MSTd neuronal basis functions for the population encoding of heading direction

Area of Science:

• Neuroscience
• Computational Neuroscience
• Visual Processing

Background:

• Basis functions are fundamental in neural computation for approximating nonlinear functions.
• The dorsal medial superior temporal (MSTd) area is crucial for processing visual information related to self-motion and navigation.

Purpose of the Study:

• To investigate if MSTd neurons utilize basis functions for simultaneous encoding of heading direction, eye position, and ocular pursuit velocity.
• To determine the neural coding format for head-centered focus of expansion (FOE), eye position, and pursuit direction in MSTd.

Main Methods:

• Utilized optimal linear estimators to analyze single-trial responses from 144 MSTd neurons.
• Quantified the accuracy of estimating head-centered FOE, eye position, and pursuit direction.
• Examined the neural code format, specifically looking for simultaneous encoding and nonlinear interactions predicted by the basis function hypothesis.

Main Results:

• MSTd neurons accurately estimated head-centered FOE, eye position, and pursuit direction within 2-3 degrees.
• 95% of MSTd neurons encoded at least two signals simultaneously, with 76% encoding all three.
• 90% of neurons encoding multiple signals exhibited nonlinear interactions between variables.

Conclusions:

• Findings support the hypothesis that MSTd neurons employ basis functions to represent optic flow FOE, eye position, and pursuit.
• MSTd neurons demonstrate complex, nonlinear coding strategies essential for integrating multiple visual and motor signals for navigation.