This research is studying changes in awareness and metabolism in the brain that may take place in various brain regions stimulated with ultrasound (low-intensity focused ultrasound pulsation or LIFUP) while undergoing magnetic resonance imaging (MRI)-based brain measurements.
Participants must be right-handed, English-speaking, and capable of providing written informed consent.
Participants must have normal or corrected-to-normal vision while wearing contact lenses,
Participants must have a body mass index of less than 30
Participants must not be taking medications for any neurological, psychological, or psychiatric condition.
Participants will be excluded if they have any contraindication to MRI scanning, including possible pregnancy, current breastfeeding BMI greater than 30, metallic substances or implants in the body, claustrophobia, anxiety that would prevent MRI scanning, Participants with tattoos in the head or neck region will also be excluded, while tattoos in other locations will be evaluated by the investigators to determine whether they pose a safety concern.
cardiopulmonary disease, or an intracranial structural abnormality identified on T1-weighted MRI.
Women of childbearing potential will be required to complete a study-funded pregnancy test before participation and must have a negative result.
vision that is not 20/20 or corrected to 20/20 with contact lenses, a history of significant head injury involving loss of consciousness
Parallel
Low-intensity focused ultrasound pulsation (LIFUP)
DeviceLIFUP will be used to stimulate specific brain regions and assess their causal involvement in the control of conscious state and contents.
Functional Magnetic Resonance Imaging (fMRI)
DeviceWhole-brain functional images will be acquired using a multiband gradient-echo echo-planar imaging sequence with the following parameters: 60 slices, repetition time (TR) = 800 ms, echo time (TE) = 30 ms, flip angle = 52°, multiband acceleration factor = 6, slice thickness = 2.4 mm, in-plane resolution = 2.4 × 2.4 mm, FOV = 216 × 216 mm, and image matrix = 90 × 90. MRI acquisition and associated study procedures will be completed within a scanning visit lasting no more than approximately 2 hours.
Magnetic Resonance Spectroscopy
DeviceSingle-voxel proton magnetic resonance spectroscopy will be performed. A nominal 15 × 15 × 10 mm spectroscopy voxel will be positioned at the prespecified brain target using the participant's anatomical MRI. Glutamate plus glutamine (Glx) will be measured using a short-echo-time spectroscopy sequence with an acquisition time of approximately 5 minutes. GABA will be measured using an edited spectroscopy sequence with an acquisition time of approximately 8 minutes. An unsuppressed water-reference scan will also be acquired for signal correction and metabolite quantification. Voxel placement, shimming, and other sequence parameters may be adjusted slightly based on target anatomy, scanner requirements, and data quality while maintaining the planned procedures and approximate acquisition times.
Multi-modal glymphatic function MRI
DeviceThe study team will collect three separate measurements related to glymphatic function. (i) Multi-delay pseudo-continuous arterial spin labeling (PCASL) MRI with a 3D stack of spirals (SOS) gradient and spin echo (GRASE) read-out. Labeling durations from 500 to 2000 ms, TR = 6 sec., background suppression. FOV = 24 cm with 3x3x5 mm resolution. (ii) Tissue-to-fluid Water exchange rate using T2 selective saturation labeling pulses using the same resolution parameters. (iii) Velocity Spectrum Imaging using velocity selective preparation pulses followed by spherical spiral projection imaging (FOV = 24 cm, velocity bandwidth = \[-1, 1\] cm/s, isotropic spatial resolution = 3.5 mm).
Blood Oxygen Level Dependent (BOLD) response to visual stimuli
Changes in task-evoked blood oxygen level-dependent responses to visual stimuli will be measured using functional MRI before, during, and after LIFUP across the five stimulation parameter conditions.
Perceptual criterion (c) derived from the Signal Detection Theory (SDT)
The perceptual response criterion, c, will be calculated from participants' recognition responses using Signal Detection Theory to quantify their tendency to report conscious recognition of a visual stimulus. For each scanning session, the study team will calculate sensitivity (d') and criterion (c) using subjective reports of recognition as "yes" or "no".
Perceptual sensitivity (d') derived from the Signal Detection Theory (SDT)
Perceptual sensitivity, d', will be calculated from participants' visual discrimination responses using Signal Detection Theory to quantify their ability to distinguish intact object images from control stimuli. For each scanning session, the study team will calculate sensitivity (d') and criterion (c) using subjective reports of recognition as "yes" or "no".
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University of Michigan
Lead sponsor
National Institute of General Medical Sciences (NIGMS)
Collaborator
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