This study directly supports the hypothesis that OCD is associated with functional alterations of brain corticostriatal networks. Specifically, our findings emphasize abnormal and heightened functional connectivity of ventrolimbic corticostriatal regions in patients with OCD.

Silent word generation lateralizes to the left cerebral hemisphere in both handedness groups, but right-hemisphere participation is frequent in normal left-handed subjects. Exclusive right-hemisphere activation rarely occurred in the frontal lobe region studied.

BackgroundThe growing concern about cannabis use, the most commonly used illicit drug worldwide, has led to a significant increase in the number of human studies using neuroimaging techniques to determine the effect of cannabis on brain structure and function. We conducted a systematic review to assess the evidence of the impact of chronic cannabis use on brain structure and function in adults and adolescents.MethodsPapers published until August 2012 were included from EMBASE, Medline, PubMed and LILACS databases following a comprehensive search strategy and pre-determined set of criteria for article selection. Only neuroimaging studies involving chronic cannabis users with a matched control group were considered.ResultsOne hundred and forty-two studies were identified, of which 43 met the established criteria. Eight studies were in adolescent population. Neuroimaging studies provide evidence of morphological brain alterations in both population groups, particularly in the medial temporal and frontal cortices, as well as the cerebellum. These effects may be related to the amount of cannabis exposure. Functional neuroimaging studies suggest different patterns of resting global and brain activity during the performance of several cognitive tasks both in adolescents and adults, which may indicate compensatory effects in response to chronic cannabis exposure.LimitationsHowever, the results pointed out methodological limitations of the work conducted to date and considerable heterogeneity in the findings.ConclusionChronic cannabis use may alter brain structure and function in adult and adolescent population. Further studies should consider the use of convergent methodology, prospective large samples involving adolescent to adulthood subjects, and data-sharing initiatives.

The notion of a ''default mode of brain function'' has taken on certain relevance in human neuroimaging studies and in relation to a network of lateral parietal and midline cortical regions that show prominent activity fluctuations during passive imaging states, such as rest. In this study, we perform three fMRI experiments that demonstrate consistency and specialization in the default mode network. Correlated activity fluctuations of default mode network regions are identified during (i) eyes-closed spontaneous rest, (ii) activation by moral dilemma, and (iii) deactivation by Stroop task performance. Across these imaging states, striking uniformity is shown in the basic anatomy of the default mode network, but with both tasks clearly and differentially modulating this activity compared with spontaneous fluctuations of the network at rest. Against rest, moral dilemma is further shown to evoke regionally specific activity increases of hypothesized functional relevance. Mapping spontaneous and task-related brain activity will help to constrain the meaning of the default mode network. These findings are discussed in relation to recent debate on the topic of default modes of brain function.activation ͉ deactivation ͉ default mode ͉ functional MRI ͉ spontaneous activity

Fibromyalgia (FM) patients show characteristically enhanced unpleasantness to painful and non-painful sensations accompanied by altered neural responses. The diagnostic potential of such neural alterations, including their sensitivity and specificity to FM (vs. healthy controls) is unknown. We identify a brain signature that characterizes FM central pathophysiology at the neural systems level. We included 37 FM patients and 35 matched healthy controls, and analyzed fMRI responses to (i) painful pressure and (ii) non-painful multisensory (visual-auditory-tactile) stimulation. We used machine-learning techniques to identify a brain-based FM signature. When exposed to the same painful stimuli, FM patients showed greater Neurologic Pain Signature (NPS, Wager 2013) responses. In addition, a new pain-related classifier (‘FM-pain’) revealed augmented responses in sensory integration (insula/operculum) and self-referential (e.g., medial prefrontal) regions in FM, and reduced responses in the lateral frontal cortex. A ‘Multisensory’ classifier trained on non-painful sensory stimulation revealed augmented responses in insula/operculum, posterior cingulate, and medial prefrontal regions, and reduced responses in primary/secondary sensory cortices, basal ganglia and cerebellum. Combined activity in the NPS, FM-pain, and Multisensory patterns classified patients vs. controls with 92% sensitivity and 94% specificity in out-of-sample individuals. Enhanced NPS responses partly mediated mechanical hypersensitivity, and correlated with depression and disability(puncorrected<0.05); FM-pain and Multisensory responses correlated with clinical pain(puncorrected<0.05). The study provides initial characterization of individual FM-patients based on pathophysiological, symptom-related brain features. If replicated, these brain features may constitute objective neural targets for therapeutic interventions. The results establish a framework for assessing therapeutic mechanisms and predicting treatment response at the individual level.

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To locate structural changes in the brain accounting for the increasing effectiveness in cognition and skills that occurs at the final stage of behavioral development, we attempted to determine the age at which the corpus callosum completes its active growth period. We assessed the growth rate of the corpus callosum by measuring its area twice on midsagittal magnetic resonance imaging scans separated by a 2-year interval, in a series of 90 subjects with a wide range of ages. We observed an increase in the size of the corpus callosum as long as human mentation expands, up to the middle 20s. Clinical and experimental data about the corpus callosum, together with the present findings, suggest that the corpus callosum is part of the highest order-latest maturing neural network of the brain.

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