This paper describes a new method for detecting structural brain differences based on the analysis of deformation fields. Deformations are obtained by an intensity-based nonlinear registration routine that transforms one brain onto another one. We present a general multivariate statistical approach to analyze deformation fields in different subjects. This method was applied to the brains of 85 schizophrenic patients and 75 healthy volunteers to examine whether low frequency deformations are sufficiently sensitive to detect regional deviations in the brains of both groups. We observed significant changes caused by volume reduction in brains of schizophrenics bilaterally in the thalamus and in the superior temporal gyrus. On the left side, the superior frontal gyrus and precentral gyrus are found to be changed, while on the right side, the middle frontal gyrus was altered. In addition, there were significant changes in the occipital lobe (left lingual gyrus) and in the left cerebellum. Volume enlargement in brains of schizophrenics was observed in the right putamen and in the adjacent white matter of the thalamic region. Our data suggest a disturbance in the nodes of a prefrontal-thalamic-cerebellar circuitry. This provides further support for the model of ''cognitive dysmetria,'' which postulates a disruption in these nodes. We have demonstrated the application of deformation-based morphometry by detecting structural changes in the whole brain. This technique is fully automatic, thus allowing for the inclusion of large samples, with no user bias or a priori-defined regions of interest.
Academic Press
Most research with 31P-magnetic resonance spectroscopy (31P-MRS) in affective disorders has been done in the field of bipolar disturbances. Reduced frontal and temporal lobe phosphomonoester (PME) concentrations were measured in the euthymic state, whereas increased values were found in the depressed state. In bipolar-II patients reduced phosphocreatine (PCr) concentrations were reported in the euthymic, depressed, and manic state. The aim of the present study was to explore whether PME and PCr were also altered in the frontal lobe of major depressed, unipolar patients. Therefore, we used 31P-MRS to investigate the relative phospholipid and high-energy phosphate concentrations in the frontal lobe of 14 unipolar patients, mostly medicated, and 8 age-matched controls. We found increased PME and decreased ATP values. Other 31P-MRS parameters were not different in both groups. Phosphomonoester percentages correlated negatively with the degree of depression. Thus, the main alterations found in bipolar depressed patients could also be demonstrated in unipolar depressed patients. The results are discussed with regard to disturbed phospholipid and intracellular high-energy phosphate metabolism in depressed patients.
We report the first experimental observation of terahertz (THz) radiation from the rear surface of a solid target while interacting with an intense laser pulse. Experimental and two-dimensional particle-in-cell simulations show that the observed THz radiation is mostly emitted at large angles to the target normal. Numerical results point out that a large part of the emission originates from a micron-scale plasma sheath at the rear surface of the target, which is also responsible for the ion acceleration. This opens a perspective for the application of THz radiation detection for on-site diagnostics of particle acceleration in laser-produced plasmas.
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