Incoming sensory information is often ambiguous, and the brain has to make decisions during perception. "Predictive coding" proposes that the brain resolves perceptual ambiguity by anticipating the forthcoming sensory environment, generating a template against which to match observed sensory evidence.
Summerfield et al have observed a neural representation of predicted perception in the medial frontal cortex, while human subjects decided whether visual objects were faces or not. Perceptual decisions about faces were associated with an increase in top-down connectivity from the frontal cortex to face-sensitive visual areas, consistent with the matching of predicted and observed evidence for the presence of faces.
Figure: A simple dynamic causal model with hierarchically ordered bidirectional connections between vMFC (ventromedial frontal cortex), amygdala, FFA (fusiform face area), and IOG (inferior occipital gyrus). Face and nonface stimuli were modeled as inputs to IOG, and face sets as inputs to vMFC.
Predictive coding seems a very interesting concept. It would appear to me that this might account for a lot of the enhanced processing of faces seen in so many papers. Have you attempted a misleading anitciaption where the subject is expecting to see another image, thus priming the perceptual system for that class of stimuli, but followed with the presentation of a face stimulus? I'm sure this is in the paper cited, but was there any activation in the FFA prior to the dsiplay of the display of the image for discrimination?
ReplyDeleteI'll need some time to do the homework needed to respond properly to your questions.. I'm a bit overwhelmed at the moment.
ReplyDeleteHere is the link to the PDF of the article: http://dericbownds.net/uploaded_images/summerfield.pdf
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