Shin Teng

Early detection of periodic sharp wave complexes on EEG by independent component analysis in patients with Creutzfeldt-Jakob disease.

Summary: Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common human prion disease. EEG is the method of choice to support the diagnosis of a human prion disease. Periodic sharp wave complexes (PSWCs) on the EEG usually indicate a progressive stage of CJD. However, PSWCs only become obvious at around 8 to 12 weeks after the onset of clinical symptoms, and in a few cases, even later. Independent component analysis (ICA) is a new technique to separate statistically independent components from a mixture of data. This study recruited seven patients who fit the criteria of CJD between 2002 and 2005 and 10 patients with Alzheimer’s disease (AD) as control subjects. Using an ICA algorithm, we were able to split typical PSWCs into several independent temporal components in conjunction with spatial maps. The PSWCs were not observed in the initial EEG studies of patients with either AD or CJD. However, the ICA algorithm was able to extract periodic discharges and epileptiform discharges from raw EEG of patients with CJD at as early as 3 to 5 weeks after disease onset. Such discharges otherwise could hardly be discerned by visual inspection. In conclusion, ICA may increase the sensitivity of EEG and facilitate the early diagnosis of CJD.

Disrupted cerebellar connectivity reduces whole-brain network efficiency in multiple system atrophy

Multiple system atrophy of the cerebellar type is a sporadic neurodegenerative disorder of the central nervous system. We hypothesized that the white matter degeneration of the cerebellum and pons in this disease may cause a breakdown of cerebellar structural networks and further reduce the network efficiency of cerebellar‐connected cerebral regions. Diffusion tensor tractography was used to construct the structural networks of 19 cerebellar‐type multiple system atrophy patients, who were compared with 19 age‐ and sex‐matched controls. Graph theory was used to assess the small‐world properties and topological organization of structure networks in both the control and patient groups. Our results showed that the cerebellar‐type multiple system atrophy patients exhibited altered small‐world architecture with significantly increased characteristic shortest path lengths and decreased clustering coefficients. We also found that white matter degeneration in the cerebellum was characterized by reductions in network strength (number and integrity of fiber connections) of the cerebellar regions, which further induced extensively decreased network efficiency for numerous cerebral regions. Finally, we found that the reductions in nodal efficiency of the cerebellar lobules and bilateral sensorimotor, prefrontal, and basal ganglia regions negatively correlated with the severity of ataxia for the cerebellar‐type multiple system atrophy patients. This study demonstrates for the first time that the brains of cerebellar‐type multiple system atrophy patients exhibit disrupted topological organization of white matter structural networks. Thus, this study provides structural evidence of the relationship between abnormalities of white matter integrity and network efficiency that occurs in cerebellar‐type multiple system atrophy.

Reorganization of functional connectivity during the motor task using EEG time–frequency cross mutual information analysis

OBJECTIVE This study investigates the functional organization of cortical networks during self-determinant arm movement using the time sequences of the alpha (8-12 Hz) and beta (16-25 Hz) bands. METHODS The time-frequency cross mutual information (TFCMI) method was used to estimate the EEG functional connectivity in the alpha and beta bands for seven healthy subjects during four functional states: the resting, preparing, movement-onset, and movement-offset states. RESULTS In the preparing state, the maintenance of the central-executive network (CEN, prefrontal-parietal connection) suppressed the motor network in the alpha band to plan the next movement, whereas the CEN was deactivated in the beta band to retain visual attention (the frontal-occipital connection). A significant decrease of the CEN in the alpha band occurred after a visual cue in the movement-onset state, followed by a significant increase in motor-network connectivity in the beta band until the movement-offset state. CONCLUSIONS The temporal-spectral modulation mechanism allows the brain to manifest multiple functions subject to energy budget. SIGNIFICANCE The TFCMI method was employed to estimate EEG functional connectivity and effectively demonstrate the reorganization process between four functional states.

Altered Resting-State Functional Connectivity of Striatal-Thalamic Circuit in Bipolar Disorder

Bipolar disorder is characterized by internally affective fluctuations. The abnormality of inherently mental state can be assessed using resting-state fMRI data without producing task-induced biases. In this study, we hypothesized that the resting-state connectivity related to the frontal, striatal, and thalamic regions, which were associated with mood regulations and cognitive functions, can be altered for bipolar disorder. We used the Pearsons correlation coefficients to estimate functional connectivity followed by the hierarchical modular analysis to categorize the resting-state functional regions of interest (ROIs). The selected functional connectivities associated with the striatal-thalamic circuit and default mode network (DMN) were compared between bipolar patients and healthy controls. Significantly decreased connectivity in the striatal-thalamic circuit and between the striatal regions and the middle and posterior cingulate cortex was observed in the bipolar patients. We also observed that the bipolar patients exhibited significantly increased connectivity between the thalamic regions and the parahippocampus. No significant changes of connectivity related to the frontal regions in the DMN were observed. The changed resting-state connectivity related to the striatal-thalamic circuit might be an inherent basis for the altered emotional and cognitive processing in the bipolar patients.

Blind Source Separation of Concurrent Disease-Related Patterns from EEG in Creutzfeldt–Jakob Disease for Assisting Early Diagnosis

Creutzfeldt–Jakob disease (CJD) is a rare, transmissible and fatal prion disorder of brain. Typical electroencephalography (EEG) patterns, such as the periodic sharp wave complexes (PSWCs), do not clearly emerge until the middle stage of CJD. To reduce transmission risks and avoid unnecessary treatments, the recognition of the hidden PSWCs forerunners from the contaminated EEG signals in the early stage is imperative. In this study, independent component analysis (ICA) was employed on the raw EEG signals recorded at the first admissions of five patients to segregate the co-occurrence of multiple disease-related features, which were difficult to be detected from the smeared EEG. Clear CJD-related waveforms, i.e., frontal intermittent rhythmical delta activity (FIRDA), fore PSWCs (triphasic waves) and periodic lateralized epileptiform discharges (PLEDs), have been successfully and simultaneously resolved from all patients. The ICA results elucidate the concurrent appearance of FIRDA and PLEDs or triphasic waves within the same EEG epoch, which has not been reported in the previous literature. Results show that ICA is an objective and effective means to extract the disease-related patterns for facilitating the early diagnosis of CJD.

Classification of bipolar disorder using basal-ganglia-related functional connectivity in the resting state

The emotional and cognitive symptoms of bipolar disorder (BD) are suggested to involve in a distributed neural network. The resting-state functional magnetic resonance imaging (fMRI) offers an important tool to investigate the alterations in brain network level of BD. The aim of this study was to discriminate BD patients from healthy controls using whole-brain resting-state functional connectivity patterns. The majority of most discriminating functional connectivities were between the basal ganglia and three core neurocognitive networks, including the default mode, executive control and salience networks. Using these resting-state functional connectivities between the basal ganglia and three core neurocognitive networks as the features, the clustering accuracy achieved 90%.

Sculpting the Intrinsic Modular Organization of Spontaneous Brain Activity by Art.

Artistic training is a complex learning that requires the meticulous orchestration of sophisticated polysensory, motor, cognitive, and emotional elements of mental capacity to harvest an aesthetic creation. In this study, we investigated the architecture of the resting-state functional connectivity networks from professional painters, dancers and pianists. Using a graph-based network analysis, we focused on the art-related changes of modular organization and functional hubs in the resting-state functional connectivity network. We report that the brain architecture of artists consists of a hierarchical modular organization where art-unique and artistic form-specific brain states collectively mirror the mind states of virtuosos. We show that even in the resting state, this type of extraordinary and long-lasting training can macroscopically imprint a neural network system of spontaneous activity in which the related brain regions become functionally and topologically modularized in both domain-general and domain-specific manners. The attuned modularity reflects a resilient plasticity nurtured by long-term experience.

A neuronal fiber tracking study for major depressive disorder using MR diffusion tensor imaging with fiber tractography

Diffusion tensor imaging (DTI) had been proved to be a powerful tool to investigate the white matter integrity and visualize the neuronal axons in vivo. Most of the DTI-based studies mainly used the region-of-interest approach to investigate the abnormalities in areas of white matter tracts involved in mood regulation for patients with major depressive disorder (MDD). In this study, we explored the structure of the fiber connections in whole-brain white matter for both major depressive patients and healthy subjects based on the DTI tractography. With the automatic anatomical labeling (AAL) process, each individual brain can be partitioned into ninety regions in normalized space so that the number of the connected fibers and histograms of the fiber lengths between any paired regions can be estimated. Twenty-three MDD patients and twenty-four age and gender-matched normal subjects were recruited. Our results concluded that: 1) the numbers of connected fibers revealed significant increase (pvalue ≪ 0.005) in the MDD group compared with the normal group in mood-regulation related region pairs consisting of right superior frontal gyrus to right pallidum, right putamen to right precuneus, left pallidum to left precuneus, left superior parietal gyrus to right superior occipital gyrus, left middle occipital gyrus to right middle temporal gyrus, and both side lingual gyrus to both side superior temporal gyrus. Only two region pairs manifested significant decrease (p-value ≪ 0.005) in patient group, which were right insula to right superior temporal gyrus, and right precuneus to right inferior temporal gyrus; 2) the distributions of the connected fiber lengths for the detected region pairs with the increasing or decreasing fibers in MDD group were between 10 to 30 mm.

Dynamics of hemoglobin states in the sensorimotor cortex during motor tasks: A functional near infrared spectroscopy study

In this study, we used functional near infrared spectroscopy (fNIRS) imaging to investigate the independent levels of oxygenated, deoxygenated, and total hemoglobin (oxy-Hb, deoxy-Hb, and total-Hb, respectively) at the sensorimotor cortex during hand-grasping motor tasks. Our results showed that the activation of contralateral primary motor cortex (M1) exhibited increased oxy-Hb and reduced dexoy-Hb after hand grasping began. Meanwhile, the contralateral primary somatosensory cortex (S1) was deactivated with reductions of both oxy-Hb and deoxy-Hb concentration. The Hb circulation patterns indicated that the hand grasping demanded rapid and sufficient O2 supply at contralateral M1, which was achieved by the local vasodilation. The contralateral S1 presented decreased total-Hb via the mechanism of vasoconstriction, and maintained the local oxygenation level in a relatively stable state (mostly with O2 debt) to compensate the blood demanding at nearby M1. This study presented that fNIRS data can efficiently differentiate the activation of M1 from the deactivation of S1 during motor tasks, which can provide full interpretations of hemodynamic response to the neuronal activation in comparison with the Blood Oxygenation Level Dependent signal of functional magnetic resonance imaging.

Investigation of differences on cortical connectivity between patients with major depressive disorder and normal subjects using MR diffusion tensor imaging

Functional and structural neuroimaging studies of major depression disorder (MDD) have identified neurophysiologic abnormalities in multiple areas of the prefrontal cortex, the insula, the amygdale and the related parts of the striatum and thalamus. The functional knowledge of MDD was mainly obtained from the fMRI and PET studies, which reveal the local differences in blood oxygenation and metabolism of the specific neurotransmitters, respectively. For the structural studies, the T1-based and DTI (diffusion tensor image)-based studies, which defined the abnormalities in cortical thickness and the integrity of the white matter, respectively, were commonly used. However, most of these studies only addressed the local differences compared to the normal subjects and were limited to provide the overall associations of the cortical connectivity within the patient group. In this study, we employed the DTI-based fiber bundle tracking technique along with the graph theoretical analysis to investigate the difference of cortical connectivity between the patients with MDD and the normal group from both the global (mean properties for all regions) and local (region-by-region) aspects. Out results concluded that: 1) there were no globally but locally significant difference between two groups, specifically, the increase of the local connectivity in parietal and occipital lobes to compensate the decrease of the connectivity in frontal and temporal lobe; 2) the connection strength from left insula to left superior temporal pole was stronger in normal group than that in MDD group; 3) the connection strengths from left putamen to left triangular inferior frontal gyrus and left precuneus, were stronger in patient group than that in normal group.