title: Tactile spatial resolution in blind braille readers.
abstract: OBJECTIVE
  To determine if blind people have heightened tactile spatial acuity.
  
  
  BACKGROUND
  Recently, studies using magnetic source imaging and somatosensory evoked potentials have shown that the cortical representation of the reading fingers of blind Braille readers is expanded compared to that of fingers of sighted subjects. Furthermore, the visual cortex is activated during certain tactile tasks in blind subjects but not sighted subjects. The authors hypothesized that the expanded cortical representation of fingers used in Braille reading may reflect an enhanced fidelity in the neural transmission of spatial details of a stimulus. If so, the quantitative limit of spatial acuity would be superior in blind people.
  
  
  METHODS
  The authors employed a grating orientation discrimination task in which threshold performance is accounted for by the spatial resolution limits of the neural image evoked by a stimulus. The authors quantified the psychophysical limits of spatial acuity at the middle and index fingers of 15 blind Braille readers and 15 sighted control subjects.
  
  
  RESULTS
  The mean grating orientation threshold was significantly (p = 0.03) lower in the blind group (1.04 mm) compared to the sighted group (1.46 mm). The self-reported dominant reading finger in blind subjects had a mean grating orientation threshold of 0.80 mm, which was significantly better than other fingers tested. Thresholds at non-Braille reading fingers in blind subjects averaged 1.12 mm, which were also superior to sighted subjects' performances.
  
  
  CONCLUSIONS
  Superior tactile spatial acuity in blind Braille readers may represent an adaptive, behavioral correlate of cortical plasticity.
authors.affiliation: Department of Neurology, Northwestern University Medical School, Chicago, IL, USA. robert_vanboven@nih.gov
authors.forename: R W
authors.initials: RW
authors.lastname: Van Boven
authors.forename: R H
authors.initials: RH
authors.lastname: Hamilton
authors.forename: T
authors.initials: T
authors.lastname: Kauffman
authors.forename: J P
authors.initials: JP
authors.lastname: Keenan
authors.forename: A
authors.initials: A
authors.lastname: Pascual-Leone
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001766:Blindness; D004193:Discrimination Learning / Q000502:physiology; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D006941:Hyperesthesia / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D009949:Orientation / Q000502:physiology; D012682:Sensory Aids; D012684:Sensory Thresholds / Q000502:physiology; D012737:Sex Factors; D013499:Surface Properties; D014110:Touch / Q000502:physiology*