Disruption of Limbic Pathways in a Case of Profound Amnesia

We report a case of episodic amnesia in which the anatomical basis of injury was investigated by diffusion tensor imaging (DTI). Two months after an adult male suffered severe closed head injury, conventional magnetic resonance imaging (CMRI) revealed only a right superior frontal lesion. However, 14 years later, DTI revealed structural anomalies not visible on CMRI involving limbic white matter tracts, notably the fornix, which could explain the amnesia.     

Neural activation for actual and imagined movement following unilateral hand transplantation: a case study

ABSTRACT

Transplantation of a donor hand has been successful as a surgical treatment following amputation, but little is known regarding the brain mechanisms contributing to the recovery of motor function. We report functional magnetic resonance imaging (fMRI) findings for neural activation related to actual and imagined movement, for a 54-year-old male patient, who had received a donor hand transplant 50 years following amputation. Two assessments, conducted 3 months and 6 months post-operatively, demonstrate engagement of motor-control related brain regions for the transplanted hand, during both actual and imagined movement of the fingers. The intact hand exhibited a more intense and focused pattern of activation for actual movement relative to imagined movement, whereas activation for the transplanted hand was more widely distributed and did not clearly differentiate actual and imagined movement. However, the spatial overlap of actual-movement and imagined-movement voxels, for the transplanted hand, did increase over time to a level comparable to that of the intact hand. At these relatively early post-operative assessments, brain regions outside of the canonical motor-control networks appear to be supporting movement of the transplanted hand.     

Plasticity of language pathways in patients with low-grade glioma A diffusion tensor imaging study

Knowledge of the plasticity of language pathways in patients with low-grade glioma is important for neurosurgeons to achieve maximum resection while preserving neurological function. The current study sought to investigate changes in the ventral language pathways in patients with low-grade glioma located in regions likely to affect the dorsal language pathways. The results revealed no significant difference in fractional anisotropy values in the arcuate fasciculus between groups or between hemispheres. However, fractional anisotropy and lateralization index values in the left inferior longitudinal fasciculus and lateralization index values in the left inferior fronto-occpital fasciculus were higher in patients than in healthy subjects. These results indicate plasticity of language pathways in patients with low-grade glioma. The ventral language pathways may perform more functions in patients than in healthy subjects. As such, it is important to protect the ventral language pathways intraoperatively.     

Exploring the neural mechanisms that underlie motor difficulties in children with Attention Deficit Hyperactivity Disorder

Background: Attention Deficit Hyperactivity Disorder (ADHD) is the most common neurobehavioural disorder of childhood. Motor performance appears to be impaired for an important sub-set of this population.

Objectives: This structured review draws attention to the neurological mechanisms that could potentially explain these difficulties.

Methods: In August 2010, Medline, PsychINFO and Embase databases were searched with keywords related to ADHD, neuroimaging modalities and motor performance.

Results: Four studies were retrieved that examined both motor performance and possible neural substrates. Each study explored different hypotheses and no common conclusion is emerging. The cortical activation dysregulation hypothesis, the cerebellar dysfunction hypothesis and the delayed white matter maturation hypothesis were proposed, applying combinations of motor observations and neuroimaging findings.

Conclusion: Published literature to date is insufficient to confirm specific hypotheses. Additional studies coupling discrete motor evaluations to neuroimaging techniques are needed in children with ADHD to better understand the neurobiological mechanisms of their motor difficulties.     

Using a motion-tracking device to facilitate motion control in children with ASD for neuroimaging

ABSTRACT

Purpose: Conducting neurological scans of children with disabilities is difficult because participants exhibit excessive motion. We examined whether a motion-tracking system that combined real-time visual feedback with positive reinforcement and shaping could facilitate motion control in two children with autism spectrum disorder.

Methods: Using a modified changing criterion design, we evaluated whether the intervention could facilitate decreases in the participants’ range of motion and increases in duration of motion control in a mock scanner.

Results: Participants restricted head motion to increasingly smaller distance windows for 2 min. Once participants limited head displacement to 3 mm for 2 min, duration of motion control increased to a range of 7–20 min. Summary-level data from the actual scan suggests increases in motion control generalized outside of the intervention context.

Conclusion: This study adds to the limited research on the use of behavioral interventions to increase motion control for neuroimaging in children with disabilities.     

Prenatal stress and limbic-prefrontal white matter microstructure in children aged 6–9 years: a preliminary diffusion tensor imaging study

Objectives. Maternal prenatal stress is associated with elevated risk of adverse behavioural outcomes in offspring. This association may involve developmental disruption to limbic-prefrontal white matter circuitry, of which the uncinate fasciculus is the major tract. One potential candidate for modulating brain development is maternal prenatal stress. We provide the first prospective study of prenatal stress and white matter microstructure in children. Methods. A total of 22 healthy children (mean age 7 years) of mothers recruited in pregnancy underwent diffusion tensor magnetic resonance imaging. We examined correlations between prenatal stressful life events and white matter microstructural organisation indices (fractional anisotropy (FA) and perpendicular diffusivity (D_perp)) of the uncinate fasciculus and a “control” tract. Results. Maternal prenatal stressful life events were correlated positively with right uncinate fasciculus FA, and negatively with right uncinate fasciculus D_perp in their child, with a similar trend with left uncinate fasciculus D_perp. Prenatal stress was not associated with control tract properties; sociodemographic/obstetric variables were not associated with FA/D_perp of either tract. Conclusions. Variation in maternal prenatal stress may be associated with differences in the development of white matter within brain networks underlying child social behaviour.