Habituation and sensitization of components of the human eyeblink reflex

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The supraorbital branch of the right trigeminal nerve was stimulated in 5 20–26 yr olds with trains of electric shocks, 10 in each train, with interpulse intervals of 1, 2, or 5 sec. EMG reflex activity in the palpebral musculature was measured to each pulse in the train. Each response consisted of 2 components, a fast brief ipsilateral burst (R1) and a slower prolonged bilateral burst (R2). Over the 10-pulse series, the amplitudes of R1 increased in strength (sensitization), whereas the allied R2 amplitudes declined (habituation). Both of these effects were enhanced as the interpulse interval was reduced. A consideration of the anatomical substrate for each reflex component, together with some other data in the literature, suggests that reflex sensitization occurred in the efferent limb of this brain-stem reflex while, simultaneously, habituation occurred in its central link. (15 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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