Hand asymmetries of tactile attention in younger and older adults.

Background/Objectives: The allocation of attention can alter the perception of magnitude. When performing line bisections, young adults deviate leftward (pseudoneglect), a bias thought to be induced by right hemisphere dominance for allocating spatial attention. However, when performing body bisections young adults deviate rightward, suggesting left hemisphere dominance for allocating body-centered attention. With aging, there is a reduction of pseudoneglect thought to result from either an age-related decrease in right hemispheric functions (right hemi-aging) or from hemispheric asymmetry reduction in older adults (HAROLD). The goal of this study was to learn if there are tactile body-centered perceptual-attentional right-left asymmetries in that change with aging. Methods: The participants were younger and older healthy adults. Semmes-Weinstein Monofilaments were used to test for differences in the perceived magnitude of pressure differences between a reference stimulus and test stimuli applied to the right and left palmar thenar eminence. Results: Young adults perceived the magnitude of difference in the lightest pressure stimuli applied to the right hand as being greater than the older adults. Young adults perceived the magnitude of difference between the lightest pressure and reference applied to the right hand to be greater than the left hand, but older adults perceived a lighter stimulus greater on the left compared to the right. Conclusions: Whereas the right hemisphere appears to be dominant in mediating spatial attention, the left hemisphere may play a dominant role in the allocation of body-centered attention. Like the aging-related reduction of the visual perception of the magnitude (length) of the left side of a line, this tactile reduction in magnitude (pressure) perception in older adults suggests that with aging, there is a reduction of left-hemispheric mediated allocation of tactile attention, and this result is not fully consistent with either the HAROLD or hemi-aging models.