Measuring hand sensory function and force control in older adults: Are current hand assessment tools enough?

Background The ability to grasp and manipulate objects is essential for performing activities of daily living. However, there is limited information regarding age-related behavioral differences in hand sensorimotor function due, in part, to the lack of assessment tools capable of measuring subtle but important differences in hand function. The purpose of this study was to demonstrate performance differences in submaximal force control and tactile pattern recognition in healthy older adults using two custom-designed sensorimotor assessment tools. Methods Sensorimotor function was assessed in 13 healthy older adults (mean age 72.2 ±5.5y, range: 65-84y) and 13 young adults (mean age 20 ±1.4y, range: 19-23y). Clinical assessments included the Montreal Cognitive Assessment (MoCA), monofilament testing, maximum voluntary contraction (MVC), and Grooved Pegboard Test. Sensorimotor assessments included submaximal (5, 20% MVC) grip force step-tracking and tactile pattern recognition tasks. Results Clinical assessments revealed no or minimal group differences in MVC, monofilament thresholds, and MoCA. However, sensorimotor assessments showed that older adults took longer to discriminate tactile patterns and had poorer accuracy than young adults. Older adults also produced submaximal forces less smoothly than young adults at the 20% force level while greater variability in force maintenance was seen at 5% but not 20% MVC. Conclusions These results demonstrate the ability to integrate higher-order tactile information and control low grip forces is impaired in older adults despite no differences in grip strength or cognition. These findings underscore the need for more sensitive evaluation methods that focus on sensorimotor ability reflective of daily activities.

Measuring Hand Function in Older Adults: The Need for Better Assessment Tools

Aging is associated with a decline in hand muscle strength, dexterity, and tactile perception, leading to difficulties in activities of daily living and reduced independence (Millan-Calenti et al., 2010). However, current assessments do not adequately capture sensorimotor skills that underlie everyday activities such as dressing and food preparation. This study examined the ability of two novel assessment devices to detect age-related changes in hand force control and tactile pattern discrimination. Sensorimotor function was assessed in 13 healthy older adults (mean age 72.2 +/- 5.5y) and 13 young adults (mean age 20 +/- 1.4y). Maximum grip force (MVC), tactile sensation, and hand dexterity were measured using standard clinical techniques. Novel assessments consisted of submaximal (5-20% MVC) grip force tracking and computer-controlled tactile pattern recognition. Monofilament testing of tactile sensation was normal in the older group. In contrast, both the accuracy and speed associated with identifying tactile patterns was significantly worse in older (p<0.001) compared to young adults for both hands. While maximum grip force was similar in both groups, the ability to smoothly produce (p<0.05) and maintain (p<0.02) low grip force levels was compromised in older adults. Manual dexterity (Grooved Pegboard test) was significantly reduced in the older group (p<0.001) regardless of hand. These results indicate that the ability to extract meaningful information from tactile feedback and control low levels of force - aspects of fine hand control associated with activities of daily living – are impaired in older adults and underscore the need for more sensitive measures of hand function.

Sound Coding Color to Improve Artwork Appreciation by People with Visual Impairments

The recent development of color coding in tactile pictograms helps people with visual impairments (PVI) appreciate the visual arts. The auditory sense, in conjunction with (or possibly as an alternative to) the tactile sense, would allow PVI to perceive colors in a way that would be difficult to achieve with just a tactile stimulus. Sound coding colors (SCCs) can replicate three characteristics of colors, i.e., hue, chroma, and value, by matching them with three characteristics of sound, i.e., timbre, intensity, and pitch. This paper examines relationships between sound (melody) and color mediated by tactile pattern color coding and provides sound coding for hue, chroma, and value to help PVI deepen their relationship with visual art. Our two proposed SCC sets use melody to improve upon most SCC sets currently in use by adding more colors (18 colors in 6 hues). User experience and identification tests were conducted with 12 visually impaired and 8 sighted adults, and the results suggest that the SCC sets were helpful for the participants.

Age differences in tactile pattern recognition at the fingertip

Young (21-26 years, n=20) and Old (55-86 years, n=25) participants were tested for their ability to recognize raised letters (6-mm high, 1-mm relief) by touch. Spatial resolution thresholds were also measured with grating domes to derive an index of the degree of afferent innervation at the fingertip. Letter recognition in the young group was very consistent and highly accurate (mean, 86% correct), contrasting with the performance of the old group, which was more variable and comparatively low in accuracy (mean, 53% correct). In both groups, spatial resolution thresholds accounted for a substantial portion of the variance in the performance, suggesting a strong link between age-dependant variations in tactile innervation and recognition accuracy. The patterns of errors in the old group showed that an inability to encode internal elements specific to certain letters was at the source of most confusion among letters. Whether this inability reflected only deficient peripheral encoding mechanisms or some other alterations at the central level is discussed.