Inflexibility in Autism Spectrum Disorder: Need for certainty and atypical emotion processing share the blame.

Although ASD (Autism Spectrum Disorder) diagnosis requires the co-occurrence of socio-emotional deficits and inflexible behaviors, the interaction between these two domains remains unexplored. We used an emotional Wisconsin Card Sorting Test adapted to fMRI to explore this question. ASD and control participants matched a central card (a face) with one of four surrounding cards according to one of three rules: frame color, facial identity or expression.

Deciphering human motion to discriminate social interactions: a developmental neuroimaging study.

Non-verbal communication plays a major role in social interaction understanding. Using functional magnetic resonance imaging, we explored the development of the neural networks involved in social interaction recognition based on human motion in children (8-11), adolescents (13-17), and adults (20-41). Participants watched point-light videos depicting two actors interacting or moving independently and were asked whether these agents were interacting or not.

Decision-making in a changing world: a study in autism spectrum disorders.

To learn to deal with the unexpected is essential to adaptation to a social, therefore often unpredictable environment. Fourteen adults with autism spectrum disorders (ASD) and 15 controls underwent a decision-making task aimed at investigating the influence of either a social or a non-social environment, and its interaction with either a stable (with constant probabilities) or an unstable (with changing probabilities) context on their performance. Participants with ASD presented with difficulties in accessing underlying statistical rules in an unstable context, a deficit especially enhanced in the social environment.

Modular structure of functional networks in olfactory memory.

Graph theory enables the study of systems by describing those systems as a set of nodes and edges. Graph theory has been widely applied to characterize the overall structure of data sets in the social, technological, and biological sciences, including neuroscience. Modular structure decomposition enables the definition of sub-networks whose components are gathered in the same module and work together closely, while working weakly with components from other modules.

Different neural networks are involved in audiovisual speech perception depending on the context.

How are we able to easily and accurately recognize speech sounds despite the lack of acoustic invariance? One proposed solution is the existence of a neural representation of speech syllable perception that transcends its sensory properties. In the present fMRI study, we used two different audiovisual speech contexts both intended to identify brain areas whose levels of activation would be conditioned by the speech percept independent from its sensory source information. We exploited McGurk audiovisual fusion to obtain short oddball sequences of syllables that were either (a) acoustically different but perceived as similar or (b) acoustically identical but perceived as different.

Brain correlates of automatic visual change detection.

A number of studies support the presence of visual automatic detection of change, but little is known about the brain generators involved in such processing and about the modulation of brain activity according to the salience of the stimulus. The study presented here was designed to locate the brain activity elicited by unattended visual deviant and novel stimuli using fMRI. Seventeen adult participants were presented with a passive visual oddball sequence while performing a concurrent visual task.

Perfumers' expertise induces structural reorganization in olfactory brain regions.

The human brain's ability to adapt to environmental changes is obvious in specific sensory domains of experts, and olfaction is one of the least investigated senses. As we have previously demonstrated that olfactory expertise is related to functional brain modifications, we investigated here whether olfactory expertise is also coupled with structural changes. We used voxel-based morphometry to compare the gray-matter volume in student and professional perfumers, as well as untrained control subjects, and accounted for all methodological improvements that have been recently developed to limit possible errors associated with image processing.

True and false recognition memories of odors induce distinct neural signatures.

Neural bases of human olfactory memory are poorly understood. Very few studies have examined neural substrates associated with correct odor recognition, and none has tackled neural networks associated with incorrect odor recognition. We investigated the neural basis of task performance during a yes-no odor recognition memory paradigm in young and elderly subjects using event-related functional magnetic resonance imaging.

Cortical dynamics of a self driven choice: a MEG study during a card sorting task.

Objective: The aim of this study was to disclose the dynamics of the frontal processes involved in a task shifting between two attentional states.

Methods: Magnetoencephalographic activities were recorded during a Wisconsin Card Sorting Test where subjects had to match card stimuli according to one of three possible dimensions ("maintained condition"). The matching dimension was intermittently changed and subjects, after feedback presentation, had to identify the new correct dimension ("shifted condition").

Abnormal cerebral effective connectivity during explicit emotional processing in adults with autism spectrum disorder.

Several recent studies suggest that autism may result from abnormal communication between brain regions. We directly assessed this hypothesis by testing the presence of abnormalities in a model of the functional cerebral network engaged during explicit emotion processing in adults with high functioning autism or Asperger syndrome. Comparison of structural equation models revealed abnormal patterns of effective connectivity, with the prefrontal cortex as a key site of dysfunction.

Schizophrenia and frontal cortex: where does it fail?

Schizophrenia is characterized by cognitive, social, and emotional impairments and by psychotic symptoms. Neuroimaging studies have reported abnormalities within the prefrontal cortex and it has been hypothesized that schizophrenia results from poor or miswired anatomical/functional connections. We have compared the functional connectivity within the frontal cortex in control and schizophrenic subjects during the realization of a Continuous Performance Task.

Relationship between task-related gamma oscillations and BOLD signal: new insights from combined fMRI and intracranial EEG.

Cognitive neuroscience relies on two sets of techniques to map the neural networks underlying cognition in humans: recordings of either regional metabolic changes (fMRI or PET) or fluctuations in the neural electromagnetic fields (EEG and MEG). Despite major advances in the last few years, an explicit linkage between the two is still missing and the neuroimaging community faces two complementary but unrelated sets of functional descriptions of the human brain. Such an explicit framework, linking the two approaches in potentially complex cognitive tasks and in a variety of brain regions would permit to combine them into fine spatio-temporally-grained human brain mapping procedures.

Effect of initial fMRI data modeling on the connectivity reported between brain areas.

Nearly all neuroimaging data analysis rests upon some form of variance partitioning. Conventional analyses, with a general linear model (GLM), partition the variance in the measured response variable into partitions described by a design matrix of explanatory variables. This approach can also be adopted in the initial modeling of the data in studies using data-led methods to summarize functional connectivity, such as principle component analysis, or studies of effective connectivity, using for example structural equation modeling.

Functional and effective connectivity in an fMRI study of an auditory-related task.

This study investigates the sets of brain areas that are functionally connected during an auditory goal-directed task. We used a paradigm including a resting state condition and an active condition, which consisted in active listening to the footsteps of walking humans. The regional brain activity was measured using fMRI and the adjusted values of activity in brain regions involved in the task were analysed using both principal component analysis and structural equation modelling.

Listening in silence activates auditory areas: a functional magnetic resonance imaging study.

Directing attention to some acoustic features of a sound has been shown repeatedly to modulate the stimulus-induced neural responses. On the contrary, little is known about the neurophysiological impact of auditory attention when the auditory scene remains empty. We performed an experiment in which subjects had to detect a sound emerging from silence (the sound was detectable after different durations of silence).

Listening to a walking human activates the temporal biological motion area.

A vivid perception of a moving human can be evoked when viewing a few point-lights on the joints of an invisible walker. This special visual ability for biological motion perception has been found to involve the posterior superior temporal sulcus (STSp). However, in everyday life, human motion can also be recognized using acoustic cues.

A relation between rest and the self in the brain?

Neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) are widely used to identify the cerebral correlates of cognitive tasks. The resting state presents the advantage to serve as a reference in all experiments but is also an ill-defined mental state because it may vary both from one subject to another and within the same subject. The most challenging question concerns the areas whose activity (revealed by PET or fMRI imaging) is greater in rest state than in an active condition.

Changes of effective connectivity between the lateral and medial parts of the prefrontal cortex during a visual task.

Structural equation modelling was used to study the change of connectivity during a visual task with continuous variation of the attention load. The model was based on areas defined by the haemodynamic responses described elsewhere [Mazoyer, P., Wicker, B.

Perception and judgement of physical causality involve different brain structures.

One basic type of 'mechanical' causality is that which occurs between physical objects. Subjects were presented with mechanically causal events (ball collides with and causes movement of another ball) or two non-causal events (a ball either passes underneath another ball, or rolls across the screen and changes colour). We investigated which brain regions exhibit increased activity during the judgement of causality ('judged causality') as compared with judgement of movement direction ('perceived causality').

Generalized least-squares method applied to fMRI time series with empirically determined correlation matrix.

Functional magnetic resonance imaging (fMRI) time series analysis and statistical inferences about the effect of a cognitive task on the regional cerebral blood flow (rCBF) are largely based on the linear model. However, this method requires that the error vector is a gaussian variable with an identity correlation matrix. When this assumption cannot be accepted, statistical inferences can be made using generalized least squares.

A neural network elicited by parametric manipulation of the attention load.

We used a parametric experimental design to identify the rCBF variations related to a continuous variation of the attention load. The experiment involved goal-directed visual tasks. The length of time during which the subject's attention was engaged toward the external stimulus was taken as the factor of interest.

How the brain perceives causality: an event-related fMRI study.

Detection of the causal relationships between events is fundamental for understanding the world around us. We report an event-related fMRI study designed to investigate how the human brain processes the perception of mechanical causality. Subjects were presented with mechanically causal events (in which a ball collides with and causes movement of another ball) and non-causal events (in which no contact is made between the balls).

Does perception of biological motion rely on specific brain regions?

Perception of biological motions plays a major adaptive role in identifying, interpreting, and predicting the actions of others. It may therefore be hypothesized that the perception of biological motions is subserved by a specific neural network. Here we used fMRI to verify this hypothesis.

New aspects of motion perception: selective neural encoding of apparent human movements.

Perception of apparent motion operates somewhat differently for objects and human figures. Depending on the interstimulus interval, the latter d may give rise to either perception of a direct path (i.e.

Susceptibility of differentiated thyrocytes in primary culture to undergo apoptosis after exposure to hydrogen peroxide: relation with the level of expression of apoptosis regulatory proteins, Bcl-2 and Bax.

Thyrocytes, that generate and use hydrogen peroxide (H2O2) to synthesize thyroid hormones, undergo apoptosis, as do most cell types, when exposed in vitro to H2O2. We have studied 1) the kinetics and the amplitude of the apoptotic response to H2O2 and 2) the relationship between the extent of the apoptosis-inducing effect of H2O2, the H2O2 degradation activity, and the level of expression of apoptosis regulatory proteins, Bcl-2 and Bax, in pig thyrocytes in primary culture. Cells were seeded at high density to obtain confluent monolayers and were cultured in the presence of TSH to maintain the expression of differentiation.