Accessibility and Connectivity of the Scent Circuit
(Workbook Page 48)
Scent is of great interest in trying to deal with pain because of the scent circuit’s connection to the amygdala and it’s tracing of the subsequent pain circuit. Review the graphic on page 48 of the Neuroplastic Transformation workbook and note the strong overlap of scent and pain circuits. Scent receptors are buried in the upper 1/3 of the mucous membrane in the nose designed to pick up odors and mingle these with taste receptors to come up with the array of scents that people are capable of distinguishing from each other. These include 300 to 400 specific scent receptors in nasal mucus membranes, that when combined allow for a vast array of scent discrimination.
Nerve endings for the scent receptors that start in the nose move through a series of small holes at the top of the nose and the base of the skull. The multiple nerve endings move from there to the first synapses in the olfactory bulb. The second synapse in the scent circuit is in the amygdala, the wild area of the brain responsible for such things as survival, raw emotional perception, emotional memory encoding and retrieval, as well as pain perception. The amygdala is the area where transition from automatic brain to thinking and perceiving brain occurs. It is here where we first perceive pain. Extreme emotions mix with the perception of pain danger, activating fight flight mechanisms. Reactive brain function selectively shuts off the higher brain’s ability to down regulate the emotional impact from the amygdala and sift through that input for problem solving and planning. Literally the amygdala takes over the rest of the thinking brain.
The scent circuit closely parallels the pain circuit. The first synapse for scent is in the olfactory bulb of the brainstem. The next synapses include Amygdala, Insula, Prefrontal Cortex, Anterior Cingulate Cortex, Posterior Cingulate Cortex and Posterior Parietal Cortex. All of these overlap with pain and mood circuits. Stimulating pleasant sensory experiences counter stimulates pain, anxiety and depression, while evoking powerful autobiographical memories.