The effect of exogenous and endogenous visual cues on the spatial and temporal features of movements performed during a rapid target aiming task


Both visual and auditory exogenous cues have been shown to bias movement trajectories when participants are required to initiate a goal-directed movement prior to knowing the final target. Comparing exogenous and endogenous cues can provide information about attentional processing during movement performance. This study assessed the temporal and spatial features of movements in response to exogenous versus endogenous visual cues during a rapid decision making aiming task. Twelve right-handed individuals (19-23 years-old; 4males/8females) performed rapid reaching movements toward four targets displayed on a touchscreen monitor. Reaching movements were initiated in response to an auditory cue prior to target identification. 50ms following movement initiation the target was identified by an exogenous (filled square) or endogenous (central arrow) cue. Target conditions were blocked and counter-balanced according to cue type. An Optotrak 3D Investigator (NDI) was used to record participant reach trajectories at 500Hz. Performance variables were analyzed using a 2 condition by 2 location repeated measures ANOVA and movement trajectories using a 2 condition by 2 target by 7 percent of MT. MT was significantly shorter towards the right and in response to exogenous cues. Significant trajectory deviations between the left and right began at 60% of movement trajectory and continued until movement completion, despite cue type. Therefore, spatial averaging occurred for the initial 60% of movement trajectory and was not contingent on cue type. Overall, online attentional processing occurred more rapidly in response to directly interpretable stimuli and spatial characteristics of the trajectory deviation did not vary based on cue type.

Acknowledgments: Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC)