Beyond the labeled line: variation in visual reference frames from intraparietal cortex to frontal eye fields and the...

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Accurate visual perception relies on integrating eye position and retinal information, especially during rapid eye movements (saccades).
• Understanding how the brain transforms visual information across different reference frames is crucial for explaining stable visual perception.
• Key brain regions involved in visuomotor control include the frontal eye fields (FEF), intraparietal cortex (LIP/MIP), and superior colliculus (SC).

Purpose of the Study:

• To investigate the coordinate transformations of visual receptive fields across different eye positions in FEF, LIP/MIP, and SC.
• To determine how neural representations of visual space are maintained or transformed during saccadic eye movements.
• To elucidate the role of these interconnected brain structures in achieving stable visual perception despite retinal motion.

Main Methods:

• Single-unit activity was recorded in head-restrained monkeys performing visually guided saccades.
• Receptive field properties were analyzed across varying initial fixation positions.
• Neural responses were characterized in terms of eye-centered, head-centered, and hybrid coordinate frames.

Main Results:

• Intraparietal cortex (LIP/MIP) neurons exhibited receptive fields that shifted irregularly with eye position (hybrid coordinates).
• Superior colliculus (SC) neurons demonstrated receptive fields stable in eye-centered coordinates.
• Frontal eye fields (FEF) showed intermediate representations, with ~60% eye-centered and the remainder hybrid or head-centered.

Conclusions:

• The frontal eye fields (FEF) may serve as a transitional area for coordinate transformations between the intraparietal cortex (LIP/MIP) and the superior colliculus (SC).
• The superior colliculus (SC) provides a stable, labeled-line code for visual stimuli across saccades, crucial for stable perception.
• Mixed neural representations across cortical areas necessitate complex readout mechanisms for stable visual perception.