scholarly journals Simultaneous fMRI and fast-scan cyclic voltammetry bridges oxygenation and neurotransmitter dynamics across spatiotemporal scales

2021 ◽  
Author(s):  
Lindsay Walton ◽  
Matthew Verber ◽  
Sung-Ho Lee ◽  
Tzu-Hao Harry Chao ◽  
R. Mark Wightman ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Techniques ◽  
Brain Regions ◽  
Blood Oxygenation ◽  
Tissue Oxygen ◽  
Spatiotemporal Resolution ◽  
Fast Scan Cyclic Voltammetry ◽  
Bold Fmri ◽  
Time Courses ◽  
Hemodynamic Information

The vascular contributions of neurotransmitters to the hemodynamic response are gaining more attention in neuroimaging studies, as many neurotransmitters are vasomodulatory. To date, well-established electrochemical techniques that detect neurotransmission in high magnetic field environments are limited. Here, we propose an experimental setting enabling simultaneous fast-scan cyclic voltammetry (FSCV) and blood oxygenation-dependent functional magnetic imaging (BOLD fMRI) to measure both local tissue oxygen and dopamine responses, and global BOLD changes, respectively. By using MR-compatible materials and the proposed data acquisition schemes, FSCV detected physiological analyte concentrations with high spatiotemporal resolution inside of a 9.4 T MRI bore. We found that tissue oxygen and BOLD correlate strongly, and brain regions that encode dopamine amplitude differences can be identified via modeling simultaneously acquired dopamine FSCV and BOLD fMRI time-courses. This technique provides complementary neurochemical and hemodynamic information and expands the scope of studying the influence of local neurotransmitter release over the entire brain.

scholarly journals Nuisance Effects and the Limitations of Nuisance Regression in Dynamic Functional Connectivity fMRI

2018 ◽  
Author(s):  
Alican Nalci ◽  
Bhaskar D. Rao ◽  
Thomas T. Liu
Keyword(s):  
Functional Connectivity ◽  
Resting State Fmri ◽  
Brain Regions ◽  
Blood Oxygenation ◽  
Dynamic Functional Connectivity ◽  
Temporal Fluctuations ◽  
Before And After ◽  
The Difference ◽  
Time Courses ◽  
The Relationship

AbstractIn resting-state fMRI, dynamic functional connectivity (DFC) measures are used to characterize temporal changes in the brain’s intrinsic functional connectivity. A widely used approach for DFC estimation is the computation of the sliding window correlation between blood oxygenation level dependent (BOLD) signals from different brain regions. Although the source of temporal fluctuations in DFC estimates remains largely unknown, there is growing evidence that they may reflect dynamic shifts between functional brain networks. At the same time, recent findings suggest that DFC estimates might be prone to the influence of nuisance factors such as the physiological modulation of the BOLD signal. Therefore, nuisance regression is used in many DFC studies to regress out the effects of nuisance terms prior to the computation of DFC estimates. In this work we examined the relationship between DFC estimates and nuisance factors. We found that DFC estimates were significantly correlated with temporal fluctuations in the magnitude (norm) of various nuisance regressors, with significant correlations observed in the majority (76%) of the cases examined. Significant correlations between the DFC estimates and nuisance regressor norms were found even when the underlying correlations between the nuisance and fMRI time courses were relatively small. We then show that nuisance regression does not eliminate the relationship between DFC estimates and nuisance norms, with significant correlations observed in the majority (71%) of the cases examined after nuisance regression. We present theoretical bounds on the difference between DFC estimates obtained before and after nuisance regression and relate these bounds to limitations in the efficacy of nuisance regression with regards to DFC estimates.

scholarly journals A line through the brain: implementation of human line-scanning at 7T for ultra-high spatiotemporal resolution fMRI

2021 ◽  
pp. 0271678X2110372
Author(s):  
Luisa Raimondo ◽  
Tomas Knapen ◽  
ĺcaro A.F Oliveira ◽  
Xin Yu ◽  
Serge O Dumoulin ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
Visual Stimulation ◽  
Sampling Rate ◽  
Blood Oxygenation ◽  
Spatiotemporal Resolution ◽  
Scanning Method ◽  
Bold Fmri ◽  
Line Scanning ◽  
Human Line

Functional magnetic resonance imaging (fMRI) is a widely used tool in neuroscience to detect neurally evoked responses, e.g. the blood oxygenation level-dependent (BOLD) signal. Typically, BOLD fMRI has millimeter spatial resolution and temporal resolution of one to few seconds. To study the sub-millimeter structures and activity of the cortical gray matter, the field needs an fMRI method with high spatial and temporal resolution. Line-scanning fMRI achieves very high spatial resolution and high sampling rate, at the cost of a sacrifice in volume coverage. Here, we present a human line-scanning implementation on a 7T MRI system. First, we investigate the quality of the saturation pulses that suppress MR signal outside the line. Second, we established the best coil combination for reconstruction. Finally, we applied the line-scanning method in the occipital lobe during a visual stimulation task, showing BOLD responses along cortical depth, every 250 µm with a 200 ms repetition time (TR). We found a good correspondence of t-statistics values with 2D gradient-echo echo planar imaging (GE-EPI) BOLD fMRI data with the same temporal resolution and voxel volume (R = 0.6 ± 0.2). In summary, we demonstrate the feasibility of line-scanning in humans and this opens line-scanning fMRI for applications in cognitive and clinical neuroscience.

scholarly journals Sub-second striatal dopamine dynamics assessed by simultaneous fast-scan cyclic voltammetry and fluorescence biosensor

2022 ◽  
Author(s):  
Armando G Salinas ◽  
Jeong Oen Lee ◽  
Shana M Augustin ◽  
Shiliang Zhang ◽  
Tommaso Patriarchi ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Time Scale ◽  
Electrochemical Method ◽  
Brain Regions ◽  
Fast Scan Cyclic Voltammetry ◽  
Fluorescent Biosensors ◽  
Freely Behaving ◽  
Fluorescence Biosensor ◽  
Motivation And Learning

Fast-scan cyclic voltammetry (FSCV) is an electrochemical method used to detect dopamine on a subsecond time scale. Recordings using FSCV in freely behaving animals revolutionized the study of behaviors associated with motivation and learning. Despite this advance, FSCV cannot distinguish between catecholamines, which limits its use to brain regions where dopamine is the predominant neurotransmitter. It has also been difficult to detect dopamine in vivo in some striatal subregions with FSCV. Recently, fluorescent biosensors for dopamine were developed, allowing for discrimination between catecholamines. However, the performance of these biosensors relative to FSCV has not been determined. Thus, we compared fluorescent photometry responses of the dopamine biosensor, dLight, with FSCV. We also used dLight photometry to assess changes in tonic and phasic dopamine, which has not been possible with FSCV. Finally, we examined dopamine dynamics during Pavlovian conditioning in striatal subregions, including the dorsolateral striatum where dopamine measurements are challenging with FSCV.

scholarly journals Functional Activities Detected in the Olfactory Bulb and Associated Olfactory Regions in the Human Brain Using T2-Prepared BOLD Functional MRI at 7T

2021 ◽  
Vol 15 ◽  
Author(s):  
Xinyuan Miao ◽  
Adrian G. Paez ◽  
Suraj Rajan ◽  
Di Cao ◽  
Dapeng Liu ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Orbitofrontal Cortex ◽  
Brain Regions ◽  
Vital Role ◽  
Blood Oxygenation ◽  
Olfactory Stimulation ◽  
Planar Imaging ◽  
Susceptibility Artifacts ◽  
Bold Fmri ◽  
Susceptibility Effects

Olfaction is a fundamental sense that plays a vital role in daily life in humans, and can be altered in neuropsychiatric and neurodegenerative diseases. Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) using conventional echo-planar-imaging (EPI) based sequences can be challenging in brain regions important for olfactory processing, such as the olfactory bulb (OB) and orbitofrontal cortex, mainly due to the signal dropout and distortion artifacts caused by large susceptibility effects from the sinonasal cavity and temporal bone. To date, few studies have demonstrated successful fMRI in the OB in humans. T2-prepared (T2prep) BOLD fMRI is an alternative approach developed especially for performing fMRI in regions affected by large susceptibility artifacts. The purpose of this technical study is to evaluate T2prep BOLD fMRI for olfactory functional experiments in humans. Olfactory fMRI scans were performed on 7T in 14 healthy participants. T2prep BOLD showed greater sensitivity than GRE EPI BOLD in the OB, orbitofrontal cortex and the temporal pole. Functional activation was detected using T2prep BOLD in the OB and associated olfactory regions. Habituation effects and a bi-phasic pattern of fMRI signal changes during olfactory stimulation were observed in all regions. Both positively and negatively activated regions were observed during olfactory stimulation. These signal characteristics are generally consistent with literature and showed a good intra-subject reproducibility comparable to previous human BOLD fMRI studies. In conclusion, the methodology demonstrated in this study holds promise for future olfactory fMRI studies in the OB and other brain regions that suffer from large susceptibility artifacts.

scholarly journals On the Role of Bilateral Brain Hypofunction and Abnormal Lateralization of Cortical Information Flow as Neural Underpinnings of Conventional Metaphor Processing Impairment in Schizophrenia: An fMRI and EEG Study

2021 ◽  
Author(s):  
Przemysław Adamczyk ◽  
Martin Jáni ◽  
Tomasz S. Ligeza ◽  
Olga Płonka ◽  
Piotr Błądziński ◽  
...  
Keyword(s):  
Information Flow ◽  
Language Processing ◽  
Time Course ◽  
Figurative Language ◽  
Neural Circuits ◽  
Effective Connectivity ◽  
Brain Regions ◽  
Blood Oxygenation ◽  
Control Group ◽  
Metaphor Processing

AbstractFigurative language processing (e.g. metaphors) is commonly impaired in schizophrenia. In the present study, we investigated the neural activity and propagation of information within neural circuits related to the figurative speech, as a neural substrate of impaired conventional metaphor processing in schizophrenia. The study included 30 schizophrenia outpatients and 30 healthy controls, all of whom were assessed with a functional Magnetic Resonance Imaging (fMRI) and electroencephalography (EEG) punchline-based metaphor comprehension task including literal (neutral), figurative (metaphorical) and nonsense (absurd) endings. The blood oxygenation level-dependent signal was recorded with 3T MRI scanner and direction and strength of cortical information flow in the time course of task processing was estimated with a 64-channel EEG input for directed transfer function. The presented results revealed that the behavioral manifestation of impaired figurative language in schizophrenia is related to the hypofunction in the bilateral fronto-temporo-parietal brain regions (fMRI) and various differences in effective connectivity in the fronto-temporo-parietal circuit (EEG). Schizophrenia outpatients showed an abnormal pattern of connectivity during metaphor processing which was related to bilateral (but more pronounced at the left hemisphere) hypoactivation of the brain. Moreover, we found reversed lateralization patterns, i.e. a rightward-shifted pattern during metaphor processing in schizophrenia compared to the control group. In conclusion, the presented findings revealed that the impairment of the conventional metaphor processing in schizophrenia is related to the bilateral brain hypofunction, which supports the evidence on reversed lateralization of the language neural network and the existence of compensatory recruitment of alternative neural circuits in schizophrenia.

Carbon Fiber Multielectrode Array (CFMEA) for Multiplexing Neurochemical Measurements with Fast Scan Cyclic Voltammetry

2021 ◽  
Vol MA2021-02 (55) ◽  
pp. 1606-1606
Author(s):  
Alexander George Zestos ◽  
Favian Alberto Liu ◽  
Thomas Asrat ◽  
Harmain Rafi
Keyword(s):  
Cyclic Voltammetry ◽  
Carbon Fiber ◽  
Multielectrode Array ◽  
Fast Scan Cyclic Voltammetry

scholarly journals Beyond BOLD: in search of genuine diffusion fMRI contrast in human brain

2021 ◽  
Author(s):  
Wiktor Olszowy ◽  
Yujian Diao ◽  
Ileana O Jelescu
Keyword(s):  
Human Brain ◽  
Brain Activity ◽  
Blood Oxygenation ◽  
Alternative Methods ◽  
Functional Responses ◽  
Spatiotemporal Resolution ◽  
Apparent Diffusion ◽  
Oxygenation Level ◽  
Vascular Origin ◽  
Positive Correlations

Functional Magnetic Resonance Imaging (fMRI) is an essential method to measure brain activity non-invasively. While fMRI almost systematically relies on the blood oxygenation level-dependent (BOLD) contrast, there is an increasing interest in alternative methods that would not rely on neurovascular coupling. A promising but controversial such alternative is diffusion fMRI (dfMRI), which relies instead on dynamic fluctuations in apparent diffusion coefficient (ADC) due to microstructural changes underlying neuronal activity. However, it is unclear whether genuine dfMRI contrast, distinct from BOLD contamination, can be detected in the human brain in physiological conditions. Here, we present the first dfMRI study in humans attempting to minimize all BOLD contamination sources and comparing functional responses at two field strengths (3T and 7T), both for task and resting-state (RS) fMRI. Our study benefits from unprecedented high spatiotemporal resolution and harnesses novel denoising strategies. We report task-induced decrease in ADC with temporal and spatial features distinct from the BOLD response and yielding more specific activation maps. Furthermore, we report dfMRI RS connectivity which, compared to its BOLD counterpart, is essentially free from physiological artifacts and preserves positive correlations but preferentially suppresses anti-correlations, which are likely of vascular origin. A careful acquisition and processing design thus enable the detection of genuine dfMRI contrast on clinical MRI systems. As opposed to BOLD, diffusion functional contrast could be particularly well suited for low-field MRI.

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