Diffusion-tensor MR tractography of somatotopic organization of corticospinal tracts in the internal capsule: initial anatomic results in contradistinction to prior reports.

The goal of this study was to use diffusion-tensor magnetic resonance (MR) imaging to define the location and organization of corticospinal tracts (CSTs) in the posterior limb of the internal capsule (PLIC). The Institutional Review Board approved the study, and informed consent was obtained from all subjects. Eight volunteers and two patients with brain tumor were imaged at 3 T. All CSTs were found to lie in a compact area in one part of the PLIC: If the PLIC is divided into four equal quarters from anterior to posterior, the CST was shown to be in the third quarter. Seventeen of 20 CSTs were organized somatotopically, with hand fibers anterolateral to foot fibers, not anteromedial as is currently believed. In three of 20, hand and foot fibers were intermixed. Classically, it was thought that the CST was located in the anterior third of the PLIC. The present data confirm recent results that the CST is located more posteriorly. In the majority of cases, however, the CST is organized somatotopically

Frontostriatal microstructure modulates efficient recruitment of cognitive control

Many studies have linked activity in a frontostriatal network with the capacity to suppress inappropriate thoughts and actions, but relatively few have examined the role of connectivity between these structures. Here, we use diffusion tensor imaging to assess frontostriatal connectivity in 21 subjects (ages 7--31 years). Fifteen subjects were tested on a go/no-go task, where they responded with a button press to a visual stimulus and inhibited a response to a second infrequent stimulus. An automated fiber tracking algorithm was used to delineate white matter fibers adjacent to ventral prefrontal cortex and the striatum, and the corticospinal tract, which was not expected to contribute to control per se. Diffusion in frontostriatal and corticospinal tracts became more restricted with age. This shift was paralleled by an increase in efficiency of task performance. Frontostriatal radial diffusivities predicted faster reaction times, independent of age and accuracy, and this correlation grew stronger for trials expected to require greater control. This was not observed in the corticospinal tract. On trials matched for speed of task performance, adults were significantly more accurate, and accuracies were correlated with frontostriatal, but not corticospinal, diffusivities. These findings suggest that frontostriatal connectivity may contribute to developmental and individual differences in the efficient recruitment of cognitive control

Differential patterns of striatal activation in young children with and without ADHD

Background: Cognitive control, defined as the ability to suppress inappropriate thoughts and actions, is compromised in attention-deficit/hyperactivity disorder (ADHD). This study examines the neural basis of this deficit. Methods: We used a paradigm that incorporates a parametric manipulation within a go/nogo task, so that the number of go trials preceding a nogo trial is varied to tax the neural systems underlying cognitive control with increasing levels of interference. Results: Using this paradigm in combination with eventrelated functional magnetic resonance imaging (fMRI), we show that children without ADHD have increased susceptibility to interference with increasing numbers of go trials preceding a nogo trial, but children with ADHD have difficulty even with a single go trial preceding a nogo trial

Distribution of microstructural damage in the brains of professional boxers: A diffusion MRI study

PURPOSE: To investigate and localize cerebral abnormalities in professional boxers with no history of moderate or severe head trauma. MATERIALS AND METHODS: Diffusion tensor imaging (DTI) was used to determine the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in the brains of 81 professional male boxers and 12 male control subjects. Voxel-based analysis (VBA) of both the diffusion and anisotropy values was performed using statistical parametric mapping (SPM). From this objective analysis, regions of microstructural abnormalities in the brains of the boxers were located. RESULTS: Increases in the ADC, and decreases in FA were identified in deep white matter (WM), while decreases in ADC were identified in cortical gray matter (GM). Regions of positive correlation between ADC and age were also found in both the boxer and control groups, although the regions and strength of the correlation were not the same in each group. CONCLUSION: Using VBA, we localized previously unreported abnormalities in the brains of professional boxers. These abnormalities are assumed to reflect cumulative (chronic) brain injury resulting from nonsevere head trauma.status: publishe