Twenty-eight healthy participants were recruited from the database held by the University Hospital of Pediatric Neurology (Kiel, Germany).
3 The participants were divided into two groups with 14 in each: participants with photosensitivity, who had a PPR in the EEG response to intermittent photic stimulation (age range, 11–53 years, mean age ± SD: 26.8 ± 12.8 years, seven men) and participants with no PPR in the EEG (age range, 11–47 years, mean age ± SD: 25.9 ± 9.2 years, eight men). Thirteen from each group had participated in the study on TMS.
7 None had a history of any neurologic or psychiatric disorder, drug abuse, or alcoholism. None had epilepsy, but they were included in the hospital database because they had family members who had photosensitive epilepsy. (In our clinic, if anyone shows PPR in a routine EEG recording, his or her first-degree relatives are also investigated, resulting in a database containing healthy subjects who have never had epilepsy or PPR, healthy subjects who have never had epilepsy but who do have PPR, and patients with epilepsy and PPR). They had been assessed initially between 1 and 5 years earlier (mean, 33.72 ± 12.9, minimum 13, and maximum 58 months) and were assessed a second time within 2 weeks before the present experiment to ensure that they had the same classification (Verrotti et al.
2 ). The participants were interviewed about their state of health and were not taking any medication chronically or on the day of the experiments. The sample size was dictated by the availability of participants with photosensitivity who fulfilled these criteria. None of them was aware of the purpose of the experiment. All had normal or corrected-to-normal visual acuity, as assessed by the Snellen chart, intact confrontation visual fields, normal visual fixation, and normal smooth pursuit and saccadic eye movements. All the participants gave their written, informed consent and were paid for participating. The study was performed according to the Declaration of Helsinki and was approved by the ethics committee of the University of Kiel.