  Brain representations of curvature may be formed on the basis of either
vision or touch. Experimental and theoretical work by the author and her
colleagues has shown that the processing underlying such representations
directly depends on specific two-dimensional geometric properties of the curved
object, and on the symmetry of curvature. Virtual representations of curves
with mirror symmetry were displayed in 2D on a computer screen to sighted
observers for visual scaling. For tactile (haptic) scaling, the physical
counterparts of these curves were placed in the two hands of sighted observers,
who were blindfolded during the sensing experiment, and of congenitally blind
observers, who never had any visual experience. All results clearly show that
curvature, whether haptically or visually sensed, is statistically linked to
the same curve properties. Sensation is expressed psychophysically as a power
function of any symmetrical curve's aspect ratio, a scale invariant geometric
property of physical objects. The results of the author's work support
biologically motivated models of sensory integration for curvature processing.
They also promote the idea of a universal power law for adaptive brain control
and balancing of motor responses to environmental stimuli across sensory
modalities.
