Neural Circuitry for Stress Information of Environmental and Internal Odor Worlds

Abstract

In mammals, odor information detected in the olfactory epithelium is converted to a topographic map of activated glomeruli in the olfactory bulb. Odor signals are then conveyed by projection neurons to the olfactory cortex for decision making. Odor information is processed by two distinct pathways, one is innate and the other is learned, which are separately activated during exhalation and inhalation, respectively. There are two types of odor signals, exteroceptive and interoceptive, which are also processed in different phases of respiration. Exteroceptive sensory information whether attractive/pleasant or aversive/stressful, is evaluated by the valence regions in the amygdala. Stress is an alert signal telling the body to take an action so that the normal condition can be recovered. When the odor quality is negative, the brain sets up a behavioral strategy to avoid the danger or to improve the situation. In this review article, we will describe the recent progress in the study of olfactory perception focusing on stress responses to external and internal odors.

Circuit formation and sensory perception in the mouse olfactory system

“…We previously proposed another hypothesis that each lateral and medial map in the OB may separately process orthonasal/exteroceptive and retronasal/interoceptive odor information, respectively (Mori and Sakano, 2022b). Here we further propose that the BF GABAergic input to the glomerular circuit is respiration-phase coherent and gates the orthonasal and retronasal odor inputs.…”

Circadian rhythm mechanism in the suprachiasmatic nucleus and its relation to the olfactory system

“…In addition to light, possible conditions include food availability, the presence of predators, and environmental temperature, which in turn affect the wake–sleep states and the brain’s information processing mode ( Pickel and Sung, 2020 ; Franken and Dijk, 2024 ). From this perspective, the olfactory system, which is important for feeding, finding mates, and escaping predators, is thought to be closely related to circadian rhythms and wake–sleep states ( Mori and Sakano, 2022 ). Because the OB has the unique property of generating a circadian rhythm without the SCN, investigating the relationship between diurnal variation in olfactory information processing and circadian rhythms of the SCN is an interesting target for future research.…”