Journal of Vision - How does saccade adaptation affect visual perception?, by Hernandez, Levitan, Banks, & Schor

Teresa D. Hernandez	Vision Science Group, School of Optometry, University of California, Berkeley, CA, USA
Carmel A. Levitan	Joint Graduate Group in Bioengineering, University of California, San Francisco and Berkeley, CA, USA
Martin S. Banks	Vision Science Group, School of Optometry, Department of Psychology, and Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA
Clifton M. Schor	Vision Science Group, School of Optometry, and Joint Graduate Group in Bioengineering, University of California, Berkeley, CA, USA

Three signals are used to visually localize targets and stimulate saccades: (1) retinal location signals for intended saccade amplitude, (2) sensory-motor transform (SMT) of retinal signals to extra-ocular muscle innervation, and (3) estimates of eye position from extra-retinal signals. We investigated effects of adapting saccade amplitude to a double-step change in target location on perceived direction. In a flashed-pointing task, subjects pointed an unseen hand at a briefly displayed eccentric target without making a saccade. In a sustained-pointing task, subjects made a horizontal saccade to a double-step target. One second after the second step, they pointed an unseen hand at the final target position. After saccade-shortening adaptation, there was little change in hand-pointing azimuth toward the flashed target suggesting that most saccade adaptation was caused by changes in the SMT. After saccade-lengthening adaptation, there were small changes in hand-pointing azimuth to flashed targets, indicating that 1/3 of saccade adaptation was caused by changes in estimated retinal location signals and 2/3 by changes in the SMT. The sustained hand-pointing task indicated that estimates of eye position adapted inversely with changes of the SMT. Changes in perceived direction resulting from saccade adaptation are mainly influenced by extra-retinal factors with a small retinal component in the lengthening condition.