Age differences in reactive strategies and execution time during choice stepping with visual interference

Keeping in step with the young: Chronometric and kinematic data show intact procedural locomotor sequence learning in older adults

Sequence learning in serial reaction time tasks (SRTT) is an established, lab-based experimental paradigm to study acquisition and transfer of skill based on the detection of predictable stimulus and motor response sequences. Sequence learning has been mainly studied in key presses using visual target stimuli and is demonstrated by better performance in predictable sequences than in random sequences. In this study, we investigated sequence learning in the context of more complex locomotor responses. To this end, we developed a novel goal-directed stepping SRTT with auditory target stimuli in order to subsequently assess the effect of aging on sequence learning in this task, expecting that age-related performance reductions in postural control might disturb the acquisition of the sequence. We used pressure-sensitive floor mats to characterise performance across ten blocks of trials. In Experiment 1, 22 young adults demonstrated successful acquisition of the sequence in terms of the time to step on the target mat and percent error and thus validated our new paradigm. In Experiment 2, in order to contrast performance improvements in the stepping SRTT between 27 young and 22 old adults, motion capture of the feet was combined with the floor mat system to delineate individual movement phases during stepping onto a target mat. The latencies of several postural events as well as other movement parameters of a step were assessed. We observed significant learning effects in the latency of step initiation, the time to step on the target mat, and motion parameters such as stepping amplitude and peak stepping velocity, as well as in percent error. The data showed general age-related slowing but no significant performance differences in procedural locomotor sequence learning between young and old adults. The older adults also had comparable conscious representations of the sequence of stimuli as the young adults. We conclude that sequence learning occurred in this locomotor learning task that is much more complex than typical finger-tapping sequence learning tasks, and that healthy older adults showed similar learning effects compared to young adults, suggesting intact locomotor sequence learning capabilities despite general slowing and normal age-related decline in sensorimotor function.

Balance tasks requiring inhibitory control; a scoping review of studies in older adults

BACKGROUND

Age-related changes in inhibitory control (IC) affect cognitive as well as physical functioning, but how it affects performance of tasks that integrate IC and balance control is unclear. This review study aims to identify specific tasks that have been used to determine effects of IC on balance performance in older adults, and analyse task-specific features as well as reported effects.

METHODS

Based on a comprehensive literature search, a scoping review considered all studies that involved IC as part of static or dynamic balance tasks in healthy adults over 65. Studies which only involved IC as part of an -additional- cognitive task during a balance task were excluded.

RESULTS

Eleven studies met the inclusion criteria for this review. Eight out of the 11 studies focused on voluntary stepping; two studies used gait or gait initiation, and one study used foot lift as a balance task. Ten studies included conditions that required some form of perceptual inhibition, and 6 out of the 11 studies included conditions involving some form of motor inhibition. With few exceptions, all inhibitory control conditions showed a decreased task performance in older adults.

DISCUSSION

Although most studies addressed IC during some form of stepping, the approaches were heterogeneous in terms of tasks, outcome measures and standardisation. Despite the heterogeneity, the available studies unequivocally demonstrate the importance of IC for task performance. The discussion addresses aspects which are important in furthering our understanding of age-related changes in IC and its impact on performance.

Frontal Hemodynamic Response During Step Initiation Under Cognitive Conflict in Older and Young Healthy People

Gait initiation is a daily challenge even for healthy individuals as it requires the timely coupling between the automatic anticipatory postural adjustment (APA) and the voluntary step according to the context. Modulation of this motor event has been thought to involve higher level brain control, including cognitive inhibitory circuitries. Despite the known participation of the supplementary motor area (SMA) in the modulation of some parameters of APA, the participation of areas controlling inhibition during gait initiation still needs to be investigated. In this study, the hemodynamic responses of the SMA and dorsolateral prefrontal cortex (DLPFC) were assessed using functional near-infrared spectroscopy (fNIRS) during a gait initiation task under cognitive conflict to select the foot to step (congruent [CON] and incongruent [INC] conditions). The older group (OG) showed worse inhibitory control than the young group (YG) along with more impairments in APA parameters. OG also had a lower amplitude of hemodynamic responses in both areas than YG in the INC. The INC increased the correlation between SMA and DLPFC only in the YG. Aging seems to impair the interaction between the hemodynamic responses of SMA and DLPFC, which influences APA performance in gait initiation under cognitive conflict.

Auditory stimulus has a larger effect on anticipatory postural adjustments in older than young adults during choice step reaction

PURPOSE

The study aim was to compare the influence of an auditory stimulus (AS) on anticipatory postural adjustments (APAs) between young and older adults during a choice step reaction.

METHODS

Sixteen young and 19 older adults stepped forward in response to a visual imperative stimulus of an arrow. We used a choice reaction time (CRT) task and a Simon task which consisted of congruent and incongruent conditions. The direction of the presented arrow and its spatial location matched in the congruent condition while they did not in the incongruent condition. The AS was presented randomly and simultaneously with the visual stimulus. Incorrect weight shifts before lifting off the foot, termed APA errors, stepping errors, temporal parameters, and APA amplitudes were analyzed.

RESULTS

The APA error rate was higher in trials with than without AS in all task conditions for the older group, while this increase occurred only in the incongruent condition for the young group. The stepping error rate was also increased in the presence of AS in the incongruent condition for the older group. Reaction times were faster with AS in both groups. The APA amplitude of erroneous APA trials became larger with AS in the incongruent condition for both groups, and this effect appeared greater for the older group.

CONCLUSIONS

The effect of AS on APAs is larger in the elderly during a choice step reaction. In the presence of incongruent visual information, this effect becomes even greater, potentially inducing not only APA errors but also stepping errors.