Neuroscience - What makes the brain's tickers tock

The first brain waves to be observed were measured at a frequency of ten cycles per second — that is, 10 Hz. Since then, waves have been detected at frequencies of 5, 40 and 200 Hz. But what do they do? One group has found that the 40-Hz waves are involved in a feedback-inhibition mechanism for coding 'events' (such as memories) in the brain. Another group has studied the 200-Hz waves, and they conclude that synchronization of neuron firing, which causes these waves, is due to gap junctions between nearby axons.