Mes: junio 2015

BACKGROUND: The dimensional approach to autism spectrum disorder (ASD) considers ASD as the extreme of a dimension traversing through the entire population. We explored the potential utility of electroencephalography (EEG) functional connectivity as a biomarker. We hypothesized that individual differences in autistic traits of typical subjects would involve a long-range connectivity diminution within the delta band. METHODS: Resting-state EEG functional connectivity was measured for 74 neurotypical subjects. All participants also provided a questionnaire (Social Responsiveness Scale, SRS) that was completed by an informant who knows the participant in social settings. We conducted multivariate regression between the SRS score and functional connectivity in all EEG frequency bands. We explored modulations of network graph metrics characterizing the optimality of a network using the SRS score. RESULTS: Our results show a decay in functional connectivity mainly within the delta and theta bands (the lower part of the EEG spectrum) associated with an increasing number of autistic traits. When inspecting the impact of autistic traits on the global organization of the functional network, we found that the optimal properties of the network are inversely related to the number of autistic traits, suggesting that the autistic dimension, throughout the entire population, modulates the efficiency of functional brain networks. CONCLUSIONS: EEG functional connectivity at low frequencies and its associated network properties may be associated with some autistic traits in the general population.

La cognición social es dependiente de la información sutil e implícita presente en el contexto durante interacciones sociales. Presentamos y describimos un modelo anatomofuncional, denominado SCNM (del inglés Social Context Network Model), que pretende explicar cómo se procesa el contexto en situaciones sociales. Además, muestra cómo diferentes alteraciones de sus redes subyacen a los déficits en cognición social de pacientes con demencia frontotemporal, lesiones fronto-insulares, enfermedades del neurodesarrollo y otros cuadros neuropsiquiátricos. Se presentan estudios precursores basados en el SCNM y se los contrapone al enfoque descontextualizado de abordajes clásicos en cognición social. El SCNM es un modelo teórico que provee un conjunto de hipótesis que permiten examinar y comprender mejor los procesos subyacentes a los déficits en cognición social. A nivel clínico, propone el desarrollo de herramientas más ecológicas que las tradicionales que permitirían una mejor detección y caracterización de distintas enfermedades neurológicas y psiquiátricas, como así también la implementación de ambientes en rehabilitación que imiten mejor las situaciones de la vida cotidiana

It is commonly assumed thatearly emotional signals provide relevant informationfor social cognition tasks. The goal of this study was to test the association between (a) cortical markers of face emotional processing and (b) social-cognitive measures,and also to build a model which can predictthis association (a & b) in healthy volunteers as well as in different groups of psychiatric patients. Thus, we investigated the early cortical processing of emotional stimuli (N170, using a face and word valence task) and their relationship with the social-cognitive profiles (SCPs, indexed by measures of theory of mind, fluid intelligence, speed processing, and executive functions). Group comparisons and individual differences were assessed among schizophrenia (SCZ) patients and their relatives, individuals with attention deficit hyperactivity disorder (ADHD), individuals with euthymic bipolar disorder (BD) and healthy participants (educational level, handedness, age and gendermatched). Our results provide evidence of emotional N170 impairments in the affected groups (SCZ and relatives, ADHD and BD) as well as subtle group differences. Importantly, cortical processing of emotional stimuli predicted the social cognition profile (SCP), as evidenced by a structural equation model (SEM) analysis. This is the first study to report anassociation model of brain markers of emotional processing and SCP.

Is it permissible to harm one to save many? Classic moral dilemmas are often defined by the conflict between a putatively rational response to maximize aggregate welfare (i.e., the utilitarian judgment) and an emotional aversion to harm (i.e., the non-utilitarian judgment). Here, we address two questions. First, what specific aspect of emotional responding is relevant for these judgments? Second, is this aspect of emotional responding selectively reduced in utilitarians or enhanced in non-utilitarians? The results reveal a key relationship between moral judgment and empathic concern in particular (i.e., feelings of warmth and compassion in response to someone in distress). Utilitarian participants showed significantly reduced empathic concern on an independent empathy measure. These findings therefore reveal diminished empathic concern in utilitarian moral judges.

Individual differences in theory of mind (ToM) are affected by a variety of factors. We investigated the relationship between empathy, sex and fluid intelligence (FI) as predictors of ToM in a random probabilistic sample of secondary students. First, we explored whether sex, as well as high, average or low levels of empathy and FI affect ToM performance. Furthermore, we assessed the contribution of empathy, sex and FI in predicting ToM by using a path analysis. This method allows testing of causal models of directed dependencies among a set of variables. The causal dependencies of empathy, sex and fluid intelligence were confirmed and identified. In addition, the model confirmed the direct effect of empathy, sex and fluid intelligence on ToM; and the indirect effect of sex mediated by empathy. Thus, individual differences in ToM levels are partially attributable to sex, empathy and fluid intelligence variability, raising important considerations for clinical research as well as ToM‟s theoretical models of domain specificity.

Hierarchical predictive coding suggests that attention in humans emerges from increased precision in probabilistic inference, whereas expectation biases attention in favor of contextually anticipated stimuli. We test these notions within auditory perception by independently manipulating top-down expectation and attentional precision alongside bottom-up stimulus predictability. Our findings support an integrative interpretation of commonly observed electrophysiological signatures of neurodynamics, namely mismatch negativity (MMN), P300, and contingent negative variation (CNV), as manifestations along successive levels of predictive complexity. Early first-level processing indexed by the MMN was sensitive to stimulus predictability: here, attentional precision enhanced early responses, but explicit top-down expectation diminished it. This pattern was in contrast to later, second-level processing indexed by the P300: although sensitive to the degree of predictability, responses at this level were contingent on attentional engagement and in fact sharpened by top-down expectation. At the highest level, the drift of the CNV was a fine-grained marker of top-down expectation itself. Source reconstruction of high-density EEG, supported by intracranial recordings, implicated temporal and frontal regions differentially active at early and late levels. The cortical generators of the CNV suggested that it might be involved in facilitating the consolidation of context-salient stimuli into conscious perception. These results provide convergent empirical support to promising recent accounts of attention and expectation in predictive coding.

Executive dysfunction may result from prefrontal circuitry involvement occurring in both neurodegenerative diseases and psychiatric disorders. Moreover, multiple neuropsychiatric conditions, may present with overlapping behavioral and cognitive symptoms, making differential diagnosis challenging, especially during earlier stages. In this sense, cognitive assessment may contribute to the differential diagnosis by providing an objective and quantifiable set of measures that has the potential to distinguish clinical conditions otherwise perceived in everyday clinical settings as quite similar. OBJECTIVE: The goal of this study was to investigate the utility of the INECO Frontal Screening (IFS) for differentiating bv-FTD patients from patients with Major Depression. METHODS: We studied 49 patients with bv-FTD diagnosis and 30 patients diagnosed with unipolar depression compared to a control group of 26 healthy controls using the INECO Frontal Screening (IFS), the Mini Mental State Examination (MMSE) and the Addenbrooke’s Cognitive Examination-Revised (ACE-R). RESULTS: Patient groups differed significantly on the motor inhibitory control (U=437.0, p<0.01), verbal working memory (U=298.0, p<0.001), spatial working memory (U=300.5, p<0.001), proverbs (U=341.5, p<0.001) and verbal inhibitory control (U=316.0, p<0.001) subtests, with bv-FTD patients scoring significantly lower than patients with depression. CONCLUSION: Our results suggest the IFS can be considered a useful tool for detecting executive dysfunction in both depression and bv-FTD patients and, perhaps more importantly, that it has the potential to help differentiate these two conditions.

Even though cerebellar activation has been described during theory of mind (ToM) tasks in neuroimaging studies, no previous studies have investigated ToM in a group of patients with cerebellar strokes. In the present study, we assessed 11 patients with cerebellar infarction on a variety of executive tests and with the Faux Pas test of ToM. Even if cerebellar patients showed significant deficits on executive tasks relative to a control group, no significant differences were found between the groups on the Faux Pas test. This is the first group study to demonstrate that focal cerebellar lesions do not affect ToM.

Converging neuroscientific evidence suggests the existence of close links between language and sensorimotor cognition. Accordingly, during the comprehension of meaningful actions, our brain would recruit semantic-related operations similar to those associated with the processing of language information. Consistent with this view, electrophysiological findings show that the N400 component, traditionally linked to the semantic processing of linguistic material, can also be elicited by action-related material. This review outlines recent data from N400 studies that examine the understanding of action events. We focus on three specific domains, including everyday action comprehension, co-speech gesture integration, and the semantics involved in motor planning and execution. Based on the reviewed findings, we suggest that both negativities (the N400 and the action-N400) reflect a common neurocognitive mechanism involved in the construction of meaning through the expectancies created by previous experiences and current contextual information. To shed light on how this process is instantiated in the brain, a testable contextual fronto-temporo-parietal model is proposed.

Cockayne syndrome (CS) is an autosomal recessive disease associated with premature aging, progressive multiorgan degeneration, and nervous system abnormalities including cerebral and cerebellar atrophy, brain calcifications, and white matter abnormalities. Although several clinical descriptions of CS patients have reported developmental delay and cognitive impairment with relative preservation of social skills, no previous studies have carried out a comprehensive neuropsychological and social cognition assessment. Furthermore, no previous research in individuals with CS has examined the relationship between brain atrophy and performance on neuropsychological and social cognition tests. This study describes the case of an atypical late-onset type III CS patient who exceeds the mean life expectancy of individuals with this pathology. The patient and a group of healthy controls underwent a comprehensive assessment that included multiple neuropsychological and social cognition (emotion recognition, theory of mind, and empathy) tasks. In addition, we compared the pattern of atrophy in the patient to controls and to its concordance with ERCC8 gene expression in a healthy brain. The results showed memory, language, and executive deficits that contrast with the relative preservation of social cognition skills. The cognitive profile of the patient was consistent with his pattern of global cerebral and cerebellar loss of gray matter volume (frontal structures, bilateral cerebellum, basal ganglia, temporal lobe, and occipito-temporal/occipito-parietal regions), which in turn was anatomically consistent with the ERCC8gene expression level in a healthy donor’s brain. The study of exceptional cases, such as the one described here, is fundamental to elucidating the processes that affect the brain in premature aging diseases, and such studies provide an important source of information for understanding the problems associated with normal and pathological aging.