Tactile spatial acuity differs between fingers: A study comparing two testing paradigms

Abstract

Tactile spatial acuity (TSA) is a reliable and reproducible measure of somatosensory system function that has been used to study abroad range of subject populations. Although TSA is most often assessed at the fingertip, published studies employing identical stimuli disagree on whether TSA differs between the fingers of neurologically normal subjects. Using a validated grating orientation discrimination task, we determined TSA bilaterally at the index and ring fingers of 16 healthy young adults. Motivated by earlier work, we utilized two stimulus presentation paradigms, the method of constant stimuli (MCS) and a staircase (SC) method. We found that TSA was significantly higher (the discrimination threshold was lower) at the index than at the ring finger, which was consistent with a prior study. Although mean thresholds at both fingers were higher when measured with the SC than with the MCS paradigm, this difference did not reach statistical significance (p = .14). These findings should facilitate both design and interpretation of future studies investigating TSA.

Tactile Spatial Acuity Enhancement in Blindness: Evidence for Experience-Dependent Mechanisms

“…We found further that acuity worsens from index to middle to ring fingertips, consistent with previous reports show- ing significant effects or trends in this direction (Sathian and Zangaladze, 1996;Vega-Bermudez and Johnson, 2001;Grant et al, 2006;Duncan and Boynton, 2007).…”

Time, frequency and volumetric differences of high-frequency neuromagnetic oscillation between left and right somatosensory cortices

“…The index finger is very convenient for electrode ring set-up. It also has a highly reliable sensitivity (Demirci and Sonel, 2004) and an excellent tactile spatial acuity, which can improve reliability as an indicator of somatosensory function (Grant et al, 2006). The paradigm can be easily expanded to map all fingers.…”

Laterality and sex differences in tactile detection and two-point thresholds modified by body surface area and body fat ratio

“…The direction of the result, with high BFRs associated with lower thresholds, suggests that the double deformation caused by two points is a sensory feature that is detectable by the receptors. Thresholds for grating stimuli, also involving relatively high forces, are likewise sensitive to skin deformation (Grant et al 2006).…”

“…Testing two-point discrimination involves systematically separating two points, such as the two sides of a caliper, until the participant senses two separate points of stimulation. Although a better method of testing tactile spatial acuity exists, involving discriminating the orientation of gratings (e.g., Craig and Johnson 2000;Vega-Bermudez and Johnson 2004;Grant et al 2006;Peters et al 2009), it is not common in clinical practice, perhaps in part because readily available stimuli are suitable only for the most sensitive areas of skin such as the hands and lips (Gibson and Craig 2005). In any case, two-point discrimination is the most widely used measure for determining spatial resolution (Essick 1992;Craig and Johnson 2000).…”