Showing papers on "Working memory published in 1977"

Maturation of prefrontal cortex in the monkey revealed by local reversible cryogenic depression.

Abstract: THE emergence of increasingly complex cognitive functions with age is widely assumed to reflect in part the maturation of connections within the central nervous system, but the neural bases of cognitive development have resisted identification. There is some evidence to indicate that the dorsolateral prefrontal association cortex in monkeys acquires its adult functional capacities over a protracted span of postnatal development1–3. Most of this evidence, however, has come from studies involving surgical ablation. The study of cerebral development in brain-damaged subjects is complicated by anterograde and retrograde degenerative changes, as well as by the possibility of compensatory neural reorganisation which could occur during the weeks or months between surgical ablation and assessment of behavioural performance4. It is now possible to study the functions of specific brain sites without producing permanent brain damage by localised cortical cooling, a method which allows reversible inactivation of restricted regions of cortex in otherwise normal animals. The latter are able to serve as their own controls before and after the episodes of cortical hypothermia5–7. This method has previously been used only in research on mature animals. In this study, local hypothermia was produced for the first time in the dorsolateral prefrontal cortex of young, developing rhesus monkeys during repeated assessment of their performance on a delayed-response task. Such performance in adult monkeys is known to be dependent on the integrity of that region8. Our findings provide direct evidence that part of the dorsolateral prefrontal association cortex does not become functionally mature until at least 34–36 month of age, that is, close to sexual maturity in this species.

Brain self-stimulation: direct evidence for the involvement of dopamine in the prefrontal cortex

Abstract: Rats were trained to self-stimulate the medial prefrontal cortex, a region rich in dopaminergic terminals. After the region adjacent to the electrode site was labeled with [14C]dopamine, it was perfused repeatedly by means of push-pull cannulas. Electrical stimulation of this cortical area in six animals enhanced the release of dopamine and its associated metabolites in nine of 16 experiments. Thus in vivo evidence is provided that dopamine is involved in the brain self-stimulation mechanism within the frontal cortex.

Limits to conceptual rule‐learning by schizophrenic patients

Abstract: Two studies of conceptual rule-learning by 36 hospitalized psychiatric patients revealed that (a) while all were clinically diagnosed as schizophrenic, they differed widely in their ability to discover abstract rules; (b) the Whitaker Index of Schizophrenic Thinking (WIST) strongly predicted the patients' ability to learn and to apply a conceptual rule; and (c) regardless of severity of conceptual impairment, the patients were unaffected by modest levels of externally generated irrelevant information as presented through the modality of vision. Deficits in abstractive ability, when they exist, are believed to be due to a schizophrenic patient's inability to prevent task-irrelevant information that originates in long-term memory from spilling into and despoiling the operations of working memory.