Introduction

Voxel-mirror homotopic connectivity (VMHC) is a reliable and reproducible measurement from the whole brain level which has been developed rapidly recently. Through the method, the functional connections can be quantified between each voxel in the one hemisphere and the mirror voxel in the other hemisphere at resting state and the intensity reflects the synergy between the hemispheres. In other word, it mainly reflects the information exchange and coordination function between hemispheres by describing the high synchronization of spontaneous activities in the symmetrical regions of the left and right hemispheres. The good coordination of brain regions between hemispheres plays an important role in integrating cognitive and behavioral related brain functions. Therefore, the study of homotopic functional connection across the cerebral hemispheres might help to further understand the neural mechanisms of radiologists following night shift–related sleep deprivation.

Methods

We recruited right-handed 24 healthy volunteers（14men, age range 23 to 46 years, 28.12±3.69years）working in the radiology department. All participants had regular sleep pattern for at least 8 days before enrollment. In this study, the MRI imaging data was collected using a 3T MR scanner (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany) with 64-channel head and neck coil. The sequence of gradient-echo and echo-planar imaging pulses was used for resting-state fMRI data. The scanning parameters were as follows: TR = 1000 ms, TE = 38 ms, flip angle = 52°, FOV = 208 mm × 208 mm, slice thickness = 2 mm, 72 slices. Each participant underwent two scans, one immediately after night shift and another at the same time after a 7-day rest. VMHC analysis was performed based on the DPABI_V6.1 software. The time series of each voxel were extracted in the one hemisphere of the participants. Pearson correlation coefficient was calculated between the time series and the corresponding time series in the symmetric hemisphere. Subsequently, the obtained correlation coefficient was converted to a Z value through Fisher’s Z transformation in order to generate the VMHC map of the entire brain for each participant. Finally, the VMHC map of each participant were used for paired t-test between night shift and seven days of rest. We considered that voxel p<0.005 and cluster p<0.05 were statistically significant. Before each MR scan, a Pyramid Vision Transformer(PVT) test was conducted on each patient, using PC-PVT2.01. The mean VMHC values of abnormal brain regions were extracted for correlation analysis with PVT Reaction time.

Results

Compared to the data after seven days' rest, radiologists following night shift showed increased VMHC in the supramarginal gyrus , superior temporal gyrus, paracentral lobule, middle cingulum, lingual bilateral postcentral gyrus, supplementary motor area, thalamus, fusiform, putamen (Figure.1). The supramarginal gyrus VMHC values were negatively related to reaction time (Figure. 2), with p=0.01, r=-0.51.

Discussion and Conclusion

Several studies have concluded that the mechanism behind VMHC deficiency may be linked to dysfunction in local gray matter structure2. Our research results showed that there were significant differences between radiologists after the day of the night shift and following seven days of rest. The results of this study may be a preliminary exploration in understanding central mechanism responses after sleep or habitual sleep deprivation. It may help us understand the situation of radiologists during the night shift and provide theoretical support for formulating appropriate night shift policies in the future.

Acknowledgements

No acknowledgement found.

References

1. Reifman, J., Kumar, K., Khitrov, M. Y., et al. (2018). PC-PVT 2.0: An updated platform for psychomotor vigilance task testing, analysis, prediction, and visualization. Journal of neuroscience methods, 304, 39–45. 2. Ding W, Cao W, Wang Y, et al. Altered functional connectivity in patients with subcortical vascular cognitive impairment--a resting-state functional magnetic resonance imaging study. PLoS One. 2015 Sep 16;10(9): e0138180.