Wiki: Amygdala
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The amygdalae (pronounced /əˈmɪɡdəliː/; singular: amygdala; also corpus amygdaloideum) (Latin, from Greek αμυγδαλή, amygdalē, ‘almond’, ‘tonsil’, listed in the Gray’s Anatomy as the nucleus amygdalæ)[1] are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans.[2] Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.[3]
Emotional learning
In complex vertebrates, including humans, the amygdalae perform primary roles in the formation and storage of memories associated with emotional events. Research indicates that, during fear conditioning, sensory stimuli reach the basolateral complexes of the amygdalae, particularly the lateral nuclei, where they form associations with memories of the stimuli. The association between stimuli and the aversive events they predict may be mediated by long-term potentiation, a sustained enhancement of signalling between affected neurons.[3]
Memories of emotional experiences imprinted in reactions of synapses in the lateral nuclei elicit fear behavior through connections with the central nucleus of the amygdalae and the bed nuclei of the stria terminalis (BNST). The central nuclei are involved in the genesis of many fear responses, including freezing (immobility), tachycardia (rapid heartbeat), increased respiration, and stress-hormone release. Damage to the amygdalae impairs both the acquisition and expression of Pavlovian fear conditioning, a form of classical conditioning of emotional responses.[3]
The amygdalae are also involved in appetitive (positive) conditioning. It seems that distinct neurons respond to positive and negative stimuli, but there is no clustering of these distinct neurons into clear anatomical nuclei.[9]
Different nuclei within the amygdala have different functions in appetitive conditioning.[10
Neuropsychological correlates of amygdalar activity
Early research on primates provided explanations as to the functions of the amygdala, as well as a basis for further research. As early as 1888, rhesus monkeys with a lesioned temporal cortex (including the amygdala) were observed to have significant social and emotional deficits.[16] Heinrich Klüver and Paul Bucy later expanded upon this same observation by showing that large lesions to the anterior temporal lobe produced noticeable changes, including overreaction to all objects, hypoemotionality, loss of fear, hypersexuality, and hyperorality, a condition in which inappropriate objects are placed in the mouth. Some monkeys also displayed an inability to recognize familiar objects and would approach animate and inanimate objects indiscriminately, exhibiting a loss of fear towards the experimenters. This behavioral disorder was later named Klüver-Bucy syndromeaccordingly.[17] Later studies served to focus on the amygdala specifically, as the temporal cortex encompasses a broad set of brain structures, making it difficult to find which ones specifically may have correlated with certain symptoms. Monkey mothers who had amygdala damage showed a reduction in maternal behaviors towards their infants, often physically abusing or neglecting them.[18] In 1981, researchers found that selective radio frequency lesions of the whole amygdala caused Klüver-Bucy Syndrome.[19]
With advances in neuroimaging technology such as MRI, neuroscientists have made significant findings concerning the amygdala in the human brain. Consensus of data shows the amygdala has a substantial role in mental states, and is related to many psychological disorders. In a 2003 study, subjects with Borderline personality disorder showed significantly greater left amygdala activity than normal control subjects. Some borderline patients even had difficulties classifying neutral faces or saw them as threatening.[20] Individuals with psychopathy show reduced autonomic responses, relative to comparison individuals, to instructed fear cues.[21] In 2006, researchers observed hyperactivity in the amygdala when patients were shown threatening faces or confronted with frightening situations. Patients with more severe social phobia showed a correlation with increased response in the amygdala.[22] Similarly, depressed patients showed exaggerated left amygdala activity when interpreting emotions for all faces, and especially for fearful faces. Interestingly, this hyperactivity was normalized when patients went on antidepressants.[23] By contrast, the amygdala has been observed to relate differently in people with Bipolar Disorder. A 2003 study found that adult and adolescent bipolar patients tended to have considerably smaller amygdala volumes and somewhat smaller hippocampal volumes.[24] Many studies have focused on the connections between the amygdala and autism.[25] Additional studies have shown a link between the amygdala and schizophrenia, noting that the right amygdala is significantly larger than the left in schizophrenic patients.[26]
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.[27][28]However, the amygdala is not necessary for the 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.[29]
Recent research suggests that parasites, in particular toxoplasma, form cysts in the brain of rats, often taking up residence in the amygdala. This may provide clues as to how specific parasites may contribute to the development of disorders, including paranoia.[30]
Visit this page for more on the Amygdala: http://en.wikipedia.org/wiki/Amygdala
Enjoy the following Amygdala-related articles:
Social Defeat Changes Young Brains
Rockefeller University researchers conducted a rather interesting study determine how young brains change in response to negative social situations.
Amygdala Size Connected to Rich, Varied Social Life in Humans
Summary article from ScienceDaily Scientists have discovered that the amygdala, a small almond shaped structure deep within the temporal lobe, is important to a rich and varied social life among humans. The finding was published this week in a new study in Nature Neuroscience and is similar to previous findings in other primate species, which compared [...]
Video: The Amygdala in 5 Minutes | Joseph LeDoux
In this video, Neuroscientist Joseph LeDoux gives a short primer on the brain’s emotional processor. Very cool. Enjoy! ~ Marsha
Brain Scans Show Distinctive Patterns in People With Generalized Anxiety Disorder
Your amygdala — an area associated with fear, anxiety, and anger — needs to have clean lines of communication to other parts of the brain. This piece of research reveals more detail about mis-connections from the amygdala in people with a particular anxiety disorder. (If you have anxiety which is poorly controlled, and then you [...]
The Toothpaste-Tube Wars: Relationship Battles and the Brain
Tame your “wild and precious” amygdala a bit, and have fewer relationship wars. A friend of mine calls them “The Toothpaste Tube Wars.” In some households, it’s the “Battle of the Toilet Seat” or the “Why-on-Earth-Do-You-Load-the-Dishwasher-Like-That Police Action.” They start with a small skirmish over something minor, and quickly escalate into a heated battle. Over. [...]
