Whiskers provide animals with complex perceptual content. In fact, all the things that whiskers actually do are fascinating.
The dimensionality of the data can be modeled according to how an animal moves them through space:
Rat whiskers move actively in one dimension, rotating at their base in a plane roughly parallel to the ground. When the whiskers hit an object, they can be deflected backwards, upwards or downwards by contact with the object. The mechanical bending of the whisker activates many thousands of sensory receptors located in the follicle at the whisker base. The receptors, in turn, send neural signals to the brain, where a three-dimensional image is presumably generated.
Hartmann and Solomon showed that their robotic whiskers could extract information about object shape by “whisking” (sweeping) the whiskers across a small sculpted head, which was chosen specifically for its complex shape. As the whiskers move across the object, strain gauges sense the bending of the whiskers and thus determine the location of different points on the head. A computer program then â€œconnects the dotsâ€ to create a three-dimensional representation of the object.
More on that “three-dimensional image” from the end of the first paragraph — whiskers indeed construct a high resolution spatial map:
Based on discoveries in primates and cats, scientists previously thought that highly refined maps representing the complexities of the external world were the exclusive domain of the visual cortex in mammals. This new map is a miniature schematic, representing the direction a whisker is moved when it brushes against an object.
“This study is a great counter example to the prevailing view that only the visual cortex has beautiful, overlapping, multiplexed maps,” said Christopher Moore, a principal investigator at the McGovern Institute and an assistant professor in the Department of Brain and Cognitive Sciences, where he holds the Mitsui Career Development Chair.
Researchers are now working towards developing code for a whisker-like sensor array to be used for robotics. Could this software have human interface applications as well?
This reminds me of the impressive and thought-provoking Haptic Radar/Extended Skin Project. Although the sensing medium in that case was ultrasound rather than a deformable, physical substrate, and the resolution of the stimulators much lower, the researchers state that they intend to make the system more whisker-like as they develop it.
[via Science Daily]