[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.
[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.
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Full-text · Article · Jul 2012 · Brain Structure and Function
[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.
Full-text · Article · Mar 2012 · Social Cognitive and Affective Neuroscience
[Show abstract][Hide abstract] ABSTRACT: Background: According to social motivation deficit theories of autism (e.g., Schultz, 2005), the lack of interest to attend to social stimuli and to seek and enjoy reciprocal social interactions in individuals with ASD might at least partly be attributed to dysfunctions in brain regions implicated in reward processing such as fronto-striatal limbic circuitry.
Objectives: Since we currently have very little understanding of neural reactivity to motivational incentives in ASD, the present study aimed to investigate ERP and fMRI correlates in boys with and without autism while processing social compared to non-social rewards.
Twenty ASD boys and 21 male TDCs, matched for age (mean age 14.4 years), full-scale IQ, and handedness, participated in the study. In both ERP and fMRI sessions, we applied an incentive go/nogo task with social (positive facial expressions), monetary, and non-reward contingencies for successful task performance. FMRI data were collected on a 3T scanner and analyzed with BrainVoyager. High-impedance EEG recordings were obtained from 64 electrodes and processed with BrainVision Analyzer.
Results: On the behavioral level, we found that both social and monetary incentives enhanced performance accuracy and response speed in all participants, with highest improvement under monetary reinforcement, confirming previous findings (Kohls et al., 2009). Contrary to our prediction, children with ASD showed comparable performance benefit and task motivation under social reward conditions as TDCs. By contrast, both imaging methods revealed aberrant brain responses in patients to social and to monetary reinforcers. Concerning ERPs, we found compromised P300 amplitudes to reward-predicting cues in children with ASD, which were most pronounced when social rewards were at stake, and particularly when a timely reaction was required to obtain a reward. Taken the recent locus coeruleus-norepinephrine (LC-NE) P300 theory into account (Nieuwenhuis et al., 2005), the ERP data imply an attenuated state of motivational attention allocation to incentives which trigger active approach behavior in individuals with ASD, - probably mediated by malfunctions in the reward circuitry which intervenes into the LC-NE system to boost the processing of motivational signals against other neutral stimuli. This interpretation is supported by our fMRI data which clearly demonstrate broad hypoactivations in the extended mesocorticolimbic pathway in patients including substantia nigra/VTA, dorsal striatum, and prefrontal cortex/ACC for both social and monetary reinforcement. Moreover, during facial reward processing we could replicate the typical lower brain reactivity in amygdala and fusiform gyrus in children with ASD relative to controls.
Conclusions: In sum, our findings are in line with recent social motivation deficit theories of autism which highlight a hyporesponsivity in the extended reward circuitry particularly to social incentives, what might cause the reduced socially motivated behavior in affected individuals. Noteworthy, our brain data strongly suggest that the processing of non-social incentives (such as money) is compromised, too, which deserves closer attention. Furthermore, the discrepant finding of undisturbed behavioral responses and the aberrant reward circuit responsivity in children with ASD indicate that imaging methods might be better suited to uncover deviant reward functioning in patients with neurodevelopmental disorders than behavioral measures.
[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.
Preview · Article · Feb 2008 · Journal of Neuropsychiatry
[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.