Functional role of unmyelinated tactile afferents in human hairy skin: sympathetic response and perceptual localization.
In addition to A-beta fibres the human hairy skin has unmyelinated (C) fibres responsive to light touch. Previous functional magnetic resonance imaging (fMRI) studies in a subject with a neuronopathy who specifically lacks A-beta afferents indicated that tactile C afferents (CT) activate insular cortex, whereas no response was seen in somatosensory areas 1 and 2. Psychophysical tests suggested that CT afferents give rise to an inconsistent perception of weak and pleasant touch. By examining two neuronopathy subjects as well as control subjects we have now demonstrated that CT stimulation can elicit a sympathetic skin response. Further, the neuronopathy subjects' ability to localize stimuli which activate CT afferents was very poor but above chance level. The findings support the interpretation that the CT system is well suited to underpin affective rather than discriminative functions of tactile sensations.
Olausson
Håkan
H
Department of Clinical Neurophysiology, Sahlgrenska University Hospital, Blå stråket 7, 413 45, Göteborg, Sweden. olausson@physiol.gu.se
Cole
Jonathan
J
Rylander
Karin
K
McGlone
Francis
F
Lamarre
Yves
Y
Wallin
B Gunnar
BG
Krämer
Heidrun
H
Wessberg
Johan
J
Elam
Mikael
M
Bushnell
M Catherine
MC
Vallbo
Ake
A
D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D005260:Female; D005542:Forearm; D006197:Hair / Q000502:physiology*; D006801:Humans; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D008875:Middle Aged; D009443:Neuritis / Q000503:physiopathology*; D010465:Perception / Q000502:physiology*; D010812:Physical Stimulation; D012016:Reference Values; D012684:Sensory Thresholds / Q000502:physiology; D012867:Skin / Q000503:physiopathology; D012879:Skin Physiological Phenomena; D014110:Touch / Q000502:physiology*