Two-dimensional spatial tuning for saccades in human parieto-frontal cortex
Frank T M Leoné1, Ivan Toni1, W Pieter Medendorp1
1Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behavior, 6525 HR Nijmegen, The Netherlands.
Neuroimage
|October 9, 2013
Summary
Researchers found that saccade eye movements are organized in a 2D cortical space within the brain. Both direction and amplitude of saccades are separable at the voxel level in the intraparietal sulcus and frontal eye fields.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Systems Neuroscience
Background:
- Saccades, or rapid eye movements, are directed in 2D space by direction and amplitude.
- Macaque studies suggest joint neural representation of saccade dimensions in the intraparietal sulcus (IPS) and frontal eye fields (FEF).
- Human fMRI shows topographic representation of saccade direction but lacks voxel-level detail on amplitude and separability.
Purpose of the Study:
- To investigate whether saccade direction and amplitude are separable dimensions at the voxel level in humans.
- To determine if these tuning variables are organized in large-scale topographic maps within the human parieto-frontal network.
- To explore the 2D cortical organization of saccade space.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used in human subjects.
- Subjects performed an instructed-delay saccade task involving 18 distinct locations (6 directions, 3 amplitudes).
- Singular value decomposition (SVD) analyzed voxel response fields to quantify tuning separability.
Main Results:
- Saccade location tuning demonstrated separable direction and amplitude components within voxels across the parieto-frontal network.
- Amplitude gradients and direction tuning reversals were observed across voxels in the IPS and FEF.
- A medio-lateral gradient of decreasing saccade amplitude was identified along the IPS.
Conclusions:
- Saccade spatial representation is organized in a separable 2D manner within voxels in the human brain.
- Topographic maps for saccade direction and amplitude exist in the IPS and FEF.
- These findings provide insights into the 2D cortical organization of sensorimotor systems.
