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PubMed2004

Critical flicker fusion frequency: relation to resting systolic blood pressure.

OBJECTIVE: Past studies have shown that a number of factors, both acute and chronic, influence individual differences in critical flicker fusion frequency (CFF). In this study, we assessed whether CFF co-varied with resting systolic blood pressure (SBP). METHODS: SBP and CFF were assessed in one session in 221 subjects (mean age, 19.6 +/- 2.5 years), and SBP and CFF were assessed over 10 sessions in 12 subjects. CFF values were determined psychophysically using a 570 nm circular 1 degrees test field centrally fixated. Blood pressure was determined with an automated sphygmomanometer. RESULTS: There was a significant (p < 0.0002) positive relation between CFF and SBP for the larger sample (n = 221). Significant within-subject relations were found for 6 of the 12 subjects tested repeatedly. CONCLUSIONS: The combination of results strongly suggests that CFF and resting SBP are positively related.

Adolescent↗
PubMed1985

Critical flicker fusion and double flash discrimination in different parts of the visual field.

The temporal sensitivity of the visual system was investigated in fifteen healthy subjects by determining the critical flicker fusion frequency (CFF) and the performance in a double flash discrimination (DFD) task. Measurements were obtained using a small test light of 2.5 degrees diameter in the fovea and at eight different perifoveal retinal locations along the horizontal and vertical meridians. Statistically significant differences were found for both the CFF and the DFD task showing a higher temporal sensitivity of the nasal and upper than the temporal and lower retinal areas. The functional significance of the findings is discussed and related to electrophysiological and behavioral data which describe a functional superiority of the upper over the lower hemiretinal system.

Adult↗
PubMed1977

Variegated color sensations from rod-cone interactions: flicker-fusion experiments.

Multicolored images were produced by the combination of two different color-separation images, one illuminated with 656 nm light and the other illuminated with 500 nm light. Flicker-fusion frequency measurements were used to identify the conditions in which the 500 nm light was below cone threshold. Under those conditions the multicolored images were shown to be generated by rod and long-wave cone interactions.

Color Perception↗
PubMed2002

Modulation of the critical flicker fusion effects of serotonin reuptake inhibitors by concomitant pupillary changes.

RATIONALE: Serotonin reuptake inhibitors (SSRIs) have been attributed CNS-activating properties based on their ability to elevate the Critical Flicker Fusion (CFF) threshold. However, such an interpretation may be questioned since CFF elevations may also be due to SSRI-induced increases in pupil diameter. OBJECTIVES: The effect of pupillary changes on CFF assessment following SSRI administration was investigated in a double blind, crossover study. METHODS: During three periods of 15 days, 21 healthy men and women (30-50 years) received sertraline (50 mg on days 1-8, 100 mg on days 9-15), citalopram (20 mg on days 1-8, 40 mg on days 9-15) and placebo. Assessments were done on days 1, 8 and 15 and consisted of pupillary measurements and CFF assessments with and without pupillary control (a 2-mm artificial pupil) using the Leeds Psychomotor Tester. RESULTS: Both SSRIs induced an acute and steady increase in pupil diameters. CFF thresholds were depressed following acute administration of sertraline and citalopram, but this was only apparent when a control was made for the pupillary changes. No CFF effects were seen at day 8, but CFF was again reduced at day 15, with and without control for pupil size. CONCLUSIONS: Mydriasis masked the detrimental effects of both SSRIs on CFF during the acute assessments. Our results raise questions regarding the validity of the assessment of the behavioural toxicity of SSRIs based on CFF measurements without ample control for pupil size, especially when these concern acute measurements.

Adult↗
PubMed1978

Critical flicker-fusion frequency as an indicator of human receptive field-like properties.

A psychophysical function, believed to reflect receptive field-like properties, is described. It is based on the determination of the critical flicker fusion frequency (CFF) of a tiny test target, centered on a round background of fixed luminance, the size of which is varied as the test parameter. Under optimal conditions, the maximal obtained frequency difference is 10 Hz. This function is compared with the so-called sustained-like function, with which it has some common aspects. Additionally, a portion of the flicker-based function apparently derives from a non-sustained-like source.

Flicker Fusion↗
PubMedDate not supplied

[Critical flicker fusion frequency in psychopathology and psychopharmacology. Review of the literature].

As far back as the second century, Ptolemy reported the apparent immobility of wheel radius at a certain speed. The psychophysical laws of this flicker fusion phenomenon related to the frequency of the light stimulus were established in 1834-1835 by the Englishman Talbot and by the Belgian Plateau, whose thesis in Liège is described as a landmark in the field. CFF is more a measurement of cortical arousal than of visual functions. In psychophysiology, CFF underwent periods of success and oblivion, at the mercy of researcher's enthusiasm or disappointment. At the turn of this century, Pierre Janet measured CFF in the laboratory of physiology of the Salpêtrière Hospital and demonstrated its decrease 'in hysteria, in states of depression, of lowered tension'. All reviewers of CFF literature have overlooked these observations, reported by Henri Piéron in the 'Melanges dedicated to Monsieur Pierre Janet'. When CFF falls into disgrace, it is because of the variability of its results, due to differences in apparatus and designs of the trials as well as the great number and the intrication of the variables which modify CFF thresholds, among them the nonsensory variables. When CFF is reappraised, as it has been the case in psychopharmacology in recent years, the reason is that it represents a brief, easy and economical measure of vigilance which, under certain conditions, seems to be also reliable, valid and sensitive. In the present monograph, the first in French on CFF, the authors try to analyze the most important contributions of the literature from the standpoint of the most relevant variables: characteristics of the stimulus (light intensity, wave form, wavelength, light-dark-ratio, diameter of the flickering point), test procedure (light vs. dark adaptation, visual angle, continuous vs. discontinuous presentation, monocular vs. binocular vision), influence of various physiological or psychological conditions (pupillary diameter, age, training, IQ; anxiety, depression, motivation etc.). The authors summarize the prerequisite for CFF to measure vigilance or aging in psychopharmacological research. The present Monograph is dedicated to the authors' 'Maîtres', who recently became Emeritus Professors, namely the ophthalmologist Roger Weekers, the pioneer of the clinical application of CFF in Belgium, and the psychiatrist Jean Bobon, who pioneered clinical psychopharmacology in Belgium.

Adaptation, Ocular↗
PubMed2000

Critical flicker fusion threshold: a potentially useful measure for the early detection of Alzheimer's disease.

Critical Flicker Fusion Threshold (CFFT) is a psychophysical threshold and, in psychological terms, it is regarded as a measure of information processing capacity. CFFT has previously been shown to be a valid and reliable measure in young healthy volunteers and it also has a long history of use as a psychopharmacological measure in this group. Furthermore, the test satisfies many of the requirements of an 'ideal' measure for monitoring change, especially in a psychopharmacological context. Despite this, CFFT has been neglected as a research tool in elderly and Alzheimer's disease (AD) populations and was therefore investigated further in this regard. CFFT in community-based healthy elderly subjects was normally distributed, but CFFT and ascending and descending thresholds were not significantly correlated with age. The difference between ascending and descending thresholds was, however, significantly correlated with age and this relationship appeared to be due almost entirely to a change in the descending threshold. In addition, descending thresholds were found to be significantly greater than ascending thresholds in healthy elderly subjects. In contrast, patients with AD were found to have significantly lower CFFT and descending scores compared with healthy elderly subjects. Interestingly, descending thresholds were significantly lower than ascending thresholds in the patient group, a feature that may be a characteristic of AD. Mean CFFT and ascending and descending thresholds were found to have a high test-retest, split-half and inter-rater reliability, in addition to being significantly correlated with a number of psychometric measures, clinical scales and neuropsychological instruments commonly used to assess patients with AD. CFFT is a quick and simple measure to administer and patients had no difficulty completing the test. Because the measure is a psychophysical threshold, it is free from educational and cultural bias and there are no floor or ceiling effects. From the results of this work, CFFT appears to be a useful research tool in AD. It may be a suitable measure for monitoring cognitive change over time, either in community studies of AD or a clinical trial context, but further work is required. The technique might also contribute to the early detection of AD. This application would be particularly important because it would enable effective pharmacotherapies to be started early during the course of the illness before neuronal damage is too advanced and this would have significant benefits for patients. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1985

[A special flicker fusion frequency method for detection of the effects of gerontopharmaceuticals exemplified by the L-eburnamonine study].

A clear difference between active drug and placebo is not always found when using the ascending and descending thresholds of the critical flicker fusion test (CFF). We selected a test requiring attention and concentration and performed again the CFF after this 6-minute concentration-test (reactive CFF). This reactive CFF was then used in a double-blind study in 30 ambulant patients with cerebro-vascular arteriosclerosis treated for 8 weeks with 80 mg/day cervoxan or placebo. After the treatment period the reaction of the CFF after the 6-minute concentration-test demonstrated a significantly more frequent improvement of the vigilance in the Cervoxan group compared to the placebo group.

Aged↗
PubMed1983

Critical flicker fusion frequency in early chloroquine retinopathy.

Since increasing numbers of patients with connective tissue diseases are taking chloroquine and its derivatives, there is an urgent need for a simple, reasonably fast method of screening for toxic effects on the retina. Measurement of the critical flicker fusion frequency is one technique for assessing retinal function. Its screening value was assessed in a study of nine patients with bilateral visual field defects and visual acuity of 6/12 or better after various periods of chloroquine therapy and nine healthy subjects matched for age and sex who had never taken chloroquine. The control subjects' eyes consistently demonstrated the normal pattern previously described, whereas 16 of the 17 eyes tested in the patients showed one of two abnormal patterns of response.

Chloroquine↗
PubMed1990

[Evaluation of the effects of pneumogenic hypoxemia on the nervous tissue by the determination of the critical flicker fusion frequency of the central retina].

Considering the eye an extroflection of the brain it is possible to detect a decrease of nervous tissues efficiency during hypoxia through a deficit of eye function. The authors studied a highly specialized retinal function that is extremely sensitive to low values of PaO2: the so called "critical flicker fusion frequency". The authors tested 14 patients with respiratory disorders and PaO2 levels between 36.5 and 67.1 mmHg. All patients showed impairment of this function.

Adult↗
PubMed1986

Diazepam-induced changes in signal detection performance. A comparison with the effects on the Critical Flicker-Fusion Frequency and the Digit Symbol Substitution Test.

The effects of 10 mg diazepam on signal detection theory measures (stimulus sensitivity, response bias) and reaction times were studied in a 1-hour visual signal detection task with high and low signal probability, and on performance in two short-duration tasks: Critical Flicker-Fusion Frequency (CFF) and the Digit Symbol Substitution Test (DSST). 12 healthy volunteers participated in this placebo-controlled, double-blind cross-over study. Diazepam affected the stimulus sensitivity and the reaction times of hits in the signal detection task. DSST performance was also impaired while CFF did not change after diazepam treatment. No relationship between serum diazepam concentration and change in task performance was found. It is concluded that diazepam affects signal detection performance, independent of signal probability. A short-duration task like the DSST is as sensitive to the effects of diazepam as the (long-duration) signal detection task.

Adolescent↗