[thornjm]

I’m very much not an expert. I think the state of the art for measuring brain activity is the functional MRI. fMRIs have limits on their spatial, temporal and ‘activity’ resolution. I think they also measure ‘only’ blood flow and not electrical activity.

My guess is that if Neuralink does nothing more than provide a more sophisticated tool for investigating the brain than the current state of the art then it will have been a success.

A quick google suggests the highest resolution fMRIs currently have about 1 million voxels of spatial resolution at a sample rate of about 1/sec. EEGs can measure electrical activity but only at very low resolution and on the surface.

[hprotagonist]

It depends on what you mean by "measuring brain activity". fMRI has a spatial resolution on the order of the summed activity of tens of thousands of neurons and a temporal resolution of 2-4 seconds, so it's often very imprecise if you want to know what one neuron in particular is up to.

I've seen single-unit recordings done with electrodes and simultaneous Ca2+ imaging with a 2-photon microscope. You trade real-time speed and single unit specificity for a loss of knowledge about the population.

MEG can give you real-time summed behavior, but the inverse problem is indeterminate so you're less sure of _where_ that activity is coming from.

"what's the good tool to measure brain activity" is very often a function of "what do i want to find out about the brain?"