Frequency-dependent neural activity in primary angle-closure glaucoma

Figures & data

Table 1 Demographics and clinical measurements by group (mean ± SD)

Conditions	PACG	HC	T-value	P-value
Male/female	24/28	24/28	N/A	N/A
Age (years)	60.42±2.29	60.48±2.62	0.120	0.905
Handedness	52R	52R	N/A	N/A
Duration of PACG (years)	23.54±4.17	N/A	N/A	N/A
Best-corrected VA-right eye	0.13±0.07	1.25±0.25	−30.686	<0.001
Best-corrected VA-left eye	0.13±0.06	1.28±0.24	−33.267	<0.001
Retinal nerve fiber layer OD (µm)	100.37±8.55	120.13±4.17	−14.994	<0.001
Retinal nerve fiber layer OS (µm)	101.00±6.35	120.21±4.24	−18.146	<0.001
Visual field-OD (dB)	19.83±3.58	N/A	N/A	N/A
Visual field-OS (dB)	20.39±3.54	N/A	N/A	N/A

Abbreviations: HC, healthy control; N/A, not applicable; OD, oculus dexter; OS, oculus sinister; PACG, primary angle-closure glaucoma; R, right; VA, visual acuity.

Figure 1 The main effect of group on ALFF. The warm color represents a higher ALFF in PACG patients compared to NS, whereas the cool color represents a lower ALFF.

Abbreviations: ALFF, amplitude of low-frequency fluctuation; L, left; NS, normal-sighted controls; PACG, primary angle-closure glaucoma; R, right.

Table 2 The main effect of group on ALFF

Brain regions	MNI coordinates			BA	Cluster size	T-values
	X	Y	Z
PACG > NS
R-inferior occipital gyrus	33	−93	−18	18	54	5.597
R-superior frontal gyrus	9	66	3	10	85	5.159
PACG < NS
L-middle occipital gyrus	−42	−75	−9	19	40	−4.542
R-middle occipital gyrus	48	−66	6	19	136	−5.096
L-precentral/postcentral gyrus	−54	−6	21	6	75	−4.836
R-precentral gyrus	30	−33	72	6	82	−5.16
L-inferior parietal lobule	−51	−33	45	40	110	−5.368

Notes: The main effect of group on ALFF. The statistical threshold was set at the voxel level with P<0.001 for multiple comparisons using Gaussian random-field theory (repeated-measures ANOVA, voxel-level P<0.001, GRF correction, cluster-level P<0.01).

Abbreviations: ALFF, amplitude of low-frequency fluctuation; BA, Brodmann area; GRF, Gaussian random field; L, left; MNI, Montreal Neurological Institute; NS, normal-sighted controls; PACG, primary angle-closure glaucoma; R, right.

Figure 2 The main effect for frequency band on ALFF. The warm color represents a higher ALFF in the slow-4 band compared to the slow-5 band, whereas the cool color represents a lower ALFF.

Abbreviations: ALFF, amplitude of low-frequency fluctuation; L, left; R, right.

Table 3 The difference in ALFF between two frequency bands

Brain regions	MNI coordinates			BA	Cluster size	T-values
	X	Y	Z
Slow-4 > slow-5
B-posterior cingulate gyrus	6	−36	33	23/31	308	6.843
B-precuneus	−6	−69	39	7	91	5.088
Slow-4 < slow-5
B-frontal lobe	12	39	−21	11	1,901	−9.436
R-fusiform	27	9	−42	38	161	−6.857
R-cerebellum posterior lobe	15	−87	−36	–	313	−6.327

Notes: The main effect of bands on ALFF. The statistical threshold was set at the voxel level with P<0.001 for multiple comparisons using Gaussian random-field theory (repeated-measures ANOVA, voxel-level P<0.001, GRF correction, cluster-level P<0.01).

Abbreviations: ALFF, amplitude of low-frequency fluctuation; B, bilateral; BA, Brodmann area; GRF, Gaussian random field; L, left; MNI, Montreal Neurological Institute; R, right.

Figure 3 The results are obtained on comparison of ALFF between PACG and NS groups in each frequency band (post hoc two-sample t-tests, voxel-level P <0.001, GRF corrected, cluster-level P <0.01).

Notes: (A) altered ALFF values in slow-4 band between two groups, (B) altered ALFF values in slow-5 band between two groups, (C) the mean ALFF values of different brain regions in the two groups in slow-4 band, (D) the mean ALFF values of different brain regions in the two groups in slow-5 band.
Abbreviations: ALFF, amplitude of low-frequency fluctuation; GRF, Gaussian random field; IOG, inferior occipital gyrus; IPL, inferior parietal lobule; L, left; MOG, middle occipital gyrus; NS, normal-sighted controls; PACG, primary angle-closure glaucoma; postCG, postcentral gyrus; preCG, precentral gyrus; R, right.

Table 4 The difference in ALFF in each frequency band between the two groups

Frequency band/brain regions	MNI coordinates			BA	Cluster size	T-values
	X	Y	Z
Slow-4 (0.027–0.073 Hz)
PACG > NS
R-inferior occipital gyrus	6	−96	−21	18	95	3.859
PACG < NS
L-middle occipital gyrus	−39	−63	3	19	93	−3.839
L-precentral gyrus	−57	−15	33	3	60	−3.778
L-postcentral gyrus	−45	−21	63	4	52	−4.013
Slow-5 (0.001–0.027 Hz)
PACG > NS
R-inferior occipital gyrus	27	−96	−18	18	112	5.029
PACG < NS
L-inferior parietal lobule	−51	−33	45	40	−4.81	−4.81
L-postcentral gyrus	−27	−45	72	7	−3.613	−3.613
R-precentral/postcentral gyrus	30	−33	72	4/6	−4.004	−4.004

Note: The results are obtained on comparison of ALFF between the PACG and NS groups in each frequency band (post hoc two-sample t-tests, voxel-level P<0.001, GRF corrected, cluster-level P<0.01).

Abbreviations: ALFF, amplitude of low-frequency fluctuation; BA, Brodmann area; GRF, Gaussian random field; L, left; MNI, Montreal Neurological Institute; NS, normal-sighted controls; PACG, primary angle-closure glaucoma; R, right.

Figure 4 ROC curve analysis of the mean ALFF in slow-4 and slow-5 bands for altered brain regions.

Notes: (A) ROC curve in ALFF (slow-4 band): PACG > NS, for R-IOG 0.235 (P<0.001; 95% CI =0.145–0.326); PACG < NS for L-MOG 0.793 (P<0.001; 95% CI =0.708–0.879), L-preCG 0.797 (P<0.001; 95% CI =0.714–0.880), and L-postCG 0.742 (P<0.001; 95% CI =0.649–0.835). (B) ROC curve in ALFF (slow-5 band): PACG > NS, for R-IOG 0.233 (P<0.001; 95% CI =0.143–0.324); PACG < NS for L-IPL 0.843 (P<0.001; 95% CI =0.765–0.922), L-postCG 0.781 (P<0.001; 95% CI =0.693–0.869), and R-preCG/postCG 0.793 (P<0.001; 95% CI =0.707–0.880).
Abbreviations: ALFF, amplitude of low-frequency fluctuation; AUC, area under the curve; IOG, inferior occipital gyrus; IPL, inferior parietal lobule; L, left; MOG, middle occipital gyrus; NS, normal-sighted controls; PACG, primary angle-closure glaucoma; PreCG, precentral gyrus; PostCG, postcentral gyrus; R, right; ROC, receiver operating characteristic.

Figure 5 The correlations between the mean ALFF signal values of the different areas in slow-4 band and the behavioral performances.

Note: The greater mean ALFF values of the right inferior occipital gyrus were associated with (A) smaller RNFL thickness-OD (r=0.595, P<0.001); (B) OS (r=0.560, P<0.001); (C) greater VF-OD (r=−0.830, P<0.001); and (D) OS (r=−0.837, P<0.001) in the PACG group.
Abbreviations: ALFF, amplitude of low-frequency fluctuation; IOG, inferior occipital gyrus; L, left; OD, oculus dexter; OS, oculus sinister; PACG, primary angle-closure glaucoma; R, right; RNFL, retinal nerve fiber layer; VF, visual field.