The largest contributors to the EEG are the pyramidal cells. They’re aligned. It’s about whether it goes above the noise floor. Has to fire at the same time. Why would 50,000 neurons fire at the same time. An external event like detection of light, can trigger a cascade of related near processes. This is known as a perception. Internally generated events happen such as an aha! moment. Neural populations can enter a synchronized steady state firing pattern. Idle oscillations are an example of this. Alpha waves. It happens when neurons become idle. There are mechanisms that give rise to coactivated firings. Event Related Potentials and Oscillatory Process are the two major BCI-detectable EEG/MEG phenomena.
Signal Detectability Cortical correlates can indicate chemical changes, not electrical. Dopaminergic systems in the deep brain structures can be a cause of a signal. Widely scattered populations of neurons are unlikely to exhibit synchrony unless its connected via fiber tracts. Propagation from one to another, just takes way too long. More likely that spatially compact neurons fire together. There are also cases where compact clusters fire, and the electromagnetic fields cancel each other out such as in the Amygdala.
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