Higher order, multifeatural object encoding by the oculomotor system.

Area of Science:

• Cognitive Neuroscience
• Oculomotor Research
• Visual Perception

Background:

• Previous research shows behavioral relevance increases competition in saccade target selection, evidenced by increased saccade curvature and neural activity.
• These effects were previously limited to simple feature singletons, leaving open the question of whether complex object differences also modulate saccade vectors.

Purpose of the Study:

• To investigate whether complex featural differences between higher-order objects influence saccade curvature during visual search.
• To quantify the relationship between objective similarity (OS) of distractors to a target and saccade deviation.

Main Methods:

• Human participants performed a visual search saccade task with distractors flanking the target.
• Subsets of features shared between distractors and the target were systematically varied to define objective similarity (OS).
• Saccade curvature was measured as an indicator of competition during target selection.

Main Results:

• Saccades were found to deviate away from the distractor with the highest objective similarity (OS) towards the target.
• A linear relationship was observed between the magnitude of saccade deviation and the number of feature differences between the most similar distractor and the target.
• Saccade curvature occurred early in the movement, within the first 20-30 milliseconds.

Conclusions:

• Saccadic target selection processing dynamically reweights vector representations for movement planning based on behavioral relevance, even for complex, novel stimuli.
• The oculomotor system integrates visual and cognitive information from higher-order cortical processing networks for saccadic movement planning.
• These findings extend previous observations from simple feature singletons to complex object representations, highlighting the dynamic nature of oculomotor control.