Well if you want to get all metaphysical about it, and you aren't interested in scientific things like the ions and the membranes, then why bother talking about 'speed' at all?
Speed is after all a physical phenomenon, defined as distance divided by time.
Light would take less than a nanosecond to cross from one side of the brain to the other. As I've said, neuron firing rates are much much slower than this.
So go on, please tell us what two events within the brain do you think are separated by less than a nanosecond ?