Do alpha sampling rhythms of visual perception also code for temporal integration to a higher order percept?

Goodier, Kirstie (2013) Do alpha sampling rhythms of visual perception also code for temporal integration to a higher order percept? University of Glasgow.

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Abstract

Studies on the role of intrinsic cortical oscillations in the organisation of visual perception suggest that cyclic inhibitory influences participate in the temporal coding of incoming sensory information. In terms of behavioural outcome, these inhibitory influences have been related to a cyclic variation in the perceptual fate of a simple near-threshold visual stimulus at a frequency which matches cortical alpha oscillations at around 10 Hz. In the current experiment we seek to demonstrate behavioural rhythms in visual perceptual performance, following cross-modal phase locking of visual cortical rhythms, for a two frame apparent motion stimulus. Our aim was to determine if performance in this more complex perceptual task – which necessitates sampling and integration of features for motion perception – shows a cyclic variation at a similar frequency to that previously demonstrated (~10 Hz) or shows another periodicity. To this end, we assessed oscillatory patterns in near-threshold visual discrimination performance in 20 participants (15 female) while they were viewing the apparent motion and control stimuli. Results show that there was a significant interaction in the perception of the apparent motion stimulus as motion, compared with a control random noise pattern over the time course of a trial (295 ms), which was due to a cyclic oscillatory trend at a frequency of 11Hz with motion perception, which was not the case for noise percepts. This is taken to suggest that the binding of successive static visual stimuli towards an integrated and meaningful percept of apparent motion is influenced in some manner by cortical oscillations in the alpha frequency. Whether this is likely to be an effect of periodicity in sampling or alternately of encoded temporal intraphasic information is considered.