Anyone interested in 40Hz oscillations should take a look at 'Cortical oscillations
and temporal interactions in a computer simulation of piriform cortex' by M Wilson
and J Bower J Neuroscience 67:981-995, 1992.
They put forward the idea that the oscillations are simply caused by the delay-line effects of intra-cortical connections. I must say I am dubious about the importance
of any oscillations which depend critically on delay-lines (ie dependent on axonal
lengths and conduction velocities) as such a set-up doesn't strike me as being very
robust. More interesting are the slower, 5-10Hz oscillations dependent on channel time
constants (GABAb, T-type Ca current, Iq).
charles at anat.ucl.ac.uk