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PubMed1962

The electroretinogram of a diurnal gecko.

Using the electroretinogram as the criterion of retinal activity the flicker fusion frequency, course of dark adaptation, and spectral sensitivity of the pure cone retina of the diurnal gecko, Phelsuma inunguis, were investigated. Both the curve relating flicker fusion frequency to stimulus intensity and that relating the amplitude of the flicker response to stimulus intensity showed a break as the intensity was increased. The dark adaptation curve was that typical of cone retinae; there was no break, adaptation was relatively rapid, and there was a total increase of sensitivity of only about 3 log units. The spectral sensitivity curve showed two maxima, a major one at about 560 mmicro and another at about 460 mmicro. Chromatic adaptation with red and blue lights demonstrated the presence of two independent mechanisms. Although red adaptation could not have had a direct effect on the pigment responsible for the "blue" mechanism the sensitivity of this mechanism was depressed by red adaptation. The possible relationships of the two mechanisms are discussed.

Adaptation, Ocular↗
PubMed1986

Acute and subacute actions on human performance and interactions with diazepam of temelastine (SK&F93944) and diphenhydramine.

Thirteen healthy subjects participated in a combined acute and subacute double-blind, cross-over trial of two H1-antihistamines diphenhydramine (DPH) and temelastine (SKF) against placebo. The doses were DPH 50 mg b.d. and SKF 100 mg b.d. Objective (digit symbol substitution, flicker fusion, Maddox wing, attention, tracking, choice reaction) and subjective (visual analogue scales, side-effects on questionnaire) tests were done on Days 1, 4 and 5, on each occasion before drug intake and after 90 min and 3 h. On Day 1 DPH caused clear sedation of unpleasant character and impaired flicker fusion, attention and digit symbol substitution. SKF shifted the VAS assessment "drowsy/alert" towards drowsiness at 90 min, without objective impairment. On Day 4 DPH reduced exophoria and impaired flicker fusion without subjective sedation. On Day 5, diazepam 0.3 mg/kg (DZ) given with the other drugs caused subjective sedation of pleasant character and impaired various functions in the objective tests. Neither SKF nor DPH increased the effects of DZ; DPH slightly counteracted the effect of DZ on exophoria. At home, SKF did not differ from placebo while DPH proved sedative. DPH did not improve sleep but caused dry mouth and blurred vision. Measurement of plasma levels of antihistamines on each test day revealed the development of tolerance to antihistamine-induced sedation. The concentration of DZ measured by bioassay was somewhat elevated in the presence of DPH. Since the majority of the performance tests were not influenced by temelastine, it appears to be an acceptable, novel H1-antihistamine for the treatment of allergic disorders.

Adult↗
PubMed1996

Accommodation, convergence, pupil diameter and eye blinks at a CRT display flickering near fusion limit.

This study investigates possible effects of temporally modulated light stimulation near critical fusion frequency (CFF) when subjects observe a cathode ray tube (CRT) operated at different refresh rates. Various visual functions were measured in a series of tests of 2.5 min duration. In experiment 1, at a repetition rate of 50 Hz mean pupil size was 0.055 mm smaller than at 300 Hz. The precision of convergence and accommodation in binocular vision was not affected. In experiment 2, 300 Hz was compared with the lowest frequency that did not produce visible flicker for each subject. At the lower rate (55 to 90 Hz), mean accommodation in monocular vision was 0.06 D weaker, median eye blink duration was 6% shorter, and mean eye blink interval was 15% longer. Individual differences and possible fatigue effects of intermittent light at visual display units are discussed.

Accommodation, Ocular↗
PubMed2001

Comparison of clozapine and haloperidol on some autonomic and psychomotor functions, and on serum prolactin concentration, in healthy subjects.

AIMS: To compare the autonomic, neuroendocrine and psychomotor effects of single doses of the 'atypical' antipsychotic clozapine and the 'classical' antipsychotic haloperidol, in healthy male volunteers. METHODS: Clozapine (50 mg), haloperidol (3 mg) and placebo were administered to 12 healthy male volunteers at weekly intervals, according to a balanced double-blind design. Resting pupil diameter, salivary output, heart rate, blood pressure, plasma prolactin concentration, critical flicker fusion frequency and subjective 'alertness', 'contentedness' and 'anxiety' were measured at baseline and 2, 3, 4 and 5 h after drug ingestion. Data were analysed by analysis of variance with individual comparisons (Dunnett's test) with a significance criterion of P < 0.05. RESULTS: Significant treatment effects (difference from placebo [mean, 95% CI] 5 h after drug ingestion) were as follows: clozapine reduced pupil diameter (mm; -3.02 [-3.56, -2.47]), salivary output (g; -0.34 [-0.60, -0.08]), mean arterial blood pressure (mm Hg; -8.7 [-14.3, -3.1]), critical flicker fusion frequency (Hz; -3.26 [-3.94, -2.58]), and subjectively-rated 'alertness' (mm; -20.94 [-29.21, -12.67]) and 'contentedness' (mm; -12.98 [-17.90, -8.06]), whereas haloperidol increased prolactin concentration (mU l(-1); 301.3 [196.7, 405.8]) and caused small reductions in pupil diameter (mm; -0.68 [-1.23, -0.14]), mean arterial blood pressure (mm Hg; -7.0 [-12.6, -1.4]) and critical flicker fusion frequency (Hz; -1.15 [-1.83, -0.47]). CONCLUSIONS: The effects of the antipsychotics are in agreement with their receptor binding profiles: alpha(1)-adrenoceptor blockade by clozapine may contribute to reductions in pupil diameter, salivation, mean arterial blood pressure and sedation, and muscarinic cholinoceptor blockade by the drug may underlie the reduction in salivation. Conversely, D(2) dopamine receptor blockade by haloperidol is likely to be responsible for the increase in prolactin secretion evoked by the drug.

Adult↗
PubMed1991

Visual dysfunction in Alzheimer's disease: relation to normal aging.

In patients with Alzheimer's disease (AD), compared with age-matched and young healthy control subjects, visual deficits in the following functions were observed: color, stereoacuity, contrast sensitivity, and backward masking (homogeneous and pattern). Critical flicker fusion thresholds were normal, relative to age-matched healthy subjects. For color, the majority of the errors were tritanomalous (blue axis). Color and stereoacuity deficits were unrelated to severity of dementia, in accordance with models of vision that describe these functions as modular rather than diffuse for cortical localization. Although contrast sensitivity was depressed throughout the frequency range in AD, more patients were impaired at low than at high spatial frequencies, contrasting with the observed normal aging pattern of high-frequency loss. Healthy elderly subjects showed depressed critical flicker fusion thresholds and reduced contrast sensitivity at high frequencies, relative to the young group; differences between these groups were not found for the other vision tests. A subset of the AD group received detailed neuro-ophthalmological examination, and no abnormalities were found. This finding, taken together with normal thresholds for critical flicker fusion, suggests that the widespread visual dysfunction reported here is more likely to be related to known pathological changes in primary visual and association cortex in AD than to changes in the retina or optic nerve.

Adolescent↗
PubMed1978

A repeated dose comparison of the side effects of five antihistamines on objective assessments of psychomotor performance, central nervous system arousal and subjective appraisals of sleep and early morning behaviour.

The side effects of five antihistamines (chlorpheniramine maleate, mebhydrolin, clemastine hydrogen fumarate, Tavegil; ketotifen, and promethazine hydrochloride) were measured on subjective assessments of sleep and the integrity of early morning behaviour and objective assessments of complex psychomotor behaviour and central nervous system arousal. Fifty consenting volunteers each received one of the five preparations for a period of four days with the subjective effects being reported on a set of 10 cm line visual analogue scales and the objective assessments being made via a computer assisted reaction time task and critical flicker fusion thresholds. Chlorpheniramine, 4 mg t.d.s. for four days, produces a significant impairment in critical flicker fusion thresholds with respect to pretreatment baselines but none of the preparations showed any significant impairment in complex reaction time assessments. The subjective assessments of sleep and early morning hangover showed mebhydrolin and clemastine to be free from detrimental side effects, but promethazine and chlorpheniramine produce significant impairments in the integrity of early morning behaviour.

Adult↗
PubMed1994

Pharmacokinetic and -dynamic studies with a new anxiolytic, suriclone, utilizing EEG mapping and psychometry.

1. In a double-blind, placebo-controlled, cross-over study, acute pharmacokinetic, neurophysiological and psychotropic effects of suriclone, a new cyclopyrrolone derivative, were investigated and compared with alprazolam. 2. Fifteen normal young volunteers received randomized oral single doses of placebo, 0.1, 0.2 and 0.4 mg suriclone as well as 1 mg alprazolam as reference compound. Investigations were carried out before and 1, 2, 4, 6 and 8 h after drug administration. 3. Pharmacokinetic investigations by radioimmunoassay showed a dose-dependent fast rise of plasma concentrations with a peak at 1 h and a rapid decline thereafter. Both the Cmax and the AUC values exhibited a linear relationship to dose. 4. EEG brain mapping demonstrated significant CNS effects of both compounds, characteristic for tranquillizers (increase of beta, decrease of alpha and increase of delta activity; attenuation of total power and acceleration of the centroid, i.e. centre of gravity frequency). When compared with alprazolam, suriclone exerted less sedative effects. 5. Time-efficacy calculations showed the pharmacodynamic peak effect of suriclone from the 2nd to the 4th hour, and of alprazolam in the 1st hour. Dose-efficacy calculations showed that the most pronounced CNS changes occurred after 1 mg alprazolam, followed by 0.4, 0.2 and 0.1 mg suriclone. 6. Psychometric investigations demonstrated no significant effects after the two lower doses of suriclone, while 0.4 mg and 1 mg alprazolam induced a decrement both in noopsychic and thymopsychic variables seen after higher doses of anxiolytic sedatives. Psychophysiology (critical flicker fusion, pupillometry, and skin conductance measures) pulse rate, systolic and diastolic blood pressure remained unchanged. 7. Psychophysiology (critical flicker fusion, pupillometry and skin conductance measures) showed differential dose-dependent effects. Pulse rate, systolic and diastolic blood pressure remained unchanged. Anxiolytic-characteristic side-effects (tiredness, drowsiness, etc.) occurred predominantly after the highest doses 0.4 mg suriclone and 1 mg alprazolam.

Administration, Oral↗
PubMed1982

Actions and interactions of diazepam and alcohol on psychomotor skills in young and middle-aged subjects.

Healthy pretrained men participated in three separate controlled double-blind and cross-over trials. There were 10 students in Trial I, 11 army officials or policemen aged 38-59 years in Trial II, and 11 students in Trial III. After single oral doses of diazepam 10 mg (D), placebo, alcohol 0.5 g/kg (A) or D+A, given at one-week intervals in balanced order, the psychomotor skills (choice reaction, tracking, attention, flicker fusion) were repetitively measured up to 2.5 hrs. Serum D concentrations were measured by gas chromatography. D alone impaired flicker fusion in trials I and II, and also reactive and coordinative skills in trial III. A alone slightly impaired skills and failed to potentiate D effects. Increasing age rendered the performance worse but this was due to increased base-line errors rather than to enhanced responses to D. Serum D concentrations tended to rise in the presence of A suggesting an inhibition of D demethylation by alcohol. Both total and free concentrations of D were similar in both age groups. The results suggest that in spite of unaltered sensitivity to D, middle-aged subjects have a lowered margin of safety when driving or using machinery under D treatment.

Adult↗
PubMed1990

Effects of alfentanil on induction and recovery from propofol anaesthesia in day surgery.

The influence of alfentanil on induction and recovery characteristics of propofol was examined in women presenting as day cases for minor gynaecological surgery. Alfentanil reduced the incidence of pain on injection and the induction and maintenance requirements of propofol. This was at the expense of more prolonged apnoea. Immediate recovery characteristics were similar in each group although changes in Critical Flicker Fusion Threshold as a measure of psychomotor impairment were more pronounced after alfentanil. Such differences were insignificant at three hours by which time Critical Flicker Fusion Threshold had returned to baseline and patients were ready for discharge home.

Adult↗
PubMed1977

Repeated dose comparison of nomifensine, imipramine and placebo on subjective assessments of sleep and objective measures of psychomotor performance.

1. Nine normal subjects volunteered to participate in a randomized single-blind crossover study of nomifensine 75 mg and two comparators, imipramine 75 mg and placebo. 2. Each volunteer received placebo for 3 d, then the first test drug for 4 days. This sequence was repeated twice more, so that each subject received each comparator. All medication was taken three times daily. 3. Assessments were made on days 3, 5 and 7 of each sequence, and consisted of a Sleep Evaluation Questionnaire, a test of Critical Flicker Fusion and a measure of Complex Reaction Time (CRT). 4. There were no significant differences in the CRT. There was a significant increase in critical flicker fusion with nomifensine. 5. Although both nomifensine and imipramine disturbed the quality of sleep, only imipramine produced a hangover.

Adult↗
PubMed1986

Psychomotor testing of on-call anaesthetists.

The critical flicker fusion frequency and choice reaction times of 16 on-call anaesthetists were measured between 1400 and 1600, at 2300 and at 0200 hours. Critical flicker fusion decreased between the afternoon and 2300; there was no further change between 2300 and 0200. No significant differences in choice reaction times were found on any of these different occasions.

Anesthesiology↗
PubMed1988

Impaired visual contrast sensitivity in epileptic patients treated with carbamazepine.

Critical flicker fusion frequencies and visual contrast sensitivity were determined in 27 adult epileptic patients receiving carbamazepine monotherapy and in 24 healthy, drug-free control subjects. Flicker fusion thresholds were the same in patients and control subjects, whereas the contrast sensitivity was significantly reduced in the patient group at all spatial frequencies. There was a significant negative correlation between the plasma concentration of carbamazepine and the contrast sensitivity at 11.4 and 22.8 cycles per degree, indicating that the reduced contrast sensitivity was due to the drug therapy.

Adolescent↗
PubMed1992

[Light perception and flicker perimetry. Effect of refractive error, artificial media opacities and pupillary size].

The influence of defocus, artificial media opacities and pupil size on perimetric thresholds in automated light sense and flicker perimetry was investigated in 20 eyes of 20 normal subjects. Thresholds were determined at 13 locations in the central visual field. Blurring the retinal image by a small defocus or by slight artificial media opacities causes a measurable reduction in light-difference sensitivity. Flicker fusion frequency, however, is much more resistant to degradation of the retinal image. Artificial pupil size has a similar effect on both light-difference sensitivity and flicker fusion frequency. The present study shows that perimetric methods using temporal threshold criteria should be more suitable for the detection of neuronal damage in the presence of factors disturbing the quality of the retinal image than methods using static criteria.

Adult↗
PubMed1994

Effect of flumazenil on the recovery from intravenous midazolam.

Psychomotor recovery characteristics were studied in young, healthy patients undergoing intravenous sedation using midazolam for the extraction of third molars. There were significant changes to Choice Reaction Time and Critical Flicker Fusion Threshold noted half an hour after the administration of midazolam (P < 0.001). The administration of the benzodiazepine antagonist flumazenil significantly improved the Choice Reaction Times, but failed to reverse changes in Critical Flicker Fusion Threshold up to 120 minutes later. However, the use of flumazenil assured that no post-operative changes in oxygen saturation occurred in any of the patients.

Adolescent↗
PubMed1984

Visual function abnormalities in central serous retinopathy.

Eighteen patients with central serous retinopathy (CSR) underwent a battery of visual function tests when first seen and after resolution of the subretinal fluid. Eyes with CSR had minimal relative afferent pupillary defects, reduced critical flicker-fusion thresholds, prolonged visual evoked potential (VEP) latencies, increased errors on the Farnsworth-Munsell 100-hue (FM 100) test, and depressed central visual fields (Octopus). The afferent pupillary defect and critical flicker-fusion thresholds were the first to improve after resolution of the subretinal fluid. Next in rate of improvement were the visual acuity, the VEP latency, and the FM 100 test results. The threshold of the central Octopus at fixation improved the slowest and was still abnormal during long-term follow-up, indicating a prolonged depression in the threshold of central field sensitivity after resolution of the CSR. Many of these abnormalities are also seen in patients with optic nerve disease.

Adult↗
PubMed1975

A review of the effects of diazepam on cognitive and psychomotor performance.

Studies evaluating the effects of diazepam (Valium) on psychomotor and cognitive functions are reviewed an integrated. The importance of the full and clear documentation of such drug effects lies in the wide usage of diazepam today for a variety of medical, psychiatric, and dental purposes. The various tasks used to assess drug effects were classified into six major groups based on apparent similarity of functions tapped. These groupings are: reflex speed; critical flicker fusion threshold; attention and vigilance; decision making; learning and memory; psychomotor performance. In all functions except simple reflexive responding; some indications of impaired performances were reported, the results being most definitive for the critical flicker fusion where even small doses lowered the threshold and for a slower performance on letter cancellation tasks. There appeared to be some interaction between diazepam and alcohol although the nature of this interaction is still unclear. Because of the extensive use of both of these drugs and the possibility of a synergistic or a potentiation effect, it is important that this area receive further study. It was suggested that future studies either control for or analyze the data to assess the possible interactive effects of diazepam with subject variables such as sex, personality type, and for population characteristics. These variables have been shown to affect responses in other studies and hence could also interact with cognitive and psychomotor performance. It was noted that most of the studies reviewed used normal, healthy, male volunteer subjects and may not be comparable to the clinical populations for whom the drug is typically prescribed.

Attention↗
PubMedDate not supplied

Behavioral effects of 0 and 0.05% blood alcohol in male volunteers.

Five behavioral tests were evaluated to determine their sensitivity to the subtle central nervous system (CNS) depressant effects produced by ingestion of ethanol. Twenty-one adult male volunteers received 0 and 1.4 ml 100 proof vodka/kg body weight according to a "double-blind" crossover design. Behavioral tests were conducted between 15 and 65 minutes after ethanol ingestion, when blood alcohol concentrations (BAC's) were between 0.05 and 0.06%. Tests evaluated were Archimedes spiral, digit span memory, critical flicker fusion, stabilometry and tachistoscope. Multivariate analysis of variance (MANOVA) using composite scores representing the individual tests indicated that the battery as a whole was sensitive to ethanol effects. Repeated measures analysis of variance (ANOVA) on each test indicated that critical flicker fusion, stabilometry and tachistoscope contributed more to the overall sensitivity of the battery than did digit span memory and Archimedes spiral.

Animals↗
PubMed1995

Effect of combined atenolol and nifedipine administration on psychomotor performance in normal subjects.

The aim of the present study was to evaluate the central effects of single doses of the beta-adrenoceptor antagonist atenolol and the calcium antagonist nifedipine retard, alone and in combination, in normal subjects. Twelve normal males received single oral doses of atenolol 100 mg, nifedipine retard 20 mg, atenolol 100 mg and nifedipine retard 20 mg in combination, diazepam 5 mg (active control), and each of two matching placebos in a double-blind, randomised fashion. Psychomotor performance was assessed using digit symbol substitution, letter cancellation (LCT), continuous attention, choice reaction time, finger tapping, immediate recall and short-term memory. Two flash fusion and critical flicker fusion thresholds were measured and subjective assessments made using visual analogue scales (VAS). Diazepam 5 mg significantly worsened LCT scores at 4h, significantly impaired alertness at 2 h and 4 h, and tended to increase reaction time and impair continuous attention and physiological measurements. Atenolol 100 mg alone significantly reduced alertness at 2 h and 4 h, and also tended to impair physiological measurements. Nifedipine retard 20 mg produced no significant psychomotor effects. Combined atenolol and nifedipine retard administration produced a small but significant improvement in continuous attention and a reduction in body sway, with no adverse effects being evident on performance or subjective awareness. The results suggest that no significant adverse effects on psychomotor performance are produced by single doses of atenolol 100 mg and nifedipine retard 20 mg when given together in normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗