TY  - JOUR
A1  - Ohl, Sven
A1  - Brandt, Stephan A.
A1  - Kliegl, Reinhold
T1  - Secondary (micro-)saccades the influence of primary saccade end point and target eccentricity on the process of postsaccadic fixation
JF  - Vision research : an international journal for functional aspects of vision.
N2  - We examine how the size of saccadic under-/overshoot and target eccentricity influence the latency, amplitude and orientation of secondary (micro-)saccades. In our experiment, a target appeared at an eccentricity of either 6 degrees or 14 degrees of visual angle. Subjects were instructed to direct their gaze as quickly as possible to the target and hold fixation at the new location until the end of the trial. Typically, increasing saccadic error is associated with faster and larger secondary saccades. We show that secondary saccades at distant in contrast to close targets have in a specific error range a shorter latency, larger amplitude, and follow more often the direction of the primary saccade. Finally, we demonstrate that an undershooting primary saccade is followed almost exclusively by secondary saccades into the same direction while overshooting primary saccades are followed by secondary saccades into both directions. This supports the notion that under- and overshooting imply different consequences for postsaccadic oculomotor processing. Results are discussed using a model, introduced by Rolfs, Kliegl, and Engbert (2008), to account for the generation of microsaccades. We argue that the dynamic interplay of target eccentricity and the magnitude of the saccadic under-/overshoot can be explained by a different strength of activation in the two hemispheres of the saccadic motor map in this model.
KW  - Secondary saccade
KW  - Microsaccade
KW  - Saccadic error
KW  - Error-correction
KW  - Target eccentricity
Y1  - 2011
U6  - https://doi.org/10.1016/j.visres.2011.09.005
SN  - 0042-6989
SN  - 1878-5646
VL  - 51
IS  - 23-24
SP  - 2340
EP  - 2347
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Ohl, Sven
A1  - Brandt, Stephan A.
A1  - Kliegl, Reinhold
T1  - The generation of secondary saccades without postsaccadic visual feedback
JF  - Journal of vision
N2  - Primary saccades are often followed by small secondary saccades, which are generally thought to reduce the distance between the saccade endpoint and target location. Accumulated evidence demonstrates that secondary saccades are subject to various influences, among which retinal feedback during postsaccadic fixation constitutes only one important signal. Recently, we reported that target eccentricity and an orientation bias influence the generation of secondary saccades. In the present study, we examine secondary saccades in the absence of postsaccadic visual feedback. Although extraretinal signals (e.g., efference copy) have received widespread attention in eye-movement studies, it is still unclear whether an extraretinal error signal contributes to the programming of secondary saccades. We have observed that secondary saccade latency and amplitude depend on primary saccade error despite the absence of postsaccadic visual feedback. Strong evidence for an extraretinal error signal influencing secondary saccade programming is given by the observation that secondary saccades are more likely to be oriented in a direction opposite to the primary saccade as primary saccade error shifts from target undershoot to overshoot. We further show how the functional relationship between primary saccade landing position and secondary saccade characteristics varies as a function of target eccentricity. We propose that initial target eccentricity and an extraretinal error signal codetermine the postsaccadic activity distribution in the saccadic motor map when no visual feedback is available.
KW  - monocular deprivation
KW  - binocular combination
KW  - sensory balance
Y1  - 2013
U6  - https://doi.org/10.1167/13.5.11
SN  - 1534-7362
VL  - 13
IS  - 5
PB  - Association for Research in Vision and Opthalmology
CY  - Rockville
ER  -