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Christine Girges, Michael Wright, Janine Spencer, Justin O'Brien; Event-related alpha suppression in response to facial motion.. Journal of Vision 2013;13(9):182. doi: https://doi.org/10.1167/13.9.182.
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Introduction: Research has associated reductions in the alpha power of occipital and parietal EEG (alpha suppression) with visual attentional processes and memory load performance. The purpose of the current EEG study was to determine the effect of facial (biological) motion on alpha suppression. Methods: Participants viewed a continuous stream of averaged facial motion captures. The animations exhibited natural motion, were realistic in appearance and only differed in the way they moved (Hill & Johnston, 2001). The task was to discriminate between successive motion animations by indicating whether they were the same or different. Upright, inverted and polarity-inverted facial stimuli were compared. The amplitudes and latencies of maxima and minima alpha power were analysed across occipital and parietal-occipital visual areas. Results: There was an overall effect of face type on alpha at parietal-occipital locations. Although each face type reduced alpha power, there are some considerable differences to note. Relative to baseline (-100 ms to 0 ms onset), upright facial motion evoked the highest alpha amplitudes at 400 – 500 ms post onset and the most subsequent suppression compared to other stimuli. Suppression in response to upright facial motion also occurred earlier than for other face types (upright 730 ms; polarity-inverted 733 ms; inverted 754 ms). Similar observations were made at occipital sites. Conclusion: Upright facial motion is processed earlier and more efficiently than other facial motions. This highlights its importance as a mediator of social cognition (e.g. identification, emotion recognition, inferring intentions). Differential suppression at occipital and parietal-occipital sites indicates that visual processing of facial motion is affected by experimental manipulations such as inversion and polarity reversal. However, each face type reduced alpha power to some extent, implying that the visual substrates are active and trying to make sense of the visual scene regardless of manipulation.
Meeting abstract presented at VSS 2013
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