PROJECT SUMMARY
Research: Functional MRI (fMRI) has contributed enormously to our understanding of human brain function.
Today all fMRI methods use hemodynamics as an indirect proxy for brain function, and recent evidence has
shown that these hemodynamics are regulated at the level of cerebral cortical layers. Cortical layers act as inputs
and outputs of large-scale brain networks, making it crucial to measure activity across individual cortical layers
to decipher brain circuitry. However, despite advanced instrumentation and ultra-high field (≥7 Tesla) MRI
scanners, current laminar MRI methods are limited due to voxel sizes that still exceed the thickness of individual
cortical layers. To address this limitation, we propose to advance “linescan fMRI” a classic method that acquires
a one-dimensional (1D) single “line” of imaging data. This method sacrifices spatial coverage for very high spatial
resolution along the line, making it ideal for laminar MRI. Linescan fMRI is thus analogous to classic invasive
laminar electrode recordings, facilitating comparisons of fMRI findings with electrophysiology. Despite recent
progress in linescan fMRI technology, there have been limited demonstrations of its utility for human
neuroscience, and direct comparisons against conventional laminar fMRI and comprehensive characterization
are needed. The proposed set of experiments will fill this gap and benchmark linescan fMRI both by confirming
that it can be used to map known patterns of activation across layers and by applying it to novel human
neuroscience experiments. First, we will address any existing concerns about signal-to-noise ratio (SNR) in Aim
1 and directly assess SNR differences between 2D and 1D linescan acquisitions using both phantom scans and
human studies. Aim 2 will validate linescan fMRI by comparing it to conventional high-resolution fMRI, by
replicating established findings using visual stimulation and acquiring data from primary visual cortex (V1).
Finally, Aim 3 will apply linescan fMRI to map population receptive fields across layers in V1, whose profile is
well established, and measure attentional modulation across layers, with the goal of replicating findings from
prior gold-standard monkey electrophysiology experiments.
Environment & Training: My environment is ideally suited for the proposed training. Drawing on their expertise,
my Sponsor and Co-Sponsor will train me in MR physics, laminar fMRI, neurovascular coupling, hemodynamics,
and human subjects research. My Sponsor is an expert in high-resolution fMRI technology and laminar fMRI,
thus will provide ideal mentorship and training for my goals. My mentoring team, research facilities and
infrastructure at the Massachusetts General Hospital and the Martinos Center will further support my proposed
training. My training will consist of direct mentoring and didactic training including workshops in ultra-high-field
fMRI, trainings offered at larger scientific meetings, and local courses in professional development, scientific
communication, mentorship, and responsible conduct of research. This training will prepare me for a career as
an independent researcher applying leading-edge fMRI methods to understanding higher-order cognition.
