The invention relates to systems and methods for estimating a response of at least a part of a physiological system to a first deterministic stimulus signal. The methods include separating a measured first signal into a plurality of segments, each segment representing a response of the physiological system to a corresponding portion of the first stimulus signal and generating a template signal representing the plurality of segments. The methods further include calculating a measure of similarity of each segment in the plurality of segments to the template signal to provide a set of scalar quantities, and determining a metric representing a characteristic of the response of at least a part of the physiological system to the first stimulus signal.