Do head-on-trunk signals modulate disengagement of spatial attention?

Body schema is indispensable for sensorimotor control and learning, but whether it is associated with cognitive functions, such as allocation of spatial attention, remains unclear. Observations in patients with unilateral spatial neglect support this view, yet data from neurologically normal participants are inconsistent. Here, we investigated the influence of head-on-trunk positions (30° left or right, straight ahead) on disengagement of attention in healthy participants. Five experiments examined the effects of valid or invalid cues on spatial shifts of attention using the Posner paradigm. Experiment 1 used a forced-choice task. Participants quickly reported the location of a target that appeared left or right of the fixation point, preceded by a cue on the same (valid) or opposite side (invalid). Experiments 2, 3, and 4 also used valid and invalid cues but required participants to simply detect a target appearing on the left or right side. Experiment 5 used a speeded discrimination task, in which participants quickly reported the orientation of a Gabor. We observed expected influences of validity and stimulus onset asynchrony as well as inhibition of return; however, none of the experiments suggested that head-on-trunk position created or changed visual field advantages, contrary to earlier reports. Our results showed that the manipulations of the body schema did not modulate attentional processes in the healthy brain, unlike neuropsychological studies on neglect patients. Our findings suggest that spatial neglect reflects a state of the lesioned brain that is importantly different from that of the normally functioning brain.