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Biomedical subjects

L Hayward

Publications and source records attributed to L Hayward.

16 recordsLinked to original sources
PubMed1992

Sleep disordered breathing and cognitive function in a retirement village population.

Sleep disordered breathing (SDB) may be associated with cognitive dysfunction in non-demented elderly people. A random sample of 96 retirement village residents were given both neuropsychological assessment and overnight sleep monitoring with a portable microprocessor based system (Vitalog PMS-8). Respiratory disturbance index (RDI) was calculated as the number of apnoeas and hypopnoeas per hour of sleep. RDI was not associated with 'memory', 'verbal', and 'motor' factors identified from the analysis of cognitive tests, but was associated with the 'cerebral efficiency' factor (R2 = 0.21, p less than 0.0001). Seventy-three subjects had repeat neuropsychological tests, median time to follow-up being 17 months. Baseline RDI did not predict changes in scores on the two factors identified from the second analysis. We conclude that mild to moderate disturbance of breathing during sleep is not associated with cognitive dysfunction in non-demented subjects.

Activities of Daily Living↗
PubMed1992

Blood alcohol levels in suicide cases.

STUDY OBJECTIVE: The aim was to investigate the relationship between alcohol consumption prior to suicide and the act of suicide. DESIGN: This was a retrospective total ascertainment survey of a three year cohort of suicides in Western Australia. SETTING: Coroner's records of suicide in Western Australia between 1986 and 1988 inclusive. PARTICIPANTS: The study involved 515 consecutive suicides: 414 males and 101 females. MAIN RESULTS: Information on blood alcohol levels at time of death, presence of other drugs at time of death, drug and alcohol abuse history, psychiatric history, life events prior to death and method of suicide were collected. It was found that 35.8% of cases had a positive blood alcohol reading. Those who had been drinking alcohol prior to suicide were younger, more likely to be male, more likely to have chosen carbon monoxide as the method of suicide, more likely to have experienced a break up of a relationship and less likely to have sought professional help than those who had not been drinking. CONCLUSIONS: Data from the present study do not provide evidence for a causal relationship between alcohol consumption and suicide. Differences between those who had consumed alcohol and those who had not are suggestive of a contributory role of alcohol to a decision to commit suicide in a subset of suicide cases.

Alcohol Drinking↗
PubMed1991

Effects of muscle fatigue on mechanically sensitive afferents of slow conduction velocity in the cat triceps surae.

1. Group III and IV muscle afferents have been shown to be sensitive to both mechanical stimuli and metabolic and thermal changes in muscle. To establish the potential role of slowly conducting muscle afferents in regulating motor output during fatigue, we recorded from mechanically sensitive group III and nonspindle group II afferents originating in the triceps surae in barbiturate-anesthetized cats. We evaluated the response of these afferents to tetanic muscle contraction, stretch, and surface pressure, before, during, and after fatigue. 2. Our results show that muscle fatigue both increases spontaneous discharge in these mechanically sensitive afferents and sensitizes their response to muscle stretch, surface pressure, and, in a few instances, muscle contraction. These fatigue-induced changes typically occurred after 5-10 min of submaximal fatiguing stimulation. 3. During recovery from muscle fatigue, several contraction-sensitive free nerve endings, which had become sensitized to contractions during fatigue, remained sensitized after 20-30 min of rest. 4. The results of this study provide support for the hypothesis that fatigue-induced excitation of slowly conducting afferents is significant in mediating fatigue-induced inhibition of motoneuron output. However, our finding that the discharge of many slowly conducting mechanoreceptor afferents declines during the initial phase of fatigue argues against a primary role for these afferents in mediating the initial decline in motoneuron rate that is so prominent in fatiguing maximum voluntary muscular contraction.

Afferent Pathways↗
PubMed1990

Neural mechanisms underlying the clasp-knife reflex in the cat. II. Stretch-sensitive muscular-free nerve endings.

1. The goal of this study was to determine the contribution of muscular free nerve endings to the clasp-knife reflex by comparing their response properties and reflex actions to the clasp-knife reflex. 2. The responses of single muscle afferents were examined in anesthetized cats using stretch and isometric contraction of ankle extensor muscles identical to those that evoked clasp-knife inhibition in decerebrated and dorsal spinal-hemisectioned cats. 3. Fifty-three stretch-sensitive mechanoreceptor afferents were identified as free nerve ending afferents based on their conduction velocities, location within the muscle, uniformity of response, and dissimilarity to other muscle proprioceptors. The afferent conduction velocities were in both the group III (56%) and group II (44%) range, including five fast-conducting group II afferents (greater than 55 m/s). 4. The stretch response of stretch-sensitive, free nerve endings (SSFNEs) showed several characteristic features: 1) afferents were excited only by large stretches that produced significant passive force; 2) afferent activity began after a brief delay and exhibited segmentation of discharge during ramp stretch, a maximum at the end of ramp stretch, and rapid and complete decay during static stretch, and 3) afferent response adapted to repeated stretches. These properties match those of clasp-knife inhibition described in the companion paper, except that the SSFNE segmentation and maximum were more pronounced and their decay during maintained stretch was more rapid. 5. Isometric contraction produced by electrical stimulation of the muscle nerve, which induced force-evoked inhibition in decerebrated and dorsal hemisectioned cats, also consistently excited SSFNEs. Stretch evoked greater excitation than contraction, indicating that both length and force contribute to SSFNE activity. 6. Stimulation of free nerve endings by squeezing the achilles tendon in cats exhibiting the clasp-knife reflex evoked powerful, homonymous inhibition and a flexion-withdrawal pattern of reflex action--that is, inhibition of extensor and excitation of flexor muscles throughout the hindlimb, which parallels the spatial divergence of the clasp-knife reflex. 7. Intrathecal application of capsaicin, which preferentially blocks the reflex actions of small afferent fibers, blocked clasp-knife inhibition in decerebrated, dorsal hemisectioned cats. 8. The similarities between the reflex actions and response properties of SSFNEs and the properties of the clasp-knife reflex suggest that SSFNEs mediate clasp-knife inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1989

Factorial validity of the EE scales.

High 'expressed emotion' (EE) has been held to be predictive of a poor course in patients with schizophrenia, a finding that has emphasized the predictive validity of the EE measure. We review appropriate research examining properties of the EE measure to suggest that, in particular, little is known about the construct validity of the EE measure. We report a longitudinal study examining three measures of parental style (EE; Parental Bonding Instrument or PBI; and interviewer ratings). By comparing EE scale scores with ratings derived by an interviewer we find support for the accuracy of the process generating EE scale scores, and by factor analytic techniques we examine the factorial (construct) validity of the EE scales. A principal components analysis suggested two other dimensions of relevance in parents involved with a schizophrenic member (vigilance, and acceptance of illness in their child) which may be of value in predictive studies. We examined the capacity of interviewer-generated scores (as a simple clinical rating) and factor scores (as central constructs) to predict the course, and were unable to discriminate 'relapsers' and 'non-relapsers' with either predictor.

Adaptation, Psychological↗
PubMed1988

Increased inhibitory effects on close synergists during muscle fatigue in the decerebrate cat.

We compared the magnitude of reflex inhibition induced in the soleus muscle by contraction or stretch of the medial gastrocnemius (MG), before, during, and after electrically induced fatigue of the MG. Our findings are that MG fatigue is accompanied by a substantial increase in soleus inhibition, which then recovers with MG rest. This increased inhibition may explain, at least in part, the decline in motoneuron discharge rate that has been described in fatiguing human muscle.

Animals↗
PubMed1988

Parental 'expressed emotion' as a predictor of schizophrenic relapse.

Fifty-seven schizophrenic patients were initially assessed after admission to hospital, at which time their parents completed a Camberwell Family Interview, generating "expressed emotion" (EE) scores. Relapse over the next nine months was not predicted by household EE status or by individual EE scales. Multivariate analyses suggested that a poor course after hospitalization was best predicted by a poor course before admission and by living in a one-parent household. High household EE status was a predictor only in one multivariate analysis after course of illness and one-parent household status had been entered, suggesting an interaction effect. We query the causal proposition linking high EE and relapse and suggest instead that a poor illness course may elicit high EE in relatives, particularly in one-parent households, and, thus, may make the principal contribution to the proposed link.

Adult↗
PubMed1988

Prediction of schizophrenic relapse using the parental bonding instrument.

After admission, 57 schizophrenic patients completed two versions of the Parental Bonding Instrument (PBI) to assess perceived recent and earlier parenting attributes. The parents were also assessed using the Camberwell Family Interview to generate Expressed Emotion (EE) scores. The schizophrenic patients, compared to matched non-clinical controls, reported a significantly greater chance (50% vs 26%) of exposure to "affectionless control" from their father. Nine months later, the subjects were re-interviewed and their relapse status determined. The PBI measure assessing parenting over the first 16 years had greater utility than the recent parenting version of the PBI. When re-calibrated, only the father's scores on the early parenting PBI scale discriminated "relapsers" and "non-relapsers". A multivariate analysis suggested that pre-established illness criteria and other family factors were the clearest predictors, and that PBI-defined constructs (as for EE measures) failed to add significantly to the discriminant function. The extent to which EE and PBI scales might measure similar constructs was examined, with only weak links being suggested.

Adult↗
PubMed1987

Can localised brain impairment be simulated on neuropsychological test profiles?

We asked 28 registered nurses with varying degrees of experience in working with neurological and neurosurgical patients to fake results on 10 neuropsychological tests in such a way as to be congruent with a history of trauma to the left fronto-temporal cortex. We compared these data to those obtained from 21 patients who had been referred with verified cerebral injury and who had a diagnosis of left fronto-temporal dysfunction. The overall hit rate of classification for the two groups was 85.7% and 89.8%, depending on the way in which test scores were combined. Results showed that a knowledgeable group of informed fakers had great difficulty reproducing the test performance of individuals with left fronto-temporal impairment.

Adult↗
PubMed1986

Lung function and within-breath changes in resistance in patients who have had a laryngectomy.

We describe the construction of a simple device which may be used to connect a patient with a tracheostomy to standard lung function testing equipment. We compared the lung function of nine patients after laryngectomy with nine patients matched for similar degrees of airflow obstruction, and found that peak flow rate (as per cent predicted) was significantly lower than predicted FEV1 in the patients with tracheostomy. This suggests that the larynx may normally affect production of peak flow. We then compared the change in resistance over the normal tidal volume in the two groups, finding no significant difference, and obtained similar results from paired studies in two patients before and after laryngectomy. We conclude that, while the laryngeal aperture varies during tidal breathing, it plays no major part in the overall resistance changes which occur during a normal breath.

Adult↗
PubMed1985

Early sensory-perceptual changes in Huntington's disease.

Forty-four patients at risk for Huntington's disease and seventeen diagnosed as having the disease were studied longitudinally over a nine-year period to assess the evolution of cognitive impairment. Results showed that there were measurable changes in sensory-perceptual functions well in advance of the emergence of the movement disorder. Discrimination between patients with Huntington's disease and those at risk for the disease based on tests of sensory-perceptual functioning resulted in a correct classification rate of 95.1%. Subjects who had changed from being at risk to having the disease nearly all had discriminant scores from their first test sequence lying in either the disease range or the pre-symptomatic disease range. The present organic model of Huntington's disease is discussed in light of these findings and implications of the mathematical model underlying prediction are discussed.

Adolescent↗
PubMed1981

Conditioned taste preferences based on caloric density.

Conditioning involved adding one flavor (e.g., vanilla) to an artificial diet of high caloric density and a second flavor (e.g., anise) to a similar low-calorie diet. When the rats were tested with identical foods to which the flavors were added, they showed a strong preference for the high-calorie flavor. The parameters of conditioning were varied in four experiments, which showed that the conditioning of taste preferences is rapid and powerful and has generality over a range of conditioned stimulus parameters. The last experiment indicated that the unconditioned stimulus for this conditioning is probably some oral cue, such as the taste of starch, which is correlated with caloric benefit, rather than caloric benefit per se.

Animals↗
PubMedDate not supplied

Parental representations of neurotic and endogenous depressives.

Low parental care and parental overprotection have been incriminated as risk factors to depression in adult life. The relevance of these parental characteristics to broad depressive 'types' with their varying imputed aetiologies was assessed by having 26 patients with endogenous depression (ED) and 40 with neurotic depression (ND) complete the Parental Bonding Instrument (PBI) self-report measure. In comparison to their controls, the EDs did not differ on the parental care and overprotection scales. The NDs, by contrast, were more likely than their controls to report their parents as uncaring and overprotective. A PBI care scale score of less than 10 was particularly discriminating, being reported by 3.8% of the EDs and 37.5% of the NDs. While findings support the binary view of depression in terms of broad imputed aetiological factors, several response biases which might influence the findings are considered.

Adult↗