title: Exteroceptive aspects of nociception: insights from graphesthesia and two-point discrimination.
abstract: The exteroceptive capabilities of the nociceptive system have long been thought to be considerably more limited than those of the tactile system. However, most investigations of spatio-temporal aspects of the nociceptive system have largely focused on intensity coding as consequence of spatial or temporal summation. Graphesthesia, the identification of numbers "written" on the skin, and assessment of the two-point discrimination thresholds were used to compare the exteroceptive capabilities of the tactile and nociceptive systems. Numbers were "written" on the forearm and the abdomen by tactile stimulation and by painful non-contact infrared laser heat stimulation. Subjects performed both graphesthesia tasks better than chance. The tactile graphesthesia tasks were performed with 89% (82-97%) correct responses on the forearm and 86% (79-94%) correct responses on the abdomen. Tactile graphesthesia tasks were significantly better than painful heat graphesthesia tasks that were performed with 31% (23-40%) and 44% (37-51%) correct responses on the forearm and abdomen, respectively. These findings demonstrate that the central nervous system is capable of assembling complex spatio-temporal patterns of nociceptive information from the body surface into unified mental objects with sufficient accuracy to enable behavioral discrimination.
authors.affiliation: Center for Sensory-Motor Interaction, Health Science and Technology, Aalborg University, Fredrik Bajersvej 7, D3, DK-9220 Aalborg, Denmark Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
authors.forename: Carsten Dahl
authors.initials: CD
authors.lastname: Mørch
authors.forename: Ole K
authors.initials: OK
authors.lastname: Andersen
authors.forename: Alexandre S
authors.initials: AS
authors.lastname: Quevedo
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: Robert C
authors.initials: RC
authors.lastname: Coghill
mesh_terms: D000005:Abdomen / Q000294:innervation; D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D000704:Analysis of Variance; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000294:innervation; D006801:Humans; D006930:Hyperalgesia / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology*; D007834:Lasers / Q000009:adverse effects; D008297:Male; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology*; D010812:Physical Stimulation / Q000009:adverse effects; D011336:Probability; D012372:ROC Curve; D013997:Time Factors; D014110:Touch / Q000502:physiology*; D055815:Young Adult