Constructive theories of brain function such as predictive coding posit that prior knowledge affects our experience of the world quickly and directly. However, it is yet unknown how swiftly prior knowledge impacts the neural processes giving rise to conscious experience. Here we used an experimental paradigm where prior knowledge augmented perception and measured the timing of this effect with magnetoencephalography (MEG). By correlating the perceptual benefits of prior knowledge with the MEG activity, we found that prior knowledge took effect in the time-window 80–95ms after stimulus onset, thus reflecting an early influence on conscious perception. The sources of this effect were localized to occipital and posterior parietal regions. These results are in line with the predictive coding framework.

Key words: predictive coding, contents of consciousness, meg, prior knowledge, conscious perception, cognitive penetrability

The contents of consciousness are complex and dynamic and are embedded in perception and cognition. The study of consciousness and subjective experience has been central to philosophy for centuries. However, despite its relevance for understanding cognition and behaviour, the empirical study of consciousness is relatively new, embroiled by the seemingly opposing subjective and objective sources of data. Francisco Varela (1946–2001) pioneered the empirical study of consciousness by developing novel, naturalised and rich approaches in a non-reductive and comprehensive manner. In this article, we review the main conceptual distinctions and philosophical challenges of consciousness research and highlight the main contributions of Varela and his associates: the development of neurophenomenology as a methodological framework that builds a bridge between subjective and objective sources of data and the discovery of gamma-band phase synchronisation as a neural marker of perceptual awareness. Finally, we describe the work of Varela on time consciousness, his philosophical approach and the implementation of his neurophenomenological framework for its study by integrating subjective reports with neural measures.

Key words: consciousness, perception, neurophenomenology, philosophy of mind, francisco varela

Our aim in ‘Are There Neural Correlates of Consciousness?’ was to call attention to some problematic assumptions of one widespread approach to investigating the relation between consciousness and the brain – the research programme based on trying to find neural correlates of the contents of consciousness (content-NCCs). Our aim was not to cast doubt on the importance of neuroscientific research on consciousness in general (contrary to Baars’s impresssion). Nor was it to engage in philosophical debates far removed from the concerns of scientists (as McLaughlin & Bartlett may think). Rather, it was to target some problematic assumptions of a particular empirical research programme, and by bringing them to light, to suggest that there may be other, more profitable ways to investigate the contribution of brain processes to conscious experience than searching for content NCCs. Most of the commentators (Bayne, Freeman, Hardcastle, Haynes & Rees, Hohwy & Frith, Metzinger, Myin, Roy, Searle, Van Gulick), though certainly not all (Baars, Jack & Prinz, McLaughlin & Bartlett) seem to have read us this way, and we are grateful for their critical reflections on our article. In this Authors’ Reply, we cannot respond in detail to every point raised by the commentators, so we shall limit ourselves to addressing the most important issues that we see arising from the commentaries collectively.

We propose a new approach to the neuroscience of consciousness, growing out of the ‘enactive’ viewpoint in cognitive science. This approach aims to map the neural substrates of consciousness at the level of large-scale, emergent and transient dynamical patterns of brain activity (rather than at the level of particular circuits or classes of neurons), and it suggests that the processes crucial for consciousness cut across the brain–body–world divisions, rather than being brain-bound neural events. Whereas standard approaches to the neural correlates of consciousness have assumed a one-way causal-explanatory relationship between internal neural representational systems and the contents of consciousness, our approach allows for theories and hypotheses about the two-way or reciprocal relationship between embodied conscious states and local neuronal activity.