Amygdala and hippocampal activity during acquisition and extinction of human fear conditioning. Cogn Affect Behav Neurosci 4:317-325

University of Wisconsin, Milwaukee, Wisconsin 53201, USA.
Cognitive Affective & Behavioral Neuroscience (Impact Factor: 3.21). 10/2004; 4(3):317-25. DOI: 10.3758/CABN.4.3.317
Source: PubMed

ABSTRACT Previous functional magnetic resonance imaging (fMRI) studies have characterized brain systems involved in conditional response acquisition during Pavlovian fear conditioning. However, the functional neuroanatomy underlying the extinction of human conditional fear remains largely undetermined. The present study used fMRI to examine brain activity during acquisition and extinction of fear conditioning. During the acquisition phase, participants were either exposed to light (CS) presentations that signaled a brief electrical stimulation (paired group) or received light presentations that did not serve as a warning signal (control group). During the extinction phase, half of the paired group subjects continued to receive the same treatment, whereas the remainder received light alone. Control subjects also received light alone during the extinction phase. Changes in metabolic activity within the amygdala and hippocampus support the involvement of these regions in each of the procedural phases of fear conditioning. Hippocampal activity developed during acquisition of the fear response. Amygdala activity increased whenever experimental contingencies were altered, suggesting that this region is involved in processing changes in environmental relationships. The present data show learning-related amygdala and hippocampal activity during human Pavlovian fear conditioning and suggest that the amygdala is particularly important for forming new associations as relationships between stimuli change.

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Available from: David C Knight, Aug 20, 2015
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    • "This hypothesis is also supported by findings of rapid amygdala habituation during repeated exposure to generally aversive (Wendt, Weike, Lotze, and Hamm, 2011) or fear-relevant pictures (Wendt, Schmidt, Lotze, and Hamm, 2012). In the current study, however, we could not confirm the hypothesis suggested by Knight et al. (2004) that the amygdala detects changes in CS–UCS associations. Although participants had to learn a new association of the UCS and a novel geometric shape in each run, the initial amygdala differentiation between CS+ and CS− cue onset did not reappear at the first trial block of the second and third run. "
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    ABSTRACT: Studying neural networks and behavioral indices such as potentiated startle responses during fear conditioning has a long tradition in both animal and human research. However, most of the studies in humans do not link startle potentiation and neural activity during fear acquisition and extinction. Therefore, we examined startle blink responses measured with electromyography (EMG) and brain activity measured with functional MRI simultaneously during differential conditioning. Furthermore, we combined these behavioral fear indices with brain network activity by analyzing the brain activity evoked by the startle probe stimulus presented during conditioned visual threat and safety cues as well as in the absence of visual stimulation. In line with previous research, we found a fear-induced potentiation of the startle blink responses when elicited during a conditioned threat stimulus and a rapid decline of amygdala activity after an initial differentiation of threat and safety cues in early acquisition trials. Increased activation during processing of threat cues was also found in the anterior insula, the anterior cingulate cortex (ACC), and the periaqueductal grey (PAG). More importantly, our results depict an increase of brain activity to probes presented during threating in comparison to safety cues indicating an involvement of the anterior insula, the ACC, the thalamus, and the PAG in fear-potentiated startle processing during early extinction trials. Our study underlines that parallel assessment of fear-potentiated startle in fMRI paradigms can provide a helpful method to investigate common and distinct processing pathways in humans and animals and, thus, contribute to translational research. Copyright © 2015. Published by Elsevier B.V.
    International journal of psychophysiology: official journal of the International Organization of Psychophysiology 02/2015; DOI:10.1016/j.ijpsycho.2015.02.025 · 2.65 Impact Factor
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    • "Selective lesions to the amygdala impair both cued and contextual fear conditioning in animals (LeDoux, 2000). Similarly, amygdala activity increases during the acquisition relative to the extinction phase (Phelps et al., 2001; Knight et al., 2004), and there is a strong correlation between amygdala reactivity and conditioned SCRs during fear acquisition (Cheng et al., 2003; Phelps et al., 2004) in humans. The amygdala is also involved in the fast detection of potentially harming stimuli (LeDoux, 2000; Öhman and Mineka, 2001), which might represent a highly adaptive process. "
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    ABSTRACT: Avoidance is considered as a central hallmark of all anxiety disorders. The acquisition and expression of avoidance, which leads to the maintenance and exacerbation of pathological fear is closely linked to Pavlovian and operant conditioning processes. Changes in conditionability might represent a key feature of all anxiety disorders but the exact nature of these alterations might vary across different disorders. To date, no information is available on specific changes in conditionability for disorder-irrelevant stimuli in specific phobia (SP). The first aim of this study was to investigate changes in fear acquisition and extinction in spider-fearful individuals as compared to non-fearful participants by using the de novo fear conditioning paradigm. Secondly, we aimed to determine whether differences in the magnitude of context-dependent fear retrieval exist between spider-fearful and non-fearful individuals. Our findings point to an enhanced fear discrimination in spider-fearful individuals as compared to non-fearful individuals at both the physiological and subjective level. The enhanced fear discrimination in spider-fearful individuals was neither mediated by increased state anxiety, depression, nor stress tension. Spider-fearful individuals displayed no changes in extinction learning and/or fear retrieval. Surprisingly, we found no evidence for context-dependent modulation of fear retrieval in either group. Here, we provide first evidence that spider-fearful individuals show an enhanced discriminative fear learning of phobia-irrelevant (de novo) stimuli. Our findings provide novel insights into the role of fear acquisition and expression for the development and maintenance of maladaptive responses in the course of SP.
    Frontiers in Behavioral Neuroscience 10/2014; 8:328. DOI:10.3389/fnbeh.2014.00328 · 4.16 Impact Factor
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    • "Increased activation of the amygdala can be observed during the beginning of extinction learning. With increasing duration of extinction, activation of the amygdala decreases (Knight, Smith, Cheng, Stein, & Helmstetter, 2004). The recall of extinction memory is associated with the activation of the prefrontal cortex (Milad et al., 2007). "
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    ABSTRACT: This chapter begins with a case report demonstrating the core features that define specific phobias. Marked and persistent fear cued by specific objects or situations accompanied by a compelling desire to escape from or avoid such objects or situations, if possible, are the main diagnostic criteria for specific phobia. Specific phobias of natural environment type are characterized by symptom reports of dizziness and strong avoidance dispositions often accompanied by central concerns about the potential danger of the situation. With the increasing availability of virtual reality technology, it is now possible to use computer-generated interactive virtual realities (VR) including visual displays of moving objects, other sensory inputs, and body-tracking devices to conduct exposure therapy. Specific phobias are particularly responsive to exposure-based therapies and are therefore considered the treatment of choice for this disorder.
    The Wiley Handbook of Anxiety Disorders, 04/2014: pages 895-923; , ISBN: 9781118775356
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