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Biomedical subjects

S Coyle

Publications and source records attributed to S Coyle.

15 recordsLinked to original sources

The effects of age on auditory event-related potentials.

The effects of age on event-related potentials (ERPs) elicited during a two-tone discrimination ("oddball") task were examined in 97 normal subjects aged from 17-80 years. Strong relationships were found between age and the latencies of the later ERP components N200 and P300. Furthermore the correlation between age and N200 latency at Pz was marginally higher than that of age and P300 latency. For the entire sample, the increase in P300 latency as a function of age was best described at Cz and Pz by linear regression equations. However, a segmented line model better described the P300/age relationship at Fz--the increase in P300 latency with age in subjects over 61 was five times that of subjects younger than 61 years. In this study the task required button-press identification of the targets--the significance of increased age and a delay in N200 latency is discussed with reference to the possibility of N200 latency indexing the speed of cognitive processing.

Adolescent

Normal latency of the P300 event-related potential in mild-to-moderate Alzheimer's disease and depression.

A two-tone-discrimination task was used to elicit the P300 component of event-related (brain) potentials (ERPs) from patients with presumed Alzheimer's dementia of mild or moderate severity, depressed patients of older age, and cognitively normal individuals. Although the average P300 latency of the Alzheimer patients was greater than that of the depressed patients, which in turn was greater than that of older aged normals, none of the group differences in latency were statistically significant. Moreover, when latency was examined on an individual basis, less than one-quarter of the Alzheimer patients had an abnormally delayed P300 for their age. Reaction times and the percentage of correct behavioral responses to the tones did distinguish the Alzheimer from the normal group; on both measures the patients' scores were significantly worse. It was concluded that the performance of a simple tone discrimination task requiring a button-press response does not sufficiently tax those cognitive functions impaired in the earlier stages of Alzheimer's dementia to result in abnormally slowed cognitive processing of the kind reflected in P300 latency.

Aged

P300 event-related potentials in de novo Parkinson's disease.

Recent studies indicate subtle cognitive deficits in many non-demented Parkinson's disease (PD) patients. Long-latency event-related potentials (LL-ERPs) index the nature and timing of a cognitive response to a stimulus and have been used to assess cognitive function in PD. Studies to date have only assessed patients receiving long-term anti-PD therapy, which may itself affect information processing. In this study we recorded the P300 using a standard auditory oddball paradigm with a button-press response in a group of de novo patients. A P300 was absent in 2 patients and prolonged in 2 patients but there was no difference in the latency or amplitude of the P300 in the Parkinsonian group compared with the age-matched control group. The averaged P300 of the young PD group was dispersed compared with that of the young controls. Our findings suggest that the amplitude and latency of P300 elicited using the paradigm of this study are not sensitive indices for differentiating PD patients from controls. A paradigm which places a greater load on the specific cognitive deficits of PD will be investigated. The dispersion of the P300 component in the young PD group may be support for the suggestion of distinct subgroups in PD. Our findings suggest that the latency and amplitude of LL-ERP components elicited by our paradigm were not sensitive indices for distinguishing PD patients from controls. The significance of the prolonged P3-RT measure is not clear.

Adult

The relationship between reaction time and latency of the P300 event-related potential in normal subjects and Alzheimer's disease.

The latency of the P300 event-related potential is though to reflect the time it takes to conclude that a task-relevant stimulus has been presented, i.e. it is an index of cognitive processing time. Reaction time (RT) also reflects cognitive processing time, but additionally reflects the time taken physically to respond to the stimulus. If serial models of information processing are correct, then the P300 latency must be less than RT, and a positive correlation between the 2 measures is to be expected. We examined these hypotheses in 100 normal subjects aged from 18 to 92 years. The P300 component elicited via a 2-tone discrimination task, and RT to the task-relevant tones was measured simultaneously. The resulting correlation between these measures was weak (r = 0.26, p greater than 0.05), and there were instances in which RT preceded the P300 latency. These results are consistent with parallel rather than serial models of information processing. Fifteen patients with Alzheimer's disease were also examined. Three had an abnormally delayed P300 latency, and 7 had abnormally delayed RTs compared with age-matched controls. Simultaneous measurement of the P300 latency and RT may thus help resolve whether dysfunction is evident in neuronal networks concerned with stimulus evaluation or in those concerned with response execution.

Adult

The trometamol salt of fosfomycin: microbiological evaluation.

The spectrum of activity of fosfomycin and its pharmacological behaviour make it an attractive candidate for the oral treatment of uncomplicated urinary tract infection. Various factors affect the antibacterial activity so that results in different culture media vary widely. The highest activity was displayed in Eugonbroth and such results correlated well with those obtained in pooled human urine. The activity was enhanced in acid conditions such as commonly exist in infected urine. Glucose-6-phosphate potentiated the activity of fosfomycin against Escherichia coli and some other bacteria when tested in Eugonbroth (but less predictably in human urine) and the potentiating effect may be necessary in order to obtain therapeutically meaningful results in susceptibility tests. Experiments in an in vitro model of the treatment of bacterial cystitis (carried out in the absence of glucose-6-phosphate) indicated that both sensitive and 'resistant' strains of E. coli respond to concentrations of fosfomycin achievable by high-dose oral therapy with the trometamol salt. Resistance did not emerge in previously sensitive strains (or in one of the 2 'resistant' strains), providing a high peak level of antibiotic was achieved.

Culture Media

Ontogeny of striatal unit activity and effects of single or repeated haloperidol administration in rats.

Development of striatal unit activity recorded from chloral hydrate anesthetized, neonatal rats was characterized electrophysiologically following acute or repeated haloperidol administration. No spontaneously active single units were detected in 8 day old pups. Spontaneous activity was recorded by 17 days of age, although the number of active cells, firing frequency and the variety of firing patterns were less diverse than those observed in 28 day olds. There were also age related differences in striatal unit responses to haloperidol. A significant increase in activity was induced by acute haloperidol administration only in 28 day old animals. No tolerance to the acute effects was demonstrated. Both 17 and 28 day olds responded to repeated haloperidol injections, followed by a 24 h recess, with an increase in striatal activity. These results may assist our understanding of the effects of human fetal, neonatal and/or adolescent exposure to neuroleptics.

Animals

Effects of TRH, ethanol, and TRH-ethanol combination on activity in rats with altered monoamine content.

Investigations were undertaken with 5,7-dihydroxytryptamine and 6-hydroxydopamine treated rats to see whether activity changes induced by TRH, ethanol and the TRH-ethanol combination would be affected after reduced monoamine function. In keeping with earlier results, TRH increased activity, ethanol reduced activity and the TRH-ethanol combination produced activity counts greater than those for TRH alone. Neither the 5,7-dihydroxytryptamine-induced reduction of brain serotonin nor the 6-hydroxydopamine treatments which reduced brain catecholamines altered the hyperactivity induced by TRH or the TRH-ethanol combination. While reduction of brain serotonin did not affect the ethanol-induced changes in activity, preferential reduction of dopamine as well as reduction of both norepinephrine and dopamine significantly antagonized this measure of ethanol-induced depression. The reduction of dopamine alone produced the greatest effect on this action of ethanol. It can be concluded from the data that the increased locomotion induced by TRH and the TRH-ethanol combination does not depend upon endogenous monoamines, whereas the sedative effects of ethanol are apparently influenced by alterations in brain catecholamine function.

5,7-Dihydroxytryptamine

Ontogeny of tolerance to haloperidol: behavioral and biochemical measures.

Developing and adult Sprague-Dawley rats were tested after acute or repeated haloperidol administration. Although 8-day-old rat pups showed a form of immobility in response to a single injection of haloperidol (1 mg/kg), 14-day-old rats did not show any behavioral response to the neuroleptic. By 21 days of age, an acute dose of haloperidol induced a cataleptic response similar to that described for adult animals. Following 7 days of repeated haloperidol administration, the cataleptogenic effects of haloperidol were attenuated in animals aged 21 days and older, but not in 8- and 14-day-old rats. Subjects were sacrificed 70 min after the injection of the test dose of haloperidol or saline and the corpus striatum and olfactory tubercles were dissected for HPLC determination of dopamine (DA) and its metabolites, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC). In the corpus striatum, an area believed to be important for DA-related catalepsy, acute and repeated haloperidol induced a slight increase in concentrations of HVA in 8-day-old rats, and an increase in both DOPAC and HVA concentrations in animals aged 14 days and older. Tolerance after repeated haloperidol administration, in the form of an attenuation of the haloperidol-induced increase in DA metabolites, was not apparent until 35 days of age. These data contrast with the behavioral data, which indicate that the ability to develop a tolerance to the cataleptogenic effects of haloperidol matures by 21 days of age. The pattern of responses in the olfactory tubercles differed from those observed in the striatum. Following acute haloperidol, subjects did not show any increase in HVA until 14 days of age, and in both HVA and DOPAC until 21 days of age. At no age, including adults, was one week of repeated administration of haloperidol sufficient to induce tolerance to the effects of haloperidol on DA metabolites in the olfactory tubercles. In addition to providing information about the development of certain aspects of DA systems in rats, these studies suggest that an attenuation of the haloperidol-induced increase in DA metabolites is not necessary for the development of tolerance to haloperidol-induced catalepsy.

3,4-Dihydroxyphenylacetic Acid

Effects of prior aversive stimulation on heart rate responses to open field exposure in the rat.

Heart rate (HR) responses to open field (OF) exposure were compared between rats previously exposed to intense, inescapable electric shock (preshock, PS) and Controls. Results indicated that (1) Control animals showed a steady increase in HR across a 3 min exposure on each of 4 days of testing, while PS animals showed an initial HR deceleration followed by partial recovery on each day; (2) the HR response of PS animals in the OF was not related to any HR response to shock during treatment; and (3) the HR responses of both PS and Control animals were specific to the OF situation, with both groups showing steady HR deceleration across 3 min after being placed in their home cages. Results were discussed in terms of (1) the apparently altered perception of environmental change produced by PS, and (2) the possible role of HR acceleration in Controls in terms of minimizing the impact of aversive stimulation.

Animals