Biomedical subjects

Q S Dickins

Publications and source records attributed to Q S Dickins.

10 recordsLinked to original sources

PubMed1991

Sleepiness/alertness on a simulated night shift following sleep at home with triazolam.

Physiological sleep tendency during a simulated night shift schedule was examined in 15 middle-aged subjects following daytime sleep after administration of triazolam or placebo. A double-blind, counterbalanced, crossover design involving two tours of five laboratory nights and four daytime home sleep periods was used. Triazolam lengthened daytime sleep as measured by wrist actigraph and improved nighttime alertness as measured by the MSLT. Sleepiness was most profound during the early morning hours (0430 to 0630) but improved significantly across nights for both conditions. Repeated test of sustained wakefulness latencies and simulated assembly line task performance decreased slightly across the night, but there were no significant condition effects. Subjective data tended to support objective measures, although Stanford Sleepiness Scale ratings indicated that subjects did not perceive improved alertness at night after triazolam-aided daytime sleep.

Adult↗

PubMed1990

Effect of caffeine on physiological sleep tendency and ability to sustain wakefulness at night.

Marked sleepiness occurs during typical night shift work hours and this reduced alertness is associated with marked performance deficits. The effect of caffeine (versus placebo) upon sleepiness at night was studied using objective measures of physiological sleep tendency and ability to sustain wakefulness. Both measures show caffeine to reduce sleepiness at a single dose roughly the equivalent of two to four cups of coffee. Despite impressive objective differences in alertness with caffeine, subjects did not consistently differentiate between drug conditions on subjective alertness assessments. The use of CNS stimulants to promote alertness during night shift hours should be considered, particularly for occupations for which alertness is critical.

Adult↗

PubMed1989

Long-term clinical efficacy of Sinemet CR in patients with Parkinson's disease.

Sinemet CR, a controlled-release form of carbidopa/levodopa, was administered for 36 or 39 months to 8 patients with Parkinson's disease in an open-label study. On standard Sinemet each patient had experienced "wearing off" phenomena, and 5 had also experienced random "off" episodes. Daily "on" time, dyskinesia time, disability score, levodopa dosage requirement, and dosing frequency on Sinemet CR were compared with baseline values on standard Sinemet therapy. After both 3 and 36 or 39 months of Sinemet CR therapy, 5 patients showed increased daily "on" time compared with baseline. All 8 required fewer daily doses after 3 months on Sinemet CR, but only 3 were still taking fewer doses after 36 or 39 months. Disability scores remained essentially unchanged. Patients continued to elect to remain on Sinemet CR over the 3-year period, citing improved predictability of response and less severe and precipitous "off" episodes as the main reasons. This experience suggests that patient acceptance of Sinemet CR remains high. A modest improvement in "on" time can be achieved and maintained in some patients for as long as 3 years. However, as with standard Sinemet, dosing frequency for Sinemet CR may need to be gradually increased with time in order to maintain benefits achieved.

Aged↗

PubMed1988

Changes of short latency somatosensory evoked potential in sleep.

We studied how the first negative waves (frontal 'N18' and parietal 'N20') of median somatosensory evoked potentials (SEP) change from waking to sleep in 9 healthy volunteers. Frontal and parietal responses in awake subjects showed multiple fast frequency potentials (FFP) over the ascending and descending phases of the slow negative waves. The main frontal FFP consisted of N16, P17, N18, P18, N19 and P20, with an additional small FFP, n15, over the ascending phase of N16. The parietal FFP included 3 major peaks (N15, P18 and N20) and 3 small FFP (n17, n19 and n20). Frontal FFP, except for n15, were markedly attenuated or totally disappeared in stage II sleep. Only a few FFP were identified in stage IV. The FFP returned in REM sleep, but amplitude was smaller than the waking state. Parietal FFP were also attenuated in NREM and recovered in REM sleep, but these changes were less prominent compared to those of frontal FFP. Latencies of frontal P20 and parietal N20 were prolonged in NREM sleep with greater prolongation of P20 than N20. These returned to waking values in REM sleep. These findings suggest that the frontal and parietal major negative peaks ('N18' and 'N20') consist of multiple physioanatomical substrates mediated through complex thalamocortical projection systems, and that the FFP are closely related to the sleep-wake mechanism possibly reflected by mutual interaction between cortex and the thalamic reticular system.

Adult↗

PubMed1986

Basilar migraine: polarity-dependent alteration of brainstem auditory evoked potential.

We studied serial brainstem auditory evoked potentials (BAEPs) in a patient who had episodic basilar migraine. During migraine attack, significant alteration of wave IV-V was revealed only by rarefaction clicks. The alteration remained unchanged throughout the headache and reverted to normal when the headache subsided. In contrast, BAEPs with condensation clicks were normal during and after the headache.

Adult↗

PubMed1985

Topographic analysis of somatosensory evoked potentials in patients with well-localized thalamic infarctions.

After stimulation of the median nerve, three major negative peaks (NI, NII and NIII) of somatosensory evoked potentials (SEP) have different latencies along the longitudinal array of scalp electrodes: NI and NII at frontal electrodes have the shortest latency (N17, N29). There is a progressive delay toward the central (N19, N32) and parietal areas (N20, N34). NIII (N60) latency differs from one electrode to another but without consistent anterior-posterior latency shift. A variety of SEP abnormalities was observed in 17 patients with non-hemorrhagic thalamic lesions reflecting a disturbance of the complex intra-thalamic and afferent and efferent thalamic pathways. When the lesions were classified into 5 groups according to the presumed vascular territories involved, there were general but not specific characteristics of SEP abnormalities in each group of patients. In four patients with lesions involving primary sensory nuclei and presenting with the thalamic syndrome or the loss of all modalities of sensation, all SEP components after P14 were absent when the affected arm was stimulated. NI peaks were intact in two patients with thalamic sensory lacunes but NII was delayed. NI was present but delayed in three patients with anterior thalamic lesions not involving primary sensory nuclei. In patients with medial thalamic lesions, delayed central NIII was a common finding. In patients with posterior capsule or lateral thalamus lesions either NII and NIII or NIII alone were affected. NI was also affected in some with sparing of the frontal component (N17). These complex relationships between the types of SEP abnormalities and thalamic lesions are compatible with the presence of multiple, at least partially independent, thalamic generators and thalamocortical projection systems mediating regionally specific SEP components.

Adult↗

PubMed1985

Visual evoked potentials by different check sizes in patients with multiple sclerosis.

Visual evoked potentials (VEPs) were obtained using three checks of different size (25', 50', and 100' of arc) in 20 normal controls and 1,006 patients. The test was abnormal in 270 patients regardless of the check size, whereas in 53 patients, a prolongation of P100 latency occurred only with checks of a certain size. The procedure was most sensitive in detecting abnormalities with combined application of 25' and 100' checks and least sensitive with the 50' checks alone. In occasional subjects showing W-shaped responses, the use of another check size often elicited the usual V-shaped pattern, alleviating the problem of selecting the peak for latency determination.

Adolescent↗

PubMed1984

Stationary peaks from a moving source in far-field recording.

In 20 radial nerves, referential recording of antidromic sensory potentials from the digits consisted of two stationary far-field peaks, PI-NI and PII-NII. When compared with a bipolar recording of a moving source, the onset of PI and PII was coincident with the sensory potential approaching the wrist and the base of the digit, respectively. Of the two stationary positive peaks, PI was identical in latency irrespective of the digits tested. In contrast, the latency of PII was smaller for the first digit than the others, reflecting different distances from the stimulus point to the base of the respective digit. The amplitude of PII was proportional to that of the propagating sensory nerve action potential recorded at the volume conductor junction. A bipolar recording registers a near-field potential over the sensory fibers along the length of the nerve. In contrast, a referential recording represents a mixture of the near- and far-field potentials with the latter frequently producing major alterations of the classical triphasic wave. The standing far-field peaks show a temporal relationship to the traveling volleys approaching the main borders of the volume conductor. At the moment the sensory impulse reaches the boundary, current density changes suddenly in the two adjacent conducting media, giving rise to an apparent standing potential. The same mechanism probably plays an important role for the generation of some of the short latency peaks in the scalp recorded SEPs.

Action Potentials↗

PubMed1984

Brainstem auditory evoked potential and blink reflex in multiple sclerosis.

Brainstem auditory evoked potential (BAEP) and blink reflex (BR) were abnormal in 40% and 26% of 130 patients with MS. Overall, BR was affected in 53% of patients with abnormal BAEP involving I-III and 41% of those involving III-V interval. In 23 patients with unilateral BR involvement, BAEP was affected ipsilaterally in 10, contralaterally in 0 and bilaterally in 8. In 12 patients with bilateral BR abnormalities, BAEP was involved unilaterally in 1 and bilaterally in 8. We conclude: (1) pontine lesions may prolong either I-III or III-V interwave latency of BAEP, and (2) unilateral abnormalities of BAEP tend to implicate the uncrossed auditory pathways.

Adolescent↗

PubMed1983

Field distribution of antidromically activated digital nerve potentials: model for far-field recording.

In 20 median nerves, the shift in mean latency of the referentially recorded antidromic sensory potential was 0.22 to 0.38 msec per 1.5 cm across the palm and only 0.03 to 0.05 msec per 1.5 cm along the third digit. In five radial nerves, referential recording from the tip of the second digit detected a stationary positive potential that was coincident with the entry of the sensory impulse into the nerve terminal near the base of the digit. These findings are consistent with the view that, in far-field recording of a traveling impulse, a time peak could result from an abrupt change in current flow that is based on the geometry of the volume conductor without fixed neural discharges.

Adult↗