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Review
. 2021 Jan:196:101891.
doi: 10.1016/j.pneurobio.2020.101891. Epub 2020 Jul 28.

Left and right hemispheric lateralization of the amygdala in pain

Heather N Allen  1 , Harley J Bobnar  1 , Benedict J Kolber  2
Affiliations
Review

Left and right hemispheric lateralization of the amygdala in pain

Heather N Allen et al. Prog Neurobiol. 2021 Jan.

Abstract

Hemispheric asymmetries within the brain have been identified across taxa and have been extensively studied since the early 19th century. Here, we discuss lateralization of a brain structure, the amygdala, and how this lateralization is reshaping how we understand the role of the amygdala in pain processing. The amygdala is an almond-shaped, bilateral brain structure located within the limbic system. Historically, the amygdala was known to have a role in the processing of emotions and attaching emotional valence to memories and other experiences. The amygdala has been extensively studied in fear conditioning and affect but recently has been shown to have an important role in processing noxious information and impacting pain. The amygdala is composed of multiple nuclei; of special interest is the central nucleus of the amygdala (CeA). The CeA receives direct nociceptive inputs from the parabrachial nucleus (PBN) through the spino-parabrachio-amygdaloid pathway as well as more highly processed cortical and thalamic input via the lateral and basolateral amygdala. Although the amygdala is a bilateral brain region, most data investigating the amygdala's role in pain have been generated from the right CeA, which has an overwhelmingly pro-nociceptive function across pain models. The left CeA has often been characterized to have no effect on pain modulation, a dampened pro-nociceptive function, or most recently an anti-nociceptive function. This review explores the current literature on CeA lateralization and the hemispheres' respective roles in the processing and modulation of different forms of pain.

Keywords: Amygdala; Brain lateralization; Central amygdala; Functional lateralization; Left vs right brain; Pain.

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Figures

Figure 1:
Figure 1:
Overview of inputs and outputs of the central amygdala (CeA). Nociceptive input to the CeC is received from the PBN, whereas polymodal input is received from the thalamus and other amygdala nuclei. Outputs are highlighted by the red output neuron to various other brain regions. PBN: parabrachial nucleus; L: lateral amygdala; BLA: basolateral amygdala; CeC: capsular central amygdala; CeL: lateral central amygdala; CeM: medial central amygdala; BNST: bed nucleus of the stria terminalis; PAG: periaqueductal gray; RVM: rostral ventral medulla.
Figure 2:
Figure 2:
Hypothesized model for how amygdala lateralization works in acute and chronic pain.
See this image and copyright information in PMC

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