Prof. Dr. Frank Bremmer
Department
of Neurophysics
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Multisensory space representation in primate posterior parietal cortex
The primate posterior
parietal cortex is involved in the multisensory processing of spatial
information. Damage of this part of the cerebrum leads to marked, and often
long lasting, disturbances in spatial perception and in the production of visually-guided action. Much has been learned about
the underlying cortical mechanisms subserving
spatially-oriented behavior in the last twenty years,
thanks in large part to the development of awake
primate behavioral physiology and to detailed
investigations of behavioral deficit following brain
damage in humans. We aim at understanding the underlying neuronal circuits
involved in spatial processing by means of neurophysiological experiments
(single cell recordings in awake monkeys and fMRI studies in human subjects),
and psychophysical studies in human subjects. Both approaches, used in
parallel, are expected to lead to an understanding of the basic principles of
the processing of spatial information in the primate brain.
Dynamic
representation of visual space
With every saccadic eye
movement the retinal image of the world changes. We perform more than a hundred
thousand saccades every day but never experience the world to move. The brain
generates a stable percept of visual space. However, during some tens of
milliseconds before and after an eye movement this spatial stability is
violated. Visual stimuli that are briefly flashed during this time are seen at
grossly distorted positions. These effects show the process of space
representation at work. We investigate how the stable perception of space is
dynamically updated during eye movements.
Analysis of
self-motion information
Optic
flow is the visual motion pattern that we experience during self-motion. For
instance when we walk forward or drive a car the image of the world appears to
expand. This image motion is used to control our movement through space. A main
question is how the brain combines the many cues to self-motion that it has
available. These cues encompass visual, extraretinal,
and vestibular signals.We try to understand how optic
flow is analysed by the brain and how it is combined with real self-motion
information.
Marburg, 16. Oktober 2006