<p>An apparatus for recording physiological data from an ambulatory subject. The apparatus includes a sensor circuit configured to detect input analog signals including input analog signals resulting from eye movement of the ambulatory subject, and a signal processing circuit, in communication with the sensor circuit, configured to receive the input analog signals and to generate an output digital signal based at least in part on the received input analog signals. The apparatus has physical characteristics suitable for portable use by the ambulatory subject.</p>
