Online corrections can produce illusory bias during closed-loop pointing.
This experiment examined whether the impact of pictorial illusions during the execution of goal-directed reaching movements is attributable to ocular motor signaling. We analyzed eye and hand movements directed toward both the vertex of the Müller-Lyer (ML) figure in a closed-loop procedure. Participants pointed to the right vertex of a visual stimulus in two conditions: a control condition wherein the figure (in-ML, neutral, out-ML) presented at response planning remained unchanged throughout the movement, and an experimental condition wherein a neutral figure presented at response planning was perturbed to an illusory figure (in-ML, out-ML) at movement onset. Consistent with previous work from our group (Heath et al. in Exp Brain Res 158:378-384, 2004; Heath et al. in J Mot Behav 37:179-185, 2005b), action-bias present in both conditions; thus illusory bias was introduced into during online control. Although primary saccades were influenced by illusory configurations (control conditions; see Binsted and Elliott in Hum Mov Sci 18:103-117, 1999a), illusory bias developed within the secondary "corrective" saccades during experimental trials (i.e., following a veridical primary saccade). These results support the position that a unitary spatial representation underlies both action and perception and this representation is common to both the manual and oculomotor systems.
Ehresman
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Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, AB, Canada. deborah.saucier@uleth.ca
Saucier
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D
Heath
M
M
Binsted
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G
D015982:Bias; D005133:Eye Movements / Q000502:physiology*; D007839:Functional Laterality; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D009043:Motor Activity / Q000502:physiology*; D009068:Movement / Q000502:physiology; D009802:Oculomotor Nerve / Q000502:physiology*; D009903:Optical Illusions; D009949:Orientation; D010775:Photic Stimulation; D011597:Psychomotor Performance; D011930:Reaction Time; D012438:Saccades / Q000502:physiology*; D013028:Space Perception; D014785:Vision, Ocular / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*