Cortical plasticity in phantom limb pain: A fMRI study on the neural correlates of behavioral clinical manifestations.

The neural mechanism of phantom limb pain (PLP) is related to the intense brain reorganization process implicating plasticity after deafferentation mostly in sensorimotor system. There is a limited understanding of the association between the sensorimotor system and PLP. We used a novel task-based functional magnetic resonance imaging (fMRI) approach to (1) assess neural activation within a-priori selected regions-of-interested (motor cortex [M1], somatosensory cortex [S1], and visual cortex [V1]), (2) quantify the cortical representation shift in the affected M1, and (3) correlate these changes with baseline clinical characteristics. In a sample of 18 participants, we found a significantly increased activity in M1 and S1 as well as a shift in motor cortex representation that was not related to PLP intensity. In an exploratory analyses (not corrected for multiple comparisons), they were directly correlated with time since amputation; and there was an association between increased activity in M1 with a lack of itching sensation and V1 activation was negatively correlated with PLP. Longer periods of amputation lead to compensatory changes in sensory-motor areas; and itching seems to be a protective marker for less signal changes. We confirmed that PLP intensity is not associated with signal changes in M1 and S1 but in V1.

Brain function and clinical characterization in the Boston adolescent neuroimaging of depression and anxiety study.

We present a Human Connectome Project study tailored toward adolescent anxiety and depression. This study is one of the first studies of the Connectomes Related to Human Diseases initiative and is collecting structural, functional, and diffusion-weighted brain imaging data from up to 225 adolescents (ages 14-17 years), 150 of whom are expected to have a current diagnosis of an anxiety and/or depressive disorder. Comprehensive clinical and neuropsychological evaluations and longitudinal clinical data are also being collected. This article provides an overview of task functional magnetic resonance imaging (fMRI) protocols and preliminary findings (N = 140), as well as clinical and neuropsychological characterization of adolescents. Data collection is ongoing for an additional 85 adolescents, most of whom are expected to have a diagnosis of an anxiety and/or depressive disorder. Data from the first 140 adolescents are projected for public release through the National Institutes of Health Data Archive (NDA) with the timing of this manuscript. All other data will be made publicly-available through the NDA at regularly scheduled intervals. This article is intended to serve as an introduction to this project as well as a reference for those seeking to clinical, neurocognitive, and task fMRI data from this public resource.

From State-to-Trait Meditation: Reconfiguration of Central Executive and Default Mode Networks.

While brain default mode network (DMN) activation in human subjects has been associated with mind wandering, meditation practice has been found to suppress it and to increase psychological well-being. In addition to DMN activity reduction, experienced meditators (EMs) during meditation practice show an increased connectivity between the DMN and the central executive network (CEN). However, the gradual change between DMN and CEN configuration from pre-meditation, during meditation, and post-meditation is unknown. Here, we investigated the change in DMN and CEN configuration by means of brain activity and functional connectivity (FC) analyses in EMs across three back-to-back functional magnetic resonance imaging (fMRI) scans: pre-meditation baseline (trait), meditation (state), and post-meditation (state-to-trait). Pre-meditation baseline group comparison was also performed between EMs and healthy controls (HCs). Meditation trait was characterized by a significant reduction in activity and FC within DMN and increased anticorrelations between DMN and CEN. Conversely, meditation state and meditation state-to-trait periods showed increased activity and FC within the DMN and between DMN and CEN. However, the latter anticorrelations were only present in EMs with limited practice. The interactions between networks during these states by means of positive diametric activity (PDA) of the fractional amplitude of low-frequency fluctuations (fALFFs) defined as [Formula: see text] revealed no trait differences but significant increases during meditation state that persisted in meditation state-to-trait. The gradual reconfiguration in DMN and CEN suggest a neural mechanism by which the CEN negatively regulates the DMN and is probably responsible for the long-term trait changes seen in meditators and reported psychological well-being.

Child overweight and obesity are associated with reduced executive cognitive performance and brain alterations: a magnetic resonance imaging study in Mexican children.

BACKGROUND: Overweight and obesity in childhood is associated with negative physical and psychological effects. It has been proposed that obesity increase the risk for developing cognitive deficits, dementia and Alzheimer's disease and that it may be associated with marked differences in specific brain structure volumes. OBJECTIVE: The purpose of this study was a neurobiopsychological approach to examine the association between overweight and obesity, brain structure and a paediatric neuropsychological assessment in Mexican children between 6 and 8 years of age. METHODS: We investigated the relation between the body mass index (BMI), brain volumetric segmentation of subcortical gray and white matter regions obtained with magnetic resonance imaging and the Neuropsychological Assessment of Children standardized for Latin America. Thirty-three healthy Mexican children between 6 and 8 years of age, divided into normal weight (18 children) and overweight/obese (15 children) groups. RESULTS: Overweight/obese children showed reduced executive cognitive performance on neuropsychological evaluations (i.e. verbal fluidity, P = 0.03) and presented differences in brain structures related to learning and memory (reduced left hippocampal volumes, P = 0.04) and executive functions (larger white matter volumes in the left cerebellum, P = 0.04 and mid-posterior corpus callosum, P = 0.03). Additionally, we found a positive correlation between BMI and left globulus pallidus (P = 0.012, ρ = 0.43) volume and a negative correlation between BMI and neuropsychological evaluation scores (P = 0.033, ρ = -0.37). CONCLUSIONS: The findings contribute to the idea that there is a relationship between BMI, executive cognitive performance and brain structure that may underlie the causal chain that leads to obesity in adulthood.

Abnormal functioning of the thalamocortical system underlies the conscious awareness of the phantom limb phenomenon.

Phantom limb (PL), a phenomenon experienced by most patients after amputation, has mostly served as a paradigm to study experiences that appear to be associated with neural plasticity within the CNS. However, the subjective nature of PL experiences has had no definitive means of reliable assessment other than using patients' direct reports, nor was there a way to study the neural mechanisms involved in the conscious awareness of this mental phenomenon. Here we obtained patients' indirect responses to PL experiences for an objective evaluation using functional magnetic resonance imaging (fMRI). Six control subjects and six lower limb (LL) amputees participated in a motor imagery task for both the intact and the particular phantom toes. While all subjects shared neural processing of distinctive regional cerebral activations during motor imagery of the intact toes (prefrontal (PF), supplementary motor area (SMA), primary motor cortex (M1), superior temporal gyrus (STG)), it was only during motor imagery of the amputated toes in amputees that we observed an increased blood oxygen level-dependent (BOLD) signal in the contralateral basal ganglia at the medial globus pallidus (MGP), substantia nigra (SN), and thalamus. This increased BOLD signal in the basal ganglia-thalamus-cortex pathway during imaginary movement of the phantom toes may reflect an abnormal open loop functioning of the thalamocortical system underlying the conscious awareness of the phantom phenomenon. We suggest that the reduction in afferent information contributes to and coalesces with the higher-level reorganization resulting in the subjective conscious awareness of the phantom limb.