Startle Reflex Modulation: Perception, Attention, and Emotion

Abstract

In this chapter, we discuss a new method for assessing attention and affect that relies on the measurement of a simple reflex that occurs in all mammalian species — the startle reflex. The abrupt presentation of a sensory stimulus— for example, a burst of noise or a flash of light — elicits a reflexive startle response. The gross features of startle in humans include a forward thrusting of the head and a descending flexor wave reaction that extends through the trunk to the knees. The first, fastest, and most stable element in the startle sequence is the reflexive eyeblink, occurring within 30–80 ms after stimulus onset, which is a reliable motor response that is easy both to measure and to quantify.