Cortical processing of lateral skin stretch stimulation in humans.
Direction discrimination of a moving tactile stimulus requires intact dorsal columns and provides a sensitive clinical test of somatosensory dysfunction. Cortical mechanisms are poorly understood. We have applied tangential skin pulls to the right lower leg during functional magnetic resonance imaging. Healthy subjects judged the direction of the skin pulls (task experiment, n = 7) or received skin pulls passively (no task experiment, n = 8). Second somatosensory cortex (S2) was activated in the task as well as no task experiment, and there was no significant difference in cortical activation between the two experiments. Within S2 nearly all subjects had prominent activations in the caudal and superficial part, i.e., in the opercular parietal (OP) area 1. S1 was activated in only one of the subjects. Thus, S2 and especially OP 1 seems to be important for processing of lateral skin stretch stimulation. The finding suggests that a lesion of this area might cause a disturbance in tactile direction discrimination which should be relevant for clinical testing.
Institute of Neuroscience and Physiology, University of Gothenburg, Medicinaregatan 11, P.O. box 432, 405 30, Gothenburg, Sweden. backlund@physiol.gu.se
Helena
H
Backlund Wasling
Linda
L
Lundblad
Line
L
Löken
Johan
J
Wessberg
Katarina
K
Wiklund
Ulf
U
Norrsell
Håkan
H
Olausson
D000328:Adult; D000344:Afferent Pathways / Q000033:anatomy & histology / Q000502:physiology; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007866:Leg / Q000294:innervation / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D010296:Parietal Lobe / Q000033:anatomy & histology / Q000502:physiology*; D010812:Physical Stimulation; D011601:Psychophysics; D012867:Skin / Q000294:innervation*; D012879:Skin Physiological Phenomena; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000502:physiology*; D013314:Stress, Mechanical; D014110:Touch / Q000502:physiology*