Sombric, C. J. | bioRxiv Science

bioRxiv2020

Cognitive and motor perseveration are associated in older adults

Aging causes perseveration (difficulty to switch between actions) in motor and cognitive tasks, suggesting that the same neural processes could govern these abilities in older adults. To test this, we evaluated the relation between independently measured motor and cognitive perseveration in young (21.4{+/-}3.7 y/o) and older participants (76.5{+/-}2.9 y/o). Motor perseveration was measured with a locomotor task in which participants had to transition between distinct walking patterns. Cognitive perseveration was measured with a card matching task in which participants had to switch between distinct matching rules. We found that perseveration in the cognitive and motor domains were positively related in older, but not younger individuals, such that participants exhibiting greater perseveration in the motor task also perseverated more in the cognitive task. Additionally, exposure reduces motor perseveration: older adults who had practiced the motor task could transition between walking patterns as proficiently as naive, young individuals. Our results suggest an overlap in neural processes governing cognitive and motor perseveration with aging and that exposure can counteract the age-related motor perseveration. HighlightsO_LIMovement carryover from the treadmill to overground indicates motor perseveration. C_LIO_LIGreater motor and cognitive perseveration are associated in older adults. C_LIO_LIMotor perseveration in older adults can be reduced with practice. C_LIO_LINew motor memories are similarly forgotten in older and younger adults. C_LI

bioengineering↗

bioRxiv2019

Split-Belt walking induces changes in active, but not passive, perception of step length

The estimation of limbs position is critical for motor control. While motor adaptation changes the estimation of limb position in volitional arm movements, this has not been observed in locomotion. We hypothesized that split-belt walking with the legs moving at different speeds changes the estimation of the legs position when taking a step. Thus, we assessed young subjects perception of step length (i.e., inter-feet distance at foot landing) when they moved their legs (active perception) or these were moved by the experimenter (passive perception). Step lengths active, but not passive perception was altered by split-belt walking; indicating that adapted efferent inputs changed the perceived limbs position without changing information from sensory signals. These perceptual shifts were sensitive to how they were tested: they were observed in the trailing, but not the leading leg, and they were more salient when tested with short than long step lengths. Our results suggest that sensory changes following motor adaptation might arise from mismatched limb position estimates from different sensory sources (i.e., proprioception and vision), which is less prominent in walking. We also speculate that split-belt walking could improve the deficient perception of step length post-stroke, which contributes to their gait asymmetry impairing patients mobility.

neuroscience↗