Altered functional connectivity of primary visual cortex in late blindness

Brain structural changes in diabetic retinopathy patients: a combined voxel-based morphometry and surface-based morphometry study

The aim of this study was to investigate alterations in gray matter structure among individuals diagnosed with diabetic retinopathy (DR). This study included a cohort of 32 diabetic patients with retinopathy (DR group, n = 32) and 38 healthy adults (HC group, n = 38). Both cohorts underwent comprehensive psychological and cognitive assessments alongside structural magnetic resonance imaging. The brain's gray matter volume and morphology were analyzed using voxel-based morphometry (VBM) and surface-based morphometry (SBM). Partial correlation analysis was employed to investigate the associations between differences in gray matter volume (GMV) across diverse brain regions and the outcomes of cognitive psychological tests as well as clinical indicators. The VBM results revealed that, in comparison to the healthy control (HC) group, patients with diabetic retinopathy (DR) exhibited reduced gray matter volume (GMV) in the right fusiform gyrus, inferior frontal gyrus, opercular part, and left hippocampus; conversely, an increase in GMV was observed in the right thalamus. The SBM results indicated cortical thinning in the left caudal anterior cingulate cortex, left superior frontal gyrus, left parahippocampal gyrus, and bilateral lingual gyrus in the DR group. Sulcal depth (SD) exhibited increased values in the bilateral rostral middle frontal gyrus, superior frontal gyrus, frontal pole, left precentral gyrus, postcentral gyrus, lateral orbitofrontal gyrus, and right paracentral gyrus. Local gyrification indices (LGIs) decreased in the left caudal middle frontal gyrus and superior frontal gyrus. The fractal dimension (FD) decreased in the posterior cingulate gyrus and isthmus of the cingulate gyrus. The left hippocampal gray matter volume (GMV) in patients with diabetic retinopathy was negatively correlated with disease duration (r = -0.478, p = 0.008) and self-rating depression scale (SAS) score (r = -0.381, p = 0.038). The structural alterations in specific brain regions of individuals with DR, which may contribute to impairments in cognition, emotion, and behavior, provide valuable insights into the neurobiological basis underlying these dysfunctions.

Study of vision-related resting-state activity in suprasellar tumor patients with postoperative visual damage

INTRODUCTION

The objective of this study was to investigate changes in vision-related resting-state activity in patients with suprasellar tumors (ST) who experienced vision deterioration after surgery.

METHODS

Twelve patients with ST and vision deterioration after surgery were included in the study. Resting-state functional connectivity (FC) was compared before and after surgery using a seed-based analysis with a priori specified regions of interest (ROIs) within the visual areas. The differences between the two groups were identified using a paired t-test.

RESULTS

The data showed a decrease in FC within and between the dorsal and ventral pathways, as well as in the third pathway in ST patients. The middle temporal visual cortex (MT+) showed a decreased FC with more regions than other visual ROIs. The data also revealed an increase in FC between the visual ROIs and higher-order cortex. The superior frontal gyrus/BA8 showed an increased FC with more ROIs than other high-order regions, and the hOC4d was involved in an increased FC with more high-order regions than other ROIs.

CONCLUSIONS

The study results indicate significant neural reorganization in the vision-related cortex of ST patients with postoperative vision damage. Most subareas within the visual cortex showed remarkable neural dysfunction, and some highe-order cortex may be primarily involved in top-down control of the subareas within the visual cortex. The hot zones may arise in the processing of "top-down" influence.

Structural and functional activities of brain in patients with vascular cognitive impairment: A case-controlled magnetic resonance imaging study

This study aimed to identify abnormal brain regions and imaging indices of vascular cognitive impairment (VCI) and explore specific imaging diagnostic markers of VCI. In this study, 24 patients with VCI were allocated to the VCI group and 25 healthy subjects were assigned to the healthy control (HC) group. Demographic data and neuropsychological test scores were compared using SPSS 25.0. The structural and functional imaging data were post-processed and statistically analyzed using CAT12, DPARSF and SPM12 software, based on the MATLAB platform. The structural and functional indices of gray matter volume (GMV) and regional homogeneity (ReHo) were obtained, and inter-group data were analyzed using an independent-sample t test. Sex, age, years of education, and total brain volume were used as covariates. Compared to the HC group, the GMV of VCI in the VCI group decreased significantly in the rectus muscles of the bilateral gyrus, left superior temporal gyrus, left supplementary motor area (SMA), right insula, right superior temporal gyrus, right anterior cuneiform lobe, and right anterior central gyrus (PRECG) (P < .05, FWE correction), without GMV enlargement in the brain area. ReHo decreased in the right inferior temporal gyrus (ITG), right parahippocampal gyrus, and left temporal pole (middle temporal gyrus, right lingual gyrus, left posterior central gyrus, and right middle temporal gyrus), the areas of increased ReHo were the left caudate nucleus, left rectus gyrus, right anterior cingulate gyrus and lateral cingulate gyrus (P < .05, FWE correction). Correlation analysis showed that the GMV of the left superior temporal gyrus was positively correlated with the Montreal Cognitive Assessment (MoCA) score (P < .05), and the GMV of the right insula was positively correlated with the MESE and long delayed memory scores (P < .05). There was a significant positive correlation between the ReHo and short-term delayed memory scores in the middle temporal gyrus of the left temporal pole (P < .05). The volume of GMV and ReHo decreased in VCI patients, suggesting that impairment of brain structure and function in specific regions is the central mechanism of cognitive impairment in these patients. Meanwhile, the functional indices of some brain regions were increased, which may be a compensatory mechanism for the cognitive impairment associated with VCI.

Exploration of static functional connectivity and dynamic functional connectivity alterations in the primary visual cortex among patients with high myopia via seed-based functional connectivity analysis

Aim

This study was conducted to explore differences in static functional connectivity (sFC) and dynamic functional connectivity (dFC) alteration patterns in the primary visual area (V1) among high myopia (HM) patients and healthy controls (HCs) via seed-based functional connectivity (FC) analysis.

Methods

Resting-state functional magnetic resonance imaging (fMRI) scans were performed on 82 HM patients and 59 HCs who were closely matched for age, sex, and weight. Seed-based FC analysis was performed to identify alterations in the sFC and dFC patterns of the V1 in HM patients and HCs. Associations between mean sFC and dFC signal values and clinical symptoms in distinct brain areas among HM patients were identified via correlation analysis. Static and dynamic changes in brain activity in HM patients were investigated by assessments of sFC and dFC via calculation of the total time series mean and sliding-window analysis.

Results

In the left anterior cingulate gyrus (L-ACG)/left superior parietal gyrus (L-SPG) and left V1, sFC values were significantly greater in HM patients than in HCs. In the L-ACG and right V1, sFC values were also significantly greater in HM patients than in HCs [two-tailed, voxel-level P < 0.01, Gaussian random field (GRF) correction, cluster-level P < 0.05]. In the left calcarine cortex (L-CAL) and left V1, dFC values were significantly lower in HM patients than in HCs. In the right lingual gyrus (R-LING) and right V1, dFC values were also significantly lower in HM patients than in HCs (two-tailed, voxel-level P < 0.01, GRF correction, cluster-level P < 0.05).

Conclusion

Patients with HM exhibited significantly disturbed FC between the V1 and various brain regions, including L-ACG, L-SPG, L-CAL, and R-LING. This disturbance suggests that patients with HM could exhibit impaired cognitive and emotional processing functions, top-down control of visual attention, and visual information processing functions. HM patients and HCs could be distinguished from each other with high accuracy using sFC and dFC variabilities. These findings may help to identify the neural mechanism of decreased visual performance in HM patients.

Altered dynamic functional connectivity in the primary visual cortex in patients with primary angle-closure glaucoma

Purpose

Glaucoma is the main blindness-causing disease in the world. Previous neuroimaging studies demonstrated that glaucoma not only causes the loss of optic ganglion cells but also leads to the abnormal function of the optic nerve pathway and the visual cortex. However, previous studies also reported that patients with glaucoma have dysfunction in the visual cortex in a static state. Whether or not patients with primary angle-closure glaucoma (PACG) were accompanied by dynamic functional connectivity (FC) changes in the primary visual cortex (V1) remains unknown.

Methods

A total of 34 patients with PACG (23 men and 11 women) and 34 well-matched healthy controls (HCs) were enrolled in the study. The dynamic functional connectivity (dFC) with the sliding window method was applied to investigate the dynamic functional connectivity changes in the V1.

Results

Compared with HCs, patients with PACG showed increased dFC values between left V1 and bilateral calcarine (CAL). Meanwhile, patients with PACG showed increased dFC values between right V1 and bilateral CAL.

Conclusion

Our study demonstrated that patients with PACG showed increased dFC within the visual network, which might indicate the increased variability FC in the V1 in patients with PACG.

Altered functional connectivity of the right caudate nucleus in chronic migraine: a resting-state fMRI study

BACKGROUND

The definitive pathogenic mechanisms underlying chronic migraine (CM) remain unclear. Mounting evidence from functional and structural magnetic resonance imaging (MRI) studies suggests that the caudate nucleus (CN) plays a role in the cognitive, sensory, and emotional integration of pain information in patients with migraine. However, evidence concerning the role played by CN in CM patients is limited. Here, we used the CN as the seed to explore patterns of functional connectivity (FC) among healthy controls (HCs), patients with episodic migraine (EM), and patients with CM.

METHODS

We included 25 HCs, 23 EM patients, and 46 CM patients in this study. All participants underwent resting-state functional MRI scans on a GE 3.0T MRI system. We performed seed-based FC analyses among the three groups using the bilateral CNs as seeds. We also compared the subgroups of CM (with and without medication overuse headache, males and females) and performed Pearson's correlation analyses between FC values and the clinical features of CM patients.

RESULTS

FC values between the right CN and five clusters (mainly involved in emotion, cognition, and sensory-related brain regions) were higher in CM patients than in HCs. Compared to EM patients, enhanced FC values between the bilateral precuneus, left anterior cingulate gyrus, right middle cingulate cortex, right lingual gyrus, and right CN were shown in the CM patients. There were no significant differences between CM patients with and without MOH, males and females. FC values between the bilateral calcarine cortex, lingual gyrus, and right CN were positively correlated with body mass index. Moreover, right CN-related FC values in the left calcarine cortex and right lingual gyrus were inversely correlated with visual analogue scale scores for headaches.

CONCLUSION

Our results revealed abnormal right CN-based FC values in CM patients, suggesting dysfunction of brain networks associated with pain perception and multi-regulation (emotion, cognition, and sensory). Aberrant FC of the CN can provide potential neuroimaging markers for the diagnosis and treatment of CM.

Magnocellular and parvocellular contributions to brain network dysfunction during learning and memory: Implications for schizophrenia

Memory deficits are core features of schizophrenia, and a central aim in biological psychiatry is to identify the etiology of these deficits. Scrutiny is naturally focused on the dorsolateral prefrontal cortex and the hippocampal cortices, given these structures' roles in memory and learning. The fronto-hippocampal framework is valuable but restrictive. Network-based underpinnings of learning and memory are substantially diverse and include interactions between hetero-modal and early sensory networks. Thus, a loss of fidelity in sensory information may impact memorial and cognitive processing in higher-order brain sub-networks, becoming a sensory source for learning and memory deficits. In this overview, we suggest that impairments in magno- and parvo-cellular visual pathways result in degraded inputs to core learning and memory networks. The ascending cascade of aberrant neural events significantly contributes to learning and memory deficits in schizophrenia. We outline the network bases of these effects, and suggest that any network perspectives of dysfunction in schizophrenia must assess the impact of impaired perceptual contributions. Finally, we speculate on how this framework enriches the space of biomarkers and expands intervention strategies to ameliorate this prototypical disconnection syndrome.

Sight restoration reverses blindness-induced cross-modal functional connectivity changes between the visual and somatosensory cortex at rest

Resting-state functional connectivity (rsFC) has been used to assess the effect of vision loss on brain plasticity. With the emergence of vision restoration therapies, rsFC analysis provides a means to assess the functional changes following sight restoration. Our study demonstrates a partial reversal of blindness-induced rsFC changes in Argus II retinal prosthesis patients compared to those with severe retinitis pigmentosa (RP). For 10 healthy control (HC), 10 RP, and 7 Argus II subjects, four runs of resting-state functional magnetic resonance imaging (fMRI) per subject were included in our study. rsFC maps were created with the primary visual cortex (V1) as the seed. The rsFC group contrast maps for RP > HC, Argus II > RP, and Argus II > HC revealed regions in the post-central gyrus (PostCG) with significant reduction, significant enhancement, and no significant changes in rsFC to V1 for the three contrasts, respectively. These findings were also confirmed by the respective V1-PostCG ROI-ROI analyses between test groups. Finally, the extent of significant rsFC to V1 in the PostCG region was 5,961 in HC, 0 in RP, and 842 mm3 in Argus II groups. Our results showed a reduction of visual-somatosensory rsFC following blindness, consistent with previous findings. This connectivity was enhanced following sight recovery with Argus II, representing a reversal of changes in cross-modal functional plasticity as manifested during rest, despite the rudimentary vision obtained by Argus II patients. Future investigation with a larger number of test subjects into this rare condition can further unveil the profound ability of our brain to reorganize in response to vision restoration.

Resting-State Neuronal Activity and Functional Connectivity Changes in the Visual Cortex after High Altitude Exposure: A Longitudinal Study

Damage to the visual cortex structures after high altitude exposure has been well clarified. However, changes in the neuronal activity and functional connectivity (FC) of the visual cortex after hypoxia/reoxygenation remain unclear. Twenty-three sea-level college students, who took part in 30 days of teaching at high altitude (4300 m), underwent routine blood tests, visual behavior tests, and magnetic resonance imaging scans before they went to high altitude (Test 1), 7 days after they returned to sea level (Test 2), as well as 3 months (Test 3) after they returned to sea level. In this study, we investigated the hematological parameters, behavioral data, and spontaneous brain activity. There were significant differences among the tests in hematological parameters and spontaneous brain activity. The hematocrit, hemoglobin concentration, and red blood cell count were significantly increased in Test 2 as compared with Tests 1 and 3. As compared with Test 1, Test 3 increased amplitudes of low-frequency fluctuations (ALFF) in the right calcarine gyrus; Tests 2 and 3 increased ALFF in the right supplementary motor cortex, increased regional homogeneity (ReHo) in the left lingual gyrus, increased the voxel-mirrored homotopic connectivity (VMHC) value in the motor cortex, and decreased FC between the left lingual gyrus and left postcentral gyrus. The color accuracy in the visual task was positively correlated with ALFF and ReHo in Test 2. Hypoxia/reoxygenation increased functional connection between the neurons within the visual cortex and the motor cortex but decreased connection between the visual cortex and motor cortex.

Altered Spontaneous Brain Activity and Network Property in Patients With Congenital Monocular Blindness

Individuals with congenital monocular blindness may have specific brain changes since the brain is prenatally deprived of half the normal visual input. To explore characteristic brain functional changes of congenital monocular blindness, we analyzed resting-state functional MRI (rs-fMRI) data of 16 patients with unilateral congenital microphthalmia and 16 healthy subjects with normal vision to compare intergroup differences of amplitude of low frequency fluctuations (ALFFs), functional connectivity (FC), and network topolgoical properties. Compared with controls, patients with microphthalmia exhibited significantly lower ALFF values in the left inferior occipital and temporal gyri, superior temporal gyrus, inferior parietal lobe and post-central gyrus, whereas higher ALFF in the right middle and inferior temporal gyri, middle and superior frontal gyri, left superior frontal, and temporal gyri, such as angular gyrus. Meanwhile, FC between left medial superior frontal gyrus and angular gyrus, FC between left superior temporal gyrus and inferior parietal lobe and post-central gyrus decreased in the patients with congenital microphthalmia. In addition, a graph theory-analysis revealed increased regional network metrics (degree centrality and nodal efficiency) in the middle and inferior temporal gyri and middle and superior frontal gyri, while decreased values in the inferior occipital and temporal gyri, inferior parietal lobule, post-central gyrus, and angular gyrus. Taken together, patients with congenital microphthalmia had widespread abnormal activities within neural networks involving the vision and language and language-related regions played dominant roles in their brain networks. These findings may provide clues for functional reorganization of vision and language networks induced by the congenital monocular blindness.

Aberrant Amplitude of Low-Frequency Fluctuation and Degree Centrality within the Default Mode Network in Patients with Vascular Mild Cognitive Impairment

This study aimed to investigate whole-brain spontaneous activities changes in patients with vascular mild cognitive impairment (VaMCI), and to evaluate the relationships between these brain alterations and their neuropsychological assessments. Thirty-one patients with VaMCI and thirty-one healthy controls (HCs) underwent structural MRI and resting-state functional MRI (rs-fMRI) and neuropsychological assessments. The functional alterations were determined by the amplitude of low-frequency fluctuation (ALFF) and degree centrality (DC). The gray matter volume (GMV) changes were analyzed using voxel-based morphometry (VBM). Linear regression analysis was used to evaluate the relationships between the structural and functional changes of brain regions and neuropsychological assessments. The VaMCI group had significantly lower scores in the Montreal Cognitive Assessment (MoCA), and higher scores on the Hamilton Anxiety Rating Scale (HAMA) and Hamilton Depression Rating Scale (HAMD). Compared to the HCs, the VaMCI group exhibited GM atrophy in the right precentral gyrus (PreCG) and right inferior temporal gyrus (ITG). VaMCI patients further exhibited significantly decreased brain activity within the default mode network (DMN), including the bilateral precuneus (PCu), angular gyrus (AG), and medial frontal gyrus (medFG). Linear regression analysis revealed that the decreased ALFF was independently associated with lower MoCA scores, and the GM atrophy was independently associated with higher HAMD scores. The current finding suggested that aberrant spontaneous brain activity in the DMN might subserve as a potential biomarker of VaMCI, which may highlight the underlying mechanism of cognitive decline in cerebral small vessel disease.

Altered Functional Connectivity of the Primary Visual Cortex in Patients With Iridocyclitis and Assessment of Its Predictive Value Using Machine Learning

Purpose

To explore the intrinsic functional connectivity (FC) alteration of the primary visual cortex (V1) between individuals with iridocyclitis and healthy controls (HCs) by the resting-state functional magnetic resonance imaging (fMRI) technique, and to investigate whether FC findings be used to differentiate patients with iridocyclitis from HCs.

Methods

Twenty-six patients with iridocyclitis and twenty-eight well-matched HCs were recruited in our study and underwent resting-state fMRI examinations. The fMRI data were analyzed by Statistical Parametric Mapping (SPM12), Data Processing and Analysis for Brain Imaging (DPABI), and Resting State fMRI Data Analysis Toolkit (REST) software. Differences in FC signal values of the V1 between the individuals with iridocyclitis and HCs were compared using independent two-sample t-tests. Significant differences in FC between two groups were chosen as classification features for distinguishing individuals with iridocyclitis from HCs using a support vector machine (SVM) classifier that involved machine learning. Classifier performance was evaluated using permutation test analysis.

Results

Compared with HCs, patients with iridocyclitis displayed significantly increased FC between the left V1 and left cerebellum crus1, left cerebellum 10, bilateral inferior temporal gyrus, right hippocampus, and left superior occipital gyrus. Moreover, patients with iridocyclitis displayed significantly lower FC between the left V1 and both the bilateral calcarine and bilateral postcentral gyrus. Patients with iridocyclitis also exhibited significantly higher FC values between the right V1 and left cerebellum crus1, bilateral thalamus, and left middle temporal gyrus; while they displayed significantly lower FC between the right V1 and both the bilateral calcarine and bilateral postcentral gyrus (voxel-level P<0.01, Gaussian random field correction, cluster-level P<0.05). Our results showed that 63.46% of the participants were correctly classified using the leave-one-out cross-validation technique with an SVM classifier based on the FC of the left V1; and 67.31% of the participants were correctly classified based on the FC of the right V1 (P<0.001, non-parametric permutation test).

Conclusion

Patients with iridocyclitis displayed significantly disturbed FC between the V1 and various brain regions, including vision-related, somatosensory, and cognition-related regions. The FC variability could distinguish patients with iridocyclitis from HCs with substantial accuracy. These findings may aid in identifying the potential neurological mechanisms of impaired visual function in individuals with iridocyclitis.

Occipital cortex is modulated by transsaccadic changes in spatial frequency: an fMRI study

Previous neuroimaging studies have shown that inferior parietal and ventral occipital cortex are involved in the transsaccadic processing of visual object orientation. Here, we investigated whether the same areas are also involved in transsaccadic processing of a different feature, namely, spatial frequency. We employed a functional magnetic resonance imaging paradigm where participants briefly viewed a grating stimulus with a specific spatial frequency that later reappeared with the same or different frequency, after a saccade or continuous fixation. First, using a whole-brain Saccade > Fixation contrast, we localized two frontal (left precentral sulcus and right medial superior frontal gyrus), four parietal (bilateral superior parietal lobule and precuneus), and four occipital (bilateral cuneus and lingual gyri) regions. Whereas the frontoparietal sites showed task specificity, the occipital sites were also modulated in a saccade control task. Only occipital cortex showed transsaccadic feature modulations, with significant repetition enhancement in right cuneus. These observations (parietal task specificity, occipital enhancement, right lateralization) are consistent with previous transsaccadic studies. However, the specific regions differed (ventrolateral for orientation, dorsomedial for spatial frequency). Overall, this study supports a general role for occipital and parietal cortex in transsaccadic vision, with a specific role for cuneus in spatial frequency processing.

Reduced Functional Connectivity in Children With Congenital Cataracts Using Resting-State Electroencephalography Measurement

Objectives

Numerous task-based functional magnetic resonance imaging studies indicate the presence of compensatory functional improvement in patients with congenital cataracts. However, there is neuroimaging evidence that shows decreased sensory perception or cognition information processing related to visual dysfunction, which favors a general loss hypothesis. This study explored the functional connectivity between visual and other networks in children with congenital cataracts using resting state electroencephalography.

Methods

Twenty-one children with congenital cataracts (age: 8.02 ± 2.03 years) and thirty-five sex- and age-matched normal sighted controls were enrolled to investigate functional connectivity between the visual cortex and the default mode network, the salience network, and the cerebellum network during resting state electroencephalography (eyes closed) recordings.

Result

The congenital cataract group was less active, than the control group, in the occipital, temporal, frontal and limbic lobes in the theta, alpha, beta1 and beta2 frequency bands. Additionally, there was reduced alpha-band connectivity between the visual and somatosensory cortices and between regions of the frontal and parietal cortices associated with cognitive and attentive control.

Conclusion

The results indicate abnormalities in sensory, cognition, motion and execution functional connectivity across the developing brains of children with congenital cataracts when compared with normal controls. Reduced frontal alpha activity and alpha-band connectivity between the visual cortex and salience network might reflect attenuated inhibitory information flow, leading to higher attentional states, which could contribute to adaptation of environmental change in this group of patients.

Assessment of spontaneous brain activity patterns in patients with iridocyclitis: a resting-state study

Several studies demonstrated that patients with iridocyclitis were associated with vision loss and cognitive decline, whereas alterations in spontaneous brain activity occur in iridocyclitis patients remains unknown. The study aimed to explore spontaneous brain activity changes in iridocyclitis patients. Twenty-six patients with iridocyclitis and 26 healthy controls were finally included in our study. Resting-state MRI (rs-MRI) scan was conducted on both groups and the whole brain amplitude of low-frequency fluctuations (ALFFs) value was collected to assess differences in spontaneous brain activity. A receiver operating characteristic (ROC) curve was analyzed to distinguish between the fMRI data of patients with iridocyclitis and healthy controls. Patients with iridocyclitis showed significantly lower ALFF values in the right inferior parietal lobule, right calcarine, right superior temporal gyrus and right precentral gyrus compared to healthy controls and significantly higher ALFF values in the left superior frontal gyrus (P < 0.01, false discovery rate correction). The ROC curve analysis of different brain areas showed that the accuracies of ALFF value specificity between the iridocyclitis and healthy controls of the area under the curve were over 0.8. Our study highlighted an altered spontaneous activity in multiple brain regions, including the visual cortex, default-mode network, auditory area and sensorimotor areas in iridocyclitis. This may provide valuable information about underlying pathogenic mechanisms of iridocyclitis. These findings also indicate that rs-fMRI serves as a potential tool in the disease detection and evaluation of neurologic impairment in iridocyclitis.

Visual Cortex Alterations in Early and Late Blind Subjects During Tactile Perception

Involvement of visual cortex varies during tactile perception tasks in early blind (EB) and late blind (LB) human subjects. This study explored differences in sensory motor networks associated with tactile task in EB and LB subjects and between children and adolescents. A total of 40 EB subjects, 40 LB subjects, and 30 sighted controls were recruited in two subgroups: children (6-12 years) and adolescents (13-19 years). Data were acquired using a 3T MR scanner. Analyses of blood oxygen level dependent (BOLD), functional connectivity (FC), correlation, and post hoc test for multiple comparisons were carried out. Difference in BOLD activity was observed in EB and LB groups in visual cortex during tactile perception, with increased FC of visual with dorsal attention and sensory motor networks in EB. EB adolescents exhibited increased connectivity with default mode and salience networks when compared with LB. Functional results correlated with duration of training, suggestive of better performance in EB. Alteration in sensory and visual networks in EB and LB correlated with duration of tactile training. Age of onset of blindness has an effect in cross-modal reorganization of visual cortex in EB and multimodal in LB in children and adolescents.

Brain-Machine Interfaces to Assist the Blind

The loss or absence of vision is probably one of the most incapacitating events that can befall a human being. The importance of vision for humans is also reflected in brain anatomy as approximately one third of the human brain is devoted to vision. It is therefore unsurprising that throughout history many attempts have been undertaken to develop devices aiming at substituting for a missing visual capacity. In this review, we present two concepts that have been prevalent over the last two decades. The first concept is sensory substitution, which refers to the use of another sensory modality to perform a task that is normally primarily sub-served by the lost sense. The second concept is cross-modal plasticity, which occurs when loss of input in one sensory modality leads to reorganization in brain representation of other sensory modalities. Both phenomena are training-dependent. We also briefly describe the history of blindness from ancient times to modernity, and then proceed to address the means that have been used to help blind individuals, with an emphasis on modern technologies, invasive (various type of surgical implants) and non-invasive devices. With the advent of brain imaging, it has become possible to peer into the neural substrates of sensory substitution and highlight the magnitude of the plastic processes that lead to a rewired brain. Finally, we will address the important question of the value and practicality of the available technologies and future directions.

Alternation of Resting-State Functional Connectivity Between Visual Cortex and Hypothalamus in Guinea Pigs With Experimental Glucocorticoid Enhanced Myopia After the Treatment of Electroacupuncture

Excessive glucocorticoids (GC) may lead to the aggravation of several basic diseases including myopia, due to plasma hormone imbalances associated with the hypothalamic–pituitary–adrenal axis (HPAA). Electroacupuncture (EA) is an effective therapeutic method to treat many diseases, although it remains unclear whether EA at acupoints on the foot or back would be effective in treating eye diseases. It was recently found that visual cortex activity for responses to visual stimuli with spatial frequency and resting-state functional connectivity (FC) between the supramarginal gyrus and rostrolateral prefrontal cortex was significantly reduced in patients with high myopia. The present study aims to investigate the role of the alternation of resting-state FC among the bilateral visual cortex and hypothalamus in exerting anti-myopia effects of EA in GC-enhanced lens-induced myopic (LIM) guinea pigs such that the mechanisms of EA to treat GC-enhanced myopia at Shenshu (BL23) acupoints can be probed. To confirm the effects of EA, ocular parameters including axial length and GC-associated physiological parameters such as animal appearance, behavior, bodyweight, and levels of four HPAA-associated plasma hormones [free triiodothyronine (FT3), free thyroxine (FT4), estradiol (E2), and testosterone (T)] were also collected. Increased resting-state FC between the left and right visual cortex was detected in GC-enhanced lens-induced myopic guinea pigs with EA at BL23 acupoints (LIM+GC+EA) guinea pigs compared to GC-enhanced lens-induced myopic guinea pigs with EA at sham acupoints (LIM+GC+Sham) guinea pigs, as well as suppressed myopia and recovery of symptoms initially caused by overdose of GC. Recovered symptoms included improved animal appearance, behavior, bodyweight, and HPAA-associated plasma hormone levels were observed after 4 weeks of EA treatment. In contrast, the LIM+GC+Sham group showed decreased FC with elongation of axial length for myopization as compared to the control group and LIM group and exhibited a deterioration in physiological parameters including reduced body weight and balance disruption in the four measured HPAA-associated plasma hormones. Our findings suggest that EA could effectively treat GC-enhanced myopia by increasing resting-state FC between the left and right visual cortices, which may be pivotal to further understanding the application and mechanisms of EA in treating GC-enhanced myopia.

Altered Functional Connectivity Strength of Primary Visual Cortex in Subjects with Diabetic Retinopathy

OBJECTIVE

The purpose of the study was to find the differences in intrinsic functional connectivity (FC) patterns of the primary visual area (V1) among diabetic retinopathy (DR), diabetes mellitus (DM), and healthy controls (HCs) applying resting-state functional magnetic resonance imaging (rs-fMRI).

PATIENTS AND METHODS

Thirty-five subjects with DR (18 males and 17 females), 22 DM (10 males and 12 females) and 38 HCs (16 males and 22 females) matched for sex, age, and education underwent rs-fMRI scanning. Seed-based FC analysis was performed to find the alterations in the intrinsic FC patterns of V1 in DR compared with DM and HCs.

RESULTS

The study found that DR patients had a significant lower FC between the bilateral calcarine (CAL)/left lingual gyrus (LING) (BA 17/18) and the left V1, and between the bilateral CAL/left LING (BA 17/18) and the right V1 compared with the HCs. Meanwhile, patients with DR exhibited higher FC strength between the left V1 and the bilateral Caudate/Olfactory/Orbital superior frontal gyrus (OSFG), and between the bilateral Caudate/Olfactory/OSFG (BA 3/4/6) and the right V1. Compared with DM group, patients with DR showed increased FC strength between the right CAL (BA 17/18) and the right V1. DM group exhibited lower FC strength between the left fusiform and the left V1, and between the bilateral CAL and the right V1 when compared with HCs. Moreover, DM group was observed to have higher FC strength between the left superior frontal gyrus and the left V1.

CONCLUSION

Our findings indicated that DR patients exhibited FC disruptions between V1 and higher visual regions at rest, which may reflect the aberrant information communication in the V1 area of DR individuals. The findings offer important insights into the neuromechanism of vision disorder in DR patients.

Altered Temporal Dynamic Intrinsic Brain Activity in Late Blindness

Previous neuroimaging studies demonstrated that visual deprivation triggers significant crossmodal plasticity in the functional and structural architecture of the brain. However, prior neuroimaging studies focused on the static brain activity in blindness. It remains unknown whether alterations of dynamic intrinsic brain activity occur in late blindness (LB). This study investigated dynamic intrinsic brain activity changes in individuals with late blindness by assessing the dynamic amplitude of low-frequency fluctuations (dALFFs) using sliding-window analyses. Forty-one cases of late blindness (LB) (29 males and 12 females, mean age: 39.70 ± 12.66 years) and 48 sighted controls (SCs) (17 males and 31 females, mean age: 43.23 ± 13.40 years) closely matched in age, sex, and education level were enrolled in this study. The dALFF with sliding-window analyses was used to compare the difference in dynamic intrinsic brain activity between the two groups. Compared with SCs, individuals with LB exhibited significantly lower dALFF values in the bilateral lingual gyrus (LING)/calcarine (CAL) and left thalamus (THA). LB cases also showed considerably decreased dFC values between the bilateral LING/CAL and the left middle frontal gyrus (MFG) and between the left THA and the right LING/cerebelum_6 (CER) (two-tailed, voxel-level P < 0.01, Gaussian random field (GRF) correction, cluster-level P < 0.05). Our study demonstrated that LB individuals showed lower-temporal variability of dALFF in the visual cortices and thalamus, suggesting lower flexibility of visual thalamocortical activity, which might reflect impaired visual processing in LB individuals. These findings indicate that abnormal dynamic intrinsic brain activity might be involved in the neurophysiological mechanisms of LB.

Altered information flow and microstructure abnormalities of visual cortex in normal-tension glaucoma: Evidence from resting-state fMRI and DKI

Normal tension glaucoma (NTG) is a neurodegenerative disease involves multiple brain areas, but the mechanism remains unclear. The aim of this study is to investigate the correlation between structural injury and functional reorganization in the brain of NTG, using resting-state functional MRI and diffusion kurtosis imaging (DKI) data acquired for 26 NTG patients and 24 control subjects. Granger causality analysis (GCA) was used to calculate the effective connectivity (EC) between visual cortices and the whole brain to reflect the information flow. The fractional anisotropy (FA), mean kurtosis (MK), axial kurtosis (AK), and radial kurtosis (RK) derived from DKI of visual cortices were extracted to evaluate structural injury. Microstructural abnormalities were detected in bilateral BA17, BA18, and BA19. NTG patients showed significantly decreased EC from BA17 to higher visual cortices and increase EC from higher visual cortices to BA17. The EC from BA17 to posterior cingulate cortex (PCC) and from PCC to BA17 both significantly increased, while the EC from right BA18 and BA19 to PCC significantly decreased. Decreased EC between somatosensory cortex and BA17, as well as the decreased ECs between supramarginal gyrus (SMA) and BA17/BA19 were detected. Several abnormal ECs were significantly correlated with microstructural injuries of BA17 and BA18. In conclusion, NTG causes reorganization of information flows among visual cortices and other brain areas, which is consistent with brain microstructural injury.

Altered effective connectivity of primary visual cortex in primary angle closure glaucoma using Granger causality analysis

Background

Previous neuroimaging studies demonstrated that primary angle closure glaucoma patients were associated with abnormal intrinsic brain activity in primary visual cortex (V1).

Purpose

The purpose of this study was to investigate the effective connectivity patterns of V1 in patients with primary angle closure glaucoma.

Material and Methods

Thirty-seven patients with primary angle closure glaucoma (20 men, 17 women) and 36 healthy controls (20 men, 16 women) closely matched for age, sex, and education, underwent resting-state MRI scans. A voxel-wise Granger causality analysis method was performed to explore different effective connectivity pattern of V1 between the two groups.

Results

Compared with healthy controls, patients with primary angle closure glaucoma showed decreased effective connectivity from the left V1 to left cuneus and increased effective connectivity from the left V1 to left precentral gyrus and right supplementary motor area. Meanwhile, patients with primary angle closure glaucoma showed decreased effective connectivity from left precentral gyrus to left V1 and right frontal middle gyrus to left V1. In addition, patients with primary angle closure glaucoma showed a decreased effective connectivity from the right V1 to left cuneus/calcarine and increased effective connectivity from the right V1 to left inferior frontal gyrus and right caudate. Meanwhile, patients with primary angle closure glaucoma showed decreased effective connectivity from right middle frontal gyrus/precentral gyrus to right V1 and left precentral gyrus to right V1.

Conclusion

Our results highlighted that patients with primary angle closure glaucoma had abnormal effective connectivity between V1 and higher visual area, motor cortices, somatosensory cortices, and frontal lobe, which indicated that they might present with abnormal top-down modulations, visual imagery, vision-motor function, and vision-related higher cognition function.

Altered Intrinsic Functional Connectivity of the Primary Visual Cortex in Patients with Corneal Ulcer: A Resting-State fMRI Study

PURPOSE

To investigate differences in the functional connectivity (FC) of the primary visual cortex between patients with corneal ulcer (CU) and healthy controls (HCs) using resting-state functional magnetic resonance imaging.

PATIENTS AND METHODS

A total of 30 patients with CU and 30 HCs were closely matched in terms of sex, age, and level of education. Two-sample t-test, receiver operating characteristic curve, and Pearson's correlation coefficient analyses were used to determine the differences in FC between the two groups, the mean FC value of patients with CU and HCs, and the correlation between FC signal values and clinical manifestations in different brain regions of patients.

RESULTS

The CU group showed significantly elevated FC in the left and right middle frontal gyri and lower FC with the right cuneus compared with the HC group. In addition, the FC of the right cingulate and left superior frontal gyri also increased in the CU group. The receiver operating characteristic curve revealed high diagnostic value in those brain regions.

CONCLUSION

CU involves aberrant FC of the primary visual cortex in different brain areas, including visual-related and cognitive-related regions. This finding may unveil the underlying neural mechanisms of impaired visual function in CU.

Altered Intrinsic Functional Connectivity of the Primary Visual Cortex in Patients with Neovascular Glaucoma: A Resting-State Functional Magnetic Resonance Imaging Study

PURPOSE

The purpose was to investigate the differences in spontaneous functional connectivity (FC) of the primary visual cortex (V1) between patients with neovascular glaucoma (NVG) and healthy controls (HCs) using resting-state functional magnetic resonance imaging data.

METHODS

A total of 18 patients with NVG (nine males and nine females) and 18 HCs with similar age and sex background were enrolled in the study and inspected using resting-state functional magnetic resonance imaging. The differences in FC of the V1 between the two groups were compared using the independent samples t-test. We used the receiver operating characteristic (ROC) curve to compare the average FC values of NVG subjects with those of HCs.

RESULTS

FC in the left V1 and right fusiform gyrus, bilateral cuneus, and left precuneus was significantly decreased in the NVG group compared with that reported in the HC group. Meanwhile, patients with NVG presented increased FC between the right V1 and bilateral middle frontal gyrus. However, they also exhibited declining FC between the right V1 and left precuneus, and bilateral cuneus. The ROC curve analysis of each brain region indicated that the accuracy of the area under the ROC curves regarding NVG was excellent.

CONCLUSION

NVG involves aberrant FC in the V1 in different brain areas, including the visual-related and cognitive-related regions. These findings may assist in unveiling the underlying neural mechanisms of impaired visual function in NVG.

Primary Open Angle Glaucoma Is Associated With Functional Brain Network Reorganization

Background: Resting-state functional magnetic resonance imaging (rs-fMRI) is commonly employed to study changes in functional brain connectivity. The recent hypothesis of a brain involvement in primary open angle Glaucoma has sprung interest for neuroimaging studies in this classically ophthalmological pathology.

Object: We explored a putative reorganization of functional brain networks in Glaucomatous patients, and evaluated the potential of functional network disruption indices as biomarkers of disease severity in terms of their relationship to clinical variables as well as select retinal layer thicknesses.

Methods: Nineteen Glaucoma patients and 16 healthy control subjects (age: 50–76, mean 61.0 ± 8.2 years) underwent rs-fMRI examination at 3T. After preprocessing, rs-fMRI time series were parcellated into 116 regions using the Automated Anatomical Labeling atlas and adjacency matrices were computed based on partial correlations. Graph-theoretical measures of integration, segregation and centrality as well as group-wise and subject-wise disruption index estimates (which use regression of graph-theoretical metrics across subjects to quantify overall network changes) were then generated for all subjects. All subjects also underwent Optical Coherence Tomography (OCT) and visual field index (VFI) quantification. We then examined associations between brain network measures and VFI, as well as thickness of retinal nerve fiber layer (RNFL) and macular ganglion cell layer (MaculaGCL).

Results: In Glaucoma, group-wise disruption indices were negative for all graph theoretical metrics. Also, we found statistically significant group-wise differences in subject-wise disruption indexes in all local metrics. Two brain regions serving as hubs in healthy controls were not present in the Glaucoma group. Instead, three hub regions were present in Glaucoma patients but not in controls. We found significant associations between all disruption indices and VFI, RNFL as well as MaculaGCL. The disruption index based on the clustering coefficient yielded the best discriminative power for differentiating Glaucoma patients from healthy controls [Area Under the ROC curve (AUC) 0.91, sensitivity, 100%; specificity, 78.95%].

Conclusions: Our findings support a possible relationship between functional brain changes and disease severity in Glaucoma, as well as alternative explanations for motor and cognitive symptoms in Glaucoma, possibly pointing toward an inclusion of this pathology in the heterogeneous group of disconnection syndromes.

Central network changes in patients with advanced monocular blindness: A voxel-based morphometric study

OBJECTIVE

To study the changes in gray matter volume (GMV) in patients with advanced monocular blindness (MB) using voxel-based morphometry (VBM).

METHODS

Thirty-one patients with advanced MB (25 males and six females) and 31 normal controls (25 males and six females) were enrolled. The t test was applied to determine the differences in GMV, white matter volume (WMV), and volume of cerebrospinal fluid in different regions of the brain. The local characteristics of spontaneous concentrations of brain tissue were evaluated by the VBM method. The effects of blindness duration on differences in the GMV were evaluated by correlation and regression analyses.

RESULTS

Compared with the control group, the GMV was decreased in the upper right margin, bilateral insular cortex, right cingulate gyrus, left occipital gyrus, and right suboccipital lobe, and negatively correlated with blindness duration in the upper right posterior margin, bilateral insular cortex, and right cingulate cortex.

CONCLUSIONS

We found that patients with MB showed abnormal WMV and GMV, as evidenced by local changes in the brain. In addition, reduced GMV in specific parts of the brain was associated with the duration of blindness, which may indicate neuropathological mechanisms of visual loss in patients with MB.