Abstract: Physiological measuring instruments can detect and produce an electrophysiological signal from the physiological response of a biological subject (e.g., a human, an animal, or the like) to stimulus. For example, an electrode in electrical contact with an eye of a human or an animal can detect and produce an electrophysiological signal from the biological response of the eye to light stimulus. One or more noise components in the electrophysiological signal can be reduced by estimating the noise component(s) and then subtracting the estimated noise component(s) from the detected electrophysiological signal.