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: Several studies have reported the therapeutic effects of phytoncides on various mental disorders. However, little is known about the therapeutic effects of phytoncides on mild cognitive impairment (MCI), a prodromal stage of dementia. In this pilot study, we aimed to clarify the effect of inhaled phytoncides on the cognitive function of patients clinically diagnosed with MCI. : In total, 21 patients with MCI were randomly assigned to either a saline (no-odor) or phytoncide group and subsequently inhaled saline or phytoncide for 30 minutes indoors, respectively. To evaluate changes in cognitive function, we implemented functional near-infrared spectroscopy along with the Stroop task and compared task performance and hemodynamic responses in the dorsolateral/ventrolateral part of the prefrontal cortex (DLPFC/VLPFC) before and after inhalation. : While the saline group showed no significant difference in either task performance (Wilcoxon W = 18.50, p = 0.385) or hemodynamic response, a significant increase in Stroop task performance (Wilcoxon W = 1.50, p = 0.009) and hemodynamic attenuation in the left VLPFC (Wilcoxon W = 56.00, p = 0.042) were found in the phytoncide group after inhalation. : Since compensatory task-related prefrontal hyperactivation represents one of the neural indicators of cognitive dysfunction in MCI, our findings shed light on the beneficial effects of phytoncide on cognitive function in MCI.
Park et al. (Fri,) studied this question.