Frontiers in psychology
January 1, 2016
Chiara F Tagliabue, Chiara Mazzi, Chiara Bagattini et al.
69 citations
Visual conscious experience is graded rather than all-or-none, and its neural signature appears in early local brain activity without requiring later frontal involvement. Using electroencephalography, researchers recorded event-related potentials while participants viewed low-contrast visual stimuli and rated their perceptual clarity on a four-point scale. A left centro-parietal negative deflection (Visual Awareness Negativity, VAN) at 280–320 milliseconds reflected the perceptual content, and a bilateral positive deflection (Late Positivity, LP) at 510–550 milliseconds reflected post-perceptual processes. The amplitude of both deflections increased gradually with reported awareness. Source localization placed the generators of phenomenal content in the left temporal lobe.
The European journal of neuroscience
June 1, 2023
Alessandra Tafuro, Chiara Mazzi, Silvia Savazzi
Visual awareness involves a complex interplay of brain rhythms across different frequency bands. In an orientation discrimination task where response bias was induced, EEG recordings showed that alpha and beta bands are especially engaged when contrasting aware versus unaware trials, with a main power suppression for aware trials. Theta, alpha, beta, and gamma bands each contribute as prerequisites or post-perceptual processes, rather than a single frequency marking consciousness itself.
Frontiers in systems neuroscience
January 1, 2020
Chiara Mazzi, Gaetano Mazzeo, Silvia Savazzi
Contrastive analysis of EEG data is used to identify neural correlates of consciousness, but it may be confounded by processes before or after conscious perception. To isolate visual awareness from post-perceptual decision-making, participants performed an orientation discrimination task while shifting their response criterion across sessions. The N1 and P3 components were sensitive to the response criterion, and their modulation increased with criterion shifts, indicating involvement in decision-making independent of awareness. When ignoring the response criterion, both Visual Awareness Negativity (VAN) and Late Positivity (LP) were significant for aware versus unaware contrasts.