olfactory system
Acronym:
OSY
The term olfactory system (OSY) refers to a histologically and functionally defined set of sensory structures involved in the processing of oderant information and the sense of smell ( Yilmazer-Hanke-2012, Buck-2013 ). It is composed bilaterally of a main olfactory system (OSYm) and an accessory olfactory system (OSYa). Both the OSYm and OSYa are fully developed in the rat ( Swanson-2004 ) and the mouse ( AMBA-2024 ), but current evidence does not support the existence of a significantly functional OSYa in the human or the macaque ( Witt-2002, Zhang-2003, Francia-2014 ).
Evolutionary biologists attribute the virtual absence of the OSYa in primates to their greater reliance on the visual and auditory systems for adaptation to social stimuli ( Witt-2002 ). Such an interpretation is consistent with findings that the OSYa provides rodents a prominent pathway from accessory olfactory receptors (OLRa) to the medial amygdalar nucleus (MEA) where neurons sensitive to adult levels of circulating sex hormones (estrogens and androgens) ( Simerly-1990 ) enable the brain (BRN) to evaluate the age and sex of another individual compared to its own age (prepubertal vs. adult) and sex (male vs. female) by its own levels of circulating estrogenic and andorgenic hormones.
Primates, on the other hand, lacking significant input to MEA by way of an OSYa, have prominent visual and auditory pathways to MEA. One passes directly through the lateral amygdalar nucleus (LAN) to MEA and a second passes indirectly from LAN through the basolateral amygdalar nucleus (BLA) to MEA ( Amaral-1992 ).
The evolutionary interpretation of species differences in the role that olfaction plays in sexual and aggressive behavior is not inconsistent with findings that olfactory functions of the human are equally as effective as of other animals and that the human olfactory bulb (OLB) has more neurons than that of the rat ( McGann-2017 ).
In rodents, pheromone oderants trigger reproductive behaviors and physiological changes in other members of the same species ( Zhang-2003 ). They influence hormonal systems via the MEA through the hypothalamus (HYP) to the hypothalamic-pituitary-gonadal axis ( Sonne-2023 ) and mating behavior through the MEA and HYP to the periaqueductal gray (PAG) and other brainstem extrapyramidal motor nuclei (EXM) ( Bowden-2021 ). Thus, the prominent influence of social oderants on rodent behavior is mediated by the the accessory olfactory bulb (AOB) component of the OLB, and the human has no AOB ( Buck-2013 ). Final 20 Jan 2025.
Also known as: olfactory areas, olfactory nervous systemNeuroNames ID : 2867
|
|