Seminar Details
2005-12-20 (14.00 pm) : Transforming vision into a geometrically optimal reach plan
At Auditoire Euler
Organized by Mathematical Engineering
Speaker :
Blohm, Gunnar
Abstract :
A fundamental question in neuroscience is how the brain
transforms visual signals into accurate reach commands.
Many theories exist, but the complete three-dimensional
(3D) geometry linking the eyes to the head and shoulder
has never been formally modeled for reaching. Here, I
developed such a model and tested it experimentally against
the predictions of one popular alternative, the direct
transformation hypothesis, which assumes that reach plans
in eye coordinates can be used directly to control the limb.
My new model optimally accounted for the 3D orientations of
the eyes and head. In contrast, a 3D version of the direct
transformation hypothesis predicted large reaching errors.
These error patterns were never observed in human subjects.
This demonstrates that the brain uses internal estimates of
eye and head configurations to optimize the reach plan and
places constraints on algorithms that attempt to use brain
signals for the neural control of arm prostheses.
I will start introducing the neurophysiological and behavioral
background of visuo-motor transformations and provide some details
about the mathematical formalism (dual quaternions) I used for the
modeling part of this study. Dual quaternions are usually utilized
in image analysis and robotic control because of their advantageous
mathematical and numerical properties. They represent a unified
formalism describing translations and rotations but avoiding the
non-commutativity problems of rotations. At the end of the presentation,
I will also spend some time discussing the implications of this work on
our understanding of visuo-motor transformations.