Amygdala In The Limbic System

The term ‘amygdala’ was first used by Burdach (1819) and referred to a set of nuclei in the brain (Aggleton & Saunders, 2000). In 1939, researchers Klüver & Bucy inflicted bilateral lesions of the inferior temporal lobe of monkeys in a laboratory in an attempt to reduce aggression. These lesions affected the cortical areas, amygdala, and the hippocampus. Later this became known as Klüver-Bucy syndrome, and consisted of symptoms such as psychic blindness, hypermetamorphsis, oral tendencies, and changes in emotional and sexual behaviors. Lesions of the amygdala made monkeys fearless of e.g. humans or snakes, and affectively flat, tame. This research brought recognition to the notion that the amygdala plays a significant role in the

The two brain structures that are most frequently linked to human emotion are the amygdalas and the medial portions of the prefrontal lobes (Pinel, 2014). The amygdalas are only one section of the limbic system, it is the “almond-shaped nucleus in the anterior temporal lobe” (Pinel, 2014, pg. 70). The amygdalas have been researched more than any other section of the limbic system. The amygdalas are most commonly associated with the emotion of fear, however research is showing that the amygdalas actually play a role in “evaluating the emotional significance of situations”, whether the emotions being felt are positive or negative (Pinel, 2014, pg. 436). Even though research has shown the amygdalas play a larger role with emotions, brain imaging

The amygdala is responsible for our emotional memories. Damage to the amygdala could impact us negatively causing us to misinterpret our memories and our emotions related to those memories. What should cause fear and anger could be diminished to a point that could cost you significantly if the amygdala is damaged. For example, if you don’t remember a negative emotion with a certain action in a memory of the past that has impacted you negatively, you might continue to make the same mistakes over and over again. By taking the same actions without causing you any fear and anxiety of loss or damage could cause you major negative effects in your

The complex structures of the limbic system boarder the thalamus, belt around the fornix and the Corpus Callosum. The limbic system possesses an array of unique functions due to its complex and unique structures. The system contains the hypothalamus, mammillary bodies, septal area, amygdala, hippocampus, orbital and medial prefrontal cortex, nucleus accumbens, ventral striatum and cingulate gyrus (ebrain, 2016). The limbic lobe is mainly responsible for facilitating mental functions and behavior such as emotions, cognition, judgment, impulsivity, learning, memory, pain, perception, motivation, and reward (ebrain, 2016). It is generally a site for the establishment of memory, learning and emotion.

According to our textbook, “In humans, the amygdala (from the Greek word for “almond”) is an almond shaped cluster of interconnected structures perched above the brainstem, near the limbic ring.” (Goleman, D. p.14) The amygdala starts to work quickly after we hear or look at something. When we look at something, our eyes send a message to the thalamus and a translation that only our complex human mind could understand takes place. Our visual cortex then receives a majority of that initial message as it begins to work out its level of significance. If the message is related to an emotion such as fear, the amygdala gets notified, and our emotional center becomes activated. But no matter what, an emotional reaction has already taken place before

“Yet we judge people by their appearances all the time,” said David Perrett. When you find another person attractive it is your human instinct to find a mate. Women look for strong but gentle fathers for their child and men look for gentle birthing mothers for their children. This is the scientific reasoning behind composite faces. Composite faces are a mixture of the attractive features that your brain sees and understands it as beautiful. It is believed that the human brain’s occipital lobe and limbic system are responsible for the desire and feeling of attractiveness toward faces. (Perrett)

The amygdalae (Latin, also corpus amygdaloideum, singular amygdala, 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].

The amygdala is the section of the brain process the emotion experienced. When a patient has PTSD, instead of the decrease of function, there is an increase in

Those diagnosed with PTSD have shown a reduction in the volume of the hippocampus. The hippocampus helps humans remember new memories and then be able to recall them later, and also helps identify between past and present memories. The amygdala is another section of the brain affected by PTSD, and the amygdala is responsible for processing emotions and fear. The ventromedial prefrontal cortex is shown to have a decreased size in cases. The ventromedial prefrontal cortex regulates negative emotions like stress, anxiety, and fear. The strange behaviours of the patients diagnosed with PTSD can be explained by the damage to the brain. “Researchers believe that the brain changes caused by PTSD increase the tendency of a person developing other psychotic and mood disorders” (brainblogger.com). The brain is like a machine made up of small parts, and if one of these parts break, the machine does not function

The amygdala is known to learn from exposure to fear and store assessment of threat–related stimuli. The prefrontal cortex is involved in extinction and the retention of fear and is connected to the amygdala. Finally, the hippocampus encodes the context during fear learning process and sends it to the amygdala. People with PTSD have hyper-activity in the amygdala, while having hypo-activity in the prefrontal cortex and there is reduction of the hippocampus volume. This reduction may limit proper evaluation and categorization of the experience. A study on Vietnam soldiers revealed that lesions in the amygdala and prefrontal cortex resulted in the absence of PTSD. To get further into the molecular level studies been done on the hormonal system. “Stress is known to contribute to the pathogenesis of a variety of disorders, including the majority of psychiatric like major depression and posttraumatic stress disorder.” (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3825244/pdf/DM30-02-343616.pdf). Research has revealed evidence that a hormonal system known as the hypothalamic-pituitary-adrenal (HPA) axis is the one that gets disrupted in people with PTSD. The hormonal system is involved in normal stress reactions, so the disruption of this system in people with PTSD creates this “false alarm”. It has been suggested by some scientist that the dysfunction of the HPA system results in hippocampal damage in people with PTSD. Damage in the hormones is caused by damage to

The amygdala appears to be active in dear acquisition, or learning to fear an event, as well as in the early stages of fear extinction or learning to not fear” (Post-Traumatic Stress Disorder). Also researchers have studied and delved into the effects of the prefrontal cortex (PFC). The prefrontal cortex is the area of the brain that is involved in tasks such as decision-making, problem solving, and judgment. “For example, when [the PFC] deems a source of stress controllable, the medial PFC suppresses the amygdala--an alarm center deep in the brainstem that controls the stress response” (Post-Traumatic Stress Disorder). “PTSD is not diagnosed until at least one month has passed since the time a traumatic event has occurred” (Joseph Goldberg, 2014). If the doctors see the symptoms of PTSD they will then go ahead and evaluate the patient by performing a complete medical history form and then physical exam follows. The next step is for the patient to be sent a psychiatrist, psychologist, or another medical health professional to help the patient treat his or her mental illness.

Review on How the Amygdala’s Emotional Function can Affect Sufferers of Post Traumatic Stress Disorder

Limbic dopaminergic system, a part of brain reward circuit, is the main target of morphine-like drugs and all drugs of abuse (Wise and Bozarth 1984). Brain reward and motivation circuit begins from the ventral tegmental area (VTA) at the top of brainstem that sends its dopaminergic projections to the various regions of brain including nucleus accumbens (NAc), amygdala (Ghalandari-Shamami, Hassanpour-Ezatti et al. 2011), hippocampus and prefrontal cortex (mesocorticolimbic system). On the other hand, VTA receives excitatory and inhibitory projections from other regions of the brains including GABAergic neurons of the NAc which send their inhibitory projections to the VTA (Koob 1992).

The purpose of this experiment is to test the involvement of the rat amygdala in associative fear conditioning. The amygdala has been shown to be necessary for fear memory expression (Iacopo et al., 2002). Memory expression, or retrieval, is the process of recalling a previously learned association or experience (Iacopo et al., 2002). To test the function of the amygdala, electrophysiological and pharmacological experiments will be conducted. The activity of the amygdala will be measured using intracellular recordings during testing of memory expression. Firing rate will be observed to determine if there is an increase in neuronal activity when the memory is being expressed. The ability to express a memory will be tested using a contextual