I wanted to talk about ultrasound headsets as the possible next step in brain-computer interfaces after EEG headsets (pic related).
A single ultrasound node gives better detail than a single EEG node, and there’s no reason that similar methods can’t be applied to get 3D imaging with multiple nodes around the head. The only drawback I can think of is it somehow interfering with or changing the brain since it’s an active method instead of a passive one.