The Neurocognitive Bases of Meaningful Intransitive Gestures: A Systematic Review and Meta-analysis of Neuropsychological Studies.

Researchers and clinicians have long used meaningful intransitive (i.e., not tool-related; MFI) gestures to assess apraxia-a complex and frequent motor-cognitive disorder. Nevertheless, the neurocognitive bases of these gestures remain incompletely understood. Models of apraxia have assumed that meaningful intransitive gestures depend on either long-term memory (i.e., semantic memory and action lexicons) stored in the left hemisphere, or social cognition and the right hemisphere. This meta-analysis of 42 studies reports the performance of 2659 patients with either left or right hemisphere damage in tests of meaningful intransitive gestures, as compared to other gestures (i.e., MFT or meaningful transitive and MLI or meaningless intransitive) and cognitive tests. The key findings are as follows: (1) deficits of meaningful intransitive gestures are more frequent and severe after left than right hemisphere lesions, but they have been reported in both groups; (2) we found a transitivity effect in patients with lesions of the left hemisphere (i.e., meaningful transitive gestures more difficult than meaningful intransitive gestures) but a "reverse" transitivity effect in patients with lesions of the right hemisphere (i.e., meaningful transitive gestures easier than meaningful intransitive gestures); (3) there is a strong association between meaningful intransitive and transitive (but not meaningless) gestures; (4) isolated deficits of meaningful intransitive gestures are more frequent in cases with right than left hemisphere lesions; (5) these deficits may occur in the absence of language and semantic memory impairments; (6) meaningful intransitive gesture performance seems to vary according to the emotional content of gestures (i.e., body-centered gestures and emotional valence-intensity). These findings are partially consistent with the social cognition hypothesis. Methodological recommendations are given for future studies.

Seeing the forest or the tree depends on personality: Evidence from process communication model during global/local visual search task.

In everyday life, we are continuously confronted with multiple levels of visual information processes (e.g., global information, the forest, and local information, the tree) and we must select information that has to be processed. In the present study, we investigated the relation between personality and the ability to process global and local visual information. Global precedence phenomenon was assessed by a standard global/local visual search task used in many visuo-spatial precedent studies, and the 77 participants were also presented with the standard Process Communication Model (PCM) questionnaire. Results suggest that the ability to process global and local properties of visual stimuli varied according to the Base type of participants. Even if four among six Base types (Thinker, Persister, Harmonizer and Promoter) presented a classical global visual precedence, the two other Base types (Rebel and Imaginer) presented only an effect of distractors and an effect of global advantage, respectively. Taken together, these results evidenced that each human being does not equally perceive the "forest" (global information) and the "tree" (local information). Even if objectively presented with similar visual stimuli, individual responses differ according to the Base, an inter-individual variability that could be taken into account during daily life situations.

Is There Semantic Conflict in the Stroop Task?

This research addressed current controversies concerning the contribution of semantic conflict to the Stroop interference effect and its reduction by a single-letter coloring and cueing procedure. On the first issue, it provides, for the first time, unambiguous evidence for a contribution of semantic conflict to the (overall) Stroop interference effect. The reported data remained inconclusive on the second issue, despite being collected in a considerable sample and analyzed with both classical (frequentist) and Bayesian inferential approaches. Given that in all past Stroop studies, semantic conflict was possibly confounded with either response conflict (e.g., when semantic-associative items [SKYblue] are used to induce semantic conflict) or with facilitation (when color-congruent items [BLUEblue] are used as baseline to derive a magnitude for semantic conflict), its genuine contribution to the Stroop interference effect is the most critical result reported in the present study. Indeed, it leaves no doubt - in complete contrast to dominant single-stage response competition models (e.g., Roelofs, 2003) - that selection occurs at the semantic level in the Stroop task. The immediate implications for the composite (as opposed to unitary) nature of the Stroop interference effect and other still unresolved issues in the Stroop literature are outlined further.

Social cognition in schizophrenic patients: the effect of semantic content and emotional prosody in the comprehension of emotional discourse.

BACKGROUND: The recognition of the emotion expressed during conversation relies on the integration of both semantic processing and decoding of emotional prosody. The integration of both types of elements is necessary for social interaction. No study has investigated how these processes are impaired in patients with schizophrenia during the comprehension of an emotional speech. Since patients with schizophrenia have difficulty in daily interactions, it would be of great interest to investigate how these processes are impaired. We tested the hypothesis that patients present lesser performances regarding both semantic and emotional prosodic processes during emotional speech comprehension compared with healthy participants. METHODS: The paradigm is based on sentences built with emotional (anger, happiness, or sadness) semantic content uttered with or without congruent emotional prosody. The study participants had to decide with which of the emotional categories each sentence corresponded. RESULTS: Patients performed significantly worse than their matched controls, even in the presence of emotional prosody, showing that their ability to understand emotional semantic content was impaired. Although prosody improved performances in both groups, it benefited the patients more than the controls. CONCLUSION: Patients exhibited both impaired semantic and emotional prosodic comprehensions. However, they took greater advantage of emotional prosody adjunction than healthy participants. Consequently, focusing on emotional prosody during carrying may improve social communication.

Eye contact elicits bodily self-awareness in human adults.

Eye contact is a typical human behaviour known to impact concurrent or subsequent cognitive processing. In particular, it has been suggested that eye contact induces self-awareness, though this has never been formally proven. Here, we show that the perception of a face with a direct gaze (that establishes eye contact), as compared to either a face with averted gaze or a mere fixation cross, led adult participants to rate more accurately the intensity of their physiological reactions induced by emotional pictures. Our data support the view that bodily self-awareness becomes more acute when one is subjected to another's gaze. Importantly, this effect was not related to a particular arousal state induced by eye contact perception. Rejecting the arousal hypothesis, we suggest that eye contact elicits a self-awareness process by enhancing self-focused attention in humans. We further discuss the implications of this proposal.

Global interference during early visual processing: ERP evidence from a rapid global/local selective task.

Visual perception depends on the integration of local elements of a visual scene into a global frame. Evidence from behavioral studies shows that (1) the detection of the global frame is faster than the detection of the local parts, a phenomenon called the global advantage, and that (2) an interference of the global shape is also present during local processing. Together, these effects are called the global precedence effect (GPE). Even if the global advantage appears to impact neural processing as early as the first 100 ms post-stimulus, previous studies failed to find a global interference effect before 200 ms post-stimulus. Using for the first time a rapid display of letter component stimuli during a global/local selective task in which conditions with perceptual conflict, congruent and incongruent conditions were considered, the present event-related potential (ERP) study shows a global interference effect occurring as early as the time range of the N1 component. In particular, only congruent stimuli elicited similar N1 amplitude during the global and local tasks, whereas an increased of the N1 amplitude during the global task was observed (as compared to the local task) for both stimuli with perceptual conflict and incongruent stimuli. This finding corroborates the recent neural models of human visual perception.

An event-related potential study of predictive and integrative semantic context processing in subjects with schizotypal traits.

Context processing abnormalities may explain thought disorder in schizophrenia/schizotypy. This study aimed to assess predictive and integrative context processing in subjects with high or low scores on the Schizotypal Personality Questionnaire (SPQ). The N400 amplitude was recorded during semantic judgment of sentence pairs ending with a lateralized expected or unexpected word from the same or a different category (related and unrelated violation). In both groups, the N400 amplitude was less negative for expected words versus unrelated violations, regardless of which hemisphere received the stimulus, and for related versus unrelated violations, but only for left-hemisphere stimuli. The N400 amplitude for unrelated violations was less negative in subjects with high SPQ scores for both hemispheres. These results indicate that subjects with schizotypal traits use context to predict or integrate congruent words, but fail to inhibit incongruent words.

Very early modulation of brain responses to neutral faces by a single prior association with an emotional context: evidence from MEG.

Recent electrophysiological studies have demonstrated modulations of the very first stages of visual processing (<100 ms) due to prior experience. This indicates an influence of a memory trace on the earliest stages of stimulus processing. Here we investigated if emotional audio-verbal information associated with faces on first encounter can affect the very early responses to those faces on subsequent exposure. We recorded magneto-encephalographic (MEG) responses to neutral faces that had been previously associated with positive (happy), negative (angry) or neutral auditory verbal emotional contexts. Our results revealed a very early (30-60 ms) difference in the brain responses to the neutral faces according to the type of previously associated emotional context, with a clear dissociation between the faces previously associated to positive vs. negative or neutral contexts. Source localization showed that two main regions were involved in this very early association effect: the bilateral ventral occipito-temporal regions and the right anterior medial temporal region. These results provide evidence that the memory trace of a face integrates positive emotional cues present in the context of prior encounter and that this emotional memory can influence the very first stages of face processing. These experimental findings support the idea that face perception can be shaped by experience from its earliest stages and in particular through emotional association effects.

Pleasant emotional induction broadens the visual world of young children.

These experiments aimed at studying the influence of emotional context on global/local visual processing in children. Children 5 years old, known to present an immature global visual bias, and 8 years old, known to pay attention predominantly to global information, were placed in either a neutral or pleasant emotional context and subsequently presented with a global/local visual judgement task. As with previous findings for adults, both age groups presented a pronounced perceptual bias toward global information following exposure to emotionally pleasant pictures. Interestingly, younger children, who do not present a global bias during the neutral exposure, presented the same preference for global information as older children when exposed to the pleasant context. These findings indicate that emotion may strongly affect visual perception in children, with important implications for educational practice and models of cognition.

Sex-dependent modulation of activity in the neural networks engaged during emotional speech comprehension.

Studies using event related potentials have shown that men are more likely than women to rely on semantic cues when understanding emotional speech. In a previous functional Magnetic Resonance Imaging (fMRI) study, using an affective sentence classification task, we were able to separate areas involved in semantic processing and areas involved in the processing of affective prosody (Beaucousin et al., 2007). Here we searched for sex-related differences in the neural networks active during emotional speech processing in groups of men and women. The ortholinguistic abilities of the participants did not differ when evaluated with a large battery of tests. Although the neural networks engaged by men and women during emotional sentence classification were largely overlapping, sex-dependent modulations were detected during emotional sentence classification, but not during grammatical sentence classification. Greater activity was observed in men, compared with women, in inferior frontal cortical areas involved in emotional labeling and in attentional areas. In conclusion, at equivalent linguistic abilities and performances, men activate semantic and attentional cortical areas to a larger extent than women during emotional speech processing.

ERP evidence of a meaningfulness impact on visual global/local processing: when meaning captures attention.

Event-related potentials (ERPs) were recorded to investigate whether the meaningfulness of experimental stimuli impacted performances during global/local visual tasks. Participants were presented with compound stimuli, based on either meaningful letters, meaningful objects, or meaningless non-objects. The ERP recordings displayed typical early components, P1 and N1, evoked by task-related processes that affected global and local processes differently according to the meaningfulness of the stimuli. The effect of meaningfulness of the stimuli during global processing showed that P1 amplitudes were larger in response to objects and non-objects compared to letters, while letters and objects elicited larger N1 amplitudes than non-objects. Second, during local processing, the mean amplitudes of the ERPs recorded for object and letter stimuli were systematically smaller than the amplitudes recorded for non-object stimuli for both P1 and N1 components. In addition, object and letter stimuli elicited comparable mean ERP responses during local processing. These results are discussed in terms of the influences of both attentional and top-down identification processes. Taken together, these findings suggested that looking for meaning is crucial in the perception of visual scenes and that the meaningfulness nature of the stimuli should be taken into account in future studies.

A common neural system is activated in hearing non-signers to process French sign language and spoken French.

We used functional magnetic resonance imaging to investigate the areas activated by signed narratives in non-signing subjects naïve to sign language (SL) and compared it to the activation obtained when hearing speech in their mother tongue. A subset of left hemisphere (LH) language areas activated when participants watched an audio-visual narrative in their mother tongue was activated when they observed a signed narrative. The inferior frontal (IFG) and precentral (Prec) gyri, the posterior parts of the planum temporale (pPT) and of the superior temporal sulcus (pSTS), and the occipito-temporal junction (OTJ) were activated by both languages. The activity of these regions was not related to the presence of communicative intent because no such changes were observed when the non-signers watched a muted video of a spoken narrative. Recruitment was also not triggered by the linguistic structure of SL, because the areas, except pPT, were not activated when subjects listened to an unknown spoken language. The comparison of brain reactivity for spoken and sign languages shows that SL has a special status in the brain compared to speech; in contrast to unknown oral language, the neural correlates of SL overlap LH speech comprehension areas in non-signers. These results support the idea that strong relationships exist between areas involved in human action observation and language, suggesting that the observation of hand gestures have shaped the lexico-semantic language areas as proposed by the motor theory of speech. As a whole, the present results support the theory of a gestural origin of language.

Functional deficit in the medial prefrontal cortex during a language comprehension task in patients with schizophrenia.

OBJECTIVE: We and others have observed that patients with schizophrenia commonly presented a reduced left recruitment in language semantic brain regions. However, most studies include patients with leftward and rightward lateralizations for language. We investigated whether a cohort comprised purely of patients with typical lateralization (leftward) presented a reduced left recruitment in semantic regions during a language comprehension task. The goal was to reduce the inter-subject variability and thus improve the resolution for studying functional abnormalities in the language network. METHODS: Twenty-three patients with schizophrenia (DSM-IV) were matched with healthy subjects in age, sex, level of education and handedness. All patients exhibited leftward lateralization for language. Functional MRI was performed as subjects listened to a story comprising characters and social interactions. Functional MRI signal variations were analyzed individually and compared among groups. RESULTS: Although no differences were observed in the recruitment of the semantic language network, patients with schizophrenia presented significantly lower signal variations compared to controls in the medial part of the left superior frontal gyrus (MF1) (x=-6, y=58, z=20; Z(score)=5.6; p<0.001 uncorrected). This region corresponded to the Theory of Mind (ToM) network. Only 5 of the 23 patients (21.7%) and 21 of the 23 (91.3%) control subjects demonstrated a positive signal variation in this area. CONCLUSIONS: A left functional deficit was observed in a core region of the ToM network in patients with schizophrenia and typical lateralizations for language. This functional defect could represent a neural basis for impaired social interaction and communication in patients with schizophrenia.

FMRI study of emotional speech comprehension.

Little is known about the neural correlates of affective prosody in the context of affective semantic discourse. We used functional magnetic resonance imaging to investigate this issue while subjects performed 1) affective classification of sentences having an affective semantic content and 2) grammatical classification of sentences with neutral semantic content. Sentences of each type were produced half by actors and half by a text-to-speech software lacking affective prosody. Compared with neutral sentences processing, sentences with affective semantic content--with or without affective prosody--led to an increase in activation of a left inferior frontal area involved in the retrieval of semantic knowledge. In addition, the posterior part of the left superior temporal sulcus (STS) together with the medial prefrontal cortex were recruited, although not activated by neutral sentences classification. Interestingly, these areas have been described as implicated during self-reflection or other's mental state inference that possibly occurred during the affective classification task. When affective prosody was present, additional rightward activations of the human-selective voice area and the posterior part of STS were observed, corresponding to the processing of speaker's voice emotional content. Accurate affective communication, central to social interactions, requires the cooperation of semantics, affective prosody, and mind-reading neural networks.