Tactile spatial acuity at the human fingertip and lip: bilateral symmetry and interdigit variability.

We used the spatial threshold for discrimination of grating orientation to assess tactile spatial acuity at the lower lip and each fingertip, bilaterally, in seven normal human subjects. We confirmed previous findings that: (1) this test is highly reliable, and (2) acuity at the lip is substantially higher than at the fingertips. In addition, we showed that: (1) acuity does not differ significantly between right and left sides, and (2) among fingertips, acuity is lowest at the fifth digit and comparable on the other digits.