Resting-State Correlations of Fatigue Following Military Deployment

OBJECTIVE

Persistent fatigue is common among military servicemembers returning from deployment, especially those with a history of mild traumatic brain injury (mTBI). The purpose of this study was to characterize fatigue following deployment using the Multidimensional Fatigue Inventory (MFI), a multidimensional self-report instrument. The study was developed to test the hypothesis that if fatigue involves disrupted effort/reward processing, this should manifest as altered basal ganglia functional connectivity as observed in other amotivational states.

METHODS

Twenty-eight current and former servicemembers were recruited and completed the MFI. All 28 participants had a history of at least one mTBI during deployment. Twenty-six participants underwent resting-state functional MRI. To test the hypothesis that fatigue was associated with basal ganglia functional connectivity, the investigators measured correlations between MFI subscale scores and the functional connectivity of the left and right caudate, the putamen, and the globus pallidus with the rest of the brain, adjusting for the presence of depression.

RESULTS

The investigators found a significant correlation between functional connectivity of the left putamen and bilateral superior frontal gyri and mental fatigue scores. No correlations with the other MFI subscales survived multiple comparisons correction.

CONCLUSIONS

This exploratory study suggests that mental fatigue in military servicemembers with a history of deployment with at least one mTBI may be related to increased striatal-prefrontal functional connectivity, independent of depression. A finding of effort/reward mismatch may guide future treatment approaches.

Hypertrophic cardiomyopathy with shared morphology in identical twins: a case report

We report the case of identical twin sisters, both with hypertrophic cardiomyopathy, and both found to have similar echocardiographic appearances in the form of asymmetric septal hypertrophy. This is unusual, in that published reports commonly describe the heterogeneous expression of this condition in twins.

The dynamics of chromosome evolution in birds and mammals

Comparative mapping, which compares the location of homologous genes in different species, is a powerful tool for studying genome evolution. Comparative maps suggest that rates of chromosomal change in mammals can vary from one to ten rearrangements per million years. On the basis of these rates we would expect 84 to 600 conserved segments in a chicken comparison with human or mouse. Here we build comparative maps between these species and estimate that numbers of conserved segments are in the lower part of this range. We conclude that the organization of the human genome is closer to that of the chicken than the mouse and by adding comparative mapping results from a range of vertebrates, we identify three possible phases of chromosome evolution. The relative stability of genomes such as those of the chicken and human will enable the reconstruction of maps of ancestral vertebrates.

Frequency of perseveration in normal subjects

Although perseveration is a recognized sign of disturbed brain function, it also occurs in normal individuals. Determination of the frequency of perseveration in normal subjects would enable clinicians to use perseveration as a marker of possible pathology. The purpose of this study was to document the extent of perseveration in normal young and older subjects. Thirty young normal individuals between the ages of 20 and 35 years and 30 older normal individuals between the ages of 60 and 75 years were given four tasks on which perseveration has been reported in brain-damaged individuals. Four percent of all responses were perseverative. No age or gender effects on frequency were observed. Of the four neuropsychological tasks, the Modified Wisconsin Card Sorting Test elicited the greatest number of perseverations.