[caycep]

the underlying concept of EEG hasn't changed since the initial ones in 1929. Basically just electrodes trying to detect whatever LFP (aggregate electrical potentials) comes across the cranium. The clinical ones are considered a rough gauge of brain activity, good enough to reliably detect large seizures or a generalized slowing in patients who are delirious but that is about it.

There's MEG which tries to do the same thing but using magnetic detectors instead of scalp electrodes, but those systems are large and unwieldy

In surgery, they do intracranial subdural electrodes which give you better cortical LFP because the electrodes are almost directly on top of the brain and not having to measure through bone.

Then there are the single unit electrodes or things like the Black Rock systems Utah array where thin probes penetrate the brain into deeper structures but obviously have much more special circumstances where they are able to be used.