Goal-directed action planning modulates surround suppression in the visual system

Action planning has been traditionally viewed through the lens of motor command specification. However, converging evidence indicates planning also modulates early cortical sensory systems. While previous studies mainly focused on the modulation to a single target object, it remains unclear how action planning modulates the spatial interaction between target and flankers in a cluttered scene. Here we directly tested this using EEG with frequency tagging to measure visual surround suppression — a key cortical mechanism for object segregation — while participants (22 females, 14 males) planned to grasp a target among flankers. We hypothesized that surround suppression, essential for distinguishing the target from distractors, would be enhanced when planning to grasp the target compared to planning a non-target-directed action where segregation is less critical. Further, based on evidence suggesting that surround suppression when executing a grasping movement is greater for dominant than nondominant hand, we predict that this specificity should likewise exist during planning . Confirming our predictions, EEG results demonstrated that planning a grasp significantly amplified surround suppression relative to planning a simple key release. This enhancement was additively modulated by target relevance and hand dominance, being strongest when planning a dominant-hand grasp. Crucially, a control task (planning a perceptual judgment) elicited no such suppression, supporting the action-specificity of this sensory tuning. These results provide neural evidence at the level of visual mechanisms, that action preparation actively and selectively refines early sensory processing for efficient goal-directed action. Significance Statement The neural mechanisms of the top-down modulation of the motor system on the sensory system during action planning remain unclear. Previous studies mainly focused on modulation during action on a single object. Here, we demonstrate that grasp planning modulates surround suppression to enhance edge detection and facilitate figure-ground segregation—all essential for precise grasping when the target is surrounded by flankers. Our results suggest that action planning proactively enhances specific sensory computations during action preparation.