NeuroImage
-
Cardiac arrest and subsequent cardiopulmonary resuscitation (CPR) induce hippocampal damage, which has been identified using histological analysis of post-mortem brains. Voxel-based morphometry (VBM), an in-vivo assessment of regional differences in the concentration or volume of a particular tissue such as gray matter, has revealed CPR-induced decreases in gray matter in the hippocampus, where histopathological findings were observed. However, the potential link between the changes in gray matter detected by VBM and hippocampal damage has not been investigated directly. ⋯ The CPR-induced decrease in GMC was localized to CA1, which is the same brain region where neuronal loss and microglial invasion were noted in response to CPR. GMC values were positively correlated with the number of neurons and tended to be negatively correlated with the number of microglia in CA1 of CPR rats. In conclusion, these results indicate that VBM-detected alterations in gray matter can be used as a surrogate marker for hippocampal damage following CPR.
-
Randomized Controlled Trial
Impact of acoustic coordinated reset neuromodulation on effective connectivity in a neural network of phantom sound.
Chronic subjective tinnitus is an auditory phantom phenomenon characterized by abnormal neuronal synchrony in the central auditory system. As recently shown in a proof of concept clinical trial, acoustic coordinated reset (CR) neuromodulation causes a significant relief of tinnitus symptoms combined with a significant decrease of pathological oscillatory activity in a network comprising auditory and non-auditory brain areas. The objective of the present study was to analyze whether CR therapy caused an alteration of the effective connectivity in a tinnitus related network of localized EEG brain sources. ⋯ CR significantly weakened the excitatory connection between posterior cingulate cortex and primary auditory cortex and significantly strengthened inhibitory connections between auditory cortices and the dorsolateral prefrontal cortex. The overall impact of CR therapy on the entire tinnitus-related network showed up as a qualitative transformation of its spectral response, in terms of a drastic change of the shape of its averaged transfer function. Based on our findings we hypothesize that CR therapy restores a silence based cognitive auditory comparator function of the posterior cingulate cortex.
-
Comparative Study
A spatiotemporal comparison between olfactory and trigeminal event-related potentials.
The present study compared the temporal and spatial aspects of human olfactory and trigeminal processing. A relatively selective trigeminal stimulus, CO2, and a relatively selective olfactory stimulus, H2S, were delivered with an olfactometer to young, healthy volunteers. The analysis was performed in a classical (5-electrode, main ERPs peaks) and modern approach (high topographical resolution, inverse solution, source localization). ⋯ In this time range, source analysis pointed out that the olfactory stimulation involved olfactory related areas, while trigeminal stimulation involved noxious/somatosensory specific brain areas. Moreover, from 300ms on our data showed a similarity between the two processes. Statistical parametrical mapping of the differences between conditions suggested greater activation in a specific motor/sniffing network for the CO2 stimulation (probably related to a regulation of the potential noxious stimulus) and a greater activation of the ipsilateral primary olfactory cortex for H2S.
-
Chemical exchange saturation transfer (CEST) is a magnetization transfer (MT) technique to indirectly detect pools of exchangeable protons through the water signal. CEST MRI has focused predominantly on signals from exchangeable protons downfield (higher frequency) from water in the CEST spectrum. Low power radiofrequency (RF) pulses can slowly saturate protons with minimal interference of conventional semi-solid based MT contrast (MTC). ⋯ When studying 6 normal volunteers with a low-power pulsed CEST approach, the relayed-NOE CEST effect was about twice as large as the CEST effects downfield and larger in white matter than gray matter. This NOE contrast upfield from water provides a way to study mobile macromolecules in tissue. First data on a tumor patient show reduction in both relayed NOE and CEST amide proton signals leading to an increase in magnetization transfer ratio asymmetry, providing insight into previously reported amide proton transfer (APT) effects in tumors.
-
MRI templates and digital atlases are needed for automated and reproducible quantitative analysis of non-human primate PET studies. Segmenting brain images via multiple atlases outperforms single-atlas labelling in humans. We present a set of atlases manually delineated on brain MRI scans of the monkey Macaca fascicularis. We use this multi-atlas dataset to evaluate two automated methods in terms of accuracy, robustness and reliability in segmenting brain structures on MRI and extracting regional PET measures. ⋯ Compared to single atlas extractions, multi-atlas methods improve the accuracy of region definition. They also perform comparably to manually defined regions for PET quantification. Multiple atlases of Macaca fascicularis brains are now available and allow reproducible and simplified analyses.