The Flicker‐fusion Test and Its Applications*

Abstract

It is known that successive flashes of light, when presented above a certain critical frequency -usually called ' critical flicker irequency (CFF) -a r e perceived a s steady continuous light. This phenomenon was systematically investigated a s early a s 1740 (Landis, 1951). Since that time a great deal has been learned about the various aspects of flicker and fusion of intermittent light. Some of this knowledge has been expressed in the form of laws such a s the Talbot-Plateau law (1834, 1835) and the Ferry-Porter law (1892, 1902). In the course of studies of flicker-fusion, various factors determining CFF have been established and described. It has been found that the characteristics of the light source, the physiological and psychological states of the observer, and the method of measuring the flicker-fusion threshold all affect the frequency at which light appears continuous and stable. In addition to the exploration of various parameters of flicker-fusion, attention has been paid to the question of the principal locus of the fusion process in the visual system -the retina, the visual nervous pathways, o r the visual cortex. Moreover, research has been conducted to understand the flicker-fusion phenomena in terms of neurophysiology and photochemistry. Several reviews summarize research in these various areas (Brown, 1965;Landis, 1954; Pi&on, 1965; Simonson & Broiek, 1952). A bibliography of flicker-fusion phenomena, prepared by Landis (1954), covered the period from 1740 to 1952 and contained 1,149 titles. About 40 more titles can be added for this period. Since 1952, we estimate, about 1,000 more studies dealing with flickerfusion phenomena have been published. In 1961 two international symposia, convened in Amsterdam, Holland, were devoted to flicker (Henkes & van der Tweel, 1964). Forty-five papers by investigators from 14 countries were presented at these symposia.In the last 25 years another orientation in flicker-fusion studies has emerged, namely, interest in the practical applications of flicker-fusion in clinical fields, and consequently in the development of a suitable flickerfusion test. After its successful use in such areas a s photometry, illumination, comparative study of animal vision, cinematography, and television, CFF is now being considered for its potential value a s a diagnostic aid and a research tool in fields such a s clinical neurology, ophthalmology, neurophysiology, gerontology, and psychopharmacology. It is t h i s potential value

The Measurement of CFF: Some Methodological Considerations

“…Attempts to standardize the method have been carried out by Misiak (1967) and by Turner (1%4). However, quality criteria have rarily been defined.…”

Psychological Functions in Relation to Lesion Size and Site in Cryothalamectomy for Parkinsonism

“…Administration was based on standard procedures (Misiak, 1967); fusion values were derived for the right and left eyes separately. This flicker-frequency is then subjectively reported as continuous.…”

“…In the past decade we have carried out psychological sntdies on the effects of unilateral and bilateral chemo-and cryothalamectomy in Parkinsonism, with special emphasis on "integrative" functions (Riklan, Diller, Weiner & Cooper, 1960;Levita, Riklan, & Cooper, 1964;, 1967Levita, Riklan, & Cooper, 1967). The following statements represent a brief summary of pertinent findings: (1) Immediately following surgery, a mean of some 2 wk., alterations in "integrative" functions have been associated with unilateral and bilateral thalamectomy.…”

Pilot Studies on Stimulant Effects of Capsicum Spices

“…CFF, critical flicker fusion frequency [18]: We used the Bettendorff apparatus with continuous regulation, employing the method of decreasing flicker frequency. The mean of three consecutive measurements constituted a subject's score.…”