Editing Amygdala (section)

=== Anxiety ===
Feelings of anxiety start with an environmental stimulus that provokes stress. This can include various smells, sights, and internal sensations that result in anxiety. The amygdala reacts to this stimuli by preparing to either stand and fight or to turn and run. This response is triggered by the release of [[adrenaline]] into the bloodstream; the amygdala sends signals to the [[Paraventricular nucleus of hypothalamus|paraventricular nucleus of the hypothalamus]] for the initiation of the [[Hypothalamic–pituitary–adrenal axis|HPA axis]] response.<ref>{{Cite journal |last=Dedovic |first=Katarina |last2=Duchesne |first2=Annie |last3=Andrews |first3=Julie |last4=Engert |first4=Veronika |last5=Pruessner |first5=Jens C. |date=2009 |title=The brain and the stress axis: The neural correlates of cortisol regulation in response to stress |url=https://doi.org/10.1016/j.neuroimage.2009.05.074 |journal=NeuroImage |volume=47 |issue=3 |pages=864–871 |doi=10.1016/j.neuroimage.2009.05.074 |issn=1053-8119}}</ref> Consequently, blood sugar rises, becoming immediately available to the muscles for quick energy. Shaking may occur in an attempt to return blood to the rest of the body. Long-term changes in amygdala neurons may also increase anxiety after long-term or traumatic stress, led by the action of stress-related hormones within the amygdala.<ref>{{cite journal |last1=Mitra |first1=Rupshi |last2=Sapolsky |first2=Robert |year=2008 |title=Acute corticosterone treatment is sufficient to induce anxiety and amygdaloid dendritic hypertrophy |journal=Proc Natl Acad Sci U S A |volume=105 |issue=14 |pages=5573–8 |bibcode=2008PNAS..105.5573M |doi=10.1073/pnas.0705615105 |pmc=2291109 |pmid=18391224 |doi-access=free}}</ref> On the flip side, blocking the action of stress hormones in the amygdala reduces anxiety.<ref>{{cite journal |last1=Mitra |first1=Rupshi |last2=Sapolsky |first2=Robert |year=2010 |title=Expression of chimeric estrogen-glucocorticoid-receptor in the amygdala reduces anxiety |journal=Brain Res |volume=1342 |issue=1 |pages=33–8 |doi=10.1016/j.brainres.2010.03.092 |pmid=2038147 |s2cid=26769079}}</ref> There may also be a link between the amygdala and [[anxiety]].<ref name=":1">{{cite journal | vauthors = Ziabreva I, Poeggel G, Schnabel R, Braun K | title = Separation-induced receptor changes in the hippocampus and amygdala of Octodon degus: influence of maternal vocalizations | journal = The Journal of Neuroscience | volume = 23 | issue = 12 | pages = 5329–36 | date = June 2003 | pmid = 12832558 | pmc = 6741186 | doi = 10.1523/JNEUROSCI.23-12-05329.2003 }}</ref> In particular, there is a higher prevalence of females that are affected by [[anxiety disorders]].

The central nucleus of the amygdala has direct correlations to the [[hypothalamus]] and [[brainstem]]—areas directly related to fear and anxiety. (The central nucleus have high densities of [[Opioid receptor|opiate receptors]].<ref>{{Cite journal |last=Davis |first=Michael |date=1992 |title=The Role of the Amygdala in Fear and Anxiety |url=https://emotion.wisc.edu/wp-content/uploads/sites/1353/2021/03/Davis-The-Role-of-the-Amygdala-in-Fear-and-Anxiety-1992-Annual-Review-of-Neuroscience.pdf?utm_source=chatgpt.com |journal=Annual Reviews |volume=15 |issue=353-75}}</ref>) This connection is evident from studies of animals that have undergone amygdalae removal.<ref>{{Cite news |last=Bhanoo |first=Sindya N. |date=2010-12-16 |title=Humans, Like Animals, Behave Fearlessly Without the Amygdala |url=https://www.nytimes.com/2010/12/21/science/21obbrain.html |access-date=2025-02-15 |work=The New York Times |language=en-US |issn=0362-4331}}</ref> Such studies suggest that animals lacking an amygdala have less fear expression. In an experiment, [[common degu|degu]] pups were removed from their mother but allowed to hear her call. In response, the males produced increased [[serotonin receptor]]s in the amygdala but females lost them. This led to the males being less affected by the stressful situation.<ref name=":1" />

The clusters of the amygdala are activated when an individual expresses feelings of fear or aggression. This occurs because the amygdala is the primary structure of the brain responsible for [[fight-or-flight response]]. Anxiety and panic attacks can occur when the amygdala senses environmental stressors that stimulate fight-or-flight response.<ref>{{Cite journal |last=Coplan |first=Jeremy D |last2=Lydiard |first2=R.Bruce |date=1998 |title=Brain circuits in panic disorder |url=https://doi.org/10.1016/s0006-3223(98)00300-x |journal=Biological Psychiatry |volume=44 |issue=12 |pages=1264–1276 |doi=10.1016/s0006-3223(98)00300-x |issn=0006-3223|doi-access=free }}</ref><ref>{{Cite journal |last=Gorman |first=Jack M. |last2=Kent |first2=Justine M. |last3=Sullivan |first3=Gregory M. |last4=Coplan |first4=Jeremy D. |date=2000-04-01 |title=Neuroanatomical Hypothesis of Panic Disorder, Revised |url=https://psychiatryonline.org/doi/10.1176/appi.ajp.157.4.493 |journal=American Journal of Psychiatry |language=en |volume=157 |issue=4 |pages=493–505 |doi=10.1176/appi.ajp.157.4.493 |issn=0002-953X}}</ref> The amygdala is involved in the expression of [[Fear conditioning|conditioned fear]]. Conditioned fear is the framework used to explain the behavior produced when an originally neutral stimulus is consistently paired with a stimulus that evokes fear. Fear is measured by changes in autonomic activity including increased heart rate, increased blood pressure, as well as in simple [[reflex]]es such as flinching or blinking.<ref>{{Cite journal |last=Sehlström |first=Malcolm |last2=Ljungberg |first2=Jessica K. |last3=Claeson |first3=Anna-Sara |last4=Nyström |first4=Markus B. T. |date=2022 |title=The relation of neuroticism to physiological and behavioral stress responses induced by auditory startle |url=https://pubmed.ncbi.nlm.nih.gov/35403836 |journal=Brain and Behavior |volume=12 |issue=5 |pages=e2554 |doi=10.1002/brb3.2554 |issn=2162-3279 |pmc=9120885 |pmid=35403836}}</ref> Studies in 2004 and 2006 showed that normal subjects exposed to images of frightened faces or faces of people from another race will show increased activity of the amygdala, even if that exposure is [[subliminal message|subliminal]].<ref>{{cite journal |vauthors=Williams LM, Liddell BJ, Kemp AH, Bryant RA, Meares RA, Peduto AS, Gordon E |date=August 2006 |title=Amygdala-prefrontal dissociation of subliminal and supraliminal fear |journal=Human Brain Mapping |volume=27 |issue=8 |pages=652–61 |doi=10.1002/hbm.20208 |pmc=6871444 |pmid=16281289}}</ref><ref name="pmid15563325">{{cite journal |vauthors=Cunningham WA, Johnson MK, Raye CL, Chris Gatenby J, Gore JC, Banaji MR |date=December 2004 |title=Separable neural components in the processing of black and white faces |url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:12164714 |journal=Psychological Science |volume=15 |issue=12 |pages=806–13 |doi=10.1111/j.0956-7976.2004.00760.x |pmid=15563325 |s2cid=82916}} [https://www.sciencedaily.com/releases/2004/12/041208231237.htm Lay summary] available from [[Science Daily]].</ref> However, the amygdala is not necessary for the [[Fear processing in the brain|processing of fear-related stimuli]], since persons in whom it is bilaterally damaged show rapid reactions to fearful faces, even in the absence of a functional amygdala.<ref>{{cite journal |vauthors=Tsuchiya N, Moradi F, Felsen C, Yamazaki M, Adolphs R |date=October 2009 |title=Intact rapid detection of fearful faces in the absence of the amygdala |journal=Nature Neuroscience |volume=12 |issue=10 |pages=1224–5 |doi=10.1038/nn.2380 |pmc=2756300 |pmid=19718036}}</ref>