Influence of Red Light and Pattern on Photic Driving

Abstract

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.