TY  - JOUR
A1  - Ohl, Sven
A1  - Wohltat, Christian
A1  - Kliegl, Reinhold
A1  - Pollatos, Olga
A1  - Engbert, Ralf
T1  - Microsaccades Are Coupled to Heartbeat
JF  - The journal of neuroscience
N2  - During visual fixation, the eye generates microsaccades and slower components of fixational eye movements that are part of the visual processing strategy in humans. Here, we show that ongoing heartbeat is coupled to temporal rate variations in the generation of microsaccades. Using coregistration of eye recording and ECG in humans, we tested the hypothesis that microsaccade onsets are coupled to the relative phase of the R-R intervals in heartbeats. We observed significantly more microsaccades during the early phase after the R peak in the ECG. This form of coupling between heartbeat and eye movements was substantiated by the additional finding of a coupling between heart phase and motion activity in slow fixational eye movements; i.e., retinal image slip caused by physiological drift. Our findings therefore demonstrate a coupling of the oculomotor system and ongoing heartbeat, which provides further evidence for bodily influences on visuomotor functioning.
KW  - eye movements
KW  - heartbeat
KW  - microsaccades
Y1  - 2016
U6  - https://doi.org/10.1523/JNEUROSCI.2211-15.2016
SN  - 0270-6474
VL  - 36
SP  - 1237
EP  - 1241
PB  - Society for Neuroscience
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ohl, Sven
A1  - Kliegl, Reinhold
T1  - Revealing the time course of signals influencing the generation of
JF  - Vision research : an international journal for functional aspects of vision.
N2  - Saccadic eye movements are frequently followed by smaller secondary saccades which are generally assumed to correct for the error in primary saccade landing position. However, secondary saccades can also occur after accurate primary saccades and they are often as small as microsaccades, therefore raising the need to further scrutinize the processes involved in secondary saccade generation. Following up a previous study, we analyzed secondary saccades using rate analysis which allows us to quantify experimental effects as shifts in distributions, therefore going beyond comparisons of mean differences. We use Aalen’s additive hazards model to delineate the time course of key influences on the secondary saccade rate. In addition to the established effect of primary saccade error, we observed a time-varying influence of under- vs. overshooting – with a higher risk of generating secondary saccades following undershoots. Moreover, increasing target eccentricity influenced the programming of secondary saccades, therefore demonstrating that error-unrelated variables co-determine secondary saccade programs. Our results provide new insights into the generative mechanisms of small saccades during postsaccadic fixation that need to be accounted for by secondary saccade models.
KW  - Eye movements
KW  - Corrective saccades
KW  - Secondary saccades
KW  - Rate analysis
KW  - Survival analysis
Y1  - 2016
U6  - https://doi.org/10.1016/j.visres.2016.06.007
SN  - 0042-6989
SN  - 1878-5646
VL  - 124
SP  - 52
EP  - 58
PB  - Elsevier
CY  - Oxford
ER  -