John S. Yeomans

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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(More)
  • J S Yeomans
  • Neuropsychopharmacology : official publication of…
  • 1995
Cholinergic neurons of the pedunculopontine nucleus (Ch5) and laterodorsal tegmental nucleus (Ch6) monosynaptically activate dopamine neurons of the substantia nigra, zona compacta (A9), and ventral tegmental area (A10) via muscarinic and nicotinic receptors. Ch5 cells and Ch6 cells are inhibited by local injections of muscarinic agonists, suggesting the(More)
The startle reflex is elicited by intense tactile, acoustic or vestibular stimuli. Fast mechanoreceptors in each modality can respond to skin or head displacement. In each modality, stimulation of cranial nerves or primary sensory nuclei evokes startle-like responses. The most sensitive sites in rats are found in the ventral spinal trigeminal pathway,(More)
Rats were implanted with stimulating electrodes in the lateral hypothalamus, and cannulae for chemical injections in the ventral tegmentum. Injections of atropine, a muscarinic antagonist, increased thresholds for self-stimulation in a dose-dependent fashion, without slowing bar pressing rates. Thresholds increased less for a self-stimulation site(More)
The midbrain is essential for prepulse inhibition (PPI) of the startle reflex, but the exact neural circuits for PPI are not yet determined. Electrical stimulation of the superior colliculus (SC) or pedunculopontine tegmentum was used to characterize the neurons and pathways that mediate PPI and the activation of startle that also occurs at higher currents(More)
The startle reflex protects animals from blows or predatory attacks by quickly stiffening the limbs, body wall and dorsal neck in the brief time period before directed evasive or defensive action can be performed. The acoustic startle reflex in rats and cats is mediated primarily by a small cluster of giant neurons in the ventrocaudal part of the nucleus(More)
Adult mice communicate by emitting ultrasonic vocalizations (USVs) during the appetitive phases of sexual behavior. However, little is known about the genes important in controlling call production. Here, we study the induction and regulation of USVs in muscarinic and dopaminergic receptor knockout (KO) mice as well as wild-type controls during sexual(More)
Quantitative properties of the neural system mediating the rewarding and priming effects of medial forebrain bundle (MFB) stimulation in the rat have been determined by experiments that trade one parameter of the electrical stimulus against another. The first-order neurons in this substrate are for the most part long, thin, myelinated axons, coursing in the(More)
The acoustic startle reflex is a sensitive index of "anxiety" and "fear." Potentiation of startle by conditioned and unconditioned fear stimuli appears to be mediated by the amygdala. CholecystokininB (CCKB) agonists increase "anxiety" in laboratory animals and induce "panic" in humans. Here, we investigate the role CCKB receptor-mediated mechanisms in the(More)
The directly activated substrates for medial forebrain bundle (MFB) self-stimulation are primarily low threshold, myelinated axons with absolute refractory periods of 0.4 to 1.2 msec, conduction velocities of 1 to 8 m/sec and current-distance constants of 1000 to 3000 microA/mm2. When small electrode tips or high currents are used, however, a second(More)