Daniela will give a Young investigator talk at the Gordon Research Conference on Eye Movements on Monday 01 august 2011 at the University of New England http://www.grc.org/programs.aspx?year=2011&program=eyemove
Eye proprioception used for visual localization only if in conflict with
the oculomotor plan
Daniela Balslev1,2, Marc Himmelbach1, Hans-Otto Karnath1, Svenja Borchers1, Bartholomaeus Odoj1
1 Center of Neurology and Hertie Institute for Clinical Brain Research, University of Tuebingen , Germany; 2Department of Psychology, University of Copenhagen, Denmark
There are two hypotheses about how the efference copy of the motor command and the extraocular muscle proprioception are combined to locate retinal objects relative to the body: 1. only the efference copy is used whereas proprioception is a slow recalibrator of the forward model [Steinbach, 1987, Acta Psychologica, 63, 297-306] and 2. both signals are used together as a weighted average [Gauthier et al, 1990, Science, 249(4964), 58-61]. We tested these hypotheses in a patient (RW) with a circumscribed lesion of the right postcentral gyrus, that overlaps the eye proprioceptive representation [Balslev et al., 2011, Human Brain Mapping, 32, 624-631]. RW was as accurate and precise as the control group (n=19) in locating a lit LED that she viewed through the eye contralateral to the lesion (p > 0.6). However, when the task was preceded by a brief (<1s) and gentle push to the closed eye, which perturbs eye position and stimulates eye proprioceptors in the absence of a motor command, RW’s accuracy decreased (p<0.001). We suggest that eye proprioception is used only as a back-up during visual localization. Proprioception is compared with the efference copy and incorporated into the eye position estimate in conditions with a mismatch.
Acknowledgments: Funded by the Danish Medical Research Councils and a Marie Curie intra-european fellowship (DB). Grant numbers: 09-072209 and PIEF-GA-2009-252424.