Assessment of human finger position sense and the effect of vibro-tactile stimulation on proprioceptive acuity

Abstract

Finger position sense, the awareness of where our fingers are in space, is imperative for daily activities requiring manual dexterity, such as typing or opening up a jar. A deficit in this sense, associated with different movement disorders or neurodegenerative diseases would degrade the performance proportional to the amount of deficit. However, there is not yet an objective and quantitative measure of this sense. This partially contributes to the incoherent results about the development of the sense in typically developing children or the effect of tactile input on the sense.The three projects of this dissertation were designed to address these limitations. Project 1 further developed the finger position sense assessment system originally developed by Block et al. (2019). A new system was modified to accommodate individuals with different hand and finger sizes. It also minimized the effect of any sensory input other than the position sense. Finally, two acuity measures of the sense could be obtained separately: Bias, the systematic error, and Precision, the random error of the sense. Project 2 aimed to characterize the finger position sense in typically developing children from 8 to 17, using the system developed in project 1. The development of finger position sense from late childhood to young adulthood could be described as an increase in precision, but no significant change in bias. In other words, children were more uncertain about their perceptual judgments about their finger positions relative to adults, but their ability to correctly perceive the finger position was already comparable to adults. Project 3 determined the effect of vibro-tactile stimulation (VTS) on the finger position sense. Healthy young adults were tested using the system from project 1, without and with the VTS applied at one of the two positions on their index finger. In addition, to see if any neurophysiological change would accompany this altered finger position sense, participants’ cortical activity was measured. The result revealed that there was a significant location-dependent effect of VTS, with stimulating fingertip increasing bias magnitude. Stimulating lateral side of the finger decreased the measure. Cortical response to VTS also increased when participants had VTS on the lateral side of the finger with the opposite being true as well. A possible relationship between the behavioral change and the neurophysiological change was hinted, supporting that the two changes are not independent but the increase in cortical response could be associated with enhanced finger position sense, even at a short-term scale.