Development of spatial coarse-to-fine processing in the visual pathway

TL;DR

This study models the development of spatial frequency tuning in the visual pathway, emphasizing the role of thalamocortical interactions and feedback mechanisms, and how these processes evolve from kittens to adults.

Contribution

The paper introduces a thalamocortical firing-rate model that incorporates feedback and analyzes its impact on coarse-to-fine processing development.

Findings

Cortical feedback influences spatial frequency tuning more in kittens than in adults.

Antagonistic center-surround RF relationships are crucial for coarse-to-fine processing.

LGN RF parameters significantly affect cortical spatial frequency responses.

Abstract

The sequential analysis of information in a coarse-to-fine manner is a fundamental mode of processing in the visual pathway. Spatial frequency (SF) tuning, arguably the most fundamental feature of spatial vision, provides particular intuition within the coarse-to-fine framework: low spatial frequencies convey global information about an image (e.g., general orientation), while high spatial frequencies carry more detailed information (e.g., edges). In this paper, we study the development of cortical spatial frequency tuning. As feedforward input from the lateral geniculate nucleus (LGN) has been shown to have significant influence on cortical coarse-to-fine processing, we present a firing-rate based thalamocortical model which includes both feedforward and feedback components. We analyze the relationship between various model parameters (including cortical feedback strength) and responses. We confirm the importance of the antagonistic relationship between the center and surround responses in thalamic relay cell receptive fields (RFs), and further characterize how specific structural LGN RF parameters affect cortical coarse-to-fine processing. Our results also indicate that the effect of cortical feedback on spatial frequency tuning is age-dependent: in particular, cortical feedback more strongly affects coarse-to-fine processing in kittens than in adults. We use our results to propose an experimentally testable hypothesis for the function of the extensive feedback in the corticothalamic circuit.