Neuroscience is a young field, just at the beginning. The physics, nuts, and bolts mechanical processes of the brain are pretty well understood. Signals within the body and brain are composed of chemical variations and electrical changes. Though there are many types of communication within the brain, a most basic one is composed of neurons. Neurons create electrical potentials that “fire” and propagate throughout the brain. The patterns of firing in the brain can also be described as “waves”. Unlike the electric wave that is transmitted on a power line, the medium of transmission of brain waves are cells, biological material. However, as in the case of my former student, it is possible that such biological material can be destabilized by electromagnetic energy from other sources.
We know a bit more about what is going on inside brains today than we did in James’s day because we have more reliable ways of locating and measuring the electric waves and magnetic fields noted above, the core media of the brain’s activity. For example, the best and most recent brain scanning equipment, functional magnetic resonance imaging (fMRI), measures the magnetic properties of oxygen molecules in the brain. It works because hemoglobin, the most important blood protein, changes its magnetic properties depending on how much oxygen it contains. The body delivers oxygen molecules to parts of the brain that need to do more work. So fMRI does not actually measure brain activity directly but rather blood flow in the brain (changes in oxygenation).
Instead of oxygen flow, another type of brain scan called Electroencephalography (EEG), measures electricity generated by the brain. While fMRI is good at scale (spatial dimension) it is not as good as EEG at time (temporal dimension); that is, fMRI technology is too slow to capture neural processes (because it measures them indirectly by blood flow). EEG, by contrast, captures electrical signals in real time. However, EEG is limited because it only captures electrical energy at the scalp—it does not reach deep into the brain.
So EEG captures the wave pattern of firing neurons. In popular understanding these are called brain waves, but scientists call them neural oscillations. The terminology is probably reflective of the fact that brain waves are associated with the unverified notion that such waves travel outside the brain (that is, between brains). By contrast neural oscillations only apply within brains.
The patterns researchers have found in humans are usually localized (meaning they take place at characteristic places in the brain) and tend to take place during certain types of activities. For example, delta waves are characteristic for adults in slow wave or non-REM sleep and in some attention tasks; theta waves are characteristic of encoding and retrieval in memory and inhibition; alpha waves are associated with focusing of attention. A rhythmic firing pattern of up to 4 Hz. (4 cycles per second) is a delta wave, then there are theta (4-8), alpha (8-13), mu (8-13), beta (13-30), and gamma (30-100) frequencies.
Recent theories suggest that the “neural correlates” of various conscious states are not particular neurons but rather these patterns or waves firing in synchrony. The excitement over the recent discovery of mirror neurons—a type of neuron that fires both when an action is observed and when an individual performs the same action—is that they suggest such synchrony of firing is not confined to individual heads. Brain waves might not move between brains but people may still share patterns of neural activity.
Such an idea was probably first proposed by Gerald Edelman who argued that the “dynamic core” of consciousness is synchronous firing occurring globally across many brain areas. Local waves become part of consciousness when integrated into that global synchrony. Gamma waves in particular have been a focus of attention in this regard.
So like James, Edleman’s is a holistic conception of consciousness, but grounded in neuroscience.
One’s perspective on consciousness, of course, is a politico-historical subject.
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