Brains are like oceans
The brain can be likened to an ocean. On the surface of the ocean, there are waves which reflect the aggregate activity of the deeper ocean currents in some non-linear way. The waves correspond to the surface activity of the brain, in that they vaguely reflect the underlying neural activity. Moreover, the depths of the ocean can be linked to subcortical brain structures. Those structures are difficult to observe from the outside, and one needs to perform a deep dive in order to get meaningful readings. Moreover, EEG experiments are all about systematically dropping droplets into the ocean surface and studying how the dynamics change. Unfortunately, it’s difficult to pick up the droplet-related signal from the chaotic noise of the waves.