Photoparoxysmal response elicited by flickering dot pattern stimulation to the center and periphery.
OBJECTIVE
We performed this study to elucidate the roles of stimulus spatial frequency and visual field in eliciting generalized photoparoxysmal response (PPR) by flickering dot pattern (FDP) stimulation.


METHODS
We studied 20 photosensitive epilepsy patients, aged 7-48 years (means +/- SD, 21.4+/-11.7 years), producing a 20 Hz FDP stimulation with a strobo-filter. Using dot patterns (0.5, 1, 2, 4 and 6 mm in diameter), we gave FDP stimulation to the center (11x11 degrees ) and periphery (11-30x11-30 degrees ) of subjects with eyes open, and analyzed each PPR appearance latency.


RESULTS
Significant results were: latency by 1 (2.1 c/deg) and 0.5 mm (4.9 c/deg) FDP stimulation to the center was shorter than that to the periphery; latency by 4 mm (0.8 c/deg) FDP stimulation to the periphery was shorter than that to the center. As for 2 (1.5 c/deg) and 6 mm (0.5 c/deg) FDP stimuli, no significant difference could be observed.


CONCLUSIONS
A higher spatial frequency FDP stimulation to the center elicits PPR more strongly than that to the periphery, whereas a lower spatial frequency FDP stimulation showed the opposite result, with peripheral stimulation being more effective than central stimulation.
Takahashi
T
T
Yaotome Clinic, 2-12-2 Yaotome, Izumi-ku, 981-3112, Sendai, Japan. tt@dd.iij4u.or.jp
Tsukahara
Y
Y
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography; D020195:Epilepsy, Reflex / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods*