Biology of consciousness

Abstract

The Dynamic Core and Global Workspace hypotheses were independently put forward to provide mechanistic and biologically plausible accounts of how brains generate conscious mental content. The Dynamic Core proposes that reentrant neural activity in the thalamocortical system gives rise to conscious experience. Global Workspace reconciles the limited capacity of momentary conscious content with the vast repertoire of long-term memory. In this paper we show the close relationship between the two hypotheses. This relationship allows for a strictly biological account of phenomenal experience and subjectivity that is consistent with mounting experimental evidence. We examine the constraints on causal analyses of consciousness and suggest that there is now sufficient evidence to consider the design and construction of a conscious artifact.

Keywords: Dynamic Core; Global Workspace; Neural Darwinism; qualia; reentry.

Figure 1

Results of a study of human whole-head magnetoencephalographic (MEG) signals evoked by visual stimuli that were binocularly rivalrous and frequency-tagged (Srinivasan et al., 1999). The topographic map indicates the magnitude of the MEG signal power at the frequency of the perceptually conscious dominant stimulus minus that at the same frequency when the same stimulus was non-dominant and non-conscious. Conscious perception of a stimulus was associated with a significant increase in the calculated coherence between distant MEG channels at the frequency of the perceived stimulus. Pairs of MEG channels whose coherence changed with change in percept are connected in the figure by cyan straight lines. These data point to a role for increased synchrony among distinct and distant neuronal groups in the Global Workspace during conscious perception. Presumably, these widespread groups constituting the Workspace contribute to the Dynamic Core.