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Abstract
This paper addresses perceptual synthesis by comparing responses evoked by visual stimuli before and after they are recognized, depending on prior exposure. Using magnetoencephalography, we analyzed distributed patterns of neuronal activity – evoked by Mooney figures – before and after they were recognized as meaningful objects. Recognition induced changes were first seen at 100–120 ms, for both faces and tools. These early effects – in right inferior and middle occipital regions – were characterized by an increase in power in the absence of any changes in spatial patterns of activity. Within a later 210–230 ms window, a quite different type of recognition effect appeared. Regions of the brain’s value system (insula, entorhinal cortex and cingulate of the right hemisphere for faces and right orbitofrontal cortex for tools) evinced a reorganization of their neuronal activity without an overall power increase in the region. Finally, we found that during the perception of disambiguated face stimuli, a face-specific response in the right fusiform gyrus emerged at 240–290 ms, with a much greater latency than the well-known N170m component, and, crucially, followed the recognition effect in the value system regions. These results can clarify one of the most intriguing issues of perceptual synthesis, namely, how a limited set of high-level predictions, which is required to reduce the uncertainty when resolving the ill-posed inverse problem of perception, can be available before category-specific processing in visual cortex. We suggest that a subset of local spatial features serves as partial cues for a fast re-activation of object-specific appraisal by the value system. The ensuing top-down feedback from value system to visual cortex, in particular, the fusiform gyrus enables high levels of processing to form category-specific predictions. This descending influence of the value system was more prominent for faces than for tools, the fact that reflects different dependence of these categories on value-related information.
Highlights
A core assumption of cognitive neuroscience is that visual perception involves hierarchically organized processing, the outcomes of which span from low-level visual features to increasingly abstract and subjective representations
In the first part of the study, we present the results of spatiotemporal searchlight approach based on statistical parametric maps (SPM) of relations with the model representational dissimilarity matrix (RDM)
We report clusters as significant if they were greater than the 95% threshold constructed from the maximal cluster size distribution
Summary
A core assumption of cognitive neuroscience is that visual perception involves hierarchically organized processing, the outcomes of which span from low-level visual features to increasingly abstract and subjective representations. It has been suggested that perception is determined by the bottom-up propagation of information from our sensory organs, but is depends upon the top-down influence of prior knowledge in cortical hierarchies (Oliva and Torralba, 2007; Rauss et al, 2011; Gilbert and Li, 2013; Pi€ech et al, 2013; Summerfield and De Lange, 2014; de Lange et al, 2018) This experimental study was motivated by the question: how does prior knowledge affect visual processing to facilitate object recognition?. The assumption that the corresponding neural subpopulations co-exist within the same (coarse grained) cortical region was confirmed by a recent study (De Gardelle et al, 2013) and could explain why recognition facilitation experiments – in studies with low spatial resolution – evince response suppression or enhancement, depending on the specific experimental conditions (Segaert et al, 2013) or the exact level of the brain region investigated within the perceptual hierarchy (Murray et al, 2002)
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