Synopsis
We applied dual
regression to investigated functional connectivity impairments within visual
networks for minimal hepatic encephalopathy (MHE) patients’ brain. Functional
deficits within occipital and lateral visual networks (visual
area V2 and V3) were endogenous, and significantly association with
neurocognitive impairments. This maybe the reason for the compensatory enhancements
within medial visual network (visual area V1) which indicated that patients with
MHE had the potential to additionally recruit more neurological resource to process
the spatial information from visual areas V2 and V3. Our results demonstrated
the possible mechanisms for deficits in visual perception, visuo-spatial
orientation, and visuo-constructive abilities in MHE patientsPurpose
To
investigate the functional connectivity (FC) impairments within medial, occipital
and lateral visual networks (MVN, OVN, and LVN)
[1, 2]
for cirrhosis with minimal hepatic encephalopathy (MHE), and to analyze relationship
between visual networks (VNs) alterations with neurocognitive impairments.
Materials and Methods
43 cirrhotic patients without MHE (NMHE
groups), 32 cirrhotic patients with current MHE (MHE groups), and 21 healthy
controls were recruited in this study. MHE was diagnosed by the neuropsychiatric tests,
including Trail Making Test A (TMT-A), Trail Making Test B
(TMT-B), Digit Symbol Test (DST), and Block Design Test (BDT). DST and BDT
are subtests of the Wechsler Adult Intelligence Scale-Revised for China
(WAIS-RC).
The resting-state datasets were preprocessed
with AFNI (afni.nimh.nih.gov/afni) and FSL (www.fmrib.ox.ac.uk), according to
the scripts released by 1000 Functional Connectomes Project [2].
All resting-state fMRI datasets were preprocessed and normalized into standard
brain space.
Three universal templates (MVN, OVN, and
LVN) were applied to generate spatial patterns for MVN, OVN, and LVN for each
participate by dual regression, respectively. There were two steps for dual
regression: 1) regressing the spatial template into each subject's 4D dataset
to give a set of time courses; 2) regressing those time courses into the same
4D dataset to get a subject-specific set of spatial maps.
One sample t test of spatial maps for FCs
was analyzed within groups (FDR corrected, q<0.01).
One way ANOVA was performed to calculate the different FCs within VNs among
groups (AlpahSim corrected, p<0.01,
cluster size>40). Additional correlation analysis was performed between different
FCs within three VNs and behavior scores (Pearson correlation coefficient, p<0.05).
Results
Figure 1 displayed the
differences among groups.
FCs were gradually
reduced from controls, to NMHE, and to MHE within OVN and LVN, while increased
within MVN. Within visual network, the impairments of MHE patients were mostly
in left hemisphere, rather than in right hemisphere.
Within MVN, FCs of MHE patients were significantly
increased than controls and NMHE groups in right limbic lobe / posterior cingulate, and FCs of MHE and
NMHE patients were significantly increased than controls in left cerebellum anterior
lobe.
Within OVN, FCs of MHE patients were significantly
decreased than other two groups in left fusiform gyrus, and FCs were
significantly reduced from controls, to NMHE, and to MHE in bilateral lingual gyrus.
Within LVN, FCs of MHE patients were significantly
decreased than other two groups in left inferior and middle occipital gyrus (IOG and MOG),
and FCs of MHE and NMHE patients were significantly decreased than controls in
left cuneus / superior occipital gyrus (SOG).
DST scores were significantly correlated
with FC of bilateral lingual gyrus within OVN (r=0.274, p=0.007), FCs of left cuneus within LVN (r=0.226, p=0.027), and FCs
of left LOG and MOG within LVN (r=0.258,
p=0.011). BDT scores were
significantly correlated with FC of left cuneus within LVN (r=0.265, p=0.009), and FC of left LOG and MOG within LVN (r=0.243, p=0.017).
Conclusion
We applied dual
regression to investigate functional connectivity impairments within visual networks
for MHE patients’ brain. Functional deficits were endogenous
within OVN (visual area V2) and LVM (visual area V3), while
functional connectivity exhibited compensatory enhancements within MVN (primary
visual cortex). The function of visual process in MHE patients was
mostly altered in left hemisphere, rather than in right hemisphere.
The deficits in visual areas V2 and V3
(OVN and LVN) were significantly association with neurocognitive impairments
(DST and BDT). This maybe the reason for the compensatory enhancements in primary
visual cortex (MVN), which indicated that patients with current MHE had the potential
to additionally recruit more neurological resource to process the spatial
information from visual areas V2 and V3.
Our results demonstrated the possible mechanisms
for decrease of psychomotor speed, and deficits in visual perception,
visuo-spatial orientation, and visuo-constructive abilities in MHE patients [3, 4].
Therefore, the alterations
of dual regression based visual networks can be potential neuroimaging
biomarkers for MHE studies.
Acknowledgements
This work is supported
by the National Natural Science
Foundation of China (81230034, 81271739, 81501453), the Jiangsu
Provincial Special Program of Medical Science (BL2013029), and the Jiangsu
Provincial Natural Science Foundation (BK20141342).References
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al., Toward discovery science of human
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[3] Amodio, P., et
al., Characteristics of minimal hepatic
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and G.E. Smith, Minimal hepatic
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