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Abstract:
Fleming, Schofield, Mills, Adams, Stewart and Greenhalgh
(1999) investigated the M-cell pathway by introducing sequences of
differing number of quick photic stimuli that have varied 1)
inter-stimulus intervals, 2) spatial frequencies and 3) patterns to
the retina. Although neither the pattern nor the spatial frequency
of the stimulus significantly affected perceptual accuracy, the
number of pulses in a sequence and the inter-stimulus interval
between pulses did. This was further investigated by observing
visually evoked potentials (VEPs) and reaction times when the
inter-stimulus interval (ISI) and also the length of the pulse were
varied. In a second study the VEPs and perceptual accuracy,
measured as number of errors, were evaluated when the number of the
pulses (still of varying pulse length and ISI) in a train was
varied. It was found that there was no significant difference in
the resultant VEPs, but the various pulse lengths significantly
altered the reaction times, and so it was concluded that the
optimal reaction time for visual processing would occur with an ISI
of greater than 1sec. It was also found that the different pulse
lengths and the varying number of pulses in the train did not have
a significant effect on perceptual accuracy. The variables did,
however, affect the VEPs.
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