Relationships between Inter-Flash Intervals at Fusion, under Conditions Intended to Eliminate Neural “Off” Effects

Abstract

Short, low intensity photic pulses were used to study flicker perception. According to available evidence, such stimuli will induce no neural “off” effects. Although the pulse trains used in the experiment are, from a physical viewpoint, harmonically complex, absence of induced neural “off” effects makes their neurophysiological concomitants relatively uncomplicated and it is for the latter reason that stimuli of the type described were used. The data were interpreted as additional confirmation of the concept that neural impulse interval modulation is a mechanism for transmission of information in the nervous system. In the particular case of our experiment, results led us to postulate (a) that the mechanism responsible for perception of flicker, in the absence of “off” effects as cues, is the detection by the visual system of an increase in intervals between neural impulses that occur between successive photic pulses, and (b) that the time required for such detection is dependent upon and varies in direct proportion to initial periods between neural spikes induced by flashes in the stimulus train.