Abstract
To date, most studies on the event-related potential (ERP) correlates of conscious perception have examined a single perceptual modality. We compared electrophysiological correlates of visual and auditory awareness in the same experiment to test whether there are modality-specific and modality-general correlates of conscious perception. We used near threshold stimulation and analyzed event-related potentials in response to aware and unaware trials in visual, auditory and bimodal conditions. The results showed modality-specific negative amplitude correlates of conscious perception between 200 and 300 ms after stimulus onset. A combination of these auditory and visual awareness negativities was observed in the bimodal condition. A later positive amplitude difference, whose early part was modality-specific, possibly reflecting access to global workspace, and later part shared modality-general features, possibly indicating higher level cognitive processing involving the decision making, was also observed.
Highlights
An observer is aware of the external world when a specific type of activity in her brain “transforms” the upcoming sensory information into subjective conscious experience, and one of the aims of neuroscience is to figure out where and when this takes place
In electrophysio logical measurements these neural correlates of con sciousness (NCC) candidates are reflected by two separate event-related potential (ERP) difference waves between aware and unaware sensory stimuli: the Visual Awareness Negativity (VAN) and the Late Positivity (LP)
Performance in the auditory condition was most accurate, having moderate response bias and highest sensitivity. Results of these analyses suggest that participants were more sensitive to detect auditory and bimodal stimuli, and more conservative in reporting auditory and bimodal awareness compared to visual awareness in this experiment
Summary
An observer is aware of the external world when a specific type of activity in her brain “transforms” the upcoming sensory information into subjective conscious experience, and one of the aims of neuroscience is to figure out where and when this takes place. Up to date there are two main NCC candidates for visual awareness: while some research posits late activation in fronto-parietal networks as the true NCC (Dehaene and Changeux, 2011; Lau and Rosenthal, 2011), other studies argue that the visual NCC is rather an early recurrent activation in occipitotemporal areas (Koivisto and Grassini, 2016; Koi visto et al, 2016; Railo et al, 2015; Lamme, 2010). In electrophysio logical measurements these NCC candidates are reflected by two separate event-related potential (ERP) difference waves between aware and unaware sensory stimuli: the Visual Awareness Negativity (VAN) and the Late Positivity (LP) (for a recent review, see Forster et al, 2020). VAN has been found in many studies and is thought to be the earliest
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