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      Further Evidence for the Independent Reflex-Eliciting and Reflex-Inhibiting Effects of a Startle-Blink Eliciting Stimulus

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          Abstract

          A small change in the environment (a prepulse) that just precedes a startle-eliciting stimulus can reduce the size of the elicited reflex, but a prepulse does not appear to diminish the ability of the startle-eliciting stimulus to depress a startle response elicited a little later. The reflex-eliciting and reflex-modifying effects of startle stimuli seem to be independent. However, most support for this observation rests on a failure to reject the null hypothesis, and relatively little of this research has employed the acoustic startle blink in human beings. The purpose of the present study was to provide additional evidence on this issue. Participants ( n = 20) encountered trials in which a prepulse (p) and two 103 dB(A) blink-eliciting noise bursts (S1 and S2) were given in succession. The prepulse (a synchronous word and tone) occurred 150 ms prior to S1. The prepulse inhibited the startle blink to S1, and S1 depressed the blink elicited 1.5 s later by S2. However, regardless of whether p inhibited the blink to S1, S1 maintained the same capacity to depress the blink to S2. In contrast, a softer S1 (88 dB(A); S1 attenuated), which produced a blink nearly matching the size of the prepulse-inhibited blink, did not significantly depress the response to S2. Participants also judged the loudness of S1 and S2. The prepulse reduced the perceived intensity of S1, but much less so than caused by reducing the actual intensity of S1, and proportionally much less so than the prepulse reduced the blink to S1. These results provide further evidence for independent reflex-eliciting and reflex-modifying effects of a startle-eliciting stimulus and argue against the notion that prepulses strongly reduce the general sensory impact of the startle stimulus.

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          Most cited references 32

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          Prestimulus effects on human startle reflex in normals and schizophrenics.

           L Bali,  M Geyer,  I Glick (1978)
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            Brain stem circuits mediating prepulse inhibition of the startle reflex.

            Prepulse inhibition (PPI) of the startle reflex occurs when brief, non-startling tactile, acoustic or visual stimuli are presented 20-500 ms before the startling stimulus. To review information about PPI-mediating brain stem circuits and transmitters, and their functions. Midbrain systems are most critical for the fast relay of these PPI stimuli. Acoustic prepulses for PPI are relayed through the inferior colliculus (IC). The superior colliculus (SC) is important for acoustic PPI, and may be important for the mediation of tactile and visual prepulses. This collicular activation for PPI is quickly relayed through the pedunculopontine tegmental nucleus (PPTg), with lesser contributions to PPI from the laterodorsal tegmental nucleus (LDTg) and substantia nigra, pars reticulata (SNR). The transient activation of midbrain nuclei by PPI stimuli is converted into long-lasting inhibition of the giant neurons of the caudal pontine reticular nucleus (PnC). We propose that muscarinic and GABA(B) inhibitory receptors (both metabotropic receptors) on PnC giant neurons combine to produce the long-lasting inhibition of startle. Activation of mesopontine cholinergic neurons leads to cortical arousal, turning and exploratory approach responses. PPI is mediated by a circuit involving the IC, SC, PPTg, LDTg, SNR and PnC. By reducing startle, PPI allows the execution of approach responses and perceptual processing following salient stimuli.
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              The More or Less Startling Effects of Weak Prestimulation

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                Author and article information

                Journal
                jop
                Journal of Psychophysiology
                An International Journal
                Hogrefe Publishing
                0269-8803
                2151-2124
                January 2012
                : 26
                : 2
                : 63-73
                Affiliations
                [ 1 ] Department of Psychology, University of South Carolina Upstate, Spartanburg, SC, USA
                [ 2 ] The Timken Corporation, Canton, OH, USA
                Author notes
                E. Evan Krauter, Department of Psychology, University of South Carolina Upstate, Spartanburg, SC 29303, USA +1 864 503-5777, +1 864 503-5748, ekrauter@ 123456uscupstate.edu
                Article
                10.1027/0269-8803/a000068
                Product
                Self URI (journal-page): https://econtent.hogrefe.com/loi/jop
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