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

Jing Shen,Shiyu Zhou,Jianlin Wu,Mohammad A Kassir,Stephanie Y Xuan,Yongquan Ye,Jiani Hu,Qing Zhang,Qinghang Li,Antony Bayer

doi:10.1371/journal.pone.0074526

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.

Highlights

The piriform cortex and cortical amygdala (PCA) and the orbitofrontal cortex (OFC) are considered olfactory-related brain regions
Volumes of PCA, OFC, scores of Sniffin’ Sticks, and results of age-group comparisons using MANCOVA or MANOVA are presented in Table 1 and Table 2, respectively
Volumes of PCA and OFC MANCOVA with intracranial volume (ICV) as a covariate revealed no significant correlation between PCA volume and age-group (F4, 100 = 0.451, p = 0.772) or gender (F1, 100 = 0.517, p = 0.474)

Summary

Introduction

The piriform cortex and cortical amygdala (PCA) and the orbitofrontal cortex (OFC) are considered olfactory-related brain regions. Results: The volume of OFC decreased with age and significantly correlated with age-related declines in olfactory function. 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. The OFC receives odor input from the piriform cortex and forms reciprocal connections allowing it to modulate piriform cortical activity [2,3] These brain regions form a network that responds to odors based on odor memory and motivational state. Concurrent use of olfactory function tests and volumetric MRI studies can assess the relationship between changes in olfactory function and changes in olfactory-related brain regions. Few studies have been done to examine whether the volumes of PCA and OFC decrease with age, and decline in parallel to olfactory function [7,8]

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