Measuring age differences in executive control using rapid motor decisions in a robotic object hit and avoid task.

Age-related declines in executive control are commonly assessed with neuropsychological tests that also rely on sensory and motor processes that are not typically measured in those tasks. It is therefore difficult to isolate the cognitive contributions from sensorimotor contributions to performance impairments. Rapid motor decision-making tasks may also be sensitive to age differences in executive control but allow for the measurement of sensorimotor contributors to task performance. Recently developed object hit (OH) and object hit and avoid (OHA) tasks using a robotic manipulandum are sensitive to motor and cognitive aspects of performance in stroke and Parkinson's disease. However, the impact of healthy aging, and the specific cognitive mechanisms involved in these tasks has not been assessed. We administered the OH and OHA tasks to 77 younger and 59 healthy older adults to evaluate the relative age differences in the perceptual-motor/sensory, movement coordination, and cognitive measures of performance. The Trail Making Test (TMT) Parts A and B were administered to assess the extent to which the cognitive contributors to OHA task performance are associated with executive functioning. After controlling for hand movement speed, age differences were largest for cognitive measures, with smaller differences in perceptual-motor speed and sensory measures, and little differences in bimanual and spatial coordination measures of performance. The cognitive measures were associated with executive functioning measures from the TMT task. These findings provide evidence that rapid motor decision-making tasks are sensitive to age differences in executive control and can isolate the cognitive from the sensorimotor contributions to task performance. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Advanced spatial knowledge of target location eliminates age-related differences in early sensorimotor learning.

Motor learning has been shown to decline in healthy aging, particularly in the early stages of acquisition. There is now ample evidence that motor learning relies on multiple interacting learning processes that operate on different timescales, but the specific cognitive mechanisms that contribute to motor learning remain unclear. Working memory resources appear to be particularly important during the early stages of motor learning, and declines in early motor learning have been associated with working memory performance in older adults. We examined whether age differences in the early stages of motor learning could be reduced or eliminated by reducing the spatial working memory demands during a force-field adaptation task. Groups of younger and older adults made center-out reaching movements to spatial targets either in a repeating four-element sequence, or in a random order. Participants also performed a battery of cognitive tests to further investigate the potential involvement of associative memory, spatial working memory, and procedural learning mechanisms in the early stage of motor learning. Although all groups adapted their movements equally well by the end of the learning phase, older adults only adapted as quickly as younger adults in the sequence condition, with the older adults in the random group exhibiting slower learning in the earliest stage of motor learning. Across all participants, early motor learning performance was correlated with recognition memory performance on an associative memory test. Within the younger random group, who were able to adapt as quickly as the sequence groups, early motor learning performance was also correlated with performance on a test of procedural learning. These findings suggest that age differences in early stages of motor learning can be eliminated if the spatial working memory demands involved in a motor learning task are limited. Moreover, the results suggest that multiple cognitive resources may be utilized during the early stage of learning, and younger adults may be more flexible than older adults in the recruitment of additional cognitive resources to support learning when spatial working memory demands are high.

Linking actions and objects: Context-specific learning of novel weight priors.

Distinct explicit and implicit memory processes support weight predictions used when lifting objects and making perceptual judgments about weight, respectively. The first time that an object is encountered weight is predicted on the basis of learned associations, or priors, linking size and material to weight. A fundamental question is whether the brain maintains a single, global representation of priors, or multiple representations that can be updated in a context specific way. A second key question is whether the updating of priors, or the ability to scale lifting forces when repeatedly lifting unusually weighted objects requires focused attention. To investigate these questions we compared the adaptability of weight predictions used when lifting objects and judging their weights in different groups of participants who experienced size-weight inverted objects passively (with the objects placed on the hands) or actively (where participants lift the objects) under full or divided attention. To assess weight judgments we measured the size-weight illusion after every 20 trials of experience with the inverted objects both passively and actively. The attenuation of the illusion that arises when lifting inverted object was found to be context-specific such that the attenuation was larger when the mode of interaction with the inverted objects matched the method of assessment of the illusion. Dividing attention during interaction with the inverted objects had no effect on attenuation of the illusion, but did slow the rate at which lifting forces were scaled to the weight inverted objects. These findings suggest that the brain stores multiple representations of priors that are context specific, and that focused attention is important for scaling lifting forces, but not for updating weight predictions used when judging object weight.

Distinct contributions of explicit and implicit memory processes to weight prediction when lifting objects and judging their weights: an aging study.

Weight predictions used to scale lifting forces adapt quickly when repeatedly lifting unusually weighted objects and are readily updated by explicit information provided about weight. In contrast, weight predictions used when making perceptual judgments about weight are more resistant to change and are largely unaffected by explicit information about weight. These observations suggest that distinct memory systems underlie weight prediction when lifting objects and judging their weights. Here we examined whether these weight predictions differ in their reliance on declarative and nondeclarative memory resources by comparing the adaptability of these predictions in older adults, who exhibit relatively impaired declarative memory processes, to those in younger adults. In the size condition, we measured lift forces as participants repeatedly lifted a pair of size-weight inverted objects in alternation. To assess weight judgments, we measured the size-weight illusion every 10 lifts. The material condition was similar, except that we used material-weight inverted objects and measured the material-weight illusion. The strengths of these illusions prior to lifting, and the attenuation of the illusions that arise when lifting inverted objects, were similar for both groups. The magnitude of the change in the illusions was positively correlated with implicit memory performance in both groups, suggesting that predictions used when judging weight rely on nondeclarative memory resources. Updating of lifting forces also did not differ between groups. However, within the older group the success with which lifting forces were updated was positively correlated with working memory performance, suggesting that weight predictions used when lifting rely on declarative memory resources.

Integrating actions into object location memory: a benefit for active versus passive reaching movements.

We tested whether learning the mapping between objects and their locations is better when actively moving the hand to these locations, to reveal the object, compared to when the hand is passively moved by a robotic manipulandum. Recall of object locations was more accurate in the active compared to passive condition. We also found that recall was less accurate when participant made active movements that were not directed to the object locations. These results indicate that the well-established active exploration advantage for spatial memory extends to location memory for objects within reach. Such active learning is likely important for manipulation tasks.

Effects of age and cognitive load on response reprogramming.

A dual-task paradigm was used to examine the effect of cognitive load on motor reprogramming. We propose that in the face of conflict, both executive control and motor control mechanisms become more interconnected in the process of reprogramming motor behaviors. If so, one would expect a concurrent cognitive load to compromise younger adults' (YAs) motor reprogramming ability and further exacerbate the response reprogramming ability of older adults (OAs). Nineteen YAs and 14 OAs overlearned a sequence of key presses. Deviations of the practiced sequence were introduced to assess motor reprogramming ability. A Serial Sevens Test was used as the cognitive load. A 3D motion capture system was used to parse finger movements into planning and motor execution times. Global response time analysis revealed that under single-task conditions, during prepotent transitions, OAs responded as quickly as YAs, but they were disproportionately worse than YAs during conflict transitions. Under dual-task conditions, YAs performance became more similar to that of OAs. Movement data were decomposed into planning and movement time, revealing that under single-task conditions, when responding to conflicting stimuli YAs reduced their movement time in order to compensate for delayed planning time; however, additional cognitive load prevented them from exhibiting this compensatory hastening on conflict transitions. We propose that age-related declines in response reprogramming may be linked to reduced cognitive capacity. Current findings suggest that cognitive capacity, reduced in the case of OAs or YAs under divided attention conditions, influences the ability to flexibly adapt to conflicting conditions.

Fast but fleeting: adaptive motor learning processes associated with aging and cognitive decline.

Motor learning has been shown to depend on multiple interacting learning processes. For example, learning to adapt when moving grasped objects with novel dynamics involves a fast process that adapts and decays quickly-and that has been linked to explicit memory-and a slower process that adapts and decays more gradually. Each process is characterized by a learning rate that controls how strongly motor memory is updated based on experienced errors and a retention factor determining the movement-to-movement decay in motor memory. Here we examined whether fast and slow motor learning processes involved in learning novel dynamics differ between younger and older adults. In addition, we investigated how age-related decline in explicit memory performance influences learning and retention parameters. Although the groups adapted equally well, they did so with markedly different underlying processes. Whereas the groups had similar fast processes, they had different slow processes. Specifically, the older adults exhibited decreased retention in their slow process compared with younger adults. Within the older group, who exhibited considerable variation in explicit memory performance, we found that poor explicit memory was associated with reduced retention in the fast process, as well as the slow process. These findings suggest that explicit memory resources are a determining factor in impairments in the both the fast and slow processes for motor learning but that aging effects on the slow process are independent of explicit memory declines.

Detecting self-produced speech errors before and after articulation: an ERP investigation.

It has been argued that speech production errors are monitored by the same neural system involved in monitoring other types of action errors. Behavioral evidence has shown that speech errors can be detected and corrected prior to articulation, yet the neural basis for such pre-articulatory speech error monitoring is poorly understood. The current study investigated speech error monitoring using a phoneme-substitution task known to elicit speech errors. Stimulus-locked event-related potential (ERP) analyses comparing correct and incorrect utterances were used to assess pre-articulatory error monitoring and response-locked ERP analyses were used to assess post-articulatory monitoring. Our novel finding in the stimulus-locked analysis revealed that words that ultimately led to a speech error were associated with a larger P2 component at midline sites (FCz, Cz, and CPz). This early positivity may reflect the detection of an error in speech formulation, or a predictive mechanism to signal the potential for an upcoming speech error. The data also revealed that general conflict monitoring mechanisms are involved during this task as both correct and incorrect responses elicited an anterior N2 component typically associated with conflict monitoring. The response-locked analyses corroborated previous observations that self-produced speech errors led to a fronto-central error-related negativity (ERN). These results demonstrate that speech errors can be detected prior to articulation, and that speech error monitoring relies on a central error monitoring mechanism.

Context-updating processes facilitate response reprogramming in younger but not older adults.

The current study used concurrent acquisition of motion capture and event-related potential (ERP) data to test the prediction that response reprogramming relies on context-updating processes, and that age differences in conflicting-response performance are related to context-updating deficits in the elderly. Participants performed a motor sequencing task that included prepotent pairs of key presses, and conflicting pairs that started with the same first key press of the prepotent pair, but ended in an unexpected alternate response. ERP analyses were used to measure the P3b component as an electrophysiological correlate of context updating. The results revealed an age-related reduction in the ability to reprogram a response as younger, but not older, adults exhibited a negative correlation between planning and execution time for conflicting responses, such that shortened execution time led to better performance by the younger group. Both age groups demonstrated a large P3b component following conflicting, but not prepotent stimuli. The peak of this P3b was delayed, and its amplitude reduced in the older, compared with younger, adults. Noteworthy was that conflicting responses with faster execution time were associated with a larger P3b component than responses with slower execution time in younger, but not older, adults, suggesting that better context updating led to more efficient response reprogramming. These findings are novel in showing that context updating is associated with adjustments in response execution, and that older adults were less able to use these context-updating processes to support successful movement reprogramming.

Movement kinematics of prepotent response suppression in aging during conflict adaptation.

OBJECTIVES: The purpose of the current study was to explore the role of adjustments in motor control and conflict adaptation in younger and older adults' prepotent response suppression. METHODS: Participants performed repeated pairs of key-presses on a piano-type keyboard as well as key-presses that conflicted with that prepotent pair. We used motion capture to assess cognitive and motor contributions to conflicting responses presented once, twice, or three times within single trials. RESULTS: Older adults performed the first conflicting response in a series as well as young adults but at a cost to prepotent response performance. Younger adults improved performance with increased conflict frequency, whereas older adults did not. Older adults spent less time planning and more time executing their conflicting responses, with the opposite pattern in younger adults. DISCUSSION: Overall, increasing the frequency of conflicting response presentation was detrimental to older but not to younger adults' prepotent response performance. In addition, the results indicate an age-related decline in conflict adaptation. The results are discussed in terms of current models of cognitive control.

Examining prepotent response suppression in aging: a kinematic analysis.

Two experiments were designed to explore how age differences in conflict detection may contribute to poorer motor performance. In each experiment, 12 young adults (YAs) and 12 older adults (OAs) performed a finger sequencing task in which the frequency of specific critical transitions was varied. These critical transitions were contrasted with violation transitions to assess the ability to detect a conflict in response requirements. In addition to accuracy and reaction time, the authors used kinematic data to parse movements into planning and motor execution phases. OAs were differentially slower to respond to violations than YAs, in line with other research on executive control, prepotent response suppression, and aging. Kinematic analyses revealed that YAs executed movements more rapidly on violation than critical transitions, whereas OAs executed movements at the same speed regardless of response predictability and increased planning time. The authors argue that OAs are unable to reprogram prepotent movement plans to overcome slowed movement planning in cognitively challenging situations. The results are discussed in terms of the influence of age-related cognitive inefficiency on motor control.