Eccentricity Confound in EEG-based Visual Attention Decoding from Gaze-Fixated Neural Tracking of Motion in Natural Videos

TL;DR

This study examines how visual eccentricity influences EEG-based neural tracking of motion during natural videos, revealing an eccentricity confound that affects attention decoding accuracy.

Contribution

It demonstrates that neural tracking of motion is valid under gaze fixation but is significantly affected by eccentricity, highlighting a confound in current attention decoding methods.

Findings

Neural tracking of motion is possible under gaze fixation.

Tracking strength predicts attention levels.

Eccentricity significantly reduces neural tracking at larger distances.

Abstract

Objective. Decoding visual attention from brain signals during naturalistic video viewing has emerged as a new direction in brain-computer interface research. Current methods assume that stronger coupling between object motion and neural activity indicates higher attention, but this can be confounded by eye movement artifacts and stimulus properties. This study investigates how visual eccentricity (the distance between a visual object and the fixation point) affects neural responses when eye movement artifacts are controlled. Approach. EEG signals were recorded across three tasks that manipulated object eccentricity and attention conditions while participants maintained gaze fixation. Correlation analysis and match-mismatch decoding were performed to quantify the neural tracking of object motion. Main results. The analysis supports three conclusions: (1) neural tracking of object motion in natural videos works under gaze fixation; (2) the strength of neural tracking under gaze fixation is predictive of attention; and (3) there exists a significant eccentricity confound in the EEG responses, with poorer neural tracking of motion at larger eccentricities. Significance. These results provide critical evidence that findings from previous free-viewing studies reflect genuine neural processing rather than mere oculomotor artifacts. However, the identified eccentricity effect highlights a major limitation for current decoding approaches that assume coupling strength reflects attention levels alone.