No abstract

Abstract■ During childhood and adolescence, ongoing white matter maturation in the fronto-parietal cortices and connecting fiber tracts is measurable with diffusion-weighted imaging. Important questions remain, however, about the links between these changes and developing cognitive functions. Spatial working memory (SWM) performance improves significantly throughout the childhood years, and several lines of evidence implicate the left fronto-parietal cortices and connecting fiber tracts in SWM processing. Here we report results from a study of 76 typically developing children, 7 to 13 years of age. We hypothesized that better SWM performance would be associated with increased fractional anisotropy (FA) in a left fronto-parietal network composed of the superior longitudinal fasciculus (SLF), the regional white matter underlying the dorsolateral pFC, and the posterior parietal cortex. As hypothesized, we observed a significant association between higher FA in the left fronto-parietal network and better SWM skills, and the effect was independent of age. This association was mainly accounted for by variability in left SLF FA and remained significant when FA measures from global fiber tracts or right SLF were included in the model. Further, the effect of FA in left SLF appeared to be mediated primarily by decreasing perpendicular diffusivity. Such associations could be related to individual differences among children in the architecture of fronto-parietal connections and/or to differences in the pace of fiber tract development. Further studies are needed to determine the contributions of intrinsic and experiential factors to the development of functionally significant individual differences in fiber tract structure. ■

No abstract

Study design: Cross-sectional descriptive analysis of magnetic resonance imaging (MRI) and clinical outcome. Objectives: The aim of this study was to present anatomically consistent and independent spinal cord atrophy measures based on standard MRI material and analyze their specific relations to sensory and motor outcome in individuals with chronic incomplete spinal cord injury (SCI). Setting: Danish study on human SCI. Methods: We included 19 individuals with chronic incomplete SCI and 16 healthy controls. Participants underwent MRI and a neurological examination including sensory testing for light touch and pinprick, and muscle strength. Antero-posterior width (APW), left-right width (LRW) and crosssectional spinal cord area (SCA) were extracted from MRI at the spinal level of C2. The angular variation of the spinal cord radius over the full circle was also extracted and compared with the clinical scores. Results: The motor score was correlated to LRW and the sensory scores were correlated to APW. The scores correlated also well with decreases in spinal cord radius in oblique angles in coherent and non-overlapping sectors for the sensory and motor qualities respectively. Conclusion: APW and LRW can be used to assess sensory and motor function independently. The finding is corresponding well with the respective locations of the main sensory and motor pathways.

Optic neuritis (ON) is the first clinical manifestation in approximately 20% of patients with multiple sclerosis (MS). The inflammation and demyelination of the optic nerve are characterized by symptomatic visual impairment and retrobulbar pain, and associated with decreased visual acuity, decreased colour and contrast sensitivity, delayed visual evoked potentials and visual field defects. Spontaneous recovery of vision typically occurs within weeks or months after onset, depending on the resolution of inflammation, remyelination, restoration of conduction in axons which persist demyelinated and neuronal plasticity in the cortical and subcortical visual pathways. To assess where recovery takes place along the visual pathway, visual activation was studied in the lateral geniculate nucleus (LGN), the main thalamic relay nucleus in the visual pathway and in three areas of the visual cortex: the lateral occipital complexes (LOC), V1 and V2. We conducted a longitudinal functional magnetic resonance imaging (fMRI) study of regions of interest (ROI) of activation in LGN and visual cortex in 19 patients with acute ON at onset, 3 and 6 months from presentation. With fMRI we measured the activation in the ROIs and compared activation during monocular stimulation of the affected and unaffected eye. In the acute phase the activation of LGN during visual stimulation of the affected eye was significantly reduced (P < 0.01) compared to the unaffected eye. This difference in LGN activation between the affected and unaffected eye diminished during recovery, and after 180 days the difference was no longer significant (P = 0.59). The decreased difference during recovery was mainly due to an increase in the fMRI signal when stimulating the affected eye, but included a component of a decreasing fMRI signal from LGN when stimulating the unaffected eye. In LOC, V1 and V2 activation during visual stimulation of the affected eye in the acute phase was significantly reduced (P < 0.01) compared to the unaffected eye, and during recovery the difference diminished with no significant differences left after 180 days. As the pattern of activation in LOC, V1 and V2 resembled the development in LGN we found no evidence of additional cortical adaptive changes. The reduced activation of the LGN to stimulation of the unaffected eye is interpreted as a shift away from early compensatory changes established in the acute phase in LGN and may indicate very early plasticity of the visual pathways.

EPO-associated memory improvement in TRD and BD may be mediated by reversal of brain matter loss in a subfield of the left hippocampus. EPO may provide a therapeutic option for patients with mood disorders who have impaired neuroplasticity and cognition.

a b s t r a c tCognitive control of thoughts, actions and emotions is important for normal behaviour and the development of such control continues throughout childhood and adolescence. Several lines of evidence suggest that response inhibition is primarily mediated by a right-lateralized network involving inferior frontal gyrus (IFG), presupplementary motor cortex (preSMA), and subthalamic nucleus. Though the brain's fibre tracts are known to develop during childhood, little is known about how fibre tract development within this network relates to developing behavioural control. Here we examined the relationship between response inhibition, as measured with the stop-signal task, and indices of regional white matter microstructure in typically-developing children. We hypothesized that better response inhibition performance would be associated with higher fractional anisotropy (FA) in fibre tracts within right IFG and preSMA after controlling for age. Mean FA and diffusivity values were extracted from right and left IFG and preSMA. As hypothesized, faster response inhibition was significantly associated with higher FA and lower perpendicular diffusivity in both the right IFG and the right preSMA, possibly reflecting faster speed of neural conduction within more densely packed or better myelinated fibre tracts. Moreover, both of these effects remained significant after controlling for age and whole brain estimates of these DTI parameters. Interestingly, right IFG and preSMA FA contributed additively to the prediction of performance variability. Observed associations may be related to variation in phase of maturation, to activity-dependent alterations in the network subserving response inhibition, or to stable individual differences in underlying neural system connectivity.

95Background: Enlarged ventricles and reduced hippocampal volume are consistently found in patients with first-episode schizophrenia. Studies investigating brain structure in antipsychotic-naive patients have generally focused on the striatum. In this study, we examined whether ventricular enlargement and hippocampal and caudate volume reductions are morphological traits of antipsychotic-naive firstepisode schizophrenia. Methods: We obtained high-resolution 3-dimensional T 1 -weighted magnetic resonance imaging scans for 38 antipsychotic-naive first-episode schizophrenia patients and 43 matched healthy controls by use of a 3-T scanner. We warped the brain images to each other by use of a high-dimensional intersubject registration algorithm. We performed voxel-wise group comparisons with permutation tests. We performed small volume correction for the hippocampus, caudate and ventricles by use of a false discovery rate correction (p < 0.05) to control for multiple comparisons. We derived and analyzed estimates of brain structure volumes. We grouped patients as those with (n = 9) or without (n = 29) any lifetime substance abuse to examine the possible effects of substance abuse. Results: We found that hippocampal and caudate volumes were decreased in patients with first-episode schizophrenia. We found no ventricular enlargement, differences in global volume or significant associations between tissue volume and duration of untreated illness or psychopathology. The hippocampal volume reductions appeared to be influenced by a history of substance abuse. Exploratory analyses indicated reduced volume of the nucleus accumbens in patients with first-episode schizophrenia. Limitations: This study was not a priori designed to test for differences between schizophrenia patients with or without lifetime substance abuse, and this subgroup was small. Conclusion: Reductions in hippocampal and caudate volume may constitute morphological traits in antipsychotic-naive first-episode schizophrenia patients. However, the clinical implications of these findings are unclear. Moreover, past substance abuse may accentuate hippocampal volume reduction. Magnetic resonance imaging studies addressing the potential effects of substance abuse in antipsychoticnaive first-episode schizophrenia patients are warranted.