Shaving diffusion tensor images in discriminant analysis: a study into schizophrenia.

A technique called 'shaving' is introduced to automatically extract the combination of relevant image regions in a comparative study. No hypothesis is needed, as in conventional pre-defined or expert selected region of interest (ROI)-analysis. In contrast to traditional voxel based analysis (VBA), correlations within the data can be modeled using principal component analysis (PCA) and linear discriminant analysis (LDA). A study into schizophrenia using diffusion tensor imaging (DTI) serves as an application. Conventional VBA found a decreased fractional anisotropy (FA) in a part of the genu of the corpus callosum and an increased FA in larger parts of white matter. The proposed method reproduced the decrease in FA in the corpus callosum and found an increase in the posterior limb of the internal capsule and uncinate fasciculus. A correlation between the decrease in the corpus callosum and the increase in the uncinate fasciculus was demonstrated.

[Residual neuropsychological, structural and functional brain abnormalities after long-term cannabis use]. / Blijvende neuropsychologische stoornissen en structurele en functionele hersenafwijkingen na langdurig cannabisgebruik.

BACKGROUND: An important question that arises in policy discussions concerning the use of cannabis is whether the possible harmful effects of cannabis are reversible. AIM: To review studies on residual neuropsychological, structural and functional brain abnormalities that may have resulted from the long-term use of cannabis. METHOD: When we searched Medline (January 1966 - December 2003) and EMBASE (January 1988 - December 2003) using the key words 'cannabis', 'marijuana', 'neuropsychological test', 'cognition', 'CT-scan', 'MRI', 'PET', 'SPECT' and 'brain', we found 29 studies in our area of interest. We selected only those neuropsychological and functional brain imaging studies in which the patients had a controlled abstinence period longer than 98 hours. RESULTS: On the basis of six studies we concluded that there was insufficient evidence to prove conclusively that long-term cannabis use causes or does not cause residual abnormalities. The results of our review were also inconclusive whether cannabis use during adolescence may have a lasting effect on cognitive functioning and brain structure. However, we could not rule out the possibility that (1) certain cognitive and cerebral abnormalities existed in patients before cannabis use began and (2) that patients were suffering from subacute effects of cannabis. CONCLUSION: So far, research into the residual effects of cannabis use has been inadequate. Future studies should concentrate on the effect of cannabis use during early adolescence. More insight should come from longitudinal studies involving neuropsychological measurements and brain imaging before cannabis use begins. The abstinence period should be at least seven weeks.

The relationship between temperament and character and psychotic-like experiences in healthy children and adolescents.

BACKGROUND: Prior work by our group identified personality profiles associated with psychotic-like experiences (PLE's) in healthy adults that were strikingly similar to those found in schizophrenia patients, with the exception of two key differences. Specifically, higher levels of PLE's were linked to higher persistence and cooperativeness, suggesting that these characteristics might represent personality-based resilience factors. Notably, age and personality were significantly correlated in these data, raising questions about whether healthy children and adolescents would show similar results. To date, no study has examined personality profiles associated with both positive and negative PLE's in healthy children and adolescents using Cloninger's Temperament and Character Inventory (TCI). Thus, this study examined the relationship between TCI dimensions and PLE's in healthy children and adolescents. METHOD: The TCI and the Community Assessment of Psychic Experiences (CAPE) were administered to 123 healthy children and adolescents aged 8-18. Multiple regression models were used to examine personality dimensions associated with overall severity of PLE's as well as severity of positive and negative PLE's separately. RESULTS: Positive, negative, and overall PLE severity were all associated with a personality pattern of higher harm avoidance and lower self-directedness. Negative PLE severity was also associated with lower persistence. CONCLUSIONS: Personality correlates of PLE's in healthy children and adolescents were largely consistent with our past work on PLE's in healthy adults. However, our previously identified resilience factors were notably absent in this sample. These findings may suggest that these personality characteristics have not yet crystallized or emerged to aid in coping with PLE's.

Pulmonary tuberculosis in the elderly. Report of a case discovered at death.

Tuberculosis in the elderly takes on new significance. The case of an 87-year-old female nursing home resident is presented. She was admitted to the hospital with atypical pulmonary manifestations and right pleural effusion. Tuberculin skin tests were negative. The patient deteriorated and died. Disease due to Mycobacteria tuberculosis was discovered by culture after death.The prevalence of tuberculosis in the aged is increasing as the population ages. In the long-term-care setting, residents infected early in life outlive their tubercle bacilli. They are at risk of being infected again.Continuous clinical awareness in the geriatric segment of the population is essential if tuberculosis control is to be achieved. Tuberculin skin testing is important, with chemoprophylaxis for converters, and treatment for active disease.

A schizophrenia risk gene, ZNF804A, is associated with brain white matter microstructure.

Genome-wide association studies have provided strong evidence for association of the SNP rs1344706 in the ZNF804A gene with schizophrenia and bipolar disorder. Neuroimaging studies have suggested that variation at rs1344706 may be associated with neural endophenotypes such as white matter volumes and densities. However, analyses of white matter microstructure using diffusion tensor imaging (DTI) have produced conflicting results. We examined the association between rs1344706 and white matter microstructure in 107 healthy individuals using tract-based spatial statistics (TBSS). TBSS analysis showed significant association between the risk allele and lower fractional anisotropy in the corpus callosum, left forceps minor, and right parietal white matter (p<.05; FWE corrected). Post-hoc analyses indicated that this association was largely driven by alterations in radial diffusivity, consistent with an effect of genotype on myelination. In light of the strong DTI evidence for white matter microstructural abnormalities in schizophrenia, the current results implicate a potential mechanism for schizophrenia risk formation by ZNF804A rs1344706 genotype.

Polyunsaturated fatty acids and brain white matter anisotropy in recent-onset schizophrenia: a preliminary study.

Brain white matter myelin abnormalities and cell membrane fatty acid abnormalities have been implicated in schizophrenia and other psychiatric disorders. We investigated in young adults with a psychotic disorder (n=12) whether (poly)unsaturated fatty acid concentrations in erythrocyte membranes are related to an MRI measure of brain white matter, which depends on the degree of myelination. A significant correlation was found between total (poly)unsaturated fatty acid concentration and fractional anisotropy of a fronto-temporal white matter tract (r=0.503, P=0.048). Unsaturated fatty acids may be necessary for the myelinating activity of oligodendrocytes or for myelin maintenance. These results warrant further investigation.