A double dissociation between the neural bases of spatial attention and visual awareness
Neural amplification by attention is thought be a crucial factor for a stimulus to reach awareness. In this view, the typical enhancement of neural responses to attended stimuli would increase their effective contrast during visual processing and therefore facilitate conscious access. Surprisingly, this intuitively appealing assumption has never been directed tested. We performed a series of experiments in normal subjects as well as in blindsight patient GY in which we manipulated spatial attention on the one hand, and rendered stimuli barely visible by decreasing luminance or using backward masks on the other hand. We recorded magnetoencephalographic (MEG) signals while subjects attended toward or away from stimuli which were physically identical but consciously detected in about half of the trials. Each trial could therefore be classified as attended or unattended, and consciously seen or not. In this attention-by-awareness design, we consistently observed an attentional amplification of neural responses, both in event-related responses and in the gamma range, that was present for both seen and unseen stimuli. Reciprocally, we report the existence of larger neural event-related responses and gamma-band oscillations to consciously seen stimuli, independently from the locus of attention. We carefully checked that such results could not be attributed to sub-optimal spatial orienting in unaware trials or to performance confounds. Our results therefore point toward a double dissociation between endogenous spatial attention and visual awareness at the neural level, a conclusion that calls for a revision of the respective definitions of these two major cognitive functions.
Keywords:
Attention,
MEG,
Neural Response
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Symposium: Oral Presentation
Topic:
Symposium 4: Attention, awareness and control
Citation:
Tallon-Baudry
C
(2011). A double dissociation between the neural bases of spatial attention and visual awareness.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00027
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Received:
09 Nov 2011;
Published Online:
15 Nov 2011.
*
Correspondence:
Dr. Catherine Tallon-Baudry, CRICM, Paris, France, catherine.tallon-baudry@ens.fr