title: Fine-scale plasticity of microscopic saccades.
abstract: When asked to maintain their gaze steady on a given location, humans continually perform microscopic eye movements, including fast gaze shifts known as microsaccades. It has long been speculated that these movements may contribute to the maintenance of fixation, but evidence has remained contradictory. We used a miniaturized version of saccadic adaptation, an experimental procedure by which motor control of saccades is modified through intrasaccadic displacements of the target. We found that the statistical distribution of microsaccade amplitudes changes after brief exposure to systematic shifts of the fixation point during microsaccade occurrence. Shifts in the same directions as microsaccades produce movements with larger amplitudes, whereas shifts against microsaccade directions result in smaller movements. Our findings show that microsaccades are precisely monitored during fixation and that their motor program is modified if the postsaccadic target position is not at the expected retinal location. These results demonstrate that saccadic adaptation occurs even when the stimulus is already close to the foveal center and precise execution of the movement may not be critical. They support the proposal that adaptation is necessary to maintain a consistent relationship between motor control and its visual consequences and that the representation of space is intrinsically multimodal, even during fixation.
authors.affiliation: Institute for Psychology, University of Muenster, 48149 Muenster, Germany, Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Muenster, 48149 Muenster, Germany, and.
authors.forename: Katharina
authors.initials: K
authors.lastname: Havermann
authors.affiliation: Department of Psychology and Graduate Program in Neuroscience, Boston University, Boston, Massachusetts 02215.
authors.forename: Claudia
authors.initials: C
authors.lastname: Cherici
authors.affiliation: Department of Psychology and Graduate Program in Neuroscience, Boston University, Boston, Massachusetts 02215.
authors.forename: Michele
authors.initials: M
authors.lastname: Rucci
authors.affiliation: Institute for Psychology, University of Muenster, 48149 Muenster, Germany, Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Muenster, 48149 Muenster, Germany, and mlappe@uni-muenster.de.
authors.forename: Markus
authors.initials: M
authors.lastname: Lappe
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D010775:Photic Stimulation; D012438:Saccades / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: fixation; learning; microsaccades; saccadic adaptation