How does our brain generate our
consciousness? And why do we lose it during anesthesia? Influential theories
suggest that consciousness depends on the brain’s ability to discriminate
between a specific sensory input and a large set of alternatives, akin to being
able to choose one outcome among many. Several studies in humans using fMRI
have identified a rich set of resting states of cortical activity at the
anatomical macro scale, that is, at the level of large brain areas. A research
team led by Columbia University, however, hypothesized that a person’s ability
to discriminate between a set of alternatives at any moment should be rooted in
micro-patterns of activity, or microstates, at the level of local neuronal
ensembles – the functional building blocks of neural circuits.
And in a first of its kind study,
researchers from Columbia’s Rafael Yuste’s Laboratory used cellular resolution
in vivo two-photon calcium imaging in mice to investigate changes in the local
repertoire of neuronal microstates during anesthesia. The team found that
anesthesia disrupts the number of neural patterns by reducing both network
microstates and neuronal ensembles in the cortex, and confirmed their findings
in microelectrode array recordings from two human subjects. Their results,
published today in the journal, Cell Systems, indicate that the functional
connectivity of the brain during mLOC breaks down across micro- and
macro-anatomical scales. Results indicate that the loss of consciousness could
arise from alterations in the local microcircuit, which would secondarily
generate deficits in macroscale connectivity.
More information: