Scientists have long known that nerves create electromagnetic pulses that electrodes on the scalp detect as brain waves. They include alpha-beta waves at 8-38Hz, theta waves at 3-8Hz that occur in sleep and gamma waves of intense focus at 38-42Hz, but their general role is unknown.
Nerves must synchronize their firing to produce brain waves. In cat brain studies, cortical neurons synchronize firing to a high degree of precision to produce beta-gamma waves (Gray, 1989) and more recent studies relate this to the binding problem:
“… have demonstrated that response synchronization is a ubiquitous phenomenon in cortical networks and is likely to serve a variety of different functions in addition to feature binding at early levels of sensory processing.” (Uhlhaas, 2009)p1.
Nearly all neural areas in the brain beat in synchrony, which isn’t easy given nerve synapse, conductance and propagation time delays. Even distant cortical neural areas achieve zero-phase synchrony, to beat almost perfectly in time, which is an extraordinary feat:
“Early studies showed that zero-phase lag synchronization can occur even between distant neuronal assemblies, … This is particularly relevant as the conduction delays in the cortex make the occurrence of zero-phase lag synchronization difficult to accomplish.” (Uhlhaas, 2009)p3.
Entrainment was first discovered by Huygens who found that pendulum clocks set in motion would all synchronize by the next day, as out-of-phase oscillations exchange energy that drops to zero when they vibrate in phase. In the same way, playing a note on a violin makes the violin next to it play that note without touching it by resonance. Neuronal entrainment that allows resonance is ubiquitous in the brain (Lakatos, 2019).
The encapsulation principle that processing hierarchies can’t swap data suggests that nerves connecting distant brain areas don’t transmit content data. When a nerve in the visual cortex fires to register a line angle, it doesn’t encode a message like “I saw a 10° angle at location x,y,z” in a global brain language, it just fires. If a camp surrounded by beacon lights sees that one is lit, it means an enemy is coming that way and likewise when a nerve fires, its location says the rest. In computing, the simplest of signals is a ping, like a ping test that sends a no-content message to see if a web site is still active. It follows that all signals between distant brain areas are just pings, with no information content transmitted at all.
If distant nerve interactions are just pings, there is no thought information to compete for consciousness (Baars, 1988) or to broadcast a global ignition to cause consciousness (Dehaene, 2014). Nerves constantly repeat reciprocal signals between areas butthis nerve “chatter” doesn’t exchange data. Instead these pings constantly establish the phase synchronies that give the brain waves we register on the scalp.
The brain as a neural oscillator network can explore a vast domain of resonances. Models of oscillator networks with delayed links show that low frequency hubs can enable higher frequency synchronies (Vlasov & Bifone, 2017), so slow brain waves may help faster ones keep time. That the brain evolved many long-range and precise lag-free synchronies means it serves a key function and the exquisite time sensitivity of neural spikes implies that timing is critical. The neural synchrony evidence is so compelling that some suggest it is an information code, but there is no evidence for that (Uhlhaas, 2009). Others link synchrony to consciousness to conclude that:
“The central issue is how coherent, informational activity in multiple cortical areas is welded into a seamless unity that becomes aware of itself.” (John, 2005) p160.