a criterion of 9/10 avoidances and immediately following training injected with scopolamine hydrochloride (1.0 mg/kg) or saline. Retention of the avoidance learning was evaluated by testing different groups of animals 1, 3, 7, 10, 14, and 28 days following training. The retention test consisted of five trials in which the CS but not the UCS was presented. Results indicated that saline-treated mice exhibited near-perfect retention up to 14 days post-training with forgetting beginning to be apparent at 28 days. Scopolamine treatment produced strong amnesia in animals tested 1 and 3 days post-training but normal retention in animals tested 7 and 10 days after learning. The amnesia abruptly reappeared at 14 days after which time it remained stable. The marked similarity of the scopolamine retention curve to changes in the strength of memory of discrimination learning in undertrained rats reported by Deutsch suggested that scopolamine resulted in the storage of a weak memory of the avoidance response. To explore this idea further we trained mice to a criterion (4/5) which would result in a weak avoidance response and tested different groups 1, 3, 10, 14, and 28 days following learning. Results showed that strength of the memory of avoidance learning increased up to 10 days and then decreased abruptly at 14 days thus replicating the general shape of the retention curve produced by injecting scopolamine following strong training. These data suggest that scopolamine disrupts processes essential for the formation of durable memories.     

Pure agraphia and Gerstmann's syndrome as a visuospatial-language dissociation: an experimental case study

A right-handed man suffered a left parieto-occipital cerebral infarction, causing agraphia with Gerstmann's syndrome but without major aphasia, alexia, or apraxia. Oral spelling was superior to written spelling. Experiments were performed involving (1) analysis of errors in writing, (2) tasks of visual imagery, and (3) identifying letters drawn without leaving a visual trace. The results suggest that the agraphia and Gerstmann's syndrome are due to a dissociation of language skills and visuospatial skills caused by a dominant parieto-occipital lesion.     

Memory and awareness in a patient with multiple personality disorder

We studied an individual with multiple personality disorder in whom each of several personalities claimed to have no direct awareness of the others and to be unable to consciously remember the experiences of other personalities. A broad selection of implicit and explicit memory tests was used to determine the extent to which one personality had access to knowledge acquired by another and the circumstances in which that knowledge would be expressed. The implicit assessment of memory was a necessary but not sufficient condition for demonstrating interpersonality access. The degree of compartmentalization of knowledge in this patient depended largely on whether the interpretation of presented information was likely to differ across personalities.     

Studies of psychosocial influences on coronary artery atherogenesis in cynomolgus monkeys

The cynomolgus macaque provides a suitable primate model for studying how psychosocial factors contribute to coronary artery atherogenesis. Important interactions with diet, sex, and behaviorally elicited cardiovascular reactivity are described.     

Concurrent-schedule performance: Effects of relative and overall reinforcer rate

Six pigeons were trained to respond on two keys, each of which provided reinforcers on an arithmetic variable-interval schedule. These concurrent schedules ran nonindependently with a 2-s changeover delay. Six sets of conditions were conducted. Within each set of conditions the ratio of reinforcers available on the two alternatives was varied, but the arranged overall reinforcer rate remained constant. Each set of conditions used a different overall reinforcer rate, ranging from 0.22 reinforcers per minute to 10 reinforcers per minute. The generalized matching law fit the data from each set of conditions, but sensitivity to reinforcer frequency (a) decreased as the overall reinforcer rate decreased for both time allocation and response allocation based analyses of the data. Overall response rates did not vary with changes in relative reinforcer rate, but decreased with decreases in overall reinforcer rate. Changeover rates varied as a function of both relative and overall reinforcer rates. However, as explanations based on changeover rate seem unable to deal with the changes in generalized matching sensitivity, discrimination accounts of choice may offer a more promising interpretation.     

Referential communication abilities of learning-disabled, language-learning-disabled, and normal school-age children

Past research in referential communication has indicated normally developing children show developmental progression in ability to communicate a specific referent to a listener. In one paradigm subjects were given lists of word-pairs in which one member of each pair was designated as the referent. It was shown that communicating about referents found in word-pairs associated in some way was more difficult than communicating about referents in dissimilar word-pairs. The present study extended this methodology to learning-disabled children. Learning-disabled, language-learning-disabled, and normally achieving children were asked to communicate about 30 pictured referents on three different tasks. On Tasks 1 and 2 each subject was asked to give a clue for the referent that would distinguish it from the other picture. Stimuli for Task 1 were 30 pairs of pictures that were related in some way and the stimuli for Task 2 were 30 pairs of unrelated pictures. Task 3 required the subjects to evaluate the adequacy of the examiner's clues for Task 1 stimuli. The disabled subjects were matched to the normally achieving subjects on the basis of receptive vocabulary age. Few differences were noted among the groups' performances on these referential communication tasks. Implications include the importance of vocabulary and concept development to referential communication.     

Response latency measurements to visual cognitive tasks by normal hearing and deaf subjects

Visual cognitive differences between hearing (N = 16) and deaf (N = 32) high-school and middle-school students were studied. Visual tasks were presented on a microcomputer and response latencies were collected. Significant differences were noted between the deaf and normal groups but not between total communication deaf and oral deaf students. These differences support the hypothesis that deaf students prefer a visual cognitive strategy. Implications for educating the deaf are discussed.     

Listeriosis of the central nervous system in children beyond the neonatal period

Observations on three children with neurolisteriosis (one case of meningitis, two cases of meningoencephalitis, each Serovar 4 b), show that even after the neonatal period, listeriosis must not be ignored in the process of diagnosis and therapy. It is the bacteriological examination of the cerebrospinal fluid, together with the blood culture, and not clinical symptoms and serology that guarantee a timely diagnosis and therapy (ampicillin and gentamicin).