Temporal Lobe Epilepsy:Decreased Thalamic Resting State Functional Connectivity And Their Relationships With Alertness Performance

[Objectives]:Studies have reported the pathology of the thalamus in temporal lobe epilepsy (TLE) patients. The thalamus is one of the subcortical regions that are uniformly accepted as being significantly involved in alertness, particularly the right thalamus. Moreover, studies have provided evidence regarding the alertness impairment in epilepsy. The present study aimed to research the alterations of thalamic resting state functional connectivity, and their relationships with alertness performance in patients with TLE; this issue has not yet been addressed.[Methods]:A total of 16 right TLE patients and 16 healthy controls were recruited for the current study. The healthy controls were matched in terms of age, sex, and degree of education. All of the participants took part in a resting state functional magnetic resonance imaging (fMRI) scan, and an attention network test (ANT) that was used to evaluate the alertness performance. The entire bilateral thalamus were extracted respectively as two seeds for the functional connectivity analysis. Both seeds were generated in the montreal neurological institute (MNI) space using the WFU PickAtlas toolkit. The resting state fMRI data were then analyzed using the DPARSF software that is based on statistical parametric mapping(SPM8). The whole-brain voxel-wise functional connectivity analyses were conducted to extract the thalamic functional connectivity. A one sample t-test in REST soft was employed to obtain the resting state functional networks in patients with right TLE and healthy controls. However, one female right TLE patient was excluded due to the excess head motion. And the differences thalamic functional connectivity between the two groups were examined with the two sample t-test. Correlation analyses were applied to evaluate the relationships between alterations in the thalamic functional connectivity and alertness performance in right TLE patients.[Results]:(1) Compared to the healthy controls, the functional connectivity within and between bilateral thalamus was decreased in patients with right TLE (seed in left thalamus:p< 0.05, AlphaSim corrected, cluster size> 43; seed in right thalamus:p< 0.05, AlphaSim corrected, cluster size> 44). Moreover, the bilateral anterior cingulate cortex (ACC) and subcortical structures, including the bilateral brainstem, bilateral cerebellum, bilateral putamen, right caudate nucleus and right amygdala, showed decreased functional connectivity with the ipsilateral thalamus in the right TLE patient group. But none was found with the contralateral thalamus. (2) The reaction times of intrinsic alertness (IA) and phasic alertness (PA) performances of right TLE patients were significantly longer than healthy controls (IA:right TLE group VS healthy control group: 592.01 ± 67.80ms VS 511.47 ± 48.09ms, p= 0.001; PA:right TLE group VS healthy control group:550.34 ± 70.16ms VS 464.43 ± 45.52ms, p< 0.001). Meanwhile, the alertness performance was not altered in patients with right TLE (right TLE group VS healthy control group:37.69 ± 21.62ms VS 40.65±13.25ms, p= 0.66). (3) In the rTLE patient group, the decreased functional connectivity of the right thalamus and bilateral ACC was significantly correlated with the alertness effect performance (r=-0.59, p= 0.02). Such correlation, however, was not found between the alerted thalamic functional connectivity and the intrinsic or phasic alertness performances.[Conclusions]:1. Our findings show the functional importance of thalamus in the TLE pathology and suggest that the impairment of thalamic resting state functional networks exist in patients with TLE.2. The thalamus ipsilateral to the epileptogenic focus shows greater impairment in patients with rTLE.3. The intrinsic and phasic alertness performances of rTLE patients are impaired. The alertness effect performance, however, is preserved.