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.

Thresholds for detection of a target against a background grating suggest visual dysfunction in migraine with aura but not migraine without aura.

Square-wave gratings with particular spatial characteristics induce visual illusions. Patients with migraine are particularly susceptible to these illusions and report discomfort. Their discomfort tends to be greater when the gratings are illuminated by red light, a tendency not shown by controls. Gratings that induce illusions have been found to impair the recognition of optically superimposed targets in headache-free control subjects. We measured the impairment of target detection under illuminants of various chromaticities in migraineurs with and without aura and in matched controls. Migraineurs with aura had significantly higher thresholds for target detection than either migraineurs without aura or controls; in addition, the effect of chromaticity was slightly more pronounced in both migraine groups than in the control group. These findings are consistent with a recent suggestion that migraine with aura might give rise to subclinical damage to the primary visual cortex.

Precortical dysfunction of spatial and temporal visual processing in migraine.

This paper examines spatial and temporal processing in migraineurs (diagnosed according to International Headache Society criteria, 1988), using psychophysical tests that measure spatial and temporal responses. These tests are considered to specifically assess precortical mechanisms. Results suggest precortical dysfunction for processing of spatial and temporal visual stimuli in 11 migraineurs with visual aura and 13 migraineurs without aura; the two groups could not be distinguished. As precortical dysfunction seems to be common to both groups of patients, it is suggested that symptoms that are experienced by both groups, such as blurring of vision and photophobia, may have their basis at a precortical level.

Psychopharmacological effects of pyritinol in normal volunteers.

Twelve healthy male volunteers received pyritinol 600 or 1,200 mg or placebo for 3 days according to a randomised, double-blind crossover design. On the 1st and 3rd days of each of the three treatment periods subjects completed a battery of psychological tests including Critical Flicker Fusion (CFFT), Choice Reaction Time (CRT), tests of memory and subjective drug effects at 1, 2, 4 and 6 h after dosing. Significant improvements in CFFT and CRT were found after pyritinol. There were no significant differences on the other tests, however, the observed enhancement in performance could be attributed to the effect of the drug.