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Donald Kalar, Dorion Liston, Bernard Adelstein, Leland Stone; Shared positional noise in manual reaching and saccadic eye movements. Journal of Vision 2013;13(9):1223. doi: https://doi.org/10.1167/13.9.1223.
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Coordination between multiple motor systems requires effecting a motor goal in several coordinate frames. Variability in movement amplitude could, in theory, arise at one of several levels of sensorimotor processing, from input sensory noise in a central estimate of target location to output motor noise that contributes to behavioral variability. To test for a central source of sensory variability in the estimate of target location, we measured and compared movement endpoints for manual reaching and saccadic eye movements. Methods. Supine observers (n = 11) were asked to look at and point to a dim circular spot at locations eccentric (-35 to +35 degrees horizontal, +6 to -33 degrees vertical) relative to a central fixation LED. We measured motor endpoints for the reaching movement and the saccadic (eye-in-head) movements under four vibration conditions (±0.5 Gx at 8, 12, 16 Hz plus a no-vibration control), using a high-precision head and eye tracker and two touchscreen displays located symmetrically on either side the central LED. Vibration allowed us to alter the ratio of visual to motor noise. We computed endpoint error by subtracting the movement endpoint from the target location, and tested for a shared sensory drive by correlating the residual absolute error between the two movements. Results. Across observers, overall, we found a significant (p <0.05, Student’s t) non-zero correlation between the magnitude of the residual error from both movement systems. Conclusions. Our results rule out the idea that completely unshared sources of sensorimotor variability dominate manual reaching and saccadic performance. Our results are consistent with the idea that a central source of sensory positional noise propagates through the encoding of target location for both motor systems.
Meeting abstract presented at VSS 2013
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