Local opposite orientation preferences in V1: fMRI sensitivity to fine-grained pattern information

Area of Science:

• Neuroscience
• Visual Neuroscience
• Neuroimaging

Background:

• Functional magnetic resonance imaging (fMRI) is used to decode visual grating orientation in the human primary visual cortex (V1).
• The origin of this decoded information, whether from fine-grained neuronal selectivity or global areal maps, remains unclear.
• The global-areal-map account suggests fMRI decoding relies solely on V1 voxels with radial or vertical preferences.

Purpose of the Study:

• To investigate the spatial scales of neuronal selectivity contributing to fMRI orientation decoding in V1.
• To determine if fMRI reflects fine-grained patterns of neuronal selectivity beyond global areal maps.

Main Methods:

• Utilized functional magnetic resonance imaging (fMRI) with 2-mm isotropic voxels.
• Focused on a small patch of the primary visual cortex (V1) within a quarterfield representation.
• Analyzed voxel selectivities to decode visual grating orientation.

Main Results:

• Demonstrated that 2-mm isotropic voxels in V1 exhibit reliable opposite orientation selectivities within a small region.
• Showed that sets of voxels with opposite selectivities are locally intermingled.
• Confirmed that each intermingled set of voxels can independently support orientation decoding.

Conclusions:

• Global areal maps do not fully explain orientation information obtained via fMRI in V1.
• fMRI signals reflect fine-grained patterns of neuronal selectivity within the primary visual cortex.
• This finding challenges the exclusive reliance on global maps for interpreting fMRI data in visual neuroscience.