Toward a computational theory of conscious processing

Abstract

The study of the mechanisms of conscious processing has become a productive area of cognitive neuroscience. Here we review some of the recent behavioral and neuroscience data, with the specific goal of constraining present and future theories of the computations underlying conscious processing. Experimental findings imply that most of the brain's computations can be performed in a non-conscious mode, but that conscious perception is characterized by an amplification, global propagation and integration of brain signals. A comparison of these data with major theoretical proposals suggests that firstly, conscious access must be carefully distinguished from selective attention; secondly, conscious perception may be likened to a non-linear decision that 'ignites' a network of distributed areas; thirdly, information which is selected for conscious perception gains access to additional computations, including temporary maintenance, global sharing, and flexible routing; and finally, measures of the complexity, long-distance correlation and integration of brain signals provide reliable indices of conscious processing, clinically relevant to patients recovering from coma.

Figure 1

Flexible information routing and conscious processing in large-scale models of the cortex. (left) Original depiction of the Dehaene-Changeux model of a Global Neuronal Workspace [GNW; Ref. 87]. The GNW model proposes that what we subjectively experience as a conscious state is the global availability of the corresponding information. Conscious access would occur when a piece of information enters a distributed network of cortical areas tightly interconnected by long-distance axons, the GNW, which allows its flexible broadcasting to any of the brain’s many specialized processors. (right) Spiking-neuron simulation of a flexible routing system [Ref. 99]. While a first stimulus is processed and routed to an arbitrary response (left column, top to bottom), a second stimulus (right column) is also processed perceptually but is then blocked at the routing stage. This model captures in great detail two neuropsychological phenomena, the psychological refractory period and the attentional blink.