Effect of luminance level on electro-encephalogram alpha-wave synchronisation.
A control system for the remote activation of electronic devices, based on alpha-wave synchronisation, must be robust over a wide range of lighting conditions. This study investigates the effect that low light levels have on the increase in amplitude of the occipital alpha-wave component of the human electro-encephalogram spectrum in response to eye closure. Measurements of the time required for the amplitude of the occipital alpha wave to increase above a predetermined threshold, upon eye closure, were taken from 21 subjects and at four illuminances, ranging from 2 x 10(-1) lx to 2 x 10(-5) lx. The light source used to provide these illuminances was a featureless, uniformly illuminated white paper that subtended 30 degrees of the visual field. Statistical analysis showed that the time to exceed threshold (TTET) upon eye closure was not independent (p< 0.001) of illuminance, and that the main source of this lack of independence occurred at the lowest illuminance, 2 x 10(-5) lx. At this luminance, the median TTET value was 15.0s. However, at 2 x 10(-4) lx, the median value of the TTET was 4.2s. This is a sufficiently short time for device activation, and therefore a control system based on alpha-wave synchronisation is functional at very low light levels.
Maher
A M
AM
Department of Applied Physics, University of Technology, Sydney, Australia. Ann.M.Maher@uts.edu.au
Kirkup
L
L
Swift
P
P
Martin
D
D
Searle
A
A
Tran
Y
Y
Craig
A
A
D000293:Adolescent; D000328:Adult; D000513:Alpha Rhythm / Q000379:methods*; D001767:Blinking / Q000502:physiology; D003344:Cortical Synchronization; D005260:Female; D006801:Humans; D008029:Lighting; D008297:Male; D008875:Middle Aged; D011930:Reaction Time; D014584:User-Computer Interface