Human brain mapping
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Human brain mapping · Sep 2014
Longitudinal reliability of tract-based spatial statistics in diffusion tensor imaging.
Relatively little is known about reliability of longitudinal diffusion-tensor imaging (DTI) measurements despite growing interest in using DTI to track change in white matter structure. The purpose of this study is to quantify within- and between session scan-rescan reliability of DTI-derived measures that are commonly used to describe the characteristics of neural white matter in the context of neural plasticity research. DTI data were acquired from 16 cognitively healthy older adults (mean age 68.4). ⋯ The two main preprocessing steps that we found to improve TBSS reliability were (a) the use of a common individual template and (b) smoothing DTI data using a 1-voxel median filter. Overall our data indicate that small choices in the preprocessing pipeline have a significant effect on test-retest reliability, therefore influencing the power to detect change within a longitudinal study. Furthermore, differences in the data processing pipeline limit the comparability of results across studies.
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Human brain mapping · Sep 2014
Stimulus-evoked potentials contribute to map the epileptogenic zone during stereo-EEG presurgical monitoring.
Presurgical monitoring with intracerebral electrodes in patients with drug-resistant focal epilepsy represents a standard invasive procedure to localize the sites of seizures origin, defined as the epileptogenic zone (EZ). During presurgical evaluation, intracerebral single-pulse electrical stimulation (SPES) is performed to define the boundaries of eloquent areas and to evoke seizure-associated symptoms. Extensive intracranial exploration and stimulation generate a large dataset on brain connectivity that can be used to improve EZ detection and to understand the organization of the human epileptic brain. ⋯ We used connectivity patterns to construct networks and applied cluster partitioning to study the proprieties between potentials evoked/stimulated in different regions. We demonstrate that bidirectional connectivity during phase 1 is a prevalent feature that characterize contacts included in the EZ. This study shows that the application of an analytical protocol on intracerebral stimulus-evoked recordings provides useful information that may contribute to EZ detection and to the management of surgical-remediable epilepsies.
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Human brain mapping · Sep 2014
Intraoperative dorsal language network mapping by using single-pulse electrical stimulation.
The preservation of language function during brain surgery still poses a challenge. No intraoperative methods have been established to monitor the language network reliably. We aimed to establish intraoperative language network monitoring by means of cortico-cortical evoked potentials (CCEPs). ⋯ In three patients in whom high-frequency ES of the white matter produced naming impairment, this "eloquent" subcortical site directly connected AL and PL, judging from the latencies and distributions of cortico- and subcortico-cortical evoked potentials. In conclusion, this study provided the direct evidence that AL, PL, and AF constitute the dorsal language network. Intraoperative CCEP monitoring is clinically useful for evaluating the integrity of the language network.
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Human brain mapping · Sep 2014
Voxelwise lp-ntPET for detecting localized, transient dopamine release of unknown timing: sensitivity analysis and application to cigarette smoking in the PET scanner.
The "linear parametric neurotransmitter PET" (lp-ntPET) model estimates time variation in endogenous neurotransmitter levels from dynamic PET data. The pattern of dopamine (DA) change over time may be an important element of the brain's response to addictive substances such as cigarettes or alcohol. We have extended the lp-ntPET model from the original region of interest (ROI) - based implementation to be able to apply the model at the voxel level. ⋯ Sensitivity of detection for the new algorithm was greater than 80% for the case of short-lived DA changes that occur in subregions of the striatum as might be the case with cigarette smoking. Finally, in (11)C-raclopride PET data, DA movies reveal for the first time that different temporal patterns of the DA response to smoking may exist in different subregions of the striatum. These spatiotemporal patterns of neurotransmitter change created by voxelwise lp-ntPET may serve as novel biomarkers for addiction and/or treatment efficacy.
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Human brain mapping · Sep 2014
Functional lateralization of the anterior insula during feedback processing.
Effective adaptive behavior rests on an appropriate understanding of how much responsibility we have over outcomes in the environment. This attribution of agency to ourselves or to an external event influences our behavioral and affective response to the outcomes. Despite its special importance to understanding human motivation and affect, the neural mechanisms involved in self-attributed rewards and punishments remain unclear. ⋯ However, higher BOLD activity to self-attributed feedback (losses and gains) was observed in the left AI, the thalamus, and the cerebellar vermis. These results suggest a functional lateralization of the AI. The right AI, together with the midbrain and the ACC, is mainly involved in processing the salience of the outcome, whereas the left is part of a cerebello-thalamic-cortical pathway involved in cognitive control processes important for subsequent behavioral adaptations.