Journal Article

Spatial specificity of the functional MRI blood oxygenation response relative to neuronal activity

Chaimow, Denis, Shmuel, Amir, Yacoub, Essa, Uğurbil, Kâmil

2018

Overview

Previous attempts at characterizing the spatial specificity of the blood oxygenation level dependent functional MRI (BOLD fMRI) response by estimating its point-spread function (PSF) have conventionally relied on retinotopic spatial representations of visual stimuli in area V1. Consequently, their estimates were confounded by the width and scatter of receptive fields of V1 neurons. Here, we circumvent these limits by instead using the inherent cortical spatial organization of ocular dominance columns (ODCs) to determine the PSF for both Gradient Echo (GE) and Spin Echo (SE) BOLD imaging at 7 Tesla. By applying Markov chain Monte Carlo sampling on a probabilistic generative model of imaging ODCs, we quantified the PSFs that best predict the spatial structure and magnitude of differential ODCs' responses. Prior distributions for the ODC model parameters were determined by analyzing published data of cytochrome oxidase patterns from post-mortem histology of human V1 and of neurophysiological ocular dominance indices. The average PSF full-widths at half-maximum obtained from differential ODCs’ responses following the removal of voxels influenced by contributions from macroscopic blood vessels were 0.86 mm (SE) and 0.99 mm (GE). Our results provide a quantitative basis for the spatial specificity of BOLD fMRI at ultra-high fields, which can be used for planning and interpretation of high-resolution differential fMRI of fine-scale cortical organizations. [Display omitted] •The spread of BOLD response was previously estimated with retinotopic stimuli.•Previous estimates were confounded by width and scatter of neuronal receptive fields.•We apply Markov Chain Monte Carlo sampling to fit a model of imaging columns to data.•Average FWHM of BOLD spread, following blood vessel removal: 0.86 mm (SE) and 0.99 mm (GE).•Our findings support planning and interpretation of high-resolution differential fMRI.

• Publisher: Elsevier Inc,Elsevier Limited
• Subject: Blood oxygenation level dependent / Blood vessels / BOLD / Cortex / Cortical columns / Data processing / Functional magnetic resonance imaging / Gradient-Echo functional MRI / High-resolution functional MRI / Magnetic fields / Markov chain Monte Carlo / NMR / Nuclear magnetic resonance / Ocular dominance / Ocular dominance map / Point-spread function / Retina / Spatial discrimination / Spin-Echo functional MRI / Visual stimuli