The influence of oscillatory activity on phosphene perception - a real-time study
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1
Universität Konstanz, Germany
An increasing amount of recent studies suggest that spontaneous cortical oscillations in the pre stimulus phase influence the „fate“ of the stimulus, i.e. how the stimulus is processed. Romei et al. (2008) have shown that this also accounts for the perception of phosphenes, visual percepts induced at the visual cortex by transcranial magnetic stimulation (TMS): The probability of seeing a phosphene was higher when occipital alpha was low and vice versa. There are, however, findings that suggest that alpha power does not suffice to explain the phenomenon. We therefore used an EEG real-time experiment to trigger TMS pulses at the individual’s phosphene threshold only when occipital alpha was either low or high to test this hypothesis in a more direct way. This setup also enabled us to analyze for differences that may only occur in high or low alpha trials as already suggested in the literature. The validation of the online paradigm showed perfect separation between high- and low-alpha trials. Our behavioral analysis could not support the hypothesis as probability of phosphene perception was equal for high and low alpha trials. Analyzing trials in which a phosphene was perceived against those without perception, we found a distinction as hypothesized, although we found a small spatial offset between the results in Romei’s paper and ours. Most interestingly, we found that in high alpha trials with phosphene perception, frontal alpha was increased – a relationship we did not see for low alpha trials. Our work shows that although prestimulus oscillatory power has an impact on perceptual processing, the relationship does not seem to be as straight-forward as to be confirmed in an online experiment despite perfect trial separation. Funding: Supported by DFG, TRI, Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg.
Keywords:
brain oscillations,
Perception
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Poster Sessions: Quantitative Analysis of EEG, MEG & Brain Oscillations
Citation:
Hartmann
T and
Weisz
N
(2011). The influence of oscillatory activity on phosphene perception - a real-time study.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00141
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Received:
17 Nov 2011;
Published Online:
28 Nov 2011.
*
Correspondence:
Dr. Thomas Hartmann, Universität Konstanz, Konstanz, Germany, thomas.hartmann@th-ht.de