[show abstract][hide abstract] ABSTRACT: Individuals with autism spectrum disorder (ASD) often fail to attach context to their memories and are specifically impaired in processing social aspects of contextual information. The aim of the present study was to investigate the modulatory influence of social vs. non-social context on neural mechanisms during encoding in ASD. Using event-related fMRI, 13 boys with ASD and 13 typically developing boys comparable for age and IQ were investigated during encoding of neutral objects presented either with a social (faces) or a non-social (houses) context. A memory paradigm was then applied to identify brain activation patterns associated with encoding of subsequently recollected versus non-recollected objects. On the behavioural level, no significant between-group differences emerged. In particular, no differential effects of context on memory performance were observed. Neurally, however, context-specific group differences were observed in several brain regions. During encoding of subsequently recollected objects presented with a face, ASD subjects (compared to controls) showed reduced neural activation in the bilateral inferior frontal gyrus, bilateral middle frontal gyrus and right inferior parietal lobule. Neural activation in the right inferior frontal gyrus was positively correlated with memory performance in controls, but negatively in ASD individuals. During encoding of subsequently non-recollected objects presented in the non-social context, ASD subjects showed increased activation in the dorsal MPFC. Our findings suggest that in ASD subjects, fronto-parietal brain regions subserving memory formation and the association of contextual information are activated atypically when a social context is presented at encoding. The data add to findings from related research fields indicating that in ASD, socioemotional impairment extends into domains beyond social cognition. Increased activation in the dorsal MPFC in ASD individuals might reflect supervisory cognitive processes related to the suppression of a distracting non-social context.
[show abstract][hide abstract] ABSTRACT: Results on grey matter (GM) structural alterations in autism spectrum disorder (ASD) are inconclusive. Moreover, little is known about age effects on brain-structure abnormalities in ASD beyond childhood. Here, we aimed to examine regional GM volumes in a large sample of children, adolescents, and adults with ASD. Magnetic resonance imaging scans were obtained in 47 male ASD subjects and 51 matched healthy controls aged 8-50 years. We used whole-brain voxel-based morphometry to first assess group differences in regional GM volume across age. Moreover, taking a cross-sectional approach, group differences in age effects on regional GM volume were investigated. Compared to controls, ASD subjects showed reduced GM volumes in the anterior cingulate cortex, posterior superior temporal sulcus, and middle temporal gyrus. Investigation of group differences in age effects on regional GM volume revealed complex, region-specific alterations in ASD. While GM volumes in the amygdala, temporoparietal junction, septal nucleus and middle cingulate cortex increased in a negative quadratic fashion in both groups, data indicated that GM volume curves in ASD subjects were shifted to the left along the age axis. Moreover, while GM volume in the right precentral gyrus decreased linearly with age in ASD individuals, GM volume development in controls followed a U-shaped pattern. Based on a large sample, our voxel-based morphometry results on group differences in regional GM volumes help to resolve inconclusive findings from previous studies in ASD. Results on age-related changes of regional GM volumes suggest that ASD is characterized by complex alterations in lifetime trajectories of several brain regions that underpin social-cognitive and motor functions.
Brain Structure and Function 07/2012; · 7.84 Impact Factor
[show abstract][hide abstract] ABSTRACT: Although it has been suggested that social deficits of autism spectrum disorders (ASDs) are related to reward circuitry dysfunction, very little is known about the neural reward mechanisms in ASD. In the current functional magnetic resonance imaging study, we investigated brain activations in response to both social and monetary reward in a group of children with ASD, relative to matched controls. Participants with ASD showed the expected hypoactivation in the mesocorticolimbic circuitry in response to both reward types. In particular, diminished activation in the nucleus accumbens was observed when money, but not when social reward, was at stake, whereas the amygdala and anterior cingulate cortex were hypoactivated within the ASD group in response to both rewards. These data indicate that the reward circuitry is compromised in ASD in social as well as in non-social, i.e. monetary conditions, which likely contributes to atypical motivated behaviour. Taken together, with incentives used in this study sample, there is evidence for a general reward dysfunction in ASD. However, more ecologically valid social reward paradigms are needed to fully understand, whether there is any domain specificity to the reward deficit that appears evident in ASD, which would be most consistent with the ASD social phenotype.
Social Cognitive and Affective Neuroscience 03/2012; · 5.04 Impact Factor
[show abstract][hide abstract] ABSTRACT: Morphological abnormalities of the hippocampus might form the neurobiological basis of memory dysfunction in schizophrenia. Hippocampal volume was found to be bilaterally reduced in male, but not in female, subjects with schizophrenia. Right hippocampal volume was significantly related to impaired visual learning.
Journal of Neuropsychiatry 02/2008; 20(2):227-30. · 2.40 Impact Factor
[show abstract][hide abstract] ABSTRACT: In der vorliegenden Arbeit werden strukturell- morphologische Auffälligkeiten bestimmter Hirnregionen (Gesamthirn, Kleinhirn, Hippocampus, Supplementär- Motorisches Kortexareal) schizophrener Patienten mittels MRT- Morphometrie untersucht und mit denen gesunder Personen verglichen. Im zweiten Teil dieser Arbeit werden kognitive Defizite (Intelligenz, Gedächtnis, Aufmerksamkeit) bei der Schizophrenie dargestellt und deren Zusammenhang mit strukturellen Abweichungen überprüft. Es fand sich eine beidseitige Volumenminderung des Hippocampus sowie Gedächtnisdefizite in der Gruppe der Männer mit Schizophrenie. Eine Minderung der Intelligenz- und Aufmerksamkeitsleistung wurde sowohl bei schizophrenen Männern als auch Frauen beobachtet. Das rechte Hippocampusvolumen korrelierte positiv mit der visuellen Gedächtnisleistung und visuell- konstruktiver Intelligenz. Mögliche Ursachen eines geschlechtlichen Dimorphismus bei der Schizophrenie werden in dieser Arbeit diskutiert. We investigated morphometric changes in schizophrenic brains (total brain volume, cerebellum, hippocampus, SMA) with a ROI- analysis of structural MRI images. Also, we looked at cognitive deficits in the schizophrenic group (intelligence, memory, attention) and their correlation with structural abnormalities. We found a bilateral volume reduction of the hippocampus and memory deficits only in schizophrenic men. Impairments in the intelligence and attention domain were found for both male and female schizophrenic patients. Further, we found positive correlations of the volume of right hippocampus with visual memory and visual- constructive intelligence. Theories of a sexual dimorphism in schizophrenia are discussed in this study.