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PubMedDate not supplied

[Critical flicker fusion frequency in man during exposure to noise].

The critical frequency of flicker fusion in the central and four peripheral points of the retina was investigated in 12 test subjects during and after one hour exposure to wide-band noise of 95 dBA. The subjects showed two types of response: three displayed an increase and nine a decrease of the flicker fusion critical frequency as compared to the control level. The changes showed individual variations. No correlation was found between the sign of changes in the parameter and its pretest level or the retinal site of registration.

Adult↗
PubMed1966

The flicker fusion frequency of the blue-sensitive mechanism of colour vision.

1. The flicker fusion frequency for blue stimuli on zero background increases steadily with increasing luminance up to 50 c/s, but if a strong yellow background is added it increases steadily only to about 18 c/s, and then remains nearly independent of luminance over a range of a factor of 20.2. It is argued that the maximum flicker fusion frequency is about three times lower for the blue-sensitive mechanism of colour vision than for the red- or green-sensitive.

Color Perception↗
PubMed1989

Behavioral determination of critical flicker fusion in dogs.

Steady-state critical flicker-fusion frequencies (CFFs) were determined for four beagle dogs using the psychophysical technique of conditioned suppression. The CFFs obtained demonstrated that the dog can discriminate flicker at much faster rates than has been suggested by ERG data. In addition, dog rods may support the discrimination of flicker at much higher rates than can human rods. An indication of a psychophysical rod-cone break occurred at a luminance level intermediate to those previously reported in ERG CFF studies. This level is similar to that in the cat, but much higher than that in man. The high CFFs provide the first psychophysical evidence of a well-developed functioning cone system in the dog.

Animals↗
PubMed1979

Flicker fusion thresholds in multiple sclerosis. A functional measure of neurological damage.

Patients with multiple sclerosis (MS) have been shown to have a measurable deterioration in the ability to perceive temporal variations of light. Compared to the traditional critical flicker fusion (CFF) measure, a modified flicker fusion test showed an improved sensitivity for denoting neurological deficit in temporal vision. One hundred twenty-two patients with MS were examined. The traditional CFF test exhibited abnormalities in 48%; the modified test exhibited abnormalities in 78% of the same patients. These results appear to be independent of whether or not the demyelinating disease clinically involved the visual system. Also, the percentage of abnormalities demonstrated by combining both techniques was unexpectedly high (60% to 80%) in patients with minimal evidence of neurological involvement.

Flicker Fusion↗
PubMed1979

[Changes in psychological performance parameters of concentration and critical flicker-fusion frequency with advancing age and in relation to diffuse cerebral arterial affections of the circulation].

Psychometric performance parameters and the critical flicker-fusion frequency are studied in various groups and in patients with chronic cerebral circulation trouble. Test d2 proves to be effective in the measuring of such impaired performance. There is a higher degree of correlation with Paul's addition test. A correlation between the performance parameters and the patient's age can be statistically substantiated. Among patients up to one third in the age group 55 and over show and affection of the cerebral performance turbances in spite of the absence of pathological clinical findings. The figure is twice as high in the group of patients undergoing treatment. The increased occurrence in old age shows the significance of pathological processes. There appears to be no relationship between critical flicker-fusion frequency and performance and stress factors. Individual correlations would support other physiological relations, such as an at present only hypothetical link with the psychic state (nervousness) of the test person. Our tables are suitable for practical purposes.

Adolescent↗
PubMed1995

Responses to temporal visual stimuli in migraine: the critical flicker fusion test.

Reports of sensitivity to striped patterns and to flickering lights are not uncommon in migraineurs. Only recently, however, have objective methods been used to assess the visual sensitivity of these patients, with emphasis on their responses to spatial stimuli; responses to temporal information have been largely neglected on an experimental level. The "critical flicker fusion" (CFF) test was performed by 25 migraineurs with aura, 25 migraineurs without aura, and 25 control subjects. The CFF test is a quick, simple technique which provides information concerning the temporal responsiveness of the visual system; a sensitivity threshold is measured. A significant group difference between the migraineurs without aura and the control subjects emerged (p = 0.01). Control subjects had the highest CFF threshold, migraineurs with aura the next highest, and migraineurs without aura the lowest threshold.

Adult↗
PubMed2002

Effects of 10 mg and 15 mg oral procyclidine on critical flicker fusion threshold and cardiac functioning in healthy human subjects.

The critical flicker fusion threshold (CFFT) is thought to index alertness and cortical arousal. Sedative drugs reduce CFFT while psychostimulants increase it. Procyclidine is an anticholinergic that is used to control the extrapyramidal side-effects of antipsychotics in schizophrenia. This study examined the effects of clinically relevant doses of oral procyclidine administration on CFFT and heart rate in two separate experiments (Experiment 1, drug dose: 10 mg, n = 16; Experiment 2, drug dose: 15 mg, n = 12) involving healthy subjects using a double-blind, placebo-controlled, cross-over design. 10 mg procyclidine had no significant effect on CFFT, heart rate or self-ratings of mood, but the 15 mg dose significantly lowered CFFT at 1 h and 2 h after procyclidine administration, increased drowsiness ratings and produced a drop in heart rate. The effects observed in this study may have implications for treatment compliance of schizophrenic patients, choice of antipsychotics, prescribing to patients with heart disease and monitoring of cardiac function under treatment. Further investigations are required to quantify the effects of procyclidine on CFFT and cardiac function in patients with schizophrenia.

Adult↗
PubMed1975

[The influence of centrally acting drugs on flicker fusion frequency].

From the research results given we may conclude that the flicker fusion frequency is reduced not only by tranquillisers but also by neuroleptic drugs. The records obtained of the effect of the dosage can be seen as a measure of the efficiency of this method. It should be established by means of similar experiments, by including additional substances, in which regions of the cortico-retinal system the site of action should be presumed to be.

Caffeine↗
PubMed2005

Visual experience can substantially alter critical flicker fusion thresholds.

Studies of psychopharmacology often use the test of the critical flicker fusion (CFF) threshold as a measure of total information processing. It is true that studies of practice effects have shown that CFF thresholds are remarkably stable within and across multiple days of testing. This study confirms that subjects who undergo CFF testing on sequential days have stable thresholds, but also demonstrates that in subjects who conducted 1 h of motion training per day for 9 days the CFF thresholds increased by an average of 30%. The results show that the perceptual experience of subjects can dramatically alter the CFF thresholds and should be an important consideration in the control of studies employing the CFF as a measure.

Adult↗
PubMed1989

Effects of fasting on visual flicker fusion.

Two experiments are reported which investigated the effects of fasting on visual flicker fusion (VFF). In Exp. 1 the VFF of 40 undergraduate students, 20 men and 20 women, whose mean age was 22.5 yr., was measured in nonfasting conditions 1 to 2 weeks before and in fasting conditions during the Muslim fasting month of Ramadan. In Exp. 2 the VFF of a comparable group of 15 men and 15 women, whose mean age was 23.2 yr., was measured in a different month in both fasting and nonfasting conditions. Subjects were assigned randomly to these two conditions. Analysis shows that fasting reduced VFF significantly in both experiments. This finding indicates that fasting is likely to reduce perceptual sensitivity. The results were explained in terms of fatigue and physical exhaustion effects produced by fasting.

Adult↗
PubMed2004

Critical Flicker Fusion Threshold in patients with Alzheimer's disease and vascular dementia.

BACKGROUND: Critical Flicker Fusion Threshold (CFFT) is a psychophysical threshold and in psychological terms is regarded as a measure of information processing capacity. The test has previously been shown to be a valid and reliable measure of CNS functioning in patients with Alzheimer's disease and may be a useful as a screening measure for the early detection of Alzheimer's disease (AD). METHODS: Consecutive referrals to the Wakefield Memory Clinic who met DSM-IV criteria for AD or vascular dementia (VaD) were invited to take part in the study. A range of neuropsychological tests and CFFT were administered to the two groups using standardised protocols and the ability of these various tests to distinguish between the two conditions was investigated. RESULTS: Forty-six patients were included in the study. Of the various tests, only the descending component of CFFT and word fluency were significantly different in the two groups. In addition, the descending threshold had a sensitivity of 83% and a specificity of 69%. CONCLUSION: CFFT could be useful as a screening instrument for early AD when combined with other measures and could facilitate the decision to commence antidementia treatment at an early stage. Further longitudinal work is needed to establish this.

Aged↗
PubMed1992

Retinal and cortical activity in human subjects during color flicker fusion.

Pattern electroretinograms (PERG) and cortical visually evoked potentials (VEP) were simultaneously recorded from 7 visually normal and 1 protanopic subjects. Stimuli were color checkerboards (0.5 degrees check size), phase-reversing at 17 Hz (i.e. 34 reversals/sec). Using a stepwise sweep procedure, the luminance of the red (lambda peak = 550 nm) and green (lambda peak = 630 nm) checks varied in 11 steps in opposite directions from 0 to 30 cd/m2, embracing the subjective equiluminance point. For normal subjects at subjective equiluminance, the VEP amplitude dropped sharply down to 13 +/- 2% of the value at pure luminance contrast. The PERG, however, was only reduced to 56 +/- 10% at this point, an attenuation 4 times less than that of the VEP. In contrast to normal subjects, in the protanopic subject the PERG was sharply reduced at equiluminance, parallel to the VEP. This would be expected when L-cones are missing. Assuming that the PERG reflects the activity of the retinal ganglion cells, our findings suggest that human retinal ganglion cells respond well under the condition of equiluminant flicker fusion, which is in agreement with recent single-cell studies in the monkey. Consequently, the temporal low-pass filter, which mediates color-flicker fusion, would seem to lie central to the retinal ganglion cells.

Adult↗