EEG activation by use of stroboscope and visual stimulator SLS-5100.

Abstract

The efficiency of the following visual stimuli in activating high amplitude (over 50 μV) photic driving (PD) and photoconvulsive response (PCR) was studied in 536 cases of patients including 340 (63%) epileptics. Their ages ranged from 3 to 78 years. An intermittent photic stimulation (IPS) of 5 and 15 Hz produced by a stroboscope was given to the subjects with eyes closed and open. A visual stimulator which was designed by us and is now commercially available (SLS-5100, Nihon Kohden) was used to give red-flicker, flickering-dot-pattern and flickering-grating-pattern. The average brightness of the illuminated screen of the SLS-5100 was 20 cd/m2 and the flicker frequencies were 5 and 15 Hz. The number of cases in which high amplitude PD was evoked by (1) 5 Hz IPS to eyes closed, (2) 5 Hz IPS to eyes open, (3) 5 Hz red-flicker, and (4) 5 Hz flickering-dot-pattern was 28 (5.2%), 6 (1.1%), 44 (8.2%), and 36 (6.7%), respectively. On the other hand, PCRs provoked by the above 4 kinds of stimuli as well as (5) 15 Hz IPS to eyes closed, (6) 15 Hz IPS to eyes open, (7) 15 Hz red-flicker, and (8) 15 Hz flickering-grating-pattern were found in 5 (0.9%), 2 (0.4%), 6 (1.1%), 4 (0.7%), 5 (0.9%), 6 (1.1%), 44 (8.2%), and 36 (6.7%) cases, respectively. The total number of cases in which PCR was provoked by these 8 stimuli was 56 (10.4%) out of 536 cases. From these results, it was concluded that the visual stimuli of flickering-patterns and red-flicker produced by the visual stimulator SLS-5100 are superior to the IPS produced by the commonly used stroboscope for EEG activation.