Abnormal asymmetries in subcortical brain volume in schizophrenia.

Subcortical structures, which include the basal ganglia and parts of the limbic system, have key roles in learning, motor control and emotion, but also contribute to higher-order executive functions. Prior studies have reported volumetric alterations in subcortical regions in schizophrenia. Reported results have sometimes been heterogeneous, and few large-scale investigations have been conducted. Moreover, few large-scale studies have assessed asymmetries of subcortical volumes in schizophrenia. Here, as a work completely independent of a study performed by the ENIGMA consortium, we conducted a large-scale multisite study of subcortical volumetric differences between patients with schizophrenia and controls. We also explored the laterality of subcortical regions to identify characteristic similarities and differences between them. T1-weighted images from 1680 healthy individuals and 884 patients with schizophrenia, obtained with 15 imaging protocols at 11 sites, were processed with FreeSurfer. Group differences were calculated for each protocol and meta-analyzed. Compared with controls, patients with schizophrenia demonstrated smaller bilateral hippocampus, amygdala, thalamus and accumbens volumes as well as intracranial volume, but larger bilateral caudate, putamen, pallidum and lateral ventricle volumes. We replicated the rank order of effect sizes for subcortical volumetric changes in schizophrenia reported by the ENIGMA consortium. Further, we revealed leftward asymmetry for thalamus, lateral ventricle, caudate and putamen volumes, and rightward asymmetry for amygdala and hippocampal volumes in both controls and patients with schizophrenia. Also, we demonstrated a schizophrenia-specific leftward asymmetry for pallidum volume. These findings suggest the possibility of aberrant laterality in neural pathways and connectivity patterns related to the pallidum in schizophrenia.

MRI white matter hyperintensities, (1)H-MR spectroscopy and cognitive function in geriatric depression: a comparison of early- and late-onset cases.

UNLABELLED: BACKGROUND AND OBJECTIVES Geriatric depression is often thought to differ from that at other times of adulthood. Recently, several studies have shown that the incidence of white matter hyperintense lesions identified by brain MRI is higher in patients with geriatric depression than in healthy elderly subjects, but a consensus has not yet been reached on the relationship between the severity of white matter lesions and either cognitive impairment or depressive symptoms. METHOD: Forty-seven patients aged 50 to 75 years with major depression were divided into two groups based on age at onset of depression: early-onset (< 50 years) group (20 patients; mean age, 62.7 +/- 6.7) and late-onset (> or =50 years) group (27 patients; mean age, 65.6 +/- 5.4). The severity of hyperintense white matter lesions on MRI was classified by region, then a proton magnetic resonance spectroscopy ((1)H-MRS) focusing on the white matter of the frontal lobes, multidimensional neuropsychological tests and evaluation of depressive symptoms were conducted. RESULTS: The severity of the deep white matter lesions, the deterioration of cognitive function related to subcortical/frontal brain system and clinician-rated depressive symptoms were all more pronounced in the late-onset group compared with those in the early-onset group. It was further observed that the more severe the deep white matter lesions, the lower the levels of N-acetylaspartate/creatine. With the age of onset as the covariate, the patients with moderate deep white matter lesions had more pronounced cognitive impairment and clinician-rated depressive symptoms than those with none and/or mild lesions. CONCLUSION: These results suggest that subcortical/frontal type cognitive impairment and the persistence of depressive symptoms in geriatric depression is related to moderate deep white matter lesions more often complicated in the late-onset group. The (1)H-MRS findings were suggested to be a useful indicator of neuronal/axonal loss in the white matter of the frontal lobes which precedes cognitive impairment.

The effect of divided attention on encoding and retrieval in episodic memory revealed by positron emission tomography.

The effects of divided attention (DA) on episodic memory encoding and retrieval were investigated in 12 normal young subjects by positron emission tomography (PET). Cerebral blood flow was measured while subjects were concurrently performing a memory task (encoding and retrieval of visually presented word pairs) and an auditory tone-discrimination task. The PET data were analyzed using multivariate Partial Least Squares (PLS), and the results revealed three sets of neural correlates related to specific task contrasts. Brain activity, relatively greater under conditions of full attention (FA) than DA, was identified in the occipital-temporal, medial, and ventral-frontal areas, whereas areas showing relatively more activity under DA than FA were found in the cerebellum, temporo-parietal, left anterior-cingulate gyrus, and bilateral dorsolateral-prefrontal areas. Regions more active during encoding than during retrieval were located in the hippocampus, temporal and the prefrontal cortex of the left hemisphere, and regions more active during retrieval than during encoding included areas in the medial and right-prefrontal cortex, basal ganglia, thalamus, and cuneus. DA at encoding was associated with specific decreases in rCBF in the left-prefrontal areas, whereas DA at retrieval was associated with decreased rCBF in a relatively small region in the right-prefrontal cortex. These different patterns of activity are related to the behavioral results, which showed a substantial decrease in memory performance when the DA task was performed at encoding, but no change in memory levels when the DA task was performed at retrieval.