General Biology Seminar

We investigate human touch using microneurography, where we record the activity of single, identified nerve fibers in human peripheral nerves. We combine this technique with brain imaging using fMRI and EEG, psychohysics, and studies in patients. In this talk, I will focus on our work on unmyelinated mechanoafferents with low mechanical thresholds (CT-afferents) which has been ongoing since the early 1990s. The afferents respond well to light touch, particularly to moving stimuli at intermediate velocities, around 1-3 cm/s. In fMRI studies in patients lacking normal Abeta-fibers, we have showed that CT afferents project to the insula but not to primary somatosensory brain areas. We have proposed that this system has an important role in signaling emotional, rather than discriminative, quality of pleasant touch to the hairy skin. A number of currently ongoing investigations will be discussed. For example, CT afferents do not respond to warm or cold stimuli without concomitant skin contact, but the temperature of a touching object will modulate CT afferent activity so that afferent firing is reduced for either cold (18 degrees C) or warm (42 C) stimuli.

Johan Wessberg, Professor

Inst. of Neuroscience and Physiology

University of Gothenburg, Sweden