Our research is directed at understanding information processing in
the visual system during visual and motor judgements. Our laboratory
in Gießen includes set-ups for studies on visual perception (color
vision and perception of natural scenes) and for studies on
sensori-motor coordination, including state-of-the-art equipment for
eye-tracking (EyeLinkII, DPI Eyetracker), motion analysis
(Optotrak-3020 System, Zebris Tracking System), and for the
manipulation of visual-proprioceptive information (PHANToM- force
feedback device).
We currently primarily use psychophysical methods, but future
research questions are also directed at studying the neural correlates
of sensori-motor control. Collaborations have recently been
established within the joint graduate program Neuronal
representation and action control with the Department of
Neurophysics and
Departement of Experimental and Clinical Biopsychology at the
nearby Philipps-Universität
Marburg.
In addition, our lab participates in national and international
co-operations directed at studying the behavioral and neural aspects
of sensori-motor control (Research Training Network on Perception for Recognition and
Action funded by the European Commission; Forschungsverbund MODKOG,
funded by the BMBF).
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Color Vision
Prof. Karl Gegenfurtner, Ph.D. ,
Dr. Thorsten Hansen,
Dipl.-Psych. Lars Pracejus, &
Dipl.-Biol. Sebastian Walter
The perception of color is a central component of primate vision.
Colour facilitates object perception and recognition, and has an
important role in scene segmentation and visual memory. Despite the
long history of colour vision studies, much has still to be learned
about the physiological basis of colour perception. Recent studies are
beginning to indicate that colour is processed not in isolation, but
together withinformation about luminance and visual form to achieve a
unitary and robust representation of the visual world.
Perception and eye movements in natural scenes
Dipl.-Inf. Jan Drewes,
M.A. Psych. Brian White
We study the principles underlying the selection of fixation points
under natural viewing conditions. We study fixation patterns and
saccadic latencies of human subjects viewing under natural images and
videos of natural scenes and ask how stimulus features like contrast,
color and spatial frequency content interacts with the top-down mediated
expectations.
Sensory-motor decision making (Emmy Noether-Nachwuchsgruppe)
Dr. Knut Drewing,
Dipl.-Ing. (FH) Martin Stritzke,
Dr. Julia Trommershäuser
This research combines theoretical and experimental methods to
investigate visuo-motor strategies during the planning and execution
of goal-directed (arm) movements under risk. In the experiments, we
study human movement planning in environments where there are explicit
gains and losses associated with the outcomes of actions and compare
human performance to a model of optimal performance based on
statistical decision theory. The model comprises approaches of motor
control,statistical and Bayesian decision theory and is based on the
idea that goal-directed movements reflect a movers choice under the
constraints of the perceptual and motor system.
Smooth pursuit eye movements
Dr. Doris Braun,
Prof. Karl Gegenfurtner, Ph.D. ,
PD Dr. Dirk Kerzel,
Dipl.-Psych. Lars Pracejus,
Dipl.-Psych. Miriam Spering,
Dipl.-Psych. Nathalie Ziegler
If an object of interest moves in our environment, we are able to
elicit smooth pursuit eye movements that keep the image of the moving
object stationary on our fovea. The processing of visual motion
underlying the execution of smooth pursuit eye movements is very
similar to the processing underlying the perception of visual motion.
perception and pursuit share some of the neural signals that are a
result of objects moving across the retina. On the other hand, pursuit
has many neural connections that are not part of the perceptual system.
In addition, cognitive factors including attention, prediction and
learning have been demonstrated to influence the execution of smooth
pursuit.
Our experimental approach comprises psychophysics measurements under
simultaneous tracking of eye-movements to separate the underling
neuronal mechanisms driving perception or the ocolumotor response.
Visually guided motor behavior
Dr. Volker Franz,
Dipl.-Psych. Denise de Grave,
Dipl.-Psych. Constanze Hesse,
Dipl.-Psych. Jutta Billino
We investigate the complex mechanisms involved in interactions of
humans with the environment. The versatility of the human visuo-motor
system can be seen in the ease with which we perform everyday tasks as
reaching and grasping for objects under varying visual input. For
example, we can easily grasp fragile objects like eggs (we might even
learn to joggle with them), or we might learn to adapt quickly to the
distortions introduced by wearing left-right reversing prisms, etc. On
the other side, it is still very difficult to devise technical systems
which are capable of only a subset of the capabilities of the human
motor system.
One of the questions which we have been studying very intensively
during the last years is whether the visual guidance of motor behavior
is achieved by different processes (and neuronal substrates) as our
conscious (visual) perception. Studies on neurological patients
suggest such a division of labor in the human brain and it was
suggested that this dissociation between vision-for-action and
vision-for-perception can also be found in healthy humans. Support for
this view came from studies which found that grasping is less affected
by visual illusions than perception. Our results, to the contrary,
suggest that the motor system uses very similar processes and neuronal
signals as visual perception. This suggests that the visual brain is
more coherent than currently proposed by a number of theories in
visual neuroscience.
We use an Optotrak 3020 system to measure
precisely position and timing of grasping and pointing movements. To
control the Optotrak we use a specifically designed Matlab Toolbox
(or C++).
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