Specific components of face perception in the human fusiform gyrus studied by tomographic estimates of magnetoencephalographic signals: a tool for the evaluation of non-verbal communication in psychosomatic paradigms)

<p>Abstract</p> <p>Aims</p> <p>The aim of this study was to determine the specific spatiotemporal activation patterns of face perception in the fusiform gyrus (FG). The FG is a key area in the specialized brain system that makes possible the recognition of face with ease and speed in our daily life. Characterization of FG response provides a quantitative method for evaluating the fundamental functions that contribute to non-verbal communication in various psychosomatic paradigms.</p> <p>Methods</p> <p>The MEG signal was recorded during passive visual stimulus presentation with three stimulus types – Faces, Hands and Shoes. The stimuli were presented separately to the central and peripheral visual fields. We performed statistical parametric mapping (SPM) analysis of tomographic estimates of activity to compare activity between a pre- and post-stimulus period in the same object (baseline test), and activity between objects (active test). The time course of regional activation curves was analyzed for each stimulus condition.</p> <p>Results</p> <p>The SPM baseline test revealed a response to each stimulus type, which was very compact at the initial segment of main M_FG170. For hands and shoes the area of significant change remains compact. For faces the area expanded widely within a few milliseconds and its boundaries engulfed the other object areas. The active test demonstrated that activity for faces was significantly larger than the activity for hands. The same face specific compact area as in the baseline test was identified, and then again expanded widely. For each stimulus type and presentation in each one of the visual fields locations, the analysis of the time course of FG activity identified three components in the FG: M_FG100, M_FG170, and M_FG200 – all showed preference for faces.</p> <p>Conclusion</p> <p>Early compact face-specific activity in the FG expands widely along the occipito-ventral brain within a few milliseconds. The significant difference between faces and the other object stimuli in M_FG100 shows that processing of faces is already differentiated from processing of other objects within 100 ms. Standardization of the three face-specific MEG components could have diagnostic value for the integrity of the initial process of non-verbal communication in various psychosomatic paradigms.</p

Consciousness and its Measures: Joint Workshop for COST Actions NeuroMath and Consciousness

The main goals of COST Action NeuroMath are the same as those of the open access journal Nonlinear Biomedical Physics to show how new methods that are being developed in physical disciplines can shed new light on biological phenomena and their medical applications and to bridge the gaps between specialists in physics and biomedical specialists who use these methods in practice. Medical doctors and biologists rather avoid reading physical journals because the articles published there contain 'heavy' mathematics; on the other hand, physicists and engineers rarely read biological and medical journals because articles there are mostly descriptive. Both COST NeuroMath Action with its workshops and the journal Nonlinear Biomedical Physics were created to enable these groups to meet together. In this Supplement to Nonlinear Biomedical Physics we publish the best papers based on the presentations shown during the joint workshop for COST Actions NeuroMath (BM0601) and Consciousness (BM0605) 'Consciousness and its Measures' that took place in Limassol, Cyprus, 29 November 01 December, 2009. The papers present the newest interdisciplinary achievements in both applied and theoretical research on brain and consciousness. Transient process and synchrony of cortical activity [1], different patterns of cortical activity [2] and assessment of different conscious states [3] are presented. Neurodynamics is studied based on fMRI [4] and on high-resolution EEG signals [5]. Mutual Information is used to study yoking of eyes during saccadic movements [6] and MEG around saccades is analyzed for non-invasive characterization of the human eye fields [7]. Parameter selection for cortical potential imaging [8], and classification of ADHD patients based on independent ERP components [9] are discussed. Language processing by human brain using fMRI [10] and the influence of noise due to electromagnetic interference on processing of visual information [11] are studied. We thank the Authors and the Reviewers for the great job they all have done. We also thank Dr. Kalliopi Kostelidou, Science Officer, BMBS Domain, COST Office, Brussels, and Isobel Peters, Senior Project Manager as well as The Independent Editorial Production Team of BioMed Central, London, for their invaluable assistance in publishing this Supplement to Nonlinear Biomedical Physics

Emotion Separation Is Completed Early and It Depends on Visual Field Presentation

It is now apparent that the visual system reacts to stimuli very fast, with many brain areas activated within 100 ms. It is, however, unclear how much detail is extracted about stimulus properties in the early stages of visual processing. Here, using magnetoencephalography we show that the visual system separates different facial expressions of emotion well within 100 ms after image onset, and that this separation is processed differently depending on where in the visual field the stimulus is presented. Seven right-handed males participated in a face affect recognition experiment in which they viewed happy, fearful and neutral faces. Blocks of images were shown either at the center or in one of the four quadrants of the visual field. For centrally presented faces, the emotions were separated fast, first in the right superior temporal sulcus (STS; 35–48 ms), followed by the right amygdala (57–64 ms) and medial pre-frontal cortex (83–96 ms). For faces presented in the periphery, the emotions were separated first in the ipsilateral amygdala and contralateral STS. We conclude that amygdala and STS likely play a different role in early visual processing, recruiting distinct neural networks for action: the amygdala alerts sub-cortical centers for appropriate autonomic system response for fight or flight decisions, while the STS facilitates more cognitive appraisal of situations and links appropriate cortical sites together. It is then likely that different problems may arise when either network fails to initiate or function properly

Asymmetric random matrices: What do we need them for?

Complex systems are typically represented by large ensembles of observations. Correlation matrices provide an efficient formal framework to extract information from such multivariate ensembles and identify in a quantifiable way patterns of activity that are reproducible with statistically significant frequency compared to a reference chance probability, usually provided by random matrices as fundamental reference. The character of the problem and especially the symmetries involved must guide the choice of random matrices to be used for the definition of a baseline reference. For standard correlation matrices this is the Wishart ensemble of symmetric random matrices. The real world complexity however often shows asymmetric information flows and therefore more general correlation matrices are required to adequately capture the asymmetry. Here we first summarize the relevant theoretical concepts. We then present some examples of human brain activity where asymmetric time-lagged correlations are evident and hence highlight the need for further theoretical developments

Sleep Spindles – As a Biomarker of Brain Function and Plasticity

Alternative & renewable energy sources & technolog

Chapter Sleep Spindles – As a Biomarker of Brain Function and Plasticity

Alternative & renewable energy sources & technolog

Diffuse precordial ST-segment elevation in inferior-right myocardial infarction

A right ventricular (RV) myocardial infarction (MI) may yield precordial ST-segment elevation (STE). Accordingly, combined inferior and precordial STE may be produced during an inferior-RV MI. Such an electrocardiographic picture may be mistakenly regarded as showing wrapped left anterior descending artery (LADA) occlusion or double vessel occlusion. We present a patient with inferior-RV MI and STE in the inferior, all precordial and right chest leads, in whom the diffuse precordial STE was probably mistakenly regarded as showing anterior MI. However, the STE resolution in V1-V2 and late R&#8217; wave in V1, which were combined with a recanalized RV branch, favored the RV origin of this STE. Furthermore, the LADA was patent when V3-V6 showed severe ischemia, while its lesion was angiographically stable. Thus its simultaneous occlusion was unlikely. The late R&#8217; wave in V1 indicates RV transmural conduction delay;as highlighted herein, it is diagnostic of a RV myocardial infarction. (Cardiol J 2010; 17, 6: 628-631

Mapping the Spatiotemporal Evolution of Emotional Processing: An MEG Study Across Arousal and Valence Dimensions

Electrophysiological and functional neuroimaging findings indicate that the neural mechanisms underlying the processing of emotional dimensions (i.e., valence, arousal) constitute a spatially and temporally distributed emotional network, modulated by the arousal and/or valence of the emotional stimuli. We examined the time course and source distribution of gamma time-locked magnetoencephalographic activity in response to a series of emotional stimuli viewed by healthy adults. We used a beamformer and a sliding window analysis to generate a succession of spatial maps of event-related brain responses across distinct levels of valence (pleasant/unpleasant) and arousal (high/low) in 30–100 Hz. Our results show parallel emotion-related responses along specific temporal windows involving mainly dissociable neural pathways for valence and arousal during emotional picture processing. Pleasant valence was localized in the left inferior frontal gyrus, while unpleasant valence in the right occipital gyrus, the precuneus, and the left caudate nucleus. High arousal was processed by the left orbitofrontal cortex, amygdala, and inferior frontal gyrus, as well as the right middle temporal gyrus, inferior parietal lobule, and occipital gyrus. Pleasant by high arousal interaction was localized in the left inferior and superior frontal gyrus, as well as the right caudate nucleus, putamen, and gyrus rectus. Unpleasant by high arousal interaction was processed by the right superior parietal gyrus. Valence was prioritized (onset at ∼60 ms) to all other effects, while pleasant valence was short lived in comparison to unpleasant valence (offsets at ∼110 and ∼320 ms, respectively). Both arousal and valence × arousal interactions emerged relatively early (onset at ∼150 ms, and ∼170 ms, respectively). Our findings support the notion that brain regions differentiate between valence and arousal, and demonstrate, for the first time, that these brain regions may also respond to distinct combinations of these two dimensions within specific time windows

First activity and interactions in thalamus and cortex using raw single-trial EEG and MEG elicited by somatosensory stimulation

Introduction: One of the primary motivations for studying the human brain is to comprehend how external sensory input is processed and ultimately perceived by the brain. A good understanding of these processes can promote the identification of biomarkers for the diagnosis of various neurological disorders; it can also provide ways of evaluating therapeutic techniques. In this work, we seek the minimal requirements for identifying key stages of activity in the brain elicited by median nerve stimulation.Methods: We have used a priori knowledge and applied a simple, linear, spatial filter on the electroencephalography and magnetoencephalography signals to identify the early responses in the thalamus and cortex evoked by short electrical stimulation of the median nerve at the wrist. The spatial filter is defined first from the average EEG and MEG signals and then refined using consistency selection rules across ST. The refined spatial filter is then applied to extract the timecourses of each ST in each targeted generator. These ST timecourses are studied through clustering to quantify the ST variability. The nature of ST connectivity between thalamic and cortical generators is then studied within each identified cluster using linear and non-linear algorithms with time delays to extract linked and directional activities. A novel combination of linear and non-linear methods provides in addition discrimination of influences as excitatory or inhibitory.Results: Our method identifies two key aspects of the evoked response. Firstly, the early onset of activity in the thalamus and the somatosensory cortex, known as the P14 and P20 in EEG and the second M20 for MEG. Secondly, good estimates are obtained for the early timecourse of activity from these two areas. The results confirm the existence of variability in ST brain activations and reveal distinct and novel patterns of connectivity in different clusters.Discussion: It has been demonstrated that we can extract new insights into stimulus processing without the use of computationally costly source reconstruction techniques which require assumptions and detailed modeling of the brain. Our methodology, thanks to its simplicity and minimal computational requirements, has the potential for real-time applications such as in neurofeedback systems and brain-computer interfaces

Interocular yoking in human saccades examined by mutual information analysis

International audienceABSTRACT : BACKGROUND : Saccadic eye movements align the two eyes precisely to foveate a target. Trial-by-trial variance of eye movement is always observed within an identical experimental condition. This has often been treated as experimental error without addressing its significance. The present study examined statistical linkages between the two eyes' movements, namely interocular yoking, for the variance of eye position and velocity. METHODS : Horizontal saccadic movements were recorded from twelve right-eye-dominant subjects while they decided on saccade direction in Go-Only sessions and on both saccade execution and direction in Go/NoGo sessions. We used infrared corneal reflection to record simultaneously and independently the movement of each eye. Quantitative measures of yoking were provided by mutual information analysis of eye position or velocity, which is sensitive to both linear and non-linear relationships between the eyes' movements. Our mutual information analysis relied on the variance of the eyes movements in each experimental condition. The range of movements for each eye varies for different conditions so yoking was further studied by comparing GO-Only vs. Go/NoGo sessions, leftward vs. rightward saccades. RESULTS : Mutual information analysis showed that velocity yoking preceded positional yoking. Cognitive load increased trial variances of velocity with no increase in velocity yoking, suggesting that cognitive load may alter neural processes in areas to which oculomotor control is not tightly linked. The comparison between experimental conditions showed that interocular linkage in velocity variance of the right eye lagged that of the left eye during saccades. CONCLUSIONS : We conclude quantitative measure of interocular yoking based on trial-to-trial variance within a condition, as well as variance between conditions, provides a powerful tool for studying the binocular movement mechanism