NeuroImage
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Gradient echo myelin water imaging (GRE-MWI) is an MRI technique to measure myelin concentration and involves the analysis of signal decay characteristics of the multi-echo gradient echo data. The method provides a myelin water fraction as a quantitative biomarker for myelin. In this work, a new sequence and post-processing methods were proposed to generate high quality GRE-MWI images at 3T and 7T. ⋯ Using the method, high-quality myelin water images were successfully generated for the in-vivo human brain at both field strengths. When the myelin water fraction at 3T and 7T were compared, they showed a good correlation (R2≥ 0.88; p < 0.001) with a larger myelin water fraction at 7T. The proposed method also opens the possibility of high resolution (isotropic 1.5 mm resolution) myelin water mapping at 7T.
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Cocaine is a highly addictive drug with complex pharmacological effects. Most preclinical imaging studies investigating the effects of cocaine in the brain have been performed under anesthesia, which confounds findings. To tackle this problem, we used optical imaging to compare the effects of cocaine in the awake versus the anesthetized states. ⋯ Specifically, 1) at baseline isoflurane dilated cerebral vessels, increased cerebral blood flow and depressed neuronal Ca2+ activity compared to the awake state; 2) acute cocaine (1 mg/kg iv) vasoconstricted blood vessels (arteries and veins) and decreased cerebral blood flow and oxygenated hemoglobin in the anesthetized state but not in the awake condition; 3) cocaine increased the accumulation of mean intracellular Ca2+ in neurons in the anesthetized state but not in the awake condition; and 4) in the awake state acute cocaine increased neuronal activities (increased the frequency of Ca2+ transients) and increased neuronal synchronization. We also corroborated that in the awake state cocaine also disrupted neurovascular coupling. These findings indicate that both vascular and neuronal responses to cocaine are influenced by isoflurane anesthesia, which highlights the importance of imaging awake animals when studying the effects of cocaine or other drugs in the brain.
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Redistribution of blood flow across different brain regions, arising from the vasoactive nature of hypercapnia, can introduce errors when examining cerebrovascular reactivity (CVR) response delays. In this study, we propose a novel analysis method to characterize hemodynamic delays in the blood oxygen level dependent (BOLD) response to hypercapnia, and hyperoxia, as a way to provide insight into transient differences in vascular reactivity between cortical regions, and across tissue depths. A pseudo-continuous arterial spin labeling sequence was used to acquire BOLD and cerebral blood flow simultaneously in 19 healthy adults (12 F; 20 ± 2 years) during boxcar CO2 and O2 gas inhalation paradigms. ⋯ Furthermore, calibration of hypercapnic delays using hyperoxia revealed that deeper white matter layers may be more prone to dynamic redistribution of blood flow, which introduces response lag times ranging between 1 and 3 s in healthy subjects. These findings suggest that the combination of hypercapnic and hyperoxic gas-inhalation MRI can be used to distinguish between differences in CVR that arise as a result of delayed stimulus arrival time (due to the local architecture of the cerebrovasculature), or preferential blood flow distribution. Calibrated response delays to hypercapnia provide important insights into cerebrovascular physiology, and may be used to correct response delays associated with vascular impairment.
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Randomized Controlled Trial
Volitional limbic neuromodulation exerts a beneficial clinical effect on Fibromyalgia.
Volitional neural modulation using neurofeedback has been indicated as a potential treatment for chronic conditions that involve peripheral and central neural dysregulation. Here we utilized neurofeedback in patients suffering from Fibromyalgia - a chronic pain syndrome that involves sleep disturbance and emotion dysregulation. These ancillary symptoms, which have an amplificating effect on pain, are known to be mediated by heightened limbic activity. ⋯ Our findings suggest that Amyg-EFP-neurofeedback that specifically targets limbic activity down modulation offers a successful principled approach for volitional EEG based neuromodulation treatment in Fibromyalgia patients. Importantly, it seems that via its immediate sleep improving effect, the neurofeedback training induced a delayed reduction in the target subjective symptom of chronic pain, far and beyond the immediate placebo effect. This indirect approach to chronic pain management reflects the substantial link between somatic and affective dysregulation that can be successfully targeted using neurofeedback.
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Randomized Controlled Trial
Targeting reduced neural oscillations in patients with schizophrenia by transcranial alternating current stimulation.
Transcranial alternating current stimulation (tACS) modulates endogenous neural oscillations in healthy human participants by the application of a low-amplitude electrical current with a periodic stimulation waveform. Yet, it is unclear if tACS can modulate and restore neural oscillations that are reduced in patients with psychiatric illnesses such as schizophrenia. Here, we asked if tACS modulates network oscillations in schizophrenia. ⋯ In addition, 10Hz-tACS enhanced the 40Hz auditory steady-state response (ASSR), which is reduced in patients with schizophrenia. Importantly, clinical improvement of auditory hallucinations correlated with enhancement of alpha oscillations and the 40Hz-ASSR. Together, our findings suggest that tACS has potential as a network-level approach to modulate reduced neural oscillations related to clinical symptoms in patients with schizophrenia.