University of Michigan
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.
This study examines the effects of low-intensity focused ultrasound pulsation (LIFUP) on conscious perception and brain physiology in healthy adults using functional Magnetic resonance imaging (MRI), magnetic resonance spectroscopy, or multimodal glymphatic MRI. Participants are assigned by the study team to one of three arms, each involving up to five visits targeting different prespecified brain regions. Participants perform a visual perception task during imaging, with measurements obtained before, during, and after LIFUP. After completing their initially assigned arm, participants may re-e…
Inclusion Criteria: * 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. Exclusion Criteria: * 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…
LIFUP will be used to stimulate specific brain regions and assess their causal involvement in the control of conscious state and contents.
Whole-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.
Single-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.
The 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).
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