Hand Dominance and Age Have Interactive Effects on Motor Cortical Representations

Abstract

Older adults exhibit more bilateral motor cortical activity during unimanual task performance than young adults. Interestingly, a similar pattern is seen in young adults with reduced hand dominance. However, older adults report stronger hand dominance than young adults, making it unclear how handedness is manifested in the aging motor cortex. Here, we investigated age differences in the relationships between handedness, motor cortical organization, and interhemispheric communication speed. We hypothesized that relationships between these variables would differ for young and older adults, consistent with our recent proposal of an age-related shift in interhemispheric interactions. We mapped motor cortical representations of the right and left first dorsal interosseous muscles using transcranial magnetic stimulation (TMS) in young and older adults recruited to represent a broad range of the handedness spectrum. We also measured interhemispheric communication speed and bimanual coordination. We observed that more strongly handed older adults exhibited more ipsilateral motor activity in response to TMS; this effect was not present in young adults. Furthermore, we found opposing relationships between interhemispheric communication speed and bimanual performance in the two age groups. Thus, handedness manifests itself differently in the motor cortices of young and older adults and has interactive effects with age.

Manual dexterity in young and healthy older adults. 1. Age‐ and gender‐related differences in unimanual and bimanual performance

“…A few studies have also compared bimanual object manipulation in young and older adults. In both studies (Bernard & Seidler, 2012;Serbruyns et al, 2013), the older groups manipulated fewer pegs than younger adults, which provides evidence of age-related deficits in bimanual object manipulation. In both studies (Bernard & Seidler, 2012;Serbruyns et al, 2013), the older groups manipulated fewer pegs than younger adults, which provides evidence of age-related deficits in bimanual object manipulation.…”

“…Examples include Seidler (2012) andSerbruyns et al (2013), who compared young and older adults' performance on the bimanual tasks of the Purdue Pegboard Test (Tiffin, 1968;Tiffin & Asher, 1948) for reaching, grasping, transporting, and inserting pegs under different conditions. However, neither Bernard and Seidler (2012), nor Serbruyns et al (2013) measured kinematics, and therefore, these studies could not provide detailed information about how bimanual object manipulation changes with advanced age. However, neither Bernard and Seidler (2012), nor Serbruyns et al (2013) measured kinematics, and therefore, these studies could not provide detailed information about how bimanual object manipulation changes with advanced age.…”

“…A few studies have also compared bimanual object manipulation in young and older adults. Examples include Seidler (2012) andSerbruyns et al (2013), who compared young and older adults' performance on the bimanual tasks of the Purdue Pegboard Test (Tiffin, 1968;Tiffin & Asher, 1948) for reaching, grasping, transporting, and inserting pegs under different conditions. In both studies (Bernard & Seidler, 2012;Serbruyns et al, 2013), the older groups manipulated fewer pegs than younger adults, which provides evidence of age-related deficits in bimanual object manipulation.…”

Subcortical volumetric changes across the adult lifespan: Subregional thalamic atrophy accounts for age-related sensorimotor performance declines

“…During healthy aging, these skills have been shown to deteriorate (Bernard & Seidler, 2012;Fling & Seidler, 2012;Marneweck, Loftus, & Hammond, 2011;Serbruyns et al, 2013;Sullivan et al, 2001;Swinnen et al, 1998). However, fundamental knowledge of the neural mechanisms behind these age-related declines is rather limited.…”

Response Hand and Motor Set Differentially Modulate the Connectivity of Brain Pathways During Simple Uni-manual Motor Behavior

“…These effects are broadly consistent with previous independent studies using a similar paradigm (Asemi et al, 2015), and suggest that the induction of a motor set unfolds inherent representations of the dominant right hand through increased synchrony between key sub-networks. Moreover, these sub-networks include regions such as the thalamus and the parietal cortex that are committed to attention processing (Corbetta et al, 1998; Jagtap & Diwadkar, 2016), and the primary motor cortex (M1) and SMA wherein hand dominance is strongly expressed (Bernard & Seidler, 2012); d) In investigating hand-related differences within each task condition, the random condition induced the greatest modulation (Figure 5), specifically when responding with the non-dominant left hand. These effects are intriguing for multiple reasons: First, as previously noted the unpredictability of onsets during the random condition is challenging enough to preempt the establishment of a motor set during task epochs (Asemi et al, 2015) resulting in reactive responding.…”