Editing Amygdala (section)

== Structure ==
[[File:Mouse Amygdala.pdf|thumb|Subdivisions of the mouse amygdala]]

{{Multiple images
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| header            = T1 MRI images of amygdala in human ''(highlighted in green)''
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Thirteen [[Nucleus (neuroanatomy)|nuclei]]<ref>{{Cite journal |last=Pabba |first=Mohan |date=2013-08-28 |title=Evolutionary development of the amygdaloid complex |journal=Frontiers in Neuroanatomy |language=English |volume=7 |page=27 |doi=10.3389/fnana.2013.00027 |doi-access=free |issn=1662-5129 |pmc=3755265 |pmid=24009561}}</ref> have been identified, each with their own subdivisions and distinct connections to the rest of the brain.<ref>{{cite journal | pmid=22806915 | date=2013 | last1=Bzdok | first1=D. | last2=Laird | first2=A. R. | last3=Zilles | first3=K. | last4=Fox | first4=P. T. | last5=Eickhoff | first5=S. B. | title=An investigation of the structural, connectional, and functional subspecialization in the human amygdala | journal=Human Brain Mapping | volume=34 | issue=12 | pages=3247–3266 | doi=10.1002/hbm.22138 | pmc=4801486 }}</ref> The chief nuclei are the [[basolateral amygdala|basolateral complex]], the [[Central nucleus of the amygdala|central nucleus]], the cortical nucleus, the medial nucleus, and the [[intercalated cells of the amygdala|intercalated cell clusters]].<ref name="Bzdok Laird Zilles Fox 2013 pp. 3247–3266"/> The cortical and medial nuclei connect with the [[olfactory system]] and hypothalamus.<ref name="Bzdok Laird Zilles Fox 2013 pp. 3247–3266" /> The central nucleus has extensive projections to the [[brainstem]].<ref name="Bzdok Laird Zilles Fox 2013 pp. 3247–3266" />

The basolateral complex can be further subdivided into the lateral, the basal, and the accessory basal nuclei.<ref name="amyg-cytoarchitecture" /><ref name="emotion">{{cite web|author=Ben Best|year=2004|title=The Amygdala and the Emotions|access-date=15 March 2007|url=http://www.benbest.com/science/anatmind/anatmd9.html| archive-url= https://web.archive.org/web/20070309132748/http://www.benbest.com/science/anatmind/anatmd9.html| archive-date= 9 March 2007 | url-status= live}}</ref><ref name="Solano-Castiella">{{cite journal | vauthors = Solano-Castiella E, Anwander A, Lohmann G, Weiss M, Docherty C, Geyer S, Reimer E, Friederici AD, Turner R | title = Diffusion tensor imaging segments the human amygdala in vivo | journal = NeuroImage | volume = 49 | issue = 4 | pages = 2958–65 | date = February 2010 | pmid = 19931398 | doi = 10.1016/j.neuroimage.2009.11.027 | hdl = 11858/00-001M-0000-0010-ABE5-F | s2cid = 17137887 | hdl-access = free }}</ref> It has extensive connections with higher-order cortical areas in the [[Prefrontal cortex|prefrontal]], [[Temporal lobe|temporal]], [[Insular cortex|insular]] cortices, and the [[hippocampus]].<ref name="Bzdok Laird Zilles Fox 2013 pp. 3247–3266"/><ref name="McDonald 2020 pp. 1–38">{{cite book |last=McDonald |first=Alexander J. |title=Handbook of Behavioral Neuroscience |date=2020 |publisher=Elsevier |isbn=978-0-12-815134-1 |volume=26 |pages=1–38 |chapter=Functional neuroanatomy of the basolateral amygdala: Neurons, neurotransmitters, and circuits |doi=10.1016/b978-0-12-815134-1.00001-5 |pmc=8248694 |pmid=34220399}}</ref> The basolateral complex is surrounded by the intercalated cell net that is inhibitory and projects to a broad variety of areas in the [[basal forebrain]], [[hypothalamus]], and the amygdala.<ref name="Bzdok Laird Zilles Fox 2013 pp. 3247–3266" /><ref name="Stern Wilke Root 2023 pp. ENEURO.0238–23.2023">{{cite journal |last1=Stern |first1=Daniel B. |last2=Wilke |first2=Anna |last3=Root |first3=Cory M. |date=2023 |title=Anatomical Connectivity of the Intercalated Cells of the Amygdala |journal=eNeuro |volume=10 |issue=10 |pages=ENEURO.0238–23.2023 |doi=10.1523/ENEURO.0238-23.2023 |issn=2373-2822 |pmc=10576262 |pmid=37775310}}</ref>

===Hemispheric specializations===
The right and left portions of the amygdala have independent memory systems, but work together to store, encode, and interpret emotion.

The right hemisphere of the amygdala is associated with negative emotion.<ref>{{cite journal | vauthors = Barrett LF, Bliss-Moreau E, Duncan SL, Rauch SL, Wright CI | title = The amygdala and the experience of affect | journal = Social Cognitive and Affective Neuroscience | volume = 2 | issue = 2 | pages = 73–83 | date = June 2007 | pmid = 18392107 | pmc = 2288526 | doi = 10.1093/scan/nsl042 }}</ref><ref>{{cite journal | vauthors = Berntson GG, Bechara A, Damasio H, Tranel D, Cacioppo JT | title = Amygdala contribution to selective dimensions of emotion | journal = Social Cognitive and Affective Neuroscience | volume = 2 | issue = 2 | pages = 123–9 | date = June 2007 | pmid = 18414599 | doi = 10.1093/scan/nsm008 | pmc = 2293306 }}</ref> It plays a role in the expression of fear and in the processing of fear-inducing stimuli. [[Fear conditioning]], which occurs when a neutral stimulus acquires aversive properties, occurs within the right hemisphere. When an individual is presented with a conditioned, aversive stimulus, it is processed within the right amygdala, producing an unpleasant or fearful response. This emotional response conditions the individual to avoid fear-inducing stimuli and more importantly, to assess threats in the environment.

The right hemisphere is also linked to [[declarative memory]], which consists of facts and information from previously experienced events and must be consciously recalled. It also plays a significant role in the retention of episodic memory. [[Episodic memory]] consists of the autobiographical aspects of memory, permitting recall of emotional and sensory experience of an event. This type of memory does not require conscious recall. The right amygdala plays a role in the association of time and places with emotional properties.<ref>Markowitsch, H.  (1998). Differential contribution of right and left amygdala to affective information processing.  IOS Press.  11(4), 233–244.</ref>

In one study, electrical stimulations of the right amygdala induced [[negative affectivity|negative emotions]], especially fear and sadness. In contrast, stimulation of the left amygdala was able to induce either pleasant (happiness) or unpleasant (fear, anxiety, sadness) emotions.<ref name="amygdala_hemispheric_specialization1">{{cite journal |vauthors=Lanteaume L, Khalfa S, Régis J, Marquis P, Chauvel P, Bartolomei F |date=June 2007 |title=Emotion induction after direct intracerebral stimulations of human amygdala |journal=Cerebral Cortex |volume=17 |issue=6 |pages=1307–13 |doi=10.1093/cercor/bhl041 |pmid=16880223 |doi-access=}}</ref> Other evidence suggests that the left amygdala plays a role in the brain's [[reward system]].<ref name="amygdala_hemispheric_specialization2">{{cite book |title=The Human Amygdala |vauthors=Murray EA, Izquierdo A, Malkova L |publisher=Guilford Press |year=2009 |chapter=Amygdala function in positive reinforcement}}</ref>