In previous posts we have looked at the Insular Cortex, general models of the emotions and more recently the Hippocampus. The role of the Insular Cortex in emotions must be understood both in terms of the role of the Insular Cortex in other functions (e.g. interoception) as well as the role of other areas in emotions (e.g. the Limbic System). Although an understanding of these related areas is necessary, the understanding does not need to be too sophisticated. We need to come away with some simple assumptions that help to limit and guide the model we are interested in.
There are a number of areas that are thought to be involved in emotions. The Amygdala is one such area and the aim of this post is to look at briefly at what role the Amygdala might play in emotions and how it might do this. The paper used to inform this exploration of the Amgydala is ‘The Structural and Functional Connectivity of the Amygdala: From Normal Emotion to Pathological Anxiety‘ by Kim and colleagues (Kim et al, 2011).
The main points that I took away from this paper are that
1. The medial Prefrontal Cortex (mPFC) and Amygdala are tightly coupled and that the mPFC influences the output of the Amgydala.
2. The Amygdala is connected to many other brain regions. The authors detail the connections with the mPFC noting that diffuse tensor imaging reveals afferent projections to the Amgydala from the caudal and dorsal medial prefrontal cortex.
3. fMRI studies suggest that Amygdala activity is inversely correlated with mPFC activity during tasks involving interpretation of facial expressions.
4. Nuclei in the Amgydala include the basolateral area (BLA) and the centra nucleus (Ce). BLA receives inputs sensory inputs. The central nucleus projects to the Hypothalamus, brainstem nuclei as well as monoaminergic and cholinergic systems.
5. Research studies have shown the Amgydala to be necessary for classical conditioning and extinction.
6. Emotional regulation can be understood in terms of a competition between top-down and bottom-up processes. The Amygdala is central to the resolution of these bidirectional processes. Emotionally ambivalent signals such as fearful faces or surprised faces are interpreted by the Amgydala.
7. The Amygdala-mPFC dyad is involved in suppression or reappraisal of emotional stimuli.
8. The Amygdala-mPFC dyad is involved in pathological anxiety states. Typically there is hypoactivity of the mPFC and hyperactivity of the Amgydala in Amgydala-PFC models of pathological anxiety.
9. In social anxiety disorder there is evidence of involvement of the Amgydala-mPFC circuits including hypoactivation of the mPFC in emotional tasks as well as involvement of the Uncinate fasciculus.
10. One suggestion about Post Traumatic Stress Disorder is that there is an incomplete conditioned fear extinction. There is evidence of reduced mPFC activity in response to frightened faces.
The paper offers an interesting and simple model of the involvement of the Amygdala and medial Prefrontal Cortex in emotional regulation which can be used to contextualise the emotional function of other brain regions.
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Contributors to the Model (links are to the posts in which contributions were made – these links may contain further links directly to the contributors)
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