Two-dimensional spatial tuning for saccades in human parieto-frontal cortex

• Published in: NeuroImage (Orlando, Fla.) Vol. 87; pp. 476 - 489
• Main Authors: Leoné, Frank T.M., Toni, Ivan, Medendorp, W. Pieter
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15.02.2014; Elsevier; Elsevier Limited
• Subjects: Adult; Biological and medical sciences; Brain Mapping - methods; Cortex (frontal); Female; Frontal eye fields; Frontal Lobe - physiology; Functional magnetic resonance imaging; Fundamental and applied biological sciences. Psychology; Humans; Image Processing, Computer-Assisted; Intraparietal sulcus; Macaca; Magnetic Resonance Imaging; Male; Parietal Lobe - physiology; Phase transitions; Photic Stimulation; Saccade amplitude; Saccades - physiology; Saccadic eye movements; Sensorimotor system; Singular value decomposition; Studies; Topography; Vertebrates: nervous system and sense organs; Young Adult; Germany; Intraparietal sulcus; Saccade amplitude; Topography; Frontal eye fields; Singular value decomposition; Human; Central nervous system; Frontal cortex; Prefrontal cortex; Encephalon
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2013.09.067

Saccades in the frontoparallel plane are targeted at two-dimensional (2D) locations, defined by direction and amplitude. Macaque neurophysiology has shown that these dimensions are jointly represented in single intraparietal sulcus (IPS) and frontal eye fields (FEF) neurons, constituting multiple maps of 2D saccade space. Human fMRI has shown that the direction of the saccade is topographically represented across large neuronal groups. However, it is unknown whether both direction and amplitude are separable dimensions at the voxel level and whether these tuning variables are organized in large-scale topographic maps. We used fMRI to address these issues in subjects performing an instructed-delay saccade task to 18 locations (6 directions, 3 amplitudes). Singular value decomposition was applied to the corresponding response field of each voxel, providing an index of the separability into direction and amplitude tuning. Our findings show that saccade location tuning is composed of separable direction and amplitude components within voxels across the parieto-frontal network. In both IPS and FEF there were amplitude gradients and reversals of direction tuning across voxels, with a medio-lateral gradient of decreasing saccade amplitude along the IPS. These findings reveal the 2D cortical organization of saccade space within and across voxels and hold great potential for the study of other sensorimotor systems. [Display omitted] •Does the cortex represent saccade direction and amplitude as independent dimensions?•Applied SVD to 2D tuning curves of fMRI voxels to test independence of dimensions•Saccade direction and amplitude are independent across the cortical saccade network.•Both dimensions show topography, uninfluenced by the other dimension.