Fear-potentiated startle: A neural and pharmacological analysis

doi:10.1016/0166-4328(93)90102-V

Behavioural Brain Research

Volume 58, Issues 1–2, 20 December 1993, Pages 175-198

https://doi.org/10.1016/0166-4328(93)90102-V Get rights and content

Abstract

The fear-potentiated startle paradigm has proven to be a useful system with which to analyze neural systems involved in fear and anxiety. This test measures conditioned fear by an increase in the amplitude of a simple reflex (the acoustic startle reflex) in the presence of a cue previously paired with a shock. Fear-potentiated startle is sensitive to a variety of drugs such as diazepam, morphine, and buspirone that reduce anxiety in people and can be measured reliably in humans when the eyeblink component of startle is elicited at a time when they are anticipating a shock. Electrical stimulation techniques suggest that a visual conditioned stimulus ultimately alters acoustic startle at a specific point along the acoustic startle pathway. The lateral, basolateral and central amygdaloid nuclei and the caudal branch of the ventral amygdalofugal pathway projecting to the brainstem are necessary for potentiated startle to occur. The central nucleus of the amygdala projects directly to one of the brainstem nuclei critical for startle and electrical stimulation of this nucleus increases startle amplitude. Chemical or electrolytic lesions of either the central nucleus or the lateral and basolateral nuclei of the amygdala block the expression of fear-potentiated startle. The perirhinal cortex, which projects directly to the lateral and basolateral amygdaloid nuclei, plays a critical role in the expression of fear-potentiated startle using either visual or auditory conditioned stimuli. These latter amygdaloid nuclei may actually be the site of plasticity for fear conditioning, because local infusion of the NMDA antagonist AP5 into these nuclei blocks the acquistion of fear-potentiated startle. On the other hand, the expression of fear-potentiated startle is blocked by local infusion of the non-NMDA ionotropic antagonist CNQX or the G-protein inactivating toxin, pertussis toxin, but not by AP5. Finally, we have begun to investigate brain systems that might be involved in the inhibition of fear. Local infusion of AP5 into the amygdala was found to block the acquisition of experimental extinction, a prototypical method for reducing fear. We have also established a reliable procedure for producing both external and conditioned inhibition of fear-potentiated startle and hope to eventually understand the neural systems involved in these phenomena.

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Exp. Brain Res.

Memory: anatomical organization of candidate brain regions

The connections of the peripeduncular area studied by retrograde and anterograde transport in the rat

J. Comp. Neurol.

Ventral temporal cortex in the rat: connections of secondary auditory areas Te2 and Te3

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Behav. Neurosci.

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A contextual analysis of fear extinction

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J. Exp. Psychol. Anim. Behav. Process.

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J. Exp. Psychol. Anim. Behav. Process.

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J. Exp. Psychol.

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Long-term synaptic potentiation

Science

Involvement of the lateral amygdala and perirhinal cortex in fear potentiated startle to acoustic and visual conditioned stimuli

Soc. Neurosci. Abstr.

Long-term retention of fear-potentiated startle following a short training session

Anim. Learn. Behav.

Intraamygdala infusion of the N-methyl-D-aspartate receptor antagonist AP5 blocks acquisition but not expression of fear-potentiated startle to an auditory conditioned stimulus

Behav. Neurosci.

Fear-enhanced acoustic startle is not attenuated by acute or chronic imipramine treatment in rats

Psychopharmacology

Neural structures mediating acoustic and tactile startle reflexes and the acoustically-elicited pinna response in rats: electrolytic and ibotenic acid studies

Soc. Neurosci. Abstr.

Long-term synaptic potentiation in the amygdala

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The effect of amobarbital sodium on conditioned fear as measured by the potentiated startle response in rats

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Review: D1 dopamine receptor—the search for a function: A critical evaluation of the D1D2 dopamine receptor classification and its functional implications

Synapse

Synaptic plasticity in fear conditioning circuits: induction of LTP in the lateral nucleus of the amygdala by stimulation of the medial geniculate body

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Fear-potentiated startle: A neural and pharmacological analysis

Review: D1 dopamine receptor—the search for a function: A critical evaluation of the $D 1 D 2$ dopamine receptor classification and its functional implications