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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 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 Department 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).
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 there is still much 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 with information about luminance and visual form to achieve a unitary and robust representation of the visual world.
- Hansen, T., & Gegenfurtner, K. R. (2006). Higher level chromatic mechanisms for image segmentation. Journal of Vision, 6(3), 239\u2013259. [PDF]
- Hansen, T., Olkkonen, M., Walter, S. & Gegenfurtner, K. R. (2006). Memory modulates color appearance. Nature Neuroscience, 9(11), 1367–1368.
- Gegenfurtner, K.R. (2003) Cortical mechanisms of colour vision. Nature Reviews Neuroscience, 4, 563–572. [PDF]
- Gegenfurtner, K.R. & Kiper, D.C. (2003) Color vision. Annual Review of Neuroscience, 26, 181–206.[PDF]
Haptic perception is inherently rather active than passive. It substantially depends upon the active intake of sensory information via exploratory movements. Whereas, for example, eye movements in vision primarily serve the re-orientation of the fovea towards the stimulus of interest, in active touch it is the exploratory (hand) movements that generate the sensory signals from which the percept is then derived. In quantitative studies, we examine what the consequences of exploratory movement for haptic perception are and according to which criteria we control our exploratory movements. Further studies investigate into the combination of haptic with visual or auditory information as regards its development in childhood (cooperation with Dr. Jovanovic from Entwicklungspsychologie), its boundary conditions (cooperation with Matthias Bischoff from BION) and the multimodal guidance of motor timing.
- Drewing, K., & Ernst, M.O. (2006). Integration of force and position cues for shape perception through active touch. Brain Research 1078, 92-100.
- Drewing, K. (2006). Integration of tactile-kinesthetic and auditory (re-)afference in the timing of movements. Proceedings of the Eurohaptics international conference 2006, 43-48.
Perception and eye movements in natural scenes
We study the principles underlying the selection of fixation targets 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 interact with top-down mediated expectations.
- Thorpe, S., Gegenfurtner, K.R., Fabre-Thorpe, M. & Bülthoff, H.H. (2001) Detection of animals in natural images using far peripheral vision. European Journal of Neuroscience, 14, 869-876. <Get PDF file>
- Gegenfurtner, K.R. & Rieger, J. (2000) Sensory and cognitive contributions of color to the perception of natural scenes.Current Biology, 10, 805-808. <Get PDF file>
Eye movements and Visual Perception
Dr. Jutta Billino, Dr. Doris Braun, Prof. Karl Gegenfurtner, Ph.D.
Humans frequently move their eyes, either to fixate a new location in the visual field (saccadic eye movements), or to keep fixation on a moving object (smooth pursuit eye movements). These eye movements pose two problems. First, an appropriate target location and execution time has to be selected for the eye movements. Hence we study, which visual signals are used to guide these eye movements, i.e. how visual perception influences the control of eye movements. Second, the execution of eye movements changes the visual image on the retina. To maintain a clear and stable perception of the world, the visual system has to cope with the retinal image motion. In this context we study how visual perception is affected by the execution of concurrent eye movements.
Our experimental approach comprises psychophysics measurements under simultaneous tracking of eye movements to investigate the bidirectional relationship between perception and eye movements.
- Schütz, A.C., Braun, D.I., Kerzel, D. & Gegenfurtner, K.R. (2008) Improved visual sensitivity during smooth pursuit eye movements. Nature Neuroscience, 11, 1211-1216.
- Spering, M. & Gegenfurtner, K.R. (2008). Contextual effects on motion perception and smooth pursuit eye movements. Brain Research, 1225, 76-85.
- White, B.J., Stritzke, M. & Gegenfurtner, K.R. (2008) Saccadic facilitation in natural backgrounds. Current Biology, 18, 124-128.
Visually guided motor behavior
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 such 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 juggle them), or we might learn to adapt quickly to the distortions introduced by wearing left-right reversing prisms, etc. On the other hand, 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 we have been studying intensively during recent 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 brain is more coherent than currently proposed by a number of theories in visual neuroscience.
- V. H. Franz. Planning versus online control: Dynamic illusion effects in grasping? Spatial Vision, 16(3-4):211 - 223, 2003. [PDF]
- V. H. Franz. Action does not resist visual illusions. Trends in Cognitive Sciences, 5(11):457 - 459, 2001. [PDF]
- V. H. Franz, K. R. Gegenfurtner, H. H. Bülthoff, and M. Fahle. Grasping visual illusions: No evidence for a dissociation between perception and action. Psychological Science, 11(1):20 - 25, 2000. [PDF]