Traumatic Brain Injury and Neurocognitive Disorders
Gail S. Anderson in Biological Influences on Criminal Behavior, 2019
In another study, fMRI showed that psychopaths had reduced fear conditioning and reduced amygdala activity in comparison with controls.66 Several studies using fMRI have shown reduced amygdala activity in psychopaths in comparison with normal controls when shown images of amoral behavior and fear, and during aversive stimuli.63 Similarly, youth with conduct disorder (CD) or callous or unemotional traits showed reduced amygdala activity.63 The amygdala is important in fear and emotion conditioning and relearning, in which the brain learns from past mistakes. Fear conditioning occurs when one learns from an aversive experience; for example, touching a pot on the stove hurts, so the brain learns to avoid repeating the action. Psychopaths are known to have very little fear and do not learn from or consider the consequences of their actions. Therefore, a reduction in gray matter volume in the amygdala would explain a lack of fear awareness and ability to learn from past experiences and an inability to relate emotionally to important events.64 It has been suggested that reduced amygdala gray matter volume might be a risk factor for violence, although whether it is causal or treatable is unknown.64 Neuroimaging studies could be useful in assessing treatment options.64
Neuropsychology of Cognitive Aging in Rodents
David R. Riddle in Brain Aging, 2007
Although the spatial water maze has been frequently used as a common measure of hippocampus-dependent learning, other animal paradigms have attempted to contribute to and expand our understanding of the role of the hippocampus in learning and memory. Fear conditioning is a hippocampally mediated form of associative learning that requires an animal to associate a conditioned stimulus (CS) and a fear-producing unconditioned shock stimulus (US). For delay conditioning, the foot shock immediately follows the tone, whereas in trace conditioning, the tone and shock are often separated by a short interval (15 to 20 seconds) and then the retention of this learning is tested a discrete time late (e.g., 24 hours).
Synthesis, Enzyme Localization, and Regulation of Neurosteroids
Sheryl S. Smith in Neurosteroid Effects in the Central Nervous System, 2003
The role of the hippocampus has been described as a comparator system that can detect whether a threat is familiar or novel, thus requiring either a conditioned automatic response or higher-order processing, respectively.93 The septum, posterior cingulate, and thalamic nuclei also have been implicated in this role.94 Overall, the hippocampus is important in traumatic memory consolidation and, with the entorhi-nal cortex, in contextual fear-conditioned behaviors. Projections from the hippocampus to the bed nucleus of the stria terminalis (BNST) and from the BNST to hypothalamic and brainstem sites may be involved in the expression of contextual fear conditioning.
A novel stress re-stress model: modification of re-stressor cue induces long-lasting post-traumatic stress disorder-like symptoms in rats
Published in International Journal of Neuroscience, 2020
Santosh Kumar Prajapati, Neha Singh, Debapriya Garabadu, Sairam Krishnamurthy
SRS model also has some limitations as there are no measures of fear responses which are considered to be responsible for the development of most of the symptoms. Further, forced-swim paradigm can interfere with the results of the depressive-like behavior as animals are weekly exposed to forced swim test (FST) as a re-stress cue. Furthermore, treatment with paroxetine did not modulate FST-induced decrease in plasma corticosterone (CORT) level, suggesting a lack of predictive validity related to HPA dysfunction [7]. Therefore, it is necessary to develop a suitable model which mimics most of the clinical symptoms of PTSD. Recently, Guo et al. [23] reported that inescapable foot shock (FS) (0.8 mA, 10 sec) develops long-lasting manifestations of anxiety as well as depression-like behavior even after four weeks to the initial exposure in rats [23]. The exposure of FS also induces freezing response which is reliable to measure contextual fear response and intrusive memory [24]. The neuronal mechanism underlying fear conditioning is also involved in the development of intrusive memory [25]. Enhanced freezing behavior is considered as an indicator for formation of intrusive response [26]. Reports suggest that inescapable FS exposure of 0.5 mA for 5 sec exhibit long-lasting cognitive dysfunction [27], and 1 mA for 1 sec pulse per 60 sec affects different brain regions such as locus coeruleus, ventral tegmental area and medial prefrontal cortex and leads to HPA-axis dysfunction [28].
Fear Learning in Genital Pain: Toward a Biopsychosocial, Ecologically Valid Research and Treatment Model
Published in The Journal of Sex Research, 2023
Third, the operationalization of the US, i.e., the pain induction, needs to align with the clinical presentation of genital pain and mimic what women actually experience during sexual penetration to ensure an ecologically valid design. Administering electrical pain stimulation to the wrist, as in the study of Both et al. (2017), does not simulate penetration pain, especially because there is no solid evidence for an increased generalized pain response in women with genital pain (Dewitte et al., 2018; Hellman et al., 2015). Differences in fear learning will manifest more readily when using a disorder-specific US (Meulders, 2020; Pittig et al., 2018). This emphasizes the importance of using relevant CSs and USs and thinking about relevant control conditions and stimuli when developing experimental fear conditioning models. Dynamic sex stimuli such as videos may yield stronger conditioning effects than static sexual pictures (Dawson & Chivers, 2018). In addition, habituation of sexual stimuli occurs rapidly (Koukounas & Over, 1993; O’Donohue & Geer, 1985); therefore, the number of trials should be limited, and a rapid stimulus sequence is recommended.
Mirtazapine for chronic breathlessness? A review of mechanistic insights and therapeutic potential
Published in Expert Review of Respiratory Medicine, 2019
N. Lovell, A Wilcock, S Bajwah, S. N. Etkind, C. J. Jolley, M Maddocks, I. J. Higginson
While fear is often experienced and forgotten, the amygdala assimilates stimuli associated with previous fearful situations, and when exposed to these stimuli again, triggers a response (fear conditioning) [57]. This could explain how an episode of breathlessness and severe panic may lead to recurrent panic when the patient is exposed to a similar trigger. During interoception, the brain generates sensations referred to as priors based on expectations learned from a past experience. These priors are then compared against incoming afferent signals to generate a symptom experience [59]. These interactions can be influenced by many factors including fatigue and depression [60], and recent work has demonstrated how a rehabilitation program for breathlessness can lead to changes in associative learning and the resetting of breathlessness related priors [61]. A number of other factors have been associated with an increased perception of threat including the environment, psychiatric illness, and personality traits [62–65].
Related Knowledge Centers
- Breathing
- Classical Conditioning
- Electrodermal Activity
- Electromyography
- Heart Rate
- Memory Consolidation
- Startle Response
- Learning
- Odor
- Fear-Potentiated Startle