Objective Measurement of Tactile Mislocalization

Abstract

Stimulating the skin with intensities close to the sensory threshold causes erroneous localization of the site of stimulation. Previous studies using manual methods for applying faint tactile stimuli have shown that localization errors obey a somatotopic principle in which tactile stimuli are preferentially mislocalized to sites adjacent to the stimulated skin region. However, manual testing of mislocalization is time consuming and only partially objective because results depend on the skills of the tester. To improve the testing procedure, an automated apparatus was developed. The procedure adjusted stimulus intensity adaptively during testing to remain near the individual subject's sensory threshold, so that mislocalizations occurred often enough to assess somatotopic organization. The new method was applied to 12 healthy subjects. In each subject, the five digits of the right hand were stimulated singly in random order. Localization errors were distributed preferentially to fingers close to the stimulated finger rather than to distant fingers. The profile of mislocalization differed significantly from that expected on the basis of response bias or guessing behavior. The present results replicate previous findings obtained for manual testing with improved sensitivity and indicate that the new technique is a useful tool for the study of somatosensory processing on a perceptual level.

Differential effects of synchronous and asynchronous multifinger coactivation on human tactile performance

“…They showed that localization errors obeyed a somatotopic principle whereby stimuli are preferentially mislocalized to sites adjacent to the stimulated skin region and differ significantly from guessing behavior. These results where confirmed by objective, apparatus-based, measurements of tactile mislocalizations [48]. In the present study, we used a set of von Frey monofilaments (0.25–294 mN) and touch test filaments (0.08 and 0.20 mN) to conduct a five-alternative forced choice detection test on the fingertips of the right and left hands (for a detailed description of the test, see ref.…”

Improvement of sensorimotor functions in old age by passive sensory stimulation

“…Schweizer and colleagues (2000,2001) showed that localization errors across fingers obeyed a somatotopic principle where stimuli are preferentially mislocalized to sites adjacent to the stimulated skin region ruling out pure guessing behavior (Craig and Rhodes 1992; Braun et al 2005). In the present study, we used a set of monofilaments (0.08–294 mN) to conduct a five-alternative forced choice detection test on the fingertips of the right hand (for a detailed description of the test, see Schweizer et al 2001).…”

A Tactile Virtual Reality for the Study of Active Somatosensation

“…The participants' performance and the integrity of the vibrotactile stimulus processing pathway is usually characterized by the thresholds of various stimulus parameters, such as stimulus intensity, frequency, roughness, etc. Current standard methods to test somatosensory detection and discrimination thresholds involve von-Frey hair probes (Braun et al, 2005), custom-built non-standardized procedures (Phillips et al, 1990), raised alphabets (Vega-Bermudez et al, 1991), tactile plates of varying spatial frequencies (Cascio and Sathian, 2001;Gamzu and Ahissar, 2001), just to name a few. The lack of any standard makes it difficult to compare and interpret the results across different studies.…”