INFLUENCE OF RED-LIGHT AND PATTERN ON PHOTIC DRIVING

Takahashi, T. and Tsukahara, Y. Influence of Red Light and Pattern on Photic Driving. Tohoku J. exp. Med., 1979, 127 (1), p.45-52 -— The photic drivings (PDs) in response to the following visual stimuli were studied in 108 oases, of which 84 (78%) were epileptics; ages ranged from 5 to 57 years old. An intermittent photic stimulation (IPS) of 5 cycles/sec by a stroboscopic light was given to the subjects with eyes closed and open. Following these stimuli, red-flicker and flickering-pattern of 5 cycles/sec and 20 cd/m2 were given successively to the subjects with eyes open using a “visual stimulator”. The PDs evoked by IPS to the eyes closed and those by red-flicker were similar in the wave form and amplitude. In most of the cases, however, both stimuli failed to evoke apparent PDs (over 25 µV in amplitude), i.e., in 81% and 72%, respectively. IPS to the eyes open and flickering-pattern showed comparable effects in evoking PDs; they evoked high amplitude PDs (over 50 µV in amplitude) with a frequency of 19% by the former and 28% by the latter. In 95 out of 108 cases, both IPS to the eyes closed and red-flicker failed to evoke apparent PDs. In rare cases, IPS to eyes closed evoked high amplitude PDs; in 7 out of these 8 cases, red-flicker also evoked high amplitude PDs. In 18 out of 20 cases in which high amplitude PDs were evoked by IPS to the eyes open, flickering-pattern was also effective in evoking high amplitude PDs. Based on these findings, similarities between IPS to the eyes closed and red-flicker, and similarities between IPS to the eyes open and flickering-pattern in evoking PDs are discussed. It is concluded that flickering-pattern and red-flicker are superior to IPS to the eyes open and closed, respectively, for examining the low frequency PDs. ---photic driving; red-flicker; flickering-pattern In a preliminary study (Takahashi and Tsukahara 1975) using a visual stimulator (Tsukahara and Takahashi 1972), we showed that among the red-flicker stimuli of 5, 10, 15, 20, 25 and 30 cycles/see with the three levels of brightness of 40, 25 and 4 cd/m2, those of 15 cycles/sec revealed the strongest activating effect on paroxysmal discharges at every level of brightness. An intensity of 20 cd/m2 was found to be the lowest brightness that has a sufficiently potent activating effect on paroxysmal discharges. As for the pattern, a dot pattern (see Fig. 1) and a grating pattern were selected because the former showed a significant activating effect of lambda waves and/or rhythmic posterior slow waves, whereas the latter showed an activating effect of paroxysmal discharges. © 1979, Tohoku University Medical Press. All rights reserved.