Converging Intracranial Markers of Conscious Access

Abstract

We compared conscious and nonconscious processing of briefly flashed words using a visual masking procedure while recording intracranial electroencephalogram (iEEG) in ten patients. Nonconscious processing of masked words was observed in multiple cortical areas, mostly within an early time window (<300 ms), accompanied by induced gamma-band activity, but without coherent long-distance neural activity, suggesting a quickly dissipating feedforward wave. In contrast, conscious processing of unmasked words was characterized by the convergence of four distinct neurophysiological markers: sustained voltage changes, particularly in prefrontal cortex, large increases in spectral power in the gamma band, increases in long-distance phase synchrony in the beta range, and increases in long-range Granger causality. We argue that all of those measures provide distinct windows into the same distributed state of conscious processing. These results have a direct impact on current theoretical discussions concerning the neural correlates of conscious access.

The MVGC multivariate Granger causality toolbox: A new approach to Granger-causal inference

“…VARFIMA modelling (Section 3.3). Despite these caveats, G-causality analysis of stationary iEEG/LFP data is likely to be highly informative; see Gaillard et al (2009) for an illuminating example.…”

Classical conditioning of analgesic and hyperalgesic pain responses without conscious awareness

“…In addition to evidence for conditioning of low-level physiological responses, a recent literature challenges the idea that nonconscious processing stops at an early perceptual level (4), suggesting that higher-order cognitive representations, such as meaning and goal pursuits, can be acquired nonconsciously (15). Moreover, findings from neuroimaging studies show that nonconscious stimuli have extensive representations in the human brain, activating a large number of cortical areas (16)(17)(18) at frequency bands previously seen as markers of conscious awareness (19). Taken together, these results suggest that nonconscious stimuli have a pervasive effect on human brain function and behavior and may affect learning of complex cognitive processes such as psychologically mediated pain responses.…”

Tempo de cérebro

“…O inconsciente foi completamente intangível por muitas décadas após sua concepção. Hoje em dia, a investigação do processamento cerebral inconsciente constitui um importante programa de pesquisa (Fang;He, 2005;Gaillard et al, 2009). O advento dos computadores, capazes de triturar grandes conjuntos de dados e implementar cálculos complexos, mudou completamente a dinâmica da pesquisa, capacitando sofisticados algoritmos matemáticos e abordagens de força bruta para a análise e classificação de dados.…”

“…Afinal, mais de cem anos depois da descoberta do neurônio, já entendemos que consciência não é uma coisa nem um lugar no cérebro, e sim um processo de fluxos iônicos distribuído por várias regiões cerebrais (Gaillard et al, 2009). É claro que todas as interações do ser com o ambiente, conscientes ou não, dependem desses fluxos.…”