The spatio-temporal patterns of cortical neural activity in non-conscious conditions support the idea that neural circuits including cortical ones, obey the rules of active media with the underlying principles of diffusion-reaction processes. However, there is only a very limited number of investigations on the spatio-temporal patterns of brain activity in conscious animals.
For example, in awake monkeys, stimulus-evoked neural responses recorded with voltage sensitive dyes propagate as waves in the visual primary V1 and secondary V2 cortices and correspond to waves of transient depolarisation of excitatory and inhibitory neurons travelling across the cortex, carried primarily by the horizontal fibre network of the superficial cortical layers network of the superficial cortical layers.1
In another study of the motor cortex of conscious monkeys, propagating oscillations at the frequency of the beta waves have been recorded by a 4×4 mm array of extracellular electrodes. Recording from primary motor and premotor cortex areas corresponding to arm representations, made during instructed movements, showed consistent directionality of propagating waves at about 20cm/s between motor and premotor cortex anteriorly, and between motor and somatosensory cortex posteriorly. These recordings indicate, not surprisingly, that propagating waves observed in isolated preparations of cortex or in non-conscious conditions also occur in conscious conditions.2
However, cortical spatio-temporal patterns of activity in more intact preparations appear to show a greater degree of directionality of propagation. This suggests that longer connections from more distant parts of the cortex or subcortical structures transform the isotropic neural net observed in slices to more complex specific connectivity in the more intact brains.
An important way to investigate the relation between brain and mind is to use physical and chemical tools that alter the states of mind.