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 Does neurofeedback have to be EEG? 

The article defines neurofeedback as: ""Neurofeedback is a type of biofeedback that uses electroencephalography to provide a signal that can be used by a person to receive feedback about brain activity.""
Though, similar things can be done using fNIR and other methods, and a quick google search shows that the term seems to be used here as well.
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