Cellular Mechanisms of Conscious Processing

Highlights

• Recent breakthroughs in the study of cellular and circuit level aspects of consciousness have led to the conclusion that cortical pyramidal neurons have a central role in the mechanisms of consciousness.

• Major theories of cortical processing rely on the separation of forward and backward information flow in the cortex. This separation of information streams is mirrored at the level of single cortical pyramidal cells.

• The discovery that general anesthesia separates the two different parts of the cortical pyramidal neurons suggests that there is a way to understand consciousness from the bottom-up (i.e., from cellular mechanisms to cognitive properties of conscious processing).

• Given that consciousness has been related to distributed activity patterns in large-scale brain networks, the question emerges as to how exactly single pyramidal neurons can contribute to these macroscale dynamics and, hence, to consciousness.

Recent breakthroughs in neurobiology indicate that the time is ripe to understand how cellular-level mechanisms are related to conscious experience. Here, we highlight the biophysical properties of pyramidal cells, which allow them to act as gates that control the evolution of global activation patterns. In conscious states, this cellular mechanism enables complex sustained dynamics within the thalamocortical system, whereas during unconscious states, such signal propagation is prohibited. We suggest that the hallmark of conscious processing is the flexible integration of bottom-up and top-down data streams at the cellular level. This cellular integration mechanism provides the foundation for Dendritic Integration Theory, a novel neurobiological theory of consciousness.