Tactile Shape Processing

The broad aim of this research is to understand how the size and shape of objects are represented in the nervous system. There are three aims.

The first aim is to determine how stimuli presented to multiple fingers on the same and opposite hands interact. In these studies, single and multiple oriented edges and textured stimuli are presented to the fingers of animals performing a visual fixation task. In some cases the stimuli form coherent bars across the digits and in others, they form random patterns. The goal is to understand how information from different fingers on the same and opposite hands is integrated together.

The second aim is to investigate the response properties of neurons in somatosensory cortex in animals actively and passively touching objects that vary in shape. In these experiments the animals either actively palpate objects with their fingers or the fingers are passively positioned at different combinations of flexion and extension. The fingers are then stimulated with surfaces that simulate objects that vary in curvature. The goal is to understand how curvature is represented in the nervous system.

The third aim is to investigate the response properties of neurons in somatosensory cortex of objects that vary in size. In these experiments the finger pads of opposing digits are stimulated while the spread between digits is systematically varied.

The figure shows the response of a neuron in SII cortex to an oriented bar centered on the distal. middle, and proximal pads of the second through fifth digit. This figure demonstrates that the neurons in SII have large receptive fields with orientation tuning properties that are similar across finger pads.

Hsiao SS, Lane JW, Fitzgerald PJ (2002) Representation of Orientation in the Somatosensory System. Behav Brain Res (in press).