The aims of this project are to identify the variables important for the control of eye and hand movements used to track visual targets moving in two dimensions. The proposal is based on the premise that studying movements in two or more dimensions reveals unexpected facets of neural control mechanisms. While considerable work has been done on reflexive and saccadic eye movements in three dimensions, multi-dimensional pursuit tracking is less well understood. Recent evidence suggests that there is much more interaction between the brain centers controlling eye and limb motion than previously thought, and this proposal also aims to further the understanding of these interactions in the context of tracking. ? ? The proposal has three specific aims.
The first aim i s to characterize qualitatively and quantitatively the response of the smooth pursuit system to step changes in target direction. Normally, ocular tracking involves saccades as well as smooth pursuit. For this aim, a paradigm has been developed to minimize the probability of intervening saccades.
The second aim i s to study interactions between ocular and manual tracking of a target. Experiments are proposed in which subjects will track targets moving in two dimensions, with the eye and/or the hand. The hypothesis to be tested is that a gaze signal provides an important input to the limb motor control system and that ocular tracking will be modified to accommodate limb control. Control experiments will test the effects of attention on the ocular response.
The third aim i s to generalize the results of the first two aims, with the goal of being able to predict normal eye and hand tracking of curvilinear motion. Studies proposed under this aim will determine whether the information used to control tracking is the same as that used for target interception, whether eye and hand tracking is under intermittent control, and whether information about curvature and rate of change of curvature of target motion is utilized in tracking. Control experiments will assess the influence of expectations on the response. The results of these experiments will be incorporated into a quantitative model. ? ? The results of this work will characterize normal human tracking behavior. As such they will provide a norm for diagnostic testing in patient populations. Furthermore, this work will identify the logical operations carried out by different brain areas in transforming a visual signal into motor commands to the eyes and to the limbs, and will consequently refine our understanding of brain function.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY013704-03
Application #
6805307
Study Section
Visual Sciences B Study Section (VISB)
Program Officer
Hunter, Chyren
Project Start
2002-09-30
Project End
2006-06-30
Budget Start
2004-07-01
Budget End
2006-06-30
Support Year
3
Fiscal Year
2004
Total Cost
$259,875
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Neurosciences
Type
Schools of Medicine
DUNS #
555917996
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Kerrigan, Stephen J; Soechting, John F (2007) Anisotropies in the gain of smooth pursuit during two-dimensional tracking as probed by brief perturbations. Exp Brain Res 180:435-48
Mrotek, Leigh A; Soechting, John F (2007) Predicting curvilinear target motion through an occlusion. Exp Brain Res 178:99-114
Mrotek, Leigh A; Flanders, Martha; Soechting, John F (2006) Oculomotor responses to gradual changes in target direction. Exp Brain Res 172:175-92
Soechting, John F; Mrotek, Leigh A; Flanders, Martha (2005) Smooth pursuit tracking of an abrupt change in target direction: vector superposition of discrete responses. Exp Brain Res 160:245-58
Mrotek, Leigh A; Flanders, Martha; Soechting, John F (2004) Interception of targets using brief directional cues. Exp Brain Res 156:94-103
Soechting, John F; Mrotek, Leigh A; Flanders, Martha (2003) Time constants in the perception of a change in the direction of motion in humans. Neurosci Lett 348:56-60