Abstract
Research on somatosensory awareness has yielded highly diverse findings with putative neural correlates ranging from activity within somatosensory cortex to activation of widely distributed frontoparietal networks. Divergent results from previous studies may reside in cognitive processes that often coincide with stimulus awareness in experimental settings. To scrutinise the specific relevance of regions implied in the target detection network, we used functional magnetic resonance imaging (n = 27) on a novel somatosensory detection task that explicitly controls for stimulus uncertainty, behavioural relevance, overt reports, and motor responses. Using Bayesian Model Selection, we show that responses reflecting target detection are restricted to secondary somatosensory cortex, whereas activity in insular, cingulate, and motor regions is best explained in terms of stimulus uncertainty and overt reports. Our results emphasise the role of sensory-specific cortex for the emergence of perceptual awareness and dissect the contribution of the frontoparietal network to classical detection tasks.
Highlights
The target detection task is a standard paradigm to study the neural correlates of perceptual awareness
Using Bayesian Model Selection on the acquired functional magnetic resonance imaging (fMRI) data, we observe a transformation from physical to perceptual representations as the target is propagated through the somatosensory hierarchy
This transformation primarily occurred in SI and SII, whereas expected uncertainty was represented in insular and cingulate regions and overt reports were processed in supplementary motor cortex
Summary
The target detection task is a standard paradigm to study the neural correlates of perceptual awareness. Research on this task has identified a range of areas that correlate with target detection These include the thalamus, primary (SI) and secondary (SII) somatosensory cortices, motor areas, the anterior insular cortex (AIC), anterior cingulate cortex (ACC), as well as posterior parietal and prefrontal regions (Auksztulewicz et al, 2012; Bastuji et al, 2016; Allen et al, 2016; Bornhovd et al, 2002; Buchel et al, 2002; de Lafuente and Romo, 2005; de Lafuente and Romo, 2006; Frey et al, 2016; Hirvonen and Palva, 2016; Jones et al, 2007; Moore et al, 2013). This diversity of findings parallels results from the visual and auditory modalities (e.g. Carmel et al, 2006; Eriksson et al, 2007; Rees et al, 2002) and underlies the idea that perceptual awareness emerges when local information is propagated from sensory cortices to higher order brain regions to elicit a reverberating network of broadcast activity (Baars, 1997; Dehaene et al, 2006)
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