Direct manipulation of conscious visual perception by real-time fMRI multivoxel pattern decoded neurofeedback of frontoparietal brain activity
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2025
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Abstract
The present study addresses the problem of consciousness from the perspective of its phenomenological content (awareness). It examines the main contemporary theories concerning the neural correlates of consciousness, focusing on the Global Neuronal Workspace Model (GNWM) and the Higher-Order Theory (HOT). While the GNWM proposes that conscious access arises from the propagation of sensory information toward frontoparietal networks—particularly the dorsolateral prefrontal cortex—HOT suggests that consciousness emerges when a sensory representation is meta-represented by a higher-order representation localized in frontal regions. The former explains conscious access as a process of amplification and global broadcasting of information, whereas the latter attributes to the frontal cortex a constitutively representational role, capable of generating a conscious version of sensory inputs.Building on these perspectives, the present work aims to examine whether frontoparietal neural representations maintain an identity relationship with the subjective experience of visual stimuli, following the Neural Identity Theory (NIT), which posits that mental states and neural patterns are coextensive—two descriptions of the same phenomenon. This hypothesis was evaluated experimentally through functional magnetic resonance imaging (fMRI) and multivoxel pattern analysis (MVPA) during a Directional Motion Detection Task (DMDT).The study tested two main hypotheses: (1) frontoparietal activity varies as a function of stimulus ambiguity, being modulated by signal strength (coherence); and (2) the decodability of frontoparietal patterns provides evidence of an identity relationship between subjective experience and neural representation.The results showed that frontal activity increased under ambiguous conditions, indicating that when the stimulus was difficult to discriminate, frontal regions actively contributed to the construction of conscious experience through attentional and metarepresentational mechanisms. This involvement included the dorsolateral prefrontal, orbitofrontal, anterior cingulate, and opercular cortices.Notably, MVPA results revealed that even during trials without conscious report, information about motion direction could be decoded from patterns in the orbitofrontal and temporal cortices. This suggests that the brain maintains representations of stimuli even in the absence of conscious access. When sensory information was insufficient, participants appeared to rely on reconstructive or inferential processes dependent on memory, integrating perceptual fragments with stored knowledge. This pattern suggests that conscious experience depends not only on stimulus features but also on previous experience and the history of interactions with the environment.Taken together, these findings support a representational and integrative view of consciousness, in which the frontal cortex not only facilitates access to information but also contributes to its construction.
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Tesis (PhD degree in Neuroscience)--Pontificia Universidad Católica de Chile, 2025