, Volume 156, Issue 2–3, pp 216–224 | Cite as

Brain stem circuits mediating prepulse inhibition of the startle reflex

  • Markus Fendt
  • Liang Li
  • John S. Yeomans


Rationale: 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. Objective: To review information about PPI-mediating brain stem circuits and transmitters, and their functions. Results: 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 GABAB 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. Conclusion: 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.

Acetylcholine Attention Caudal pontine reticular nucleus GABA Inferior colliculus Laterodorsal tegmental nucleus Prepulse inhibition Peduculopontine tegmental nucleus Sensorimotor gating Startle response Substantia nigra pars reticulata Superior colliculus 


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Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Markus Fendt
    • 1
  • Liang Li
    • 2
  • John S. Yeomans
    • 3
  1. 1.Tierphysiologie, Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, GermanyGermany
  2. 2.Department of Psychology, Peking University, Beijing 100871, ChinaChina
  3. 3.Department of Psychology, University of Toronto, Toronto, Ontario, Canada M5S 3G3Canada

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