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Abstract:
Multivariate pattern analysis (MVPA) methods are a versatile tool to retrieve information from neurophysiological data obtained with functional magnetic resonance imaging (fMRI) techniques. Since fMRI is based on measuring the hemodynamic response following neural activation, the spatial specificity of the fMRI signal is inherently limited by contributions of macrovascular compartments that drain the signal from the actual location of neural activation, making it challenging to image cortical structures at the spatial scale of cortical columns and layers. By relying on information from multiple voxels, MVPA has shown promising results in retrieving information encoded in fine-grained spatial patterns. We examined the spatial specificity of the signal exploited by MVPA. Over multiple sessions, we measured ocular dominance columns (ODCs) in human primary visual cortex (V1) with different acquisition techniques at 7 T. For measurements with blood oxygenation level dependent contrast (BOLD), we included both gradient echo- (GE-BOLD) and spin echo-based (SE-BOLD) sequences. Furthermore, we acquired data using the vascular-space-occupancy (VASO) fMRI technique, which is sensitive to cerebral blood volume (CBV) changes. We used the data to decode the eye-of-origin across cortical depth. While ocularity information can be decoded with all imaging techniques, the macrovascular contributions in GE- and SE-BOLD limit their use for discriminating signals between cortical layers. However, the cortical profile of decoded ocularity information from VASO measurements better reflects the expected profile of neural activity, suggesting the combination of VASO and MVPA to be a promising approach for investigating the mesoscopic circuitry of the human cerebral cortex.
