Interactive effects of age and multi-gene profile on motor learning and sensorimotor adaptation

Abstract

The interactive association of age and dopaminergic polymorphisms on cognitive function has been studied extensively. However, there is limited research on whether age interacts with the association between genetic polymorphisms and motor learning. We examined a group of young and older adults’ performance in three motor tasks: explicit sequence learning, visuomotor adaptation, and grooved pegboard. We assessed whether individuals’ motor learning and performance were associated with their age and genotypes. We selected three genetic polymorphisms: Catechol-O-Methyl Transferase (COMT val158met) and Dopamine D2 Receptor (DRD2 G > T), which are involved with dopaminergic regulation, and Brain Derived Neurotrophic Factor (BDNF val66met) that modulates neuroplasticity and has been shown to interact with dopaminergic genes. Although the underlying mechanisms of the function of these three genotypes are different, the high performance alleles of each have been linked to better learning and performance. We created a composite polygene score based on the Number of High Performance Alleles (NHPA) that each individual carried. We found several associations between genetic profile, motor performance, and sensorimotor adaptation. More importantly, we found that this association varies with age, task type, and engagement of implicit versus explicit learning processes.

The effect of age on visuomotor learning processes

“…But, if fine-tuning of a strategy depends on convergent thinking [ 67 ], an age-related deficit in convergent thinking is consistent with the smaller benefit of instruction we see in older adults’ early adaptation. In their review of this literature, Buszard & Masters [ 18 ], suggest that indeed the evidence relating cognitive performance and visuomotor adaptation performance is weak, but stronger for sequence learning [ 13 ]. Sequence learning is used to assess skill acquisition rather than what we test here; skill maintenance.…”

“…From this literature [ 2 ], it could be inferred [ 7 ] that age-related cognitive decline [ 41 , 42 ] can also explain age-related differences in adaptation rates. While Noohi et al [ 13 ] find a lower awareness of the perturbation in older adults, this might be an issue with the questionnaire's construct validity, as the same participants show no effect of age on adaptation to a 30° rotation. In a more recent, comprehensive study, Vandevoorde & Orban de Xivry [ 14 ] show decreased explicit learning in older adults and find that this was compensated with implicit learning–which may also explain the findings of Noohi et al [ 13 ].…”

“…While Noohi et al [ 13 ] find a lower awareness of the perturbation in older adults, this might be an issue with the questionnaire's construct validity, as the same participants show no effect of age on adaptation to a 30° rotation. In a more recent, comprehensive study, Vandevoorde & Orban de Xivry [ 14 ] show decreased explicit learning in older adults and find that this was compensated with implicit learning–which may also explain the findings of Noohi et al [ 13 ]. However, other groups have shown that implicit learning is limited [ 17 , 35 ], so that implicit adaptation may only compensate for deficits in explicit learning to a limited extent or older adults may have an increased capacity for implicit learning.…”

“…A similar difference between age-groups can be seen in force-field adaptation [ 8 , 9 ] as well as prism adaptation [ 10 ] although see [ 11 ] for an alternative finding. However, when the visual perturbation is small (such as 30°), age-related differences in initial stages of motor learning are less robust: with some studies showing a deficit for older adults [ 12 ] and others not [ 4 , 7 , 11 , 13 ], sometimes within the same study [ 14 ]. Since larger rotations tend to evoke more explicit, cognitive adaptation than smaller rotations do [ 15 – 17 ], age-related cognitive decline may explain differences between age groups that are reported with larger rotations [ 4 , 18 ].…”

Physical Therapy for Neurological Conditions in Geriatric Populations

“…Older adults must frequently accommodate to the gradual deterioration of their sensory–motor systems, emotional and cognitive functions that occur associated with aging, adjust how they perform multitasks and how they manage their health ( 33 ). Individuals in the fourth age with associated neurological conditions may need to relearn previously acquired motor skills such as bathing, eating, dressing up, or keeping hygiene with limited and distorted quality of resources available and accessible to them.…”