|
Recordings of cortical activity across the entire hierarchy
of spatial scales in the brain evidence the hallmarks of complex
dynamics. At the largest scale, the human alpha rhythm (~10 Hz) is a
multistable phenomenon with erratic, but well well defined switching
behaviour between different temporal modes of activity. Beta
oscillations (15-30 Hz) exhibit erratic fluctuations that appear drawn
from an underlying "super-Gaussian" process. In this talk, these
phenomena will be defined and evidence for their existence reviewed. I
will then present a model of spiking neural populations defined on a
heirarchically-organised architecture. This enables us to understand
the role of spike-time dependent plasticity in the generation of these
non-trivial large-scale fluctuations in neuronal activity and the
conditions under which such activity can become super-critical, hence
exhibiting seizure-like spiking behaviour. From this preliminary work,
we can form a deeper intuition regarding what may be required for a
sufficient model of large-scale cortical dynamics. This involves
understanding the coupling between cortical dynamics on two time
scales - namely, the rapidly changing moments of cortical states
coupled to the more gradually changing moments of synaptic weights.
|
|