Flicker fusion

One study has reported effects on neurobehavioral function in lead-exposed workers at mean PbB levels of 50 pg/dL (Williamson and Teo 1986). Neurobehavioral function was measured using tests that are based on information processing theory in 59 lead workers and 59 controls matched for age, type of job, time on the job, education level, smoking history, and alcohol consumption. Statistically significant decreases in the lead-exposed workers were seen for critical flicker fusion reaction, simple reaction time, tracking speeds, hand steadiness tests, and sensory store memory. Sensory store memory speed showed a low but statistically significant correlation with PbB concentrations. Measurements of neurobehavioral function seemed well chosen, and repeated measures with associated appropriate statistics were used. 

The performance of the lead-exposed workers was significantly impaired. The critical flicker fusion threshold may reflect retinal or intermediate visual pathway function as well as cortical arousal. 

Brindley, G. S. et al. (1966). The flicker fusion frequency of the blue-sensitive mechanism of colour vision. Journal of Physiology (London) 183 497-500. 

More specific to the events after electrical signals have been generated in the retina are observations that critical flicker fusion thresholds, a classical measure of central processing speed relevant to the dynamic functioning of the visual system, are directly proportional (p < 0.001) to MPOD, as first reported by Hammond and Wooten (2005) and confirmed by Renzi et al. (2008a) in a larger population. 

Curran. S.. Wattis, J.P. Critical Flicker Fusion threshold a useful research tool m patients with Alzheimer s disease. Hum. Psvchopharmacol. 13, 337—355, 1998. 

Schmitt. J.E.J., Riedel, W.J.. Vuurman, E.F.P.M., et al. Modulation of the critical flicker fusion effects of serotonin reuptake inhibitors by concomitant pupillary changes. Psychopharmacology 160, 381-386, 2002. 

In healthy volunteers promethazine caused impaired cognitive function and psychomotor performance (64). The test battery consisted of critical flicker fusion, choice reaction time, compensatory tracking task, and assessment of subjective sedation. Cetirizine and loratadine at all doses tested were not significantly different from placebo in any of the tests used. 

Staal RG, Mosharov EV, Sulzer D. Dopamine neurons release transmitter via a flickering fusion pore. Nat. Neurosci. 2004 7 341-346. 

The effects of levocetirizine on cognitive function have been assessed in two comprehensive and well-controlled studies. The first analysed the effects of single and multiple doses of levocetirizine on measures of nervous system activity, using integrated measures of cognitive and psychometric performance. In a three-way crossover design, 19 healthy men took either levocetirizine 5 mg, diphenhydramine 50 mg (positive control), or placebo once-daily on five consecutive days. Critical flicker fusion tests were... 

Visual-evoked potential tests, such as flash electrore-tinography, flash and pattern visual-evoked responses, flicker fusion thresholds, and visual field perimetry, are reported to be the most rehable methods for early detection of ocular abnormahties (8,11,14). The routine use of visual-evoked potentials in the systematic followup of ethambutol-treated patients has been recommended (15). 

A double-blind crossover study in 12 healthy subjects found that a transdermal hyoscine preparation (Scopoderm-TTS) did not alter the effects of alcohol on the performance of several psychometric tests (Critical Flicker Fusion Frequency, Choice Reaction Tasks), nor was the clearance of alcohol or hyoscine changed. Blood-alcohol levels of up to 80 mg%, and 130 mg%, were studied. Nevertheless, the manufacturer suggests... 

A study in 12 healthy subjects found that both sublingual buprenorphine 400 micrograms and oral amitriptyline 50 mg impaired the performanee of a number of psychomotor tests (digit symbol substitution, flicker fusion, Maddox wing, hand-to-eye coordination, reactive skills), and the subjects felt drowsy, feeble, mentally slow and muzzy. When amitriptyline 30 mg, increased to 75 mg daily was given for 4 days before a single dose of buprenorphine, the psychomotor effects were not significantly increased, but the respiratory depressant effects of the buprenorphine were enhanced. ... 

Smart JV, Turner P. Influence of urinary pH on the degree and duration of action of amphetamine on Ae critical flicker fusion frequency in man. BrJ Pharmacol (196 26,468-72. 

Ebastine 20 mg daily did not impair the performance of a number of psy-ehomotor tests in 12 healthy subjects, although body sway and flicker fusion tests were altered. When ebastine was given with a single 15-mg dose of diazepam, it did not further impair performance compared with diazepam alone, and did not alter plasma diazepam levels. ... 

Itraconazole. Itraconazole 200 mg daily or a placebo was given to 10 healthy subjects for 4 days. On day 4 they were also given a single 10-mg oral dose of zolpidem. The mean peak serum levels of the zolpidem were increased by 12.5% and the AUC was increased by 35%, but the performance of a number of psychomotor tests (digit symbol substitution, critical flicker fusion, subjective drowsiness, postural sway) remained unaltered." Another study similarly found that itraconazole did not interact significantly with zolpidem."... 

Indometacin. Diazepam 10 to 15 mg impaired the performance of a number of psychomotor tests (digit symbol substitution, letter cancellation, tracking and flicker fusion) in 119 healthy medical students. It also caused subjective drowsiness, mental slowness and clumsiness. When indometacin 50 or 100 mg was given the effects were little different from diazepam alone, except that the feeling of dizziness (common to both drugs) was increased and caused subjective clumsiness. ... 

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