Linguistic and neurocognitive correlates of probabilistic classification learning in schizophrenia.

Individuals with schizophrenia demonstrate impaired implicit learning on cognitively complex tasks and preserved implicit motor learning. However, little is known about how implicit learning may be related to other linguistic and cognitive variables, including development of complex language including comprehension and syntax. This study explored the relationship between probabilistic classification learning, a type of implicit learning style, and linguistic and cognitive skills in schizophrenia. This was done by examining how schizophrenia patients perform on the Weather Prediction Task (WPT) relative to controls, particularly during a dual-task interference condition that assesses task automaticity. Individuals with schizophrenia (N = 34) demonstrated depressed cognitive functioning relative to the controls (N = 18) across nearly all cognitive functions. On the Weather Prediction Task, the schizophrenia group performed less accurately than the control group in later blocks and had a relatively flat learning curve. A significant Group X Block effect when controlling for age and sex suggested differential learning throughout the task. A subgroup of patients did not develop automaticity during the repeated blocks of trials. For those patients who did not develop automaticity over the course of the WPT, linguistic and cognitive skills were strongly correlated with their Block 1 performance. For patients who developed automaticity, overall neurocognitive ability was correlated with their ultimate level of performance on the WPT but not with their Block 1 performance. That language was related to differential learning emphasizes the role of explicit, verbal processes on making initial rapid improvement on the WPT.

Temporal lobe thickness and verbal memory in first-degree relatives of individuals with schizophrenia.

Cortical thinning in frontal and temporal regions has been reported in individuals diagnosed with schizophrenia and, less consistently, among their unaffected first-degree relatives. Likewise, first-degree relatives demonstrate attenuated differences in neurocognitive performance relative to healthy controls, indicating that neurocognitive performance may be an important endophenotype of the disorder. Less is known about how cortical thickness relates to neurocognitive performance in these individuals. Given the robust nature of temporal structural abnormalities in schizophrenia, this study aimed to identify how temporal lobe cortical thickness might relate to verbal memory in first-degree relatives. Unaffected parents and siblings of individuals with adult-onset schizophrenia (N=62) and individuals in healthy control families (N=70) participating in the UCLA Family Study received a structural MRI and completed a battery of neurocognitive tests. Cortical thickness was estimated across the cortex and thickness measures of all regions in the temporal lobe were summed, averaged, and residualized for age and sex to produce a variable. A verbal learning factor was derived from two common tests of verbal learning and memory, the CVLT-II and Logical Memory of the WMS-III. Results demonstrated a significant interaction between group and verbal learning in relationship to temporal lobe thickness. Post-hoc analyses revealed significant correlations between verbal learning and cortical thickness in the relatives of schizophrenia patients which were driven by immediate recall scores on the CVLT-II and Logical Memory. These findings indicate that cortical thickness in the temporal cortex may represent a structural correlate for encoding verbal information in unaffected relatives of individuals with schizophrenia.

White matter integrity of cerebellar-cortical tracts in reading impaired children: A probabilistic tractography study.

Little is known about the white matter integrity of cerebellar-cortical pathways in individuals with dyslexia. Building on previous findings of decreased volume in the anterior lobe of the cerebellum, we utilized novel cerebellar segmentation procedures and probabilistic tractography to examine tracts that connect the anterior lobe of the cerebellum and cortical regions typically associated with reading: the temporoparietal (TP), occipitotemporal (OT), and inferior frontal (IF) regions. The sample included 29 reading impaired children and 27 typical readers. We found greater fractional anisotropy (FA) for the poor readers in tracts connecting the cerebellum with TP and IF regions relative to typical readers. In the OT region, FA was greater for the older poor readers, but smaller for the younger ones. This study provides evidence for discrete, regionally-bound functions of the cerebellum and suggests that projections from the anterior cerebellum appear to have a regulatory effect on cortical pathways important for reading.

Volumetric analysis of regional variability in the cerebellum of children with dyslexia.

Cerebellar deficits and subsequent impairment in procedural learning may contribute to both motor difficulties and reading impairment in dyslexia. We used quantitative magnetic resonance imaging to investigate the role of regional variation in cerebellar anatomy in children with single-word decoding impairments (N = 23), children with impairment in fluency alone (N = 8), and typically developing children (N = 16). Children with decoding impairments (dyslexia) demonstrated no statistically significant differences in overall grey and white matter volumes or cerebellar asymmetry; however, reduced volume in the anterior lobe of the cerebellum relative to typically developing children was observed. These results implicate cerebellar involvement in dyslexia and establish an important foundation for future research on the connectivity of the cerebellum and cortical regions typically associated with reading impairment.