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Biomedical subjects

S F Crowe

Publications and source records attributed to S F Crowe.

At least 37 records · Page 2Linked to original sources
PubMed1997

Both ethanol toxicity and thiamine deficiency are necessary to produce long-term memory deficits in the young chick.

This series of studies revealed that a 2.5-mg dose of oxythiamine administered over 2 days yielded memory deficits from 10 min following passive avoidance learning. This result existed in association with slowing of righting reflex. Administration of thiamine reversed the memory deficit and the slowing of the righting reflex. A combination of oxythiamine and peripheral alcohol administration also resulted in memory deficits appearing from 10 min after training; however, in contrast to the effect of thiamine deficiency alone, the deficits induced by thiamine deficiency in association with acute administration of alcohol could not be reversed by thiamine resupplementation. The combination of alcohol and oxythiamine also slowed the righting reflex, but higher doses of thiamine also were unable to ameliorate the memory deficit caused by a combination of oxythiamine and alcohol; however, the slowing of righting reflex was reversed. The results suggest that preexistent thiamine deficiency may make the subject susceptible to the neurotoxicological effects of alcohol on memory function.

Animals↗
PubMed1997

Administration of DL-2-amino-5-phosphonovaleric acid (AP5) induces transient inhibition of reminder-activated memory retrieval in day-old chicks.

DL-2-Amino-5-phosphonovaleric acid (50 microM) administered immediately after a visual reminder presented to day-old chickens between 7.5 min and 24 h following a single trial passive avoidance learning task produced transient losses of memory on retention test, an effect not observed in the absence of a reminder or when the reminder was given 48 h post learning. The duration of the transient deficits decreased with increasing interval between training and the reminder trial. The time of onset of memory loss after the reminder trial appeared to increase with increasing interval between the training and the reminder trials. The results suggest that, for a period of at least up to 24 h after passive avoidance training, retrieval of memory may lead to processes which are sensitive to inhibition by the NMDA receptor antagonist AP5, with the duration of sensitivity post retrieval decreasing as the period of memory consolidation increases. The results extend previously reported findings and suggest the possibility that consolidation of a stable memorial representation of a learning experience may take over several days and may entail the concurrent laying down of a stable retrieval mechanism.

2-Amino-5-phosphonovalerate↗
PubMed1997

Deterioration in the production of verbal and nonverbal material as a function of time is contingent upon the meaningfulness of the items.

The performances of 100 university students were compared for their levels of production on fluency tests for verbal and nonverbal material that was manipulated to be meaningful or nonsense. For both the meaning conditions there was a significant deterioration in performance as a function of time, while production of the nonsense items remained constant. The results are consistent with the notion that the obligation for the items on the Verbal Fluency Test to be meaningful may require that the subject draws on the available word store, resulting in deterioration of performance as this word store is exhausted.

Journal Article↗
PubMed1997

Salbutamol overcomes the effect of the noradrenergic neurotoxin DSP-4 on memory function in the day-old chick.

These experiments investigated the effect of the relatively selective noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) on memory formation in day-old chicks trained on a discriminated passive avoidance task. A time course study showed that DSP-4 treatment resulted in amnesia as early as 20 min post-learning. In a second study, a series of alpha- and beta-adrenergic agonists (noradrenaline; the alpha 1 agonist phenylephrine; the beta 1 agonist dobutamine; and the beta 2 agonist salbutamol) were applied immediately after the training trial. Both noradrenaline and salbutamol were effective in ameliorating the memory deficits caused by DSP-4 treatment, and in consolidating weakly reinforced training. These studies support the notion that noradrenaline subserves a vital role in the consolidation of memory in the chick, and that the beta 2 receptor subtypes are principally involved in the intermediate phase of memory formation.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1996

Administration of lanthanum chloride following a reminder induces a transient loss of memory retrieval in day-old chicks.

Lanthanum chloride (5.0 mM) administered immediately after a visual reminder presented to day-old chickens between 7.5 min and 48 h following a single trial passive avoidance learning task produced an immediate but transient loss of memory on retention test, an effect not observed in the absence of a reminder. The duration of the transient deficit was relatively stable with lanthanum chloride consistently inducing a loss of memory that was evident 5 min after the reminder, with recovery by 10-15 min. The results suggest that, for a period of at least up to 48 h after passive avoidance training, the activation of memory retrieval by a reminder stimulus may lead to processes which are sensitive to inhibition by the calcium channel antagonist lanthanum chloride. These results extend previously reported findings implicating the involvement of glutamate-sensitive channels in a transient memory process that is also activated as a result of a reminder stimulus, but that is no longer present 48 h after training. The glutamate-sensitive mechanism appears to be a secondary mechanism activated following memory retrieval and to be dependent on the level of memory consolidation that the memory for the original experience has undergone. The results presented here suggest that lanthanum chloride, a calcium channel antagonist, inhibits memory retrieval in the day-old chick. This effect implicates calcium channel mediated processes in immediate memory recall. Further, the results suggest the lanthanum inhibits a primary mechanism, that precedes that glutamate-sensitive mechanism identified previously and that both are dependent on the activation of memory retrieval by a reminder.

Animals↗
PubMed1995

Administration of glutamate following a reminder induces transient memory loss in day-old chicks.

Monosodium glutamate (4.0 mM) administered immediately after a visual reminder presented to day-old chickens between 7.5 min and 24 h following a single trial passive avoidance learning task produced transient losses of memory on retention test, an effect not observed in the absence of a reminder or when the reminder was given 48 h post-learning. The duration of the transient deficit decreased with increasing interval between the training and the reminder trial. The time of onset of memory loss after the reminder trial appeared to increase with increasing interval between the training and the reminder trials. The results suggest that, for a period of at least up to 24 h after passive avoidance training, retrieval of memory may lead to processes which are sensitive to inhibition by glutamate, with the duration of sensitivity post-retrieval decreasing as the period of memory consolidation increases. The results extend previously reported findings with rodents and suggest the possibility that consolidation of a stable memorial representation of a learning experience may take place over several days and may entail the concurrent laying down of a stable retrieval mechanism.

Animals↗
PubMed1995

Meta-analytic comparison of the components of visual cognition in Parkinson's disease.

Controversy surrounds the presence of deficits of visual cognition in Parkinson's Disease. This literature has been seriously undermined by a number of methodological and theoretical faults that make interpretation of this hypothesis difficult. This review proposes a structure of visual cognition composed of 13 aspects. A meta-analysis of these components on 70 studies that used standardised neuropsychological tests and an appropriate normal control group indicates that the PD subjects are significantly compromised on tests of attention and concentration, complex visuospatial functions, and multifactorial spatial functions. More detailed analysis of the basic components of visual cognition was not undertaken due to low statistical power; hence, it remains unclear whether these subjects have primary visual processing deficits in association with their higher order deficits. The observed deficits may be interpreted as being a consequence of either undetermined lower level visual cognitive deficits or a compromise in executive functioning.

Adult↗
PubMed1994

2-deoxygalactose interferes with an intermediate processing stage of memory.

The effect of 2-deoxygalactose (2-D-gal), an inhibitor of glycoprotein synthesis, on memory formation was investigated with the day-old chick trained on a single-trial passive discrimination task. 2-D-gal (10 mumol/chick) was shown to inhibit memory formation at a time before the emergence of an antibiotic-sensitive long-term memory stage. The amnestic effect of 2-D-gal was successfully prevented by galactose, and more significantly by noradrenaline. In contrast, anisomycin-induced amnesia was resistant to challenge by either galactose or noradrenaline. The results are consistent with the view that some glycoprotein involvement in memory formation occurs prior to the formation of protein synthesis-dependent long-term memory, and this role of glycoproteins may be associated with the triggering of long-term memory formation by noradrenaline.

Animals↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1991

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↗
PubMed1991

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↗
PubMed1991

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↗
PubMed1991

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↗
PubMed1990

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↗
PubMed1990

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↗
PubMed1989

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↗