Photoparoxysmal response elicited by flickering dot pattern stimulation to the center and periphery. |
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Authors: | T Takahashi Y Tsukahara |
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Institution: | Yaotome Clinic, 2-12-2 Yaotome, Izumi-ku, 981-3112, Sendai, Japan. tt@dd.iij4u.or.jp |
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Abstract: | 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. |
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