NRP Fall 2023. Derek Remitar: The amygdala an avenue for therapy.

The amygdala is a subcortical structure of the brain that is commonly associated with
emotion. Like many other structures of the brain, the amygdala was named for its appearance. “Amygdala” means “almond” in Latin, and it indeed appears small and oval-shaped. It is locate bilaterally as part of the temporal lobes and is closely associated with other subcortical structures such as the caudate, hippocampus, thalamus, and hypothalamus (“The amygdala…”). The term amygdala is not necessarily singular, and most professionals use this term to refer to both structures found on either side of the brain. Scientists currently debate whether this subcortical structure is one unified region or actually composed of closely associated but separate components; nonetheless, most agree that the amygdala contains thirteen different groups of closely associated neural cells called nuclei (Šimić et al.). Through reciprocal connections to cortical and other subcortical structures, the amygdala is able to play a role in regulating autonomic or endocrine functions, influence decision-making or motivation, and lead to activation of fight-or-flight behavior as stimuli are processed (Šimić et al.).

The amygdala and its association with emotional experience presents a unique bridge between the disciplines of Biology, Psychology, and others because its abnormalities have the potential to impact emotional processing and mental health. Various lesions to the temporal lobe
have been shown to be capable of stimulating the amygdala and, depending on the severity, inducing panic attacks – recurrent episodes of feeling extreme fear without a clear cause (Wright). Conversely, other lesions that were destructive to this structure have been shown to induce tameness in animals, calm behavior in humans, and an overall flatness of affect (Wright). Thus, the amygdala serves as a brain structure that may be further explored to positively impact qualitative emotional experiences through the manipulation of biological processes.

A recent research study published in the Journal of Neuroscience by Hogri et al. demonstrated such an instance. In this study, researchers obtained a population of rats and selectively activated neurons found in their amygdala’s central nucleus through optogenetic stimulation – stimulation which occurs through activation by light. These neurons project to the lateral parabrachial nucleus found in the brainstem of mice which is known to play a role in transmitting painful stimuli. In one test, these rats were placed in a classical conditioning experiment in which they learned to associate the signal of an auditory sound with an electrical shock to the floor. This resulted in a baseline of the rats freezing in response to the auditory stimulus alone (Hogri et al. 5377). Another test exposed the paws of these rats to aversive stimuli such as heat, and the rats were assessed on whether they retracted their paws in response (Hogri et al. 5376). The researchers found that after stimulating the neurons of the central nucleus through optogenetic stimulation, these rats exhibited fewer paw withdrawal behaviors and fewer
freezing behaviors. The researchers interpreted that the rats exhibited fewer responses to
perceived pain and fewer defensive behaviors as a result of optogenetic stimulation to the
amygdala; thus, the amygdala could be a direct way to mediate the experience of pain and fear (Hogri et al. 5386).

It is important to recognize that the amygdala is not the only subcortical structure that operates during our qualitative emotional experiences or mediates the processing of such stimuli. Moreover, the field of science is likely still very far from applying these kinds of measures to the human brain despite its similarities to the test model (Hogri et al. 5382). Nonetheless, it is exciting to contemplate the possibilities that lie within a single subcortical region of the brain.

Work Cited:
Hogri, Roni, et al. “GABAergic CaMKIIα Amygdala Output Attenuates Pain and Modulates
Emotional-Motivational Behavior via Parabrachial Inhibition.” The Journal of
Neuroscience, vol. 42, no. 27, 2022, pp. 5373–5388.

Šimić, Goran, et al. “Understanding Emotions: Origins and Roles of the Amygdala.”
Biomolecules, vol. 11,6 823. 31 May. 2021, doi:10.3390/biom11060823
“The amygdala: A small part of your Brain’s biggest abilities.” Cleveland Clinic. (n.d.).
https://my.clevelandclinic.org/health/body/24894-amygdala#function

Wright, Anthony. “Chapter 6: Limbic System: Amygdala.” Neuroscience Online, Department of

Neurobiology and Anatomy, McGovern Medical School at UTHealth, 10 Oct. 2020,
https://nba.uth.tmc.edu/neuroscience/m/s4/chapter06.html.