Brain mediators of systemic oxidative stress on perceptual impairments in Parkinson’s disease

Table 3 The potential brain mediators of the relationships between oxidative stress and the different perceptual functions

Clinical variable	Anatomy name	Path a			Path b			a × b				Path c’
Clinical variable	Anatomy name	p_coef	z	p	p_coef	z	p	p_coef	z	p	p_coef	z	p
Digit symbol	MTG	−0.007	−3.97	<0.001	15.55	2.94	0.003	−0.10	−2.82	0.005	−0.11	−2.12	0.034
	IPL	−0.009	−3.30	<0.001	11.29	2.28	0.023	−0.10	−2.04	0.042	−0.11	−2.20	0.028
	HIPP	−0.004	−2.49	0.013	18.25	−1.58	0.030	−0.06	−2.03	0.042	−0.15	−2.25	0.025
	INS	−0.005	−2.84	0.005	24.73	2.38	0.017	−0.12	−2.24	0.025	−0.09	−2.17	0.030
Block design	MTG	−0.007	−3.40	<0.001	19.21	4.02	<0.001	−0.13	−2.91	0.004	−0.09	−2.67	0.008
	HIPP	−0.004	−2.46	0.014	16.85	2.53	0.011	−0.06	−2.03	0.042	−0.15	−2.55	0.011
	INS	−0.005	2.86	0.004	29.32	3.03	0.002	−0.14	−2.47	0.014	−0.07	−2.56	0.011
POI	MTG	−0.007	−3.64	<0.001	92.59	2.84	0.005	−0.63	−2.74	0.006	−0.71	−2.72	0.007
	HIPP	−0.004	−2.44	0.015	99.80	2.42	0.015	−0.34	−2.15	0.031	−1.01	−2.71	0.007
	INS	−0.005	−2.99	0.003	142.70	2.88	0.004	−0.70	−2.39	0.017	−0.65	−2.75	0.006
PIQ	MTG	−0.007	−3.59	<0.001	82.38	2.60	0.009	−0.56	−2.26	0.024	−0.68	−2.62	−0.009
PIQ	INS	−0.005	−2.96	0.003	139.79	2.83	0.005	−0.68	−2.43	0.015	−0.57	−2.56	0.010

The corresponding statistical results of each path and mediation effect between the oxidative stress (independent variable), perceptual functions (dependent variable), and anatomical regions with significant disease effect (mediators) are described in terms of corresponding path coefficient, z value, and p value. The anatomical regions were considered as potential brain mediators between oxidative stress level and perceptual functions if statistical significance, as indicated by a p of less than 0.05, was found in each of the following three effects in corresponding mediation analysis. (1) Indirect Path a: the relationship between oxidative stress level and the regional gray matter volume; (2) indirect Path b: the relationship between the regional gray matter volume and perceptual functions as determined by controlling the oxidative stress level and (3) Mediation a × b effect. All mediation analyses were conducted using the Mediation toolbox
P _coef path coefficient, HIPP hippocampus, INS insula, IPL inferior parietal lobule, MTG middle temporal gyrus, PIQ performance intelligence quotient; POI, perceptual organization index

ISSN: 1479-5876