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Keywords: Contrast mechanisms: fMRI

There has been a longstanding demand for noninvasive neuroimaging with high spatiotemporal resolution. Recently, an approach has been proposed that enables Direct Imaging of Neuronal Activity (DIANA) with milliseconds temporal resolution, demonstrated by in vivo mouse brain imaging at 9.4T. DIANA showed high correlations with neuronal spikes, capturing neuronal-activity propagation along the thalamocortical pathway. The DIANA contrast mechanism may be attributed to changes in membrane potential-associated T2 relaxation time. Finally, DIANA may require different considerations in data acquisition and analysis than BOLD-fMRI, as DIANA is directly related to neuronal activity including spontaneous ongoing  activity as well as responses to stimuli.

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Yongxian Qian¹, Xingye Chen¹, Ying-Chia Lin¹, Simon Henin^2,3, Nahbila-Malikha Kumbella¹, Liz Aguilera¹, Zena Rockowitz³, Ashley Clayton³, James Babb¹, Yulin Ge¹, Arjun Masurkar^2,3, Anli Liu^2,3, Yvonne W. Lui^1,4, and Fernando E. Boada^1,5
1Radiology, NYU Grossman School of Medicine, New York, NY, United States, ²Neurology, NYU Grossman School of Medicine, New York, NY, United States, ³Neurology, NYU Langone Health, New York, NY, United States, ⁴Radiology, NYU Langone Health, New York, NY, United States, ⁵Radiology, Stanford University, Stanford, CA, United States

Keywords: Nerves, Neuro, fMRI (task)

Neuronal firing is the electrophysiological basis of brain function. BOLD-based functional MRI indirectly detects neuronal activity through an uncertain neuro-hemodynamic mechanism and is also limited to the detection of slow neuronal activity such as postsynaptic potentials due to its relatively low temporal resolution. Recent efforts have improved temporal resolution to milliseconds or even sub-milliseconds, under the assumption that neuronal activity is exactly repeatable in time, though unlikely to be practical. Here we demonstrate the potential of quantum-sensing MRI to directly detect neuronal firing using a finger-tapping task.

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Phan Tan Toi^1,2, Sehong Oh³, and Jang-Yeon Park^1,2
1Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of, ²Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Korea, Republic of, ³Division of Biomedical Engineering, Hankuk University of Foreign Studies, Yongin, Korea, Republic of

Keywords: fMRI, Brain

There has been interested in observing neural activity dynamics in humans at high temporospatial resolution using noninvasive neuroimaging. Here, we report preliminary results of direct imaging of neuronal activity (DIANA) in humans at 3T using checkerboard pattern stimulation. The results show sequential temporospatial dynamics of activities in visual and prefrontal areas evoked by checkerboard pattern stimulation with a signal change of 0.1~0.3%. In contrast, DIANA signals were distinct from control experiments compared with checkerboard pattern stimulation ones. Our preliminary observations suggest that DIANA is feasible for human fMRI studies.

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Sean Morrison¹, Ewald Webber², Carl Dixon³, Donald Maillet³, Ernst Wolvetang¹, and Martijn A. Cloos^3
1Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St Lucia, Australia, ²School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, Australia, ³Centre for Advanced Imaging, University of Queensland, St Lucia, Australia

Keywords: Contrast Mechanisms, fMRI, DIANA

Here we describe our initial results investigating DIANA’s ability to capture neuronal activation in humans brain organoids. Following drug delivery a 3min long window with 0.5% increased signal was observed. Although tantalising, further experiments are needed to confirm these results.

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Keywords: fMRI, Contrast Mechanisms

Membrane potential is the crucial element of neuronal activation. We investigated the possibility of using MRI to detect the depolarization of membrane potential in rat cortex. To directly access brain cells, a craniotomy was performed to make a burr hole on the skull. T₂ change in the exposed cortex was measured while depolarizing it by directly perfusing artificial cerebrospinal fluid of high potassium concentration. Our findings showed that T₂ value of depolarized cortex increased by +2.7% at [K⁺] = 80 mM. This observation demonstrates that changes in membrane potential are detectable with MRI by T₂ contrast in vivo.

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Juha Valjakka¹, Jaakko Paasonen¹, Raimo A. Salo¹, Ekaterina Paasonen¹, Irina Gureviciene¹, Mikko Kettunen¹, Djaudat Idiyatullin², Shalom Michaeli², Silvia Mangia², Heikki Tanila¹, and Olli Gröhn^1
1A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Keywords: fMRI, Brain, Zero echo time

Zero echo time (ZTE) fMRI with MB-SWIFT poses an artefact free alternative to traditional EPI-based BOLD fMRI approaches. However, the exact origin of the fMRI signal captured with ZTE is unknown. In this work, we investigated the correlation between electrical brain activity and the ZTE fMRI signal during sensory stimulation in anesthetized and awake rats. It is shown that a linear model explains the relationship between the fMRI signal and electrical activity in anesthetized but not in awake rats. We conclude that MB-SWIFT fMRI provides a good proxy for neuronal activity under conventional experimental conditions.

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Keywords: fMRI, fMRI

The direct MRI detection of neural activity in humans is a long-sought goal that has been attempted by many. We posit that a key reason for prior failures is inadequate sensitivity. Spectroscopy with linear algebraic modeling (SLAM) is a compartmental imaging method that provides enormous gains in speed and signal-to-noise ratio (SNR). Here we use it to directly obtain MRI signals from arbitrarily-shaped brain regions with arguably the highest possible SNR efficiency. We successfully detect neural responses elicited by rhythmic finger-tapping at the tapping frequency in humans at 3T, as confirmed by simultaneously-acquired EEG data.

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Keywords: New Signal Preparation Schemes, Brain, fmri

We investigate a new fast readout sequence to collect blood volume image time series in using two different velocity selective pulses. We compare two classes of pulses that target the blood or the stationary tissue. The two approaches are demonstrated and compared in a simple viso-motor blood volume based functional MRI experiment.

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Keywords: fMRI, Multimodal, Preclinical

The underlying sources of negative BOLD responses (NBRs) are still debated. We have recently shown that Positive BOLD response (PBR) to NBR transitions can be induced in the visual pathway by modulating the visual frequency of stimulation, reflecting neural activation/suppression, respectively. Here, we investigate how diffusion functional MRI (dfMRI) signals, which suffer less from vessel contamination, correspond to these activation and suppression regimes. Our results show that dfMRI signals are sharper and more sensitive to suppression induced at high visual stimulation frequencies. Furthermore, striking electrophysiology characteristics such as onsets and offset peaks are more prominent in the dfMRI signals. 

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Kyu-Jin Jung¹, Chuanjiang Cui¹, Jae-Hun Lee¹, Jun-Hyeong Kim¹, Kyoung-Jin Park^1,2, SooHyoung Lee¹, SunYoung Jung³, and Dong-Hyun Kim^1
1Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea, Republic of, ²Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea, Republic of, ³Department of Biomedical Engineering, Yonsei University, Wonju, Korea, Republic of

Keywords: Electromagnetic Tissue Properties, Electromagnetic Tissue Properties

BOLD-fMRI is measured from time-series of magnitude information, whereas the phase contrast information, which is related to the electrical properties, is excluded from process. In this study, we focus on the phase information and attempt to expose the relationship between BOLD signal and conductivity activation. In addition, we investigate the potential of functional EPT relative to standard BOLD fMRI.

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Geon-Ho Jahng¹, Jeonin Jeong², Mun Bae Lee³, Jiyoon Lee², and Oh In Kwon^3
1Radiology, Kyung Hee University Hospital at Gangdong, Seoul, Korea, Republic of, ²Biomedical Engineering, Kyung Hee University, Yongin-si, Korea, Republic of, ³Mathematics, Konkuk University, Seoul, Korea, Republic of

Keywords: Electromagnetic Tissue Properties, fMRI

To investigate the neuronal response of conductivity during visual stimulation and compare that with BOLD, 30 young healthy volunteers were recruited from the local community. We performed two independent experiments of functional magnetic resonance electrical properties tomography (MREPT) MRI. We found that the conductivity value was increased during visual stimulation to some brain areas, indicating that functional MREPT MRI can be used to measure neuronal activity; therefore, conductivity-based fMRI signals may be helpful for measuring neuronal activation during stimulation.