9408719 Greenspan Somatosensory nerve cells convey information about touch, temperature, and noxious (irritating or painful) stimuli. The cutaneous somatosensory system involves the senses for mechanoreception, thermoreception, and nociception coming from the skin and surface of the body. We know far less about somatosensory processing than we do about the major senses of sight or hearing. To understand how the brain receives and represents somatosensory information, we must know how well the neural components of this system can discriminate among the various physical dimensions of stimulation. The nerve fibers coming from the skin, called the primary afferent fibers, generally are selectively responsive to only a single modality of these stimuli. Many of the nerve cells within the spinal cord, though, receive input converging from different afferent classes, and so respond to multiple types of cutaneous stimuli. This project uses a novel precisely controlled method for stimulation to get a new level of quantification of stimulus-response functions. The discrimination capabilities of these neurons then are analyzed in the context of signal detection theory. Comparing the responses of spinal neurons with the primary afferents under identical conditions allows the identifying how sensory coding transforms signals at this level of the central nervous system. Comparison of the neural activity with psychophysical data gathered using the same stimulus parameters allows determining which neuron classes can discriminate at levels comparable to human perception. Results will add a new level of sophistication to our knowledge about somatosensory capabilities, and also will be important to all neuroscience and to neuroengineering in clarifying principles of information coding.
