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Biomedical subjects

M W Donald

Publications and source records attributed to M W Donald.

At least 19 recordsLinked to original sources
PubMed1990

Brain responses to semantic incongruity in bilinguals.

Event-related potentials were examined in the first and second languages of bilinguals, and in monolinguals. Stimuli were anomalous sentences presented one word at a time on a CRT monitor. The principal dependent measure was the N400 component, and an accompanying frontal negativity, which provided an estimate of the amount of time the nervous system takes to determine the semantic incongruity of a given word. The results indicate that N400 latency is slightly, but significantly, delayed in bilinguals, with monolinguals having the shortest mean N400 latency, the first language of bilinguals next, and the second language of bilinguals longest. The frontal negativity varied in amplitude somewhat independently of the parietal N400. The amplitude of the frontal negativity was sometimes reduced in the second language, tending to be smaller in those subjects who used their second language the least. Neither N400 nor the frontal negativity varied as a function of age of acquisition of the second language. The results are discussed with reference to the relative automaticity of language in bilinguals, and the sensitivity of N400 to variations in the automaticity of language processing.

Adult↗
PubMed1984

Neuropsychological function in diabetic patients with neuropathy.

Psychometric examination of a group of diabetic patients and a group of age-matched controls failed to provide evidence of impaired intellectual functioning in the diabetic group. The cognitive status of the diabetics was not related to the duration of the illness, the age at diagnosis, or clinical ratings of peripheral or autonomic neuropathy.

Adolescent↗
PubMed1984

Psychiatric aspects of diabetes mellitus.

A descriptive study of the psychiatric findings in 50 insulin--dependent diabetics is presented. Among the symptoms found were a marked reduction in energy level, increased fatigue and irritability, depression, and delayed psychosexual maturation. Diabetes mellitus is commonly considered to be a disease that, if properly controlled, allows the patient to lead a relatively normal life. We found, however, that these symptoms often made the patients' lives uncomfortable, reduced their functional capacity, disrupted their family life, and disturbed the adolescence of those who were affected at an early age.

Adolescent↗
PubMed1984

Functional correlates of reduced central conduction velocity in diabetic subjects.

In a previous publication, we presented evidence of slowed conduction speed in the central nervous systems of insulin-dependent diabetic subjects, manifest in a delay in the latency of the brainstem auditory-evoked response (BAER). In this article, we present the results of a multivariate study conducted on a larger sample of 50 insulin-dependent, adult diabetic subjects. The purpose of the study was to determine some of the functional correlates of the BAER delay; each patient received an assessment of the BAER, the late auditory-evoked potential (EP), the conduction velocities of the sural, median, and common peroneal nerves, and intellectual and emotional function, in addition to neurologic and audiologic examinations. A nondiabetic control group was matched with the diabetic group as to age and sex. The results indicated a delay in the latency of wave V, and in interpeak latencies I-III and I-V, of the BAER. The most reliable effect was on interpeak latency I-V; this suggested that the locus of the delay was in the central auditory projections, rather than in the acoustic nerve. In addition, BAER waves I, II, III, IV, and V were reduced in amplitude, as was the N1 component of the late auditory EP; the most reliable reduction in amplitude was in wave V. The effect was similar in magnitude for males and females, relative to their counterparts in the control group. The slowed BAER response appeared early in the disease and was not related to the duration of insulin treatment. It was correlated with a chronic loss of energy and the presence of sexual dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Electromyographic biofeedback and physical therapy of the hemiplegic upper limb.

A long-term, comparison-group outcome trial with a partial crossover design was carried out on the effects of electromyographic biofeedback (EMGBF) plus physiotherapy (PT) versus PT alone in the treatment of the hemiplegic upper limb in stroke patients who were at least six months beyond the onset of their disability. Both the experimental and the control groups benefited from their treatment, but EMGBF was shown to have an additional effect, both in the experimental patients, and in the control patients when they switched over to the experimental treatment condition.

Arm↗
PubMed1982

A time-course analysis of attentional tuning of the auditory evoked response.

This study examined the time course of attentional tuning of the N1 and P3 components of the auditory evoked potential. Human subjects were presented with two concurrent sequences of pure tone stimuli, one sequence delivered to each ear. They were instructed to listen to the tones in one ear and count randomly-embedded target stimuli, identified by pitch, while ignoring concurrent and physically equivalent stimuli in the other ear. Attention was then allocated to other ear-pitch combinations in subsequent runs. The rate of stimulation was rapid, an average of three stimuli per second per channel, to maximize N1 differences between channels. Evoked potentials were sampled at various times during each experimental run, to determine the time course of amplitude change in each auditory channel, as the subject tuned his neural response to the selected stimuli. The results indicated that N1 took 30-45 s to emerge as significantly larger in the attended channel, whereas P3 was instantly larger in the attended channel upon presenting the first rare stimulus of a run. The N1 effect disappeared for standard stimuli after about 7 min of stimulation, despite a continuously high rate of target identification. However, for the rare target stimuli, N1 and P3 remained at a higher level in the attended channel throughout the typical 15 min run. The study concludes that neural selectivity proceeds in a "top-down" manner, with the longer-latency P3 component showing a selective response sooner than N1. In addition, there is evidence that the selectivity of N1 tuning increases over time, with the continued focussing of attention.

Attention↗
PubMed1981

Delayed auditory brainstem responses in diabetes mellitus.

Diabetic patients have longer interpeak latencies in the brainstem auditory evoked responses than age-matched controls. The delay is not related to clinical hearing loss or blood glucose level at time of testing. Since waves I and II are normal in latency, the conduction velocity of the eighth nerve is not involved. The delay occurs between waves II and V, which would reflect altered transmission times in auditory brainstem and midbrain structures, and suggests the presence of a central neuropathy in patients with diabetes.

Adult↗
PubMed1981

Autoregulation of skin temperature with feedback-assisted relaxation of the target limb, and controlled variation in local air temperature.

The primary aim of this study was to determine whether feed-back-assisted skin temperature regulation can be demonstrated when skeletomuscular mediation, in the form of altered local EMG activity, is prevented. A second aim was to determine whether the success of such regulation is affected by the basal temperature of the skin. 30 adult subjects were asked to increase or decrease the temperature of the index finger of the dominant hand, while the local musculature was kept in a relaxed state using EMG feedback. The local ambient air temperature surrounding the limb was set at either 10 degrees C, 24 degrees C, or 38 degrees C, resulting in large differences in basal skin temperature. Subjects were successful at both increasing and decreasing skin temperature while maintaining an integrated EMG output below 75 muV in the target limb. The magnitude of change, much smaller than those commonly reported in this field, did not vary across the air temperature levels, indicating that skin temperature autoregulation under these conditions does not conform to the law of initial value. It was concluded that autoregulation of skin temperature can be demonstrated in a virtually flaccid limb, and that the amount of temperature change achieved is not a function of basal skin temperature.

Adolescent↗