Altered spontaneous brain activity patterns in patients with corneal ulcer using amplitude of low-frequency fluctuation: An fMRI study

Abstract

The aim of the present study was to investigate the altered spontaneous brain activity in patients with corneal ulcer (CU) through the amplitude of low-frequency fluctuation (ALFF) technique and the association with their visual performance. A total of 40 patients with CU and 40 healthy controls (HCs) matched for sex, age and educational level were enrolled. Resting-state functional magnetic resonance imaging (rs-fMRI) was performed to examine the probands. Spontaneous cerebral activity variations were investigated using the ALFF technique. The average ALFF values of the CU patients and the HCs were classified by utilizing receiver operating characteristic (ROC) curves. Contrary to HCs, the CU patients had significantly lower ALFF values in the left cerebellar anterior lobe, right middle frontal gyrus and left middle frontal gyrus, but higher ALFF values in the right cerebellar inferior lobe, left cerebellar inferior lobe, left inferior temporal gyrus, right fusiform gyrus, left superior frontal gyrus, right angular gyrus and bilateral superior frontal gyrus. ROC curve analysis of each brain region indicated that the accuracy of ALFF value specificity between the CU and HCs of the area under the curve was perfect. In conclusion, abnormal spontaneous activities were detected in numerous brain regions of CU patients, which may provide useful information for understanding the dysfunction of CU. These activity changes in brain regions may be used as effective clinical indicators for CU.

Keywords: ALFF; corneal ulcer; fMRI; resting state; spontaneous activity.

Figure 1.

Significant differences in spontaneous brain activity between the CU group and HCs. Differences were observed in the left cerebellum anterior lobe, right middle frontal gyrus, left middle frontal gyrus, right cerebellar inferior lobe, left cerebellar inferior lobe, left inferior temporal gyrus, right fusiform gyrus, left superior frontal gyrus, right angular gyrus and bilateral superior frontal gyrus. The red areas denote brain regions with higher ALFF and the blue areas denote brain regions with lower ALFF [P<0.001 for multiple comparisons using Gaussian random field theory (z>2.3; P<0.001; cluster, >13 voxels; Alphasim corrected)]. ALFF, amplitude of low-frequency fluctuation; HCs, healthy controls; L, left; R, right; CU, corneal ulcer.

Figure 2.

Means of altered spontaneous brain activity compared between the CU group and HCs. The statistical threshold was set at voxel with P<0.01 for multiple comparisons using family-wise error correction (z>2.3; P<0.01; cluster, >40 voxels). *P<0.05. HCs, healthy controls; CU, corneal ulcer; ALFF, amplitude of low-frequency fluctuation; RCIL, right cerebellum inferior lobe; LCIL, left cerebellum inferior lobe; LITG, left inferior temporal gyrus; RFG, right fusiform gyrus; LSFG, left superior frontal gyrus; RAG, right angular gyrus; BSFG, bilateral superior frontal gyrus; LCAL, left cerebellum anterior lobe; RMFG, right middle frontal gyrus; LMFG, left middle frontal gyrus.

Figure 3.

ROC curve analysis of the mean ALFF values for altered brain regions. (A) The area under the ROC curve for the RCIL was 0.760 (P<0.001; 95% CI, 0.650–0.862), that for the LCIL was 0.828 (P<0.001; 95% C,: 0.741–0.915), that for the LITG was 0.754 (P<0.001; 95% CI, 0.651–0.857), that for the RFG was 0.771 (P<0.001; 95% CI, 0.670–0.872), that for the LSFG was 0.812 (P<0.001; 95% CI, 0.721–0.904), that for the RAG was 0.807 (P<0.001; 95% CI, 0.708–0.906) and that for the BSFG was 0.785 (P<0.001; 95% CI, 0.684–0.885) [CUs>HCs]. (B) The area under the ROC curve was 0.848 (P<0.001; 95% CI, 0.763–0.933) for the LCAL, while that for the RMFG was 0.778 (P<0.001; 95% CI, 0.679–0.877) and that for the LMFG 0.773 (P<0.001; 95% CI, 0.674–0.873) [CUs

Figure 4.

ALFF results of brain activity in the CU group. Compared with the HCs, the ALFF of the following regions was decreased to various extents: 1) Left cerebellar anterior lobe (t=−5.35), 2) right middle frontal gyrus (t=−4.5573), 3) left middle frontal gyrus (t=−4.1103), 4) right cerebellar inferior lobe (t=5.557), 5) left cerebellar inferior lobe (t=5.786), 6) left inferior temporal gyrus (t=4.4602), 7) right fusiform gyrus (t=4.4716), 8) left superior frontal gyrus (t=4.8905), 9) right angular gyrus (t=5.2397) and 10) bilateral superior frontal gyrus (t=4.8908). The sizes of the spots denote the degree of quantitative changes. HCs, healthy controls; ALFF, amplitude of low-frequency fluctuation; CU, corneal ulcer.