FA values in bilateral OFC were significantly higher in CA as compared to healthy controls. The results of the present study partly confirms an earlier study, where the authors reported higher cortical thickness bilaterally within OFC in CA subjects in terms of an increase in gray matter thickness (Frasnelli et al.
2013). Higher FA values and the increase in cortical thickness within the OFC, which is a secondary olfactory area, suggests the plastic nature of the brain (Sakai
2020). However, the exact implication of FA for gray matter thickness is still unknown. Nonetheless, some studies have observed that increased grey matter volume and higher FA may be related to neuroplasticity (Hsin et al.
2017). However, when we look into the FA values between groups, the differences may be subtle but, nonetheless, they are statistically significant. Some studies have shown absence of differences between both groups with no morphological alterations in primary olfactory cortex (Peter et al.
2020). The authors concluded that the lack of lifelong olfactory experience had no major effect on the primary olfactory cortex. However, there were some changes in OFC which may be the result of developmental processes and also due to the multimodal nature of the OFC. Also, no gray matter alterations in primary olfactory cortex, which includes the piriform cortex, have been seen in rodents. There, postnatal removal of olfactory bulb, severing inputs to primary olfactory cortex, produced little or no alterations in the thickness of the piriform cortex (Friedman and Price
1986; Westrum and Bakay
1986). A study by (Karstensen et al.
2018) on CA patients points to the loss of grey matter volume in medial OFC. However, inclusion of hyposmic patients in the CA group by the authors, could be responsible for such reduced volume in medial OFC as was observed by Yao and colleagues, where patients with hyposmia show atrophy in right orbitofrontal cortex (Yao et al.
2018). Based on the existing literature, and the present findings, we conclude that people with CA have higher FA values in OFC pointing towards the neuroplastic nature of the brain.