Investigating Age-related changes in fine motor control across different effectors and the impact of white matter integrity

• Published in: NeuroImage (Orlando, Fla.) Fla.), 2014-08, Vol.96, p.81-87
• Main Authors: Holtrop, Joseph L., Loucks, Torrey M., Sosnoff, Jacob J., Sutton, Bradley P.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aging; Aging - pathology; Aging - physiology; Biological and medical sciences; Brain; Brain - cytology; Brain - physiology; Diffusion tensor imaging; Efferent Pathways - physiology; Female; Fiber tracking; Fingers - innervation; Fingers - physiology; Fundamental and applied biological sciences. Psychology; Humans; Lip - innervation; Lip - physiology; Male; Middle Aged; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor Skills - physiology; Motor variability; Neural Pathways - physiology; Older people; Standard deviation; Studies; Tongue - innervation; Tongue - physiology; Vertebrates: nervous system and sense organs; White Matter - ultrastructure; Young Adult
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2014.03.045

Changes in fine motor control that eventually compromise dexterity accompany advanced age; however there is evidence that age-related decline in motor control may not be uniform across effectors. Particularly, the role of central mechanisms in effector-specific decline has not been examined but is relevant for placing age-related motor declines into the growing literature of age-related changes in brain function. We examined sub-maximal force control across three different effectors (fingers, lips, and tongue) in 18 young and 14 older adults. In parallel with the force variability measures we examined changes in white matter structural integrity in effector-specific pathways in the brain with diffusion tensor imaging (DTI). Motor pathways for each effector were identified by using an fMRI localizer task followed by tractography to identify the fiber tracts propagating to the midbrain. Increases in force control variability were found with age in all three effectors but the effectors showed different degrees of age-related variability. Motor control changes were accompanied by a decline in white matter structural integrity with age shown by measures of fractional anisotropy and radial diffusivity. The DTI metrics appear to mediate some of the age-related declines in motor control. Our findings indicate that the structural integrity of descending motor systems may play a significant role in age-related increases in motor performance variability, but that differential age-related declines in oral and manual effectors are not likely due to structural integrity of descending motor pathways in the brain. •Oral and manual fine-motor performance of young and old adults were compared•Obtained DTI neural integrity measures specific to oral and manual effectors•Effector-specific age related declines in motor control were observed•Age-related motor control declines were correlated to changes in neuronal structure•White matter integrity did not predict differential decline among the effectors