Optical Voltage-Imaging Studies of Consciousness State Transitions

A remarkable property of the brain is its ability to exist in qualitatively different states, some conscious and some not, and to transition between them within seconds or minutes. When awake, the brain has radically different electrophysiological properties and functional capabilities from when it is anesthetized or asleep, despite having all the same constituent neurons in both states. Physicists call this type of discrete transition in a system’s macroscopic properties a “state transition,” and intensive research on state transitions has greatly advanced scientific understanding of many physical systems with extraordinary attributes.

In neuroscience, multiple theories of consciousness have been proposed, but state transitions remain understudied. TWCF is funding a study led by project director Mark J. Schnitzer, professor of biology and of applied physics in the School of Humanities and Sciences at Stanford University, to conduct a series of studies using new technologies for optical voltage-imaging that will allow the team to precisely characterize the differences between conscious and unconscious brain states by studying transitions between the two. 

Similarly, they will use voltage-imaging to identify how the brain’s responses to consciously perceived sensory stimuli differ from its responses to identical stimuli that go unperceived. A key virtue of the team’s voltage-imaging methodology is its cell-type specificity, which will allow them to identify for the first time how the dynamics of different classes of cortical neurons contribute to conscious and unconscious states.

The studies will address three key questions, whose answers will require the team to quantitatively characterize the unique physical and biological properties of conscious states:

• How do neocortical neurons’ collective dynamics differ between awake and unconscious states?
• Which neuron-types and cortical areas exhibit the greatest changes when the brain transitions from a conscious to an unconscious state, and vice versa?
• In the awake brain, how do neocortical voltage responses to consciously perceived sensory stimuli differ from the responses to unperceived stimuli with otherwise identical properties?

By delineating fundamental differences between conscious and unconscious brain states, and between consciously perceived versus unperceived stimuli, these studies will open the door to an entirely new avenue of consciousness research.