Oscillatory responses to conscious and unconscious figure perception
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1
University of Utrecht, Netherlands
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2
University of Amsterdam, Netherlands
For the conscious visual perception of figures, different neuronal connection types (feedforward, feedback) are needed. Feedback processing is necessary to segregate a figure from its background and consciously perceive the figure (Lamme, 2000). Recent studies have shown that the feedforward sweep is sufficient for neural object classification, without conscious awareness of the figure (Fahrenfort et al., in preparation). Here we used EEG to study event-related and oscillatory brain responses to conscious (feedforward + feedback) and unconscious (feedforward) figure processing. Eighteen subjects saw schematic pictures of faces, houses and nonsense objects. Pictures were rendered visible (conscious) or invisible (unconscious) using a dichoptic fusion paradigm. The event-related potential showed a negative peak over midline occipital electrodes for both visible and invisible figures from 80-125 ms after stimulus onset, followed by a second negativity from 125-250 ms for the visible condition only. In response to visible figure-ground segregation only, an increase in theta (4-6 Hz) and high gamma (50-80 Hz) power, and a decrease in beta-band activity (12-20 Hz) was seen over bilateral peri-occipital electrodes. Thus, the oscillatory activity in the theta and gamma band, as seen in this study, is a reflection of recurrent processing necessary for figure-ground segregation and a conscious percept.
Keywords:
Awareness,
Feedback
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Poster Sessions: Consciousness and Awareness
Citation:
Snijders
TM,
Fahrenfort
JJ,
Lamme
VA and
Kemner
C
(2011). Oscillatory responses to conscious and unconscious figure perception.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00053
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Received:
15 Nov 2011;
Published Online:
25 Nov 2011.
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Correspondence:
Dr. Tineke M Snijders, University of Utrecht, Utrecht, Netherlands, t.snijders@donders.ru.nl