A Sensitive System for the Measurement of Brain Responses in the Intact Human

An all-electronic method is described whereby minute electrical responses in brain recordings can be measured reliably even in the presence of large noise-to-signal ratios. The signal in this instance is a discrete response to a controlled stimulus. The ``noise'' is not white noise in this case, but the normal rhythmic activity of the electroencephalogram (EEG) which is randomly related to the signal. The responses are usually invisible in the EEG recording but they can be detected by means of averaging and storing techniques. The system makes use of gated integrators and floating-grid vacuum-tube voltmeters.