NeuroImage
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Resting state fluctuations in blood oxygenation level dependent functional connectivity magnetic resonance imaging (BOLD fcMRI) time-series have been increasingly employed to study functional connectivity networks in healthy and diseased brain. FcMRI studies have been conducted under a number of different conditions, including resting eyes open, visual fixation and finger tapping. ⋯ In this study, state-dependence of functional connectivity to dorsal and ventral striatum was assessed with fcMRI during an eyes open resting state condition (REST) and during continuous 3 Hz transcutaneous electrical nerve stimulation (TENS), with the a priori hypotheses: (1) dorsal striatum connectivity with sensorimotor/attention networks will be stronger during TENS compared to REST, (2) ventral striatum connectivity with limbic system emotion-processing network will be weaker during TENS compared to REST and (3) ventral striatum connectivity with sensorimotor/attention networks will be stronger during TENS compared to REST. These hypotheses were confirmed by the results obtained, indicating that resting state BOLD fMRI networks reflect, in substantial measure, state-dependent activity.
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A distributed network of brain regions is linked to drug-related cue responding. However, the relationships between smoking cue-induced phasic activity and possible underlying differences in brain structure, tonic neuronal activity and connectivity between these brain areas are as yet unclear. Twenty-two smokers and 22 controls viewed smoking-related and neutral pictures during a functional arterial spin labeling scanning session. ⋯ Similarly, rsFC strength between dlPFC and dmPFC was positively correlated with the cue-elicited activity in dmPFC while rsFC strength between dmPFC and insula/operculum was negatively correlated with the cue-elicited activity in both dmPFC and insula/operculum, suggesting these brain circuits may facilitate the response to the salient smoking cues. Further, the gray matter density in dlPFC was decreased in smokers and correlated with cue-elicited activity in the same brain area, suggesting a neurobiological mechanism for the impaired cognitive control associated with drug use. Taken together, these results begin to address the underlying neurobiology of smoking cue salience, and may speak to novel treatment strategies and targets for therapeutic interventions.
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Research in blast-induced lung injury resulted in exposure thresholds that are useful in understanding and protecting humans from such injury. Because traumatic brain injury (TBI) due to blast exposure has become a prominent medical and military problem, similar thresholds should be identified that can put available research results in context and guide future research toward protecting war fighters as well as diagnosis and treatment. At least three mechanical mechanisms by which the blast wave may result in brain injury have been proposed-a thoracic mechanism, head acceleration, and direct cranial transmission. ⋯ There is a subset of blast conditions likely to result in TBI due to head acceleration and/or a thoracic mechanism without concomitant lung injury. These results can be used to guide experimental designs and compare additional data as they become available. Additional data are needed before actual probabilities or severity of TBI for a given exposure can be described.
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Disagreement exists regarding the extent to which persistent post-concussive symptoms (PCS) reported by Iraq combat Veterans with repeated episodes of mild traumatic brain injury (mTBI) from explosive blasts represent structural or functional brain damage or an epiphenomenon of comorbid depression or posttraumatic stress disorder (PTSD). Objective assessment of brain function in this population may clarify the issue. To this end, twelve Iraq war Veterans (32.0 ± 8.5 [mean ± standard deviation (SD)] years of age) reporting one or more blast exposures meeting American Congress of Rehabilitation Medicine criteria for mTBI and persistent PCS and 12 cognitively normal community volunteers (53.0 ± 4.6 years of age) without history of head trauma underwent brain fluorodeoxyglucose positron emission tomography (FDG-PET) and neuropsychological assessments and completed PCS and psychiatric symptom rating scales. ⋯ They also exhibited subtle impairments in verbal fluency, cognitive processing speed, attention, and working memory, similar to those reported in the literature for patients with cerebellar lesions. These FDG-PET imaging findings suggest that regional brain hypometabolism may constitute a neurobiological substrate for chronic PCS in Iraq combat Veterans with repetitive blast-trauma mTBI. Given the potential public health implications of these findings, further investigation of brain function in these Veterans appears warranted.
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Although the exact number of affected individuals is unknown, it has been estimated that approximately 20% of U. S. veterans of Operations Enduring Freedom (OEF) and Iraqi Freedom (OIF) have experienced mild traumatic brain injury (mTBI) (i.e., concussion), which is defined as a brief loss or alteration of consciousness from a blow or jolt to the head. Blast exposure is among the most common causes of concussion in OEF-OIF warriors. ⋯ MDD relative to non-MDD individuals showed greater activity during fear matching trials in the amygdala and other emotion processing structures, lower activity during fear matching trials in emotional control structures such as the dorsolateral prefrontal cortex and lower fractional anisotropy (FA) in several white matter tracts including the superior longitudinal fasciculus (SLF). Greater depressive symptom severity correlated negatively with FA in the SLF. These results suggest a biological basis of MDD in OEF-OIF veterans who have experienced blast-related concussion, and may contribute to the development of treatments aimed at improving the clinical care of this unique population of wounded warriors.