Non-target stimuli in the visual field impact movement preparation


The present work provides an empirical test of the Dynamic Field Theory (DFT) of visuospatial cognition. The DFT is in a class of bi-stable neural network models applied to explain how visual information is integrated during the preparation of reaching responses (Erlhagen & Schöner, 2002). The DFT posits that peaks of neural activation representing potential targets are represented within an activation field. Objects that are close in space produce peaks that overlap, whereas objects that are far apart produce distinct peaks with non-overlapping distributions. As such, the DFT predicts reaction times to potential targets that are close in space will be faster than those to targets that are far apart. The present work provided the first test of this prediction as it applies to reaching movements. Healthy young adults (N=13) completed reaching movements to virtual targets in the horizontal plane in two separate tasks. Visual targets were gray circles with a diameter of 3.5 cm, located 17 cm from a central start position inline with body midline. All targets appeared on the horizontal axis. In the control task, participants were shown two potential targets. After 400 ms at the start position, one of the two targets turned blue indicating it was the target for the trial. The second target remained visible for the duration of the trial. In the distractor task, the same series of events took place, however, after the first target turned blue, the second target flashed green serving as a distractor during the reaching movement. In both tasks, reaction times were fastest when the two targets were adjacent to one another and increased as the distance between targets increased. These findings support the tenets of the DFT and demonstrate that non-target stimuli in the visual field can influence movement preparation.