title: Task demand modulations of visuospatial processing measured with functional magnetic resonance imaging.
abstract: Brain imaging based on functional magnetic resonance imaging (fMRI) provides a useful tool to examine neural networks and cerebral structures subserving visuospatial function. It allows not only the qualitative determination of which areas are active during task processing, but also estimates the quantitative contribution of involved brain regions to different aspects of spatial processing. In this study, we investigated in 10 healthy subjects how the amount of task (computational) demand in an angle discrimination task was related to neural activity as measured with event-related fMRI. Task demand, indicated by behavioral performance, was modulated by presenting clocks with different angular disparity and length of hands. Significant activations were found in the cortical network subserving the visual and visuospatial processing, including the right and left superior parietal lobules (SPL), striate visual areas, and sensorimotor areas. Both blood oxygenation level-dependent (BOLD) signal strength and spatial extent of activation in right as well as left SPL increased with task demand. By contrast, no significant correlation or a very weak correlation was found between the task demand and the BOLD signal as well as between task demand and spatial extent of activations in the striate visual areas and in the sensorimotor areas. These results support the hypothesis that increased computational demand requires more brain resources. The brain regions that are most specialized for the execution of the visuospatial task can be assessed by relating the imposed task demand to the functional activation measured.
authors.affiliation: Division of Clinical Geriatrics, Neurotec Department, Karolinska Institutet, Huddinge University Hospital, 14186, Stockholm, Sweden. Patrizia.Vannini@neurotec.ki.se
authors.forename: Patrizia
authors.initials: P
authors.lastname: Vannini
authors.forename: Ove
authors.initials: O
authors.lastname: Almkvist
authors.forename: Anders
authors.initials: A
authors.lastname: Franck
authors.forename: Tomas
authors.initials: T
authors.lastname: Jonsson
authors.forename: Umberto
authors.initials: U
authors.lastname: Volpe
authors.forename: Maria
authors.initials: M
authors.lastname: Kristoffersen Wiberg
authors.forename: Lars Olof
authors.initials: LO
authors.lastname: Wahlund
authors.forename: Thomas
authors.initials: T
authors.lastname: Dierks
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011340:Problem Solving / Q000502:physiology*