- The typical areas that have been subject to study are the nuclei clusters comprising the amygdalae and the prefrontal cortex (PFC) as their functionality and activation is abnormal relative to healthy controls.
   - The amygdalae constitute part of the limbic system and play a role in the emotional response to a stimulus, most notably inducing physiological reactions to fear, anger, anxiety, and aggression.
      - Hyperarousal of the amygdalae give rise to the intense emotional responses that are characteristic of BPD.
   - The PFC is a major contributor to our executive control, influencing emotional and motivational behaviors.
      - Diminished efficacy of top-down cortical modulation—wherein the brain uses models, ideas, and expectations to interpret sensory information—is observed in BPD, as misinterpretation of events often invokes the onset of a crisis. 
- Both the amygdalae and the PFC are associated with different neural networks.
   - Within the SN, a network that detects and incorporates emotional and sensory stimuli, the amygdalae are considered a subcortical node.
   - Subsections of the PFC are classified as cortical nodes in the DFN, a network involved in various functions but guessed at being the primary determinant of the neurological basis for the self.
- Abnormal neuronal connectivity of the amygdalae and the PFC may be an underlying cause of the impaired communication between the aforementioned neural networks often reported in BPD.

Functional Connectivity in BPD

- A biological neural network, in theory, is an assemblage of structures that are able to regulate central nervous system automatisms with efficiency and pin-point accuracy.
- The concept of neural networks was originally coined in order to understand the construction of a neural circuit; it has since evolved to explaining circuitry functionality and interconnectedness with other networks and structures.
- The triple-network model of psychopathology, moreover, is representative of this idea, wherein the salience network (SN) serves as an interface between the frontoparietal network (FPN) and default mode network (DMN), allowing the integration and balance of neural processing with affective processes.

University of Minnesota - Twin Cities

Studies investigating different brain regions associated with emotion concluded that there is no singular brain region associated with a specific emotion. Rather, each emotion has different patterns of activation across several different brain regions.

Brain Regions Associated with Emotions

A group of neurons that are interconnected by synapses. They are responsible for our behaviors and experiences. Like electrical circuits, neural circuits can convey signals through two different processes: Signals that vary in strength (i.e., analog-like signals), and signals that vary in frequency (i..e, digital-like, all-or-none signals). 

Neural Circuits

Baev, K. V. (1998). Biological neural networks: Hierarchical concept of brain function. Birkhäuser. https://doi.org/10.1007/978-1-4612-4100-3

Biological neural networks: Hierarchical concept of brain function

Menon, V. (2018). The triple network model, insight, and large-scale brain organization in autism. Biological psychiatry, 84(4), 236-238. https://doi.org/10.1016/j.biopsych.2018.06.012

The triple network model, insight, and large-scale brain organization in autism

Biological Neural Network

- Experiments conducted by Andreas Bartels and Semir Zeki (2000) found that feelings of love increased activity in the insula and anterior cingulate cortex, as well as in the caudate and putamen. 

- Feelings of love also showed reduced activity in the posterior cingulate and amygdala, as well as the right prefrontal cortex. 


The Love Pathway

-PET images of adult subjects asked to reexperience episodes of happiness showed increased activity in the right posterior cingulate cortex and left insula,  as well as decreased activity in the left anterior cingulate cortex.

The Happiness Pathway

-PET images of adult subjects asked to reexperience episodes of anger showed increased activity in the left anterior cingulate cortex and pons.



Neural Pathway for Anger

-PET images of adult subjects asked to reexperience episodes of sadness showed increased activity in the anterior cingulate cortex, insula, and dorsal pons, as well as decreased activity in the posterior cingulate cortex.

The Sadness Pathway

Not only does the dorsolateral prefrontal cortex activate when one experiences disgust but so does the amygdala, ventromedial PFC, orbitofrontal cortex, insular cortex and the anterior cingulate.

The pathway for social and moral disgust is consistent with core disgust or gastrointestinal discomfort. 



The Disgust Pathway

A neuroscientist conducts a study where participants view images designed to evoke fear. Using fMRI scans, the researcher observes significant activation in the amygdala. Based on this finding, the researcher publishes a paper concluding that the amygdala is the brain's 'fear center.' Based on the contemporary understanding of how the brain processes emotions, evaluate the researcher's conclusion. Why is this conclusion likely an oversimplification?

Interpreting Brain Imaging Research

The limbic system is made up of a number of different structures that are involved in processing both emotion and memory. Three of its most important components include the amygdala, the hippocampus, and the hypothalamus.

Limbic System

A linear chain of attached neurons. It is the simplest type of neural circuit.

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