RESUMEN
The cutaneous eyeblink has 2 electromyographic components, 1 unilateral and early (R1) and 1 bilateral and late (R2), which are served by different neural pathways. These 2 reactions were measured when the eliciting stimulus was expected or relatively surprising. Forewarning was varied in 3 ways: Subjects received notice that the stimulus was about to occur on some trials (Experiment 1); delivered the stimulus to themselves on some trials (Experiments 2 & 3); or experienced a series of trials in which a tone was paired with the eliciting stimulus, followed by tone-alone trials interspersed with test trials (Experiment 4). In each case, forewarning enhanced R1 amplitudes while depressing R2 but reduced the latency of both components. This mixed pattern of effects reveals that the preparatory state provoked by forewarning focuses excitatory and inhibitory processes simultaneously on different reflex pathways: inhibition central and excitation peripheral.
Asunto(s)
Nivel de Alerta/fisiología , Parpadeo/fisiología , Inhibición Neural/fisiología , Reflejo de Sobresalto/fisiología , Disposición en Psicología , Adulto , Atención/fisiología , Condicionamiento Palpebral/fisiología , Dominancia Cerebral/fisiología , Electromiografía , Potenciales Evocados/fisiología , Extinción Psicológica/fisiología , Nervio Facial/fisiología , Humanos , Bulbo Raquídeo/fisiología , Puente/fisiología , Tiempo de Reacción/fisiología , Sinapsis/fisiología , Nervio Trigémino/fisiologíaRESUMEN
The eyeblink reflex elicited by a cutaneous stimulus is inhibited by weak auditory stimuli that are heard just before the blink. It has been shown that monaural prestimuli produce more reflex depression than binaural prestimuli do, suggesting that reflex modification is sensitive to the outcome of antagonistic connections between contralateral auditory inputs. We examined the time course of this antagonism by giving unilateral versus bilateral pairs of noise pips 100 msec before the reflex eyeblink, with the noise pips separated by 0, 1, 4, or 8 msec. Unilateral stimuli were more effective in every condition, but their advantage diminished with increased delay between the two components. The extended bilateral and unilateral trends of increasing reflex depression with increased delay meet at about 15 msec; if this extrapolation is valid, 15 msec represents the upper limit on this system's retention of the location of a brief noise impulse. The rate of convergence of the two temporal functions reflects the decay of the antagonistic effect of one noise on its contralateral counterpart.