MR Volumetric Study of Piriform-Cortical Amygdala and Orbitofrontal Cortices: The Aging Effect

Abstract

IntroductionThe piriform cortex and cortical amygdala (PCA) and the orbitofrontal cortex (OFC) are considered olfactory-related brain regions. This study aims to elucidate the normal volumes of PCA and OFC of each age groups (20.0-70.0 year old), and whether the volumes of PCA and OFC decline with increasing age and diminishing olfactory function.MethodsOne hundred and eleven healthy right-handed participants (54 males, 57 females), age 20.0 to 70.0 years were recruited to join this study after excluding all the major causes of olfactory dysfunction. Volumetric measurements of PCA and OFC were performed using consecutive 1-mm thick coronal slices of high-resolution 3-D MRIs. A validated olfactory function test (Sniffin’ Sticks) assessed olfactory function, which measured odor threshold (THD), odor discrimination (DIS), and odor identification (ID) as well as their sum score (TDI).ResultsThe volume of OFC decreased with age and significantly correlated with age-related declines in olfactory function. The volume of OFC showed significant age-group differences, particularly after 40 years old (p < 0.001), while olfactory function decreased significantly after 60 years old (p < 0.001). Similar age-related volumetric changes were not found for PCA (p = 0.772). Additionally, there was significant correlation between OFC and DIS on the Right Side (p = 0.028) and between OFC and TDI on both sides (p < 0.05). There was no similar correlation for PCA.ConclusionsAging can have a great impact on the volume of OFC and olfactory function while it has much smaller effect on the volume of PCA. The result could be useful to establish normal volumes of PCA and OFC of each age group to assess neurological disorders that affect olfactory function.

Characterizing Olfactory Function in Children with Autism Spectrum Disorder and Children with Sensory Processing Dysfunction

“…We know that facial recognition and social motivation processes are altered in people with ASD and have been associated with altered patterns of brain activity [51][52][53]. Interestingly, odor valence has also been linked to neural activity in the orbitofrontal cortex [54][55][56]. That we also observed a relationship between odor identification and valence lends further support to the implication of the orbitofrontal cortex in both social and olfactory symptoms of ASD.…”

The Affective Neuroscience of Aging

“…In some structural MRI studies, the amygdala shows no significant differences in volume across the adult lifespan, in the context of decline in other structures (Jernigan et al, 2001, Jiang et al, 2014, Li et al, 2014, Shen et al, 2013). A post-mortem study also showed no significant decrease in volume with age (Brabec et al, 2010).…”

Age-Related Olfactory Dysfunction: Epidemiology, Pathophysiology, and Clinical Management

“…Human morphometrical studies using magnetic resonance imaging (MRI) have yielded mixed results. One study suggests that among the olfactory-related brain structures, the volume of the piriform cortex and that of the amygdala cortex do not reduce with age, while the volume of the orbitofrontal cortex significantly decreases (Shen et al, 2013 ). Another study examining normal subjects across ages showed that the volume of the OB and tract showed an initial increase up to the 4th decade of life, followed by a decrease with increasing age (Yousem et al, 1998 ).…”