Ion involvement in memory formation: the potential role of astrocytes.
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Animals↗
Biomedical subjects
S F Crowe
Publications and source records attributed to S F Crowe.
Dissociation of two frontal lobe syndromes by a test of verbal fluency.
Numerous researchers have attempted to localise the behavioural manifestations of frontal pathology to the regions of the frontal lobe. Three prinicpal syndromes have been identified; the disinhibited syndrome associated with damage to the orbital area, the apathetic syndrome associated with damage to the frontal convexity, and the akinetic syndrome associated with damage to medial structures. This study attempted to determine if two of these syndromes could be dissociated from each other on the basis of a test of verbal fluency. This study used some commonly occurring clinical entities as the treatment groups. The orbitally lesioned individuals produced higher levels of disinhibited responding on the test than did non-orbitally lesioned subjects. However, all pathological groups produced lower overall levels of responding than did normals on the fluency component of the test. A number of suggestions are made as to why this may have been the case, and some guidelines for the clinical interpretation of response patterns on the fluency test are suggested.
Adult↗
Diffuse Lewy body disease and progressive dementia in a young woman.
This report details the emergence of a progressive parkinsonian syndrome, dementia and behavioural disturbance in a 33 year-old woman which can be dated to the delivery of her first child. The findings of this case indicate that cortical Lewy body disease should be considered in any patient with temporoparietal dementia and idiopathic Parkinson's disease irrespective of the age of onset.
Adult↗
Molecular mechanisms of memory formation.
Studies with neonate chicks, trained on a passive avoidance task, suggest that at least two shorter-term memory stages precede long-term, protein synthesis-dependent memory consolidation. Posttetanic neuronal hyperpolarization arising from two distinct mechanisms is postulated to underlie formation of these two early memory stages. Maintenance of the second of these stages may involve a prolonged period of hyperpolarization brought about by phosphorylation of particular proteins. A triggering mechanism for long-term consolidation is postulated to occur at a specific time during the second stage, and may involve reinforcement-contingent release of neuronal noradrenaline stimulating cAMP-dependent intracellular processes. The possibility that astroglia may have a critical role to play in these early stages of memory processing is raised.
Animals↗
Possible noradrenergic involvement in training stimulus intensity.
Day-old chicks trained on a single trial passive discrimination avoidance task using a concentrated chemical aversant, methyl anthranilate (MeA), have been shown to exhibit three stages of memory processing: short, intermediate and long term. A similar learning task with the aversant diluted to 20% in ethanol leads to short- and intermediate-term memory only, but not to long-term memory. The emergence of long-term memory has been shown to be associated with the production of a nonenergy-dependent phase of the intermediate memory stage. Subcutaneous administration of propranolol proved capable of inhibiting this nonenergy-dependent phase of memory under a number of training regimes: strongly reinforced training, and with weakly reinforced training presented twice or coupled with a selected dose of the stress-related hormone ACTH. This study supports the notion that there is a phase of memory that occurs prior to the protein synthesis-dependent phase of memory which is susceptible to interference by drugs affecting noradrenergic processes and which may be associated with the intensity of the training stimulus.
Animals↗
Forebrain noradrenaline concentration following weakly reinforced training.
Day-old chicks trained on a single-trial discriminated passive avoidance task using a concentrated taste aversant, methyl anthranilate, have been shown to exhibit three stages of memory processing; short-, intermediate-, and long-term memory. If the aversant is diluted to 20% v/v methyl anthranilate in absolute ethanol, only the short-term and some of the intermediate stage are observed. In this study we investigated the whole forebrain levels of noradrenaline in response to differing intensities of the training experience. The results show a profound difference in the level of whole forebrain NA at all training-sacrifice intervals for the trained as compared to the untrained controls, except at 15- and 20-minute posttraining, when a substantial reduction in the level of NA was achieved under all training conditions. Furthermore, subjects which received treatments which resulted in the emergence of behavioural evidence of long-term memory tended to have higher levels of whole-forebrain NA at 30 minutes after initial training. This is the time when we have postulated that triggering of protein synthesis associated with long-term memory formation takes place.
Animals↗
Neuroleptic toxicity syndromes: a clinical spectrum.
The neuroleptic malignant syndrome (NMS) has undergone a number of changes since it was first described in the 1960s. This paper presents a review of these changes from the traditional approach of rigid categorization through the more flexible operational definitions to a spectrum of neuroleptic toxicity. This spectrum spans neuroleptic-induced extrapyramidal side effects, possible stages of neuroleptic toxicity, and the full blown neuroleptic malignant syndrome. Different theoretical concepts of the syndrome have contributed to diagnostic confusion among clinicians and thus to difficulties in management. The concept of a spectrum of neuroleptic toxicity provides a coherent theoretical base for understanding NMS and thus allows for more rapid identification of the potential threat of NMS. Three cases are presented and discussed to highlight the utility of the concept of a clinical spectrum.
Adult↗
Neuropsychological dimensions of the fragile X syndrome: support for a non-dominant hemisphere dysfunction hypothesis.
This study contends that males with the fragile X syndrome feature problems in the visuospatial sphere as compared with Down syndrome males matched on vocabulary ability. Fragile X males suffer impairments of constructional functions, as demonstrated by their poor performance on block construction tests and on drawing tasks. These problems exist in association with visuoperceptive impairments, including the inability to reliably estimate angular relationships (Judgement of Line Orientation). They have shortened Digit and Corsi spans, and may feature some deficits in left hand co-ordination. The observation of a pervasive non-verbal deficit may also apply to carrier females, who despite functioning at an overall higher level, feature a similar pattern of deficits. It is possible that the deficit in non-dominant hemisphere functioning may be a pathognomonic feature of the chromosomal abnormality.
Adolescent↗
Memory consolidation of weak training experiences by hormonal treatments.
Day-old chicks trained on a single-trial passive discrimination avoidance task using a concentrated chemical aversant, methyl anthranilate (MeA), have been shown to exhibit three stages of memory processing; short-, intermediate- and long-term. A similar learning task with the aversant diluted to 20% in ethanol leads to short-and intermediate-term memory, but no long-term memory. Subcutaneous administration of selected doses of the stress-related hormones, noradrenaline, ACTH and vasopressin in close temporal proximity to the training trial, produced long-term memory in chicks trained on the weakly reinforced task, mimicking the outcome of strongly reinforced learning and of retraining with the weakly reinforced task reported previously. These effects are shown to be associated with the production of a nonenergy-dependent phase of the intermediate memory stage, postulated to be necessary for long-term memory consolidation.
2,4-Dinitrophenol↗
Memory formation processes in weakly reinforced learning.
Day-old chicks trained on a single-trail passive avoidance learning task, with varying concentrations of the aversive stimulus (methyl anthranilate), truncated retention functions for low concentrations. The retention function for a 20% v/v dilution of methyl anthranilate in absolute ethanol yielded high retention levels until approximately 40 to 45 minutes following learning. This retention function appears to consist of only the short-term and intermediate (phase A) memory stages of Gibbs and Ng's three-stage model of memory formation, with the short-term stage susceptible to inhibition by monosodium glutamate, and the intermediate stage by ouabain and dinitrophenol. The results suggest that processing of memory into the relatively permanent long-term stage may depend on the strength of the reinforcer in aversive learning.
2,4-Dinitrophenol↗
Effect of retraining trials on memory consolidation in weakly reinforced learning.
Day-old chicks given a single weakly reinforced (20% v/v methyl anthranilate in absolute ethanol) passive avoidance learning trial showed no evidence of long-term memory. A second learning trial given at 15 minutes after initial resulted in consolidation of the learning experience into long-term memory. The retention function resulting from two learning trials is similar to that observed with a single strongly reinforced learning trial, and consists of the stages postulated by Gibbs and Ng. With a dilution of 10% methyl anthranilate in ethanol, four training trials were needed to yield unequivocal evidence of long-term memory consolidation.
2,4-Dinitrophenol↗