Functional localization of the human color center by decreased water displacement using diffusion‐weighted fMRI

• Published in: Brain and behavior 2015-11, Vol.5 (11), p.e00408-n/a
• Main Authors: Williams, Rebecca J., Reutens, David C., Hocking, Julia
• Format: Article
• Language: English
• Subjects: Adult; Area V4; BOLD; Brain Mapping - methods; Color; Color Perception - physiology; DfMRI; Diffusion Magnetic Resonance Imaging - methods; diffusion MRI; Female; fMRI; Humans; Localization; magnetic resonance imaging; Male; Metabolism; Original Research; Photic Stimulation; Physiology; Studies; Temporal Lobe - physiology; Visual Cortex - physiology
• ISSN: 2162-3279; 2162-3279
• DOI: 10.1002/brb3.408

Introduction Decreased water displacement following increased neural activity has been observed using diffusion‐weighted functional MRI (DfMRI) at high b‐values. The physiological mechanisms underlying the diffusion signal change may be unique from the standard blood oxygenation level‐dependent (BOLD) contrast and closer to the source of neural activity. Whether DfMRI reflects neural activity more directly than BOLD outside the primary cerebral regions remains unclear. Methods Colored and achromatic Mondrian visual stimuli were statistically contrasted to functionally localize the human color center Area V4 in neurologically intact adults. Spatial and temporal properties of DfMRI and BOLD activation were examined across regions of the visual cortex. Results At the individual level, DfMRI activation patterns showed greater spatial specificity to V4 than BOLD. The BOLD activation patterns were more prominent in the primary visual cortex than DfMRI, where activation was localized to the ventral temporal lobe. Temporally, the diffusion signal change in V4 and V1 both preceded the corresponding hemodynamic response, however the early diffusion signal change was more evident in V1. Conclusions DfMRI may be of use in imaging applications implementing cognitive subtraction paradigms, and where highly precise individual functional localization is required. We compared functional activation sensitized to water displacement (diffusion‐weighted fMRI, DfMRI) and BOLD fMRI, using a task functionally localizing the color center of the brain. DfMRI demonstrated less primary visual activation and a faster temporal response compared to BOLD, indicating contrast reliance on distinct biological mechanisms.