Investigating mechanism of the effect of emotional facial expressions on attentional processing by data clustering approach.

To explore the mechanism of the effect of emotional facial expression on attentional process, time course and topographic map of Electroencephalographic activities affected by emotional stimuli were investigated. Emotional Stroop task was used to collect 64-channel event-related potentials (ERP) in nonclinical participants, and data clustering was applied to find significant effect of sad and happy facial expression on ERP. Several significant ERP clusters were found in the sad and happy conditions respectively. In the sad condition, the decreased N170 in the bilateral parietooccipital areas, the increased P3 in the right centroparietal region and the increased negative deflection between 600 and 650 ms in the prefrontal regions were observed, these alterations reflected inhibited perceptual processing of sad facial expression, and increased activations of the orienting network and the executive control network in attentional system, respectively. In the happy condition, increased negative slow wave was found in the left centroparietal region indicating strengthened awareness and readiness for successive trials. Importantly, nonpathological attentional bias to sad facial expression in nonclinical participants was associated with inhibited perceptual processing and increased activations of the orienting and executive control networks. It provides the basis for better understanding and application of attentional bias in psychiatric clinical utilization.

Brain Networks of Maintenance, Inhibition and Disinhibition During Working Memory.

Working memory (WM) - one of the brain ability that maintains information - can evaluate the function of brain. Activities related to memory sustention, inhibition and disinhibition have gathered significant attention for the basic neurocognitive architecture. Although researchers have proposed some brain models that attempt to explain the entire procedure of WM, little evidence can proof and describe it, and more particularly, regions and structures of maintenance, inhibition and disinhibition require more investigation. We used phase lock coherence and general partial directed coherence to construct connections among four adaptively fitted EEG sources, and we also applied previous published models to describe the brain circuits of maintenance, inhibition and disinhibition. Referring to a classical visual n-back paradigm, we recruited forty five mental health undergraduates in this experiment. We found that the bilateral prefrontal cortex (PFC) mainly focused on some cognitive components, for example, rehearsal before recognition to classify objects, inhibition to maintain positive memory and activities, and disinhibition to arouse or activate subsequent interactions in brain. Meanwhile, the right PFC sometimes could assist left PFC to implement high capacity WM tasks. By contrast, the posterior regions, PPC, tends to be engaged in attention arousing and maintaining. These two findings suggest that a) the recurrent maintenance circuit may keep the brain executing positive cognitive components, b) then the instantly monitoring inhibition would pause the deadlocked sustention function to save energy, and c) the arriving of disinhibition arouses the next step in brain to select new subject or focus on novel subjects.

Influence of traffic congestion on driver behavior in post-congestion driving.

Traffic congestion is more likely to lead to aggressive driving behavior that is associated with increased crash risks. Previous studies mainly focus on driving behavior during congestion when studying congestion effects. However, the negative effects of congestion on driving behavior may also affect drivers' post-congestion driving. To fill this research gap, this study examined the influence of traffic congestion on driver behavior on the post-congestion roads (i.e., the roads travelled right after congestion). Twenty-five subjects participated in a driving simulation study. They were asked to complete two trials corresponding to post-congestion and non-congestion conditions, respectively. Driver behavior quantified by driving performance measures, eye movement measures, and electroencephalogram (EEG) measures was compared between the two conditions. Ten features were selected from the measures with statistical significance. The selected features were integrated to characterize drivers' response patterns using a hierarchical clustering method. The results showed that driver behavior in post-congestion situations became more aggressive, more focused in the forward area but less focused in the dashboard area, and was associated with lower power of the ß-band in the temporal brain region. The clustering results showed more aggressive and lack-of-aware response patterns while driving in post-congestion situations. This study revealed that traffic congestion negatively affected driver behavior on the post-congestion roads. Practical implications for driving safety education was discussed based on the findings from the present study.

Discovering large conserved functional components in global network alignment by graph matching.

BACKGROUND: Aligning protein-protein interaction (PPI) networks is very important to discover the functionally conserved sub-structures between different species. In recent years, the global PPI network alignment problem has been extensively studied aiming at finding the one-to-one alignment with the maximum matching score. However, finding large conserved components remains challenging due to its NP-hardness. RESULTS: We propose a new graph matching method GMAlign for global PPI network alignment. It first selects some pairs of important proteins as seeds, followed by a gradual expansion to obtain an initial matching, and then it refines the current result to obtain an optimal alignment result iteratively based on the vertex cover. We compare GMAlign with the state-of-the-art methods on the PPI network pairs obtained from the largest BioGRID dataset and validate its performance. The results show that our algorithm can produce larger size of alignment, and can find bigger and denser common connected subgraphs as well for the first time. Meanwhile, GMAlign can achieve high quality biological results, as measured by functional consistency and semantic similarity of the Gene Ontology terms. Moreover, we also show that GMAlign can achieve better results which are structurally and biologically meaningful in the detection of large conserved biological pathways between species. CONCLUSIONS: GMAlign is a novel global network alignment tool to discover large conserved functional components between PPI networks. It also has many potential biological applications such as conserved pathway and protein complex discovery across species. The GMAlign software and datasets are avaialbile at https://github.com/yzlwhu/GMAlign .

Beta oscillations in major depression - signalling a new cortical circuit for central executive function.

This study aimed to examine alterations in electroencephalography (EEG) phase synchronization in working memory processing in depressed patients. Sixty-four-channel EEG signals were recorded from 33 depressed patients and 32 healthy controls during a visual n-back task. Alterations in functional connections in the patients were investigated using event-related phase coherence in terms of the phase synchronization index (PSI). Compared with the control subjects, the depressed patients showed a lower task-dependent increase in the PSI of delta, theta, and alpha oscillations in a frontoparietal network, but a higher task-dependent increase in the PSI of beta oscillations in the frontoparietal network. Additionally, depressed patients showed a lower task-dependent decrease in the PSI of delta, theta, alpha, and beta oscillations in centro-parieto-occipital sites. Insufficient phase synchronization and desynchronization during working memory processing reflects impairments in cortical inhibition, memory, and attention efficiency in major depression, while the abnormal increase in phase synchronization in beta oscillations in the frontoparietal network may indicate a new cortical circuit concerned with the repair of impaired ability in attention, memory retention, and working memory central executive processing. These findings present a compensatory mechanism for impaired cognitive function in major depression, and advance our understanding of functional aspect of beta oscillations.

Depression-Related Brain Connectivity Analyzed by EEG Event-Related Phase Synchrony Measure.

This study is to examine changes of functional connectivity in patients with depressive disorder using synchronous brain activity. Event-related potentials (ERPs) were acquired during a visual oddball task in 14 patients with depressive disorder and 19 healthy controls. Electroencephalogram (EEG) recordings were analyzed using event-related phase coherence (ERPCOH) to obtain the functional network. Alteration of the phase synchronization index (PSI) of the functional network was investigated. Patients with depression showed a decreased number of significant electrode pairs in delta phase synchronization, and an increased number of significant electrode pairs in theta, alpha and beta phase synchronization, compared with controls. Patients with depression showed lower target-dependent PSI increment in the frontal-parietal/temporal/occipital electrode pairs in delta-phase synchronization than healthy participants. However, patients with depression showed higher target-dependent PSI increments in theta band in the prefrontal/frontal and frontal-temporal electrode pairs, higher PSI increments in alpha band in the prefrontal pairs and higher increments of beta PSI in the central and right frontal-parietal pairs than controls. It implied that the decrease in delta PSI activity in major depression may indicate impairment of the connection between the frontal and parietal/temporal/occipital regions. The increase in theta, alpha and beta PSI in the frontal/prefrontal sites might reflect the compensatory mechanism to maintain normal cognitive performance. These findings may provide a foundation for a new approach to evaluate the effectiveness of therapeutic strategies for depression.

Source analysis of P3a and P3b components to investigate interaction of depression and anxiety in attentional systems.

This study examined the impact of depressive disorders, anxiety disorders and the comorbidity of these disorders on the regional electrophysiological features of brain activity. Sixty-four-channel event-related potentials (ERP) were acquired during a visual oddball task in patients with depressive disorder, patients with anxiety disorders, patients with comorbid depressive and anxiety disorders and healthy subjects. An fMRI-constrained source model was applied to ERP to identify different cortical activities in the patient and control groups. Comorbid patients showed an abnormal frontal-greater-than-parietal P3b topography in the right hemisphere and the highest P3a amplitude at frontal and central sites at the scalp midline. For P3b, depressed patients showed decreased right-lateralized activity in the precentral sulcus (PrCS) and posterior parietal cortex (PPC). Anxious patients demonstrated hyperactive prefrontal cortices (PFC). Comorbid patients presented decreased activity in the cingulate gyrus, right PrCS and right PPC and increased activity in the left PFC and left insular (INS). For P3a, hyperactive left PrCS was found in comorbid patients. Comorbid patients showed both anxiety-related and depression-related activity. A superimposition effect of depression and anxiety was identified with (1) aggravated hypo-function of the right-lateralized dorsal attention and salience networks and (2) complicated anxiety-related hyper-function of the left-lateralized ventral attention and salience networks.

[Brain electrical source analysis of the response to visual target and distractor stimuli].

In this paper, time courses of discrete cortical current sources evoked by target and distractor stimulus are presented in a visual three-stimulus oddball paradigm. 64-channel electroencephalogram (EEG) signals were recorded in healthy subjects in the paradigm where the P3b component of the P300 is evoked in the detection of rare events (target and distractor) and the P3a component is mainly produced by distractor events. A regional source model with constraints of spatial coordinates from fMRI was then applied to event-related potentials (ERPs) data in the target and distractor conditions. Activities of regional sources indicated bilateral inferior parietal lobe, posterior parietal cortex and inferior temporal cortex mainly contribute to the P3b, while the P3a was mainly produced by bilateral insula, bilateral precentral sulcus and cingulate gyrus. Target processing involved parietal lobe, inferior temporal cortex and left insula engaged in stimulus-driven attention process, goal-directed attention process, categorization of visual stimuli and memory retrieval, while distractor processing involved right insula and cingulate gyrus engaged in attention switching and reengagement of attention resource.

Dipole source analysis of auditory P300 response in depressive and anxiety disorders.

This paper is to study auditory event-related potential P300 in patients with anxiety and depressive disorders using dipole source analysis. Auditory P300 using 2-stimulus oddball paradigm was collected from 35 patients with anxiety disorder, 32 patients with depressive disorder, and 30 healthy controls. P300 dipole sources and peak amplitude of dipole activities were analyzed. The source analysis resulted in a 4-dipole configuration, where temporal dipoles displayed greater P300 amplitude than that of frontal dipoles. In addition, a right-greater-than-left hemispheric asymmetry of dipole magnitude was found in patients with anxiety disorder, whereas a left-greater-than-right hemispheric asymmetry of dipole magnitude was observed in depressed patients. Results indicated that the asymmetry was more prominent over the temporal dipole than that of frontal dipoles in patients. Patients with anxiety disorder may increase their efforts to enhance temporal dipole activity to compensate for a deficit in frontal cortex processing, while depressed patients show dominating reduction of right temporal activity. The opposite nature of results observed with hemispheric asymmetry in depressive and anxiety disorders could serve to be valuable information for psychiatric studies.

Localizing P300 generators in high-density event- related potential with fMRI.

BACKGROUND: To assess the effects of stimulus context on the P300 component, an eight-orientation Landolt ring task was introduced. As the stimulus context of this task differs from the traditional two-stimulus oddball paradigm, the purpose here was to apply EEG/fMRI integration to investigate the localization and activities of the P300 generators involved with this task. MATERIAL/METHODS: Ten healthy subjects performed the visual P300 task while fMRI and 64-channel ERP data were acquired. The voltage topographical maps of the P300 component were calculated and analyzed for the main activation foci. Furthermore, constraints from fMRI were used to identify the source activities of visual P300 ERP. RESULTS: Analysis of the hemodynamic response to the visual target stimuli revealed a distributed network of neural sources in the bilateral parietal lobules, middle and inferior frontal gyrus, precentral and postcentral cortex, and anterior cingulate gyrus. The analysis particularly showed preponderant activations of the bilateral superior parietal lobules. In this target detection design, two distinct P300 peaks were observed in the dipole waveforms, the bilateral prefrontal and the right inferior parietal dipole waveforms displayed the higher peak at short latency, while the four parietal, the anterior cingulate, and the temporal dipole waveforms had the higher peak at long latency. CONCLUSIONS: Compared with the classical oddball paradigm, the amplitude decreased in this study, which might be related to its particular stimulus context. The source technique was utilized to yield a realistic 11-dipole model and distinguish the anatomical generators of early and late components of the P300 response.

Is phosphorescence lifetime an indicator of angiogenesis in cortical sarcoma?

In this paper, the oxygen dependent phosphorescence quenching method is proposed to study the correlation between the phosphorescence lifetime and microvessel density in tumors. In the implementation, the S180 transplanted tumor in the mouse is used for the collection of the time-resolved phosphorescence, the tumor microvessel density is measured by immunohistochemical examination of FVIII, the correlation between microvessel density and phosphorescence lifetime is analyzed by multiple regression method. The results show the phosphorescence decay constant measured in tumors is enlarged in the tumor progression. Furthermore, the relative total microvessel area is positively correlative with the phosphorescence lifetime, which is estimated by a two dimension regression equation. It is concluded phosphorescence lifetime is a valuable indicator of angiogenesis during the tumor development.

Quantitative time-resolved fluorescence spectrum of the cortical sarcoma and the adjacent normal tissue.

The difference in time-resolved fluorescence spectrum between the cortical sarcoma and the adjacent normal tissue was studied in both experimental and theoretical ways. The Clinical data were obtained in vivo using a time-resolved fluorescence spectrometer employing a single fiber-optic probe for excitation and detection. Tissue was modeled as s-180 sarcoma tumor surrounded with normal muscle and was mediated by the Palladium-porphyrin photosensitizer (Pd-TCPP). The emitted fluorescence was considered as arising from the tumor tissue or the normal muscle, due to the presence of the photosensitizer. A computational code which could simulating time-resolved fluorescence emission was presented and applied to comparing fluorescence decay of photosensitizer in different stages of tumor growth. In this code the different stages of the tumor was modeled through changing the time tau, the delay of the fluorescence photon emission and z (max), the thickness of the tumor. It was found in the in vivo experiment that the fluorescence from tumor tissue decayed more quickly than from the adjacent normal muscle. For the ten rats in the first experiment day, the mean decay constant of tumor T (s) and normal tissue T (n) were 554 and 526 mus, respectively. And T (s) increased with the tumor growth, from 554 mus in the first day to 634 mus in the eighth day while T (s) kept steady. It was believed that the more adequate oxygen supplied by the normal tissue can more effectively quench the fluorescence and in the normal tissue the photosensitizer lifetime is smaller. As a result the simulated time-resolved fluorescence spectrum of normal tissue showed more quickly decay. And the thickness of the tumor can also delay the fluorescence decay. Both the experimental and simulated results indicated that the germination of the tumor would increase the decay constant of the time-resolved fluorescence spectrum. So decay constant of the tumor tissue spectrum should be larger than that of adjacent normal tissue for the reason of hypoxia and overgrowth. This fact could be of use in the tumor diagnoses.

Quantitative time-resolved fluorescence spectra of the cortical sarcoma and the adjacent normal tissue determined with an in vivo experimental method and theoretical model.

In this paper, a time-resolved fluorescence spectrum method is proposed to study the difference between the cortical sarcoma and the adjacent normal tissue. This is a fluorescence-light-intensity-independent method, which makes it more reliable in the presence of interference light emitted by nonfluorescent light absorbers and scatterers. In the implementation, a model of the tumor tissue and a model of light transport in turbid media using improved Monte Carlo simulations are proposed. In this method, the time-resolved fluorescence is collected in vivo. The improved theoretical model can interpret the fluorescence lifetime measurement. The simulation results show that the decay constant of the tumor tissue spectrum is larger than that of the adjacent normal tissue because of hypoxia and hyperplasia, which fits the theoretical analysis very well.

[Study on the influence of simulative EEG modulation magnetic field on the discharge of median raphe nuclei].

In this paper the response characteristic of the nerve fiber to the modulation magnetic field induction is studied by using the method of numeric simulation. It is found that the nerve fiber is sensitive to the low frequency modulated signal but not to the high frequency carrier wave. A simulative EEG signal generator is developed according to the change of EEG rhythm during the sleep. The simulative EEG square wave is modulated by high-frequency magnetic impulse. The modulation magnetic field is coupled into the rabbit's brain to study the influence of magnetic stimulation on the discharge of 5-hydroxytryptamine (5-HT) nerve cell. The experiment results demonstrate that discharge frequency of median raphe nuclei related to sleep changes significantly and the discharge becomes slow, which shows that magnetic stimulation can inhibit electrical activity of 5-HT nerve cell and provide a new way to improve insomnia.

[Study on the function localization during different brain calculation tasks].

The aim of this study is to define the anatomical localization of corresponding brain function area during calculating. The activating modes in brain during continuous silent calculating subtraction and repeated silent reading multiplication table were compared and investigated. Fourteen volunteers of right-handedness were enrolled in this experiment. The quite different reaction models in brain area during the two models of calculation revealed that there are different processing pathways in brain during these two operating tasks. During continuous silent calculating, the function areas were found localized on the posterior portion of superior and middle gyrus of frontal lobe and the lobule of posterior parietal lobe (P < 0.01, T = 5.41), demonstrating that these function areas play an important role in the performance of calculation and working memory. During repeated silent reading multiplication table, the activating cluster was found only located in in the gyri occipital lateral(P < 0.01, T = 4.77).