Dopamine Replacement Medication Does Not Influence Implicit Learning of a Stepping Task in People With Parkinson's Disease

Personalized practice dosages may improve motor learning in older adults compared to "standard of care" practice dosages: A randomized controlled trial

Standard dosages of motor practice in clinical physical rehabilitation are insufficient to optimize motor learning, particularly for older patients who often learn at a slower rate than younger patients. Personalized practice dosing (i.e., practicing a task to or beyond one's plateau in performance) may provide a clinically feasible method for determining a dose of practice that is both standardized and individualized, and may improve motor learning. The purpose of this study was to investigate whether personalized practice dosages [practice to plateau (PtP) and overpractice (OVP)] improve retention and transfer of a motor task, compared to low dose [LD] practice that mimics standard clinical dosages. In this pilot randomized controlled trial (NCT02898701, ClinicalTrials.gov), community-dwelling older adults (n = 41, 25 female, mean age 68.9 years) with a range of balance ability performed a standing serial reaction time task in which they stepped to specific targets. Presented stimuli included random sequences and a blinded repeating sequence. Participants were randomly assigned to one of three groups: LD (n = 15, 6 practice trials equaling 144 steps), PtP (n = 14, practice until reaching an estimated personal plateau in performance), or OVP (n = 12, practice 100% more trials after reaching an estimated plateau in performance). Measures of task-specific learning (i.e., faster speed on retention tests) and transfer of learning were performed after 2-4 days of no practice. Learning of the random sequence was greater for the OVP group compared to the LD group (p = 0.020). The OVP (p = 0.004) and PtP (p = 0.010) groups learned the repeated sequence more than the LD group, although the number of practice trials across groups more strongly predicted learning (p = 0.020) than did group assignment (OVP vs. PtP, p = 0.270). No group effect was observed for transfer, although significant transfer was observed in this study as a whole (p < 0.001). Overall, high and personalized dosages of postural training were well-tolerated by older adults, suggesting that this approach is clinically feasible. Practicing well-beyond standard dosages also improved motor learning. Further research should determine the clinical benefit of this personalized approach, and if one of the personalized approaches (PtP vs. OVP) is more beneficial than the other for older patients.

Using Motor Imagery to Access Alternative Attentional Strategies When Navigating Environmental Boundaries to Prevent Freezing of Gait – A Perspective

Freezing of gait can cause reduced independence and quality of life for many with Parkinson’s disease. Episodes frequently occur at points of transition such as navigating a doorway. Therapeutic interventions, i.e., drugs and exercise, do not always successfully mitigate episodes. There are several different, but not exclusive causes for freezing of gait. People with freezing of gait are able to navigate dynamic situations like stairways by utilizing a different attentional strategy to over-ground walking, but may freeze when passing through a doorway. The question is, is it possible to employ a special attentional strategy to prevent freezing at this point? Motor imagery allows for learning motor skills in absolute safety and has been widely employed in a variety of populations, including other neuro-compromised groups. Motor imagery is not studied in a homologous manner in people with Parkinson’s Disease, leading to conflicting results, but may have the potential to establish a different attentional strategy which allows a subject to mitigate freezing of gait episodes. This paper will identify and discuss the questions that still need to be answered in order to consider this approach i.e., can this population access motor imagery, can motor imagery alter the attentional strategy employed when moving through doorways, what is the best motor imagery approach for people with Parkinson’s Disease and freezing of gait, and what dosage is most effective, while briefly outlining future research considerations.

The feasibility and efficacy of a serial reaction time task that measures motor learning of anticipatory stepping

BACKGROUND

Motor learning has been investigated using various paradigms, including serial reaction time tasks (SRTT) that examine upper extremity reaching and pointing while seated. Few studies have used a stepping SRTT, which could offer additional insights into motor learning involving postural demands. For a task to measure motor learning, naïve participants must demonstrate a) improved performance with task practice, and b) a dose-response relationship to learning the task.

RESEARCH QUESTION

Is a stepping SRTT feasible and efficacious for measuring motor learning?

METHODS

In this prospective study, 20 participants stood on an instrumented mat and were presented with stimuli on a computer screen. They stepped to the corresponding positions on the mat as quickly as possible. Presented stimuli included random sequences and a blinded imbedded repeating sequence. Three days after completing the randomly assigned practice dose [high dose group (n = 10) performed 4320 steps; low dose group (n = 10) performed 144 steps], a retention test of 72 steps was performed. Feasibility was measured as the proportion of participants who completed the assigned practice dose without adverse events. Efficacy was measured as within-group performance improvement on the random sequences and on the repeating sequence (paired t-tests), as well as a dose-response relationship to learning both types of sequences (independent t-tests).

RESULTS

All participants (mean age 26.8 years) completed all practice sessions without adverse events, indicating feasibility. High dose practice resulted in performance improvement while low dose did not; a dose-response relationship was found, with high dose practice resulting in greater learning of the task than low dose practice, indicating efficacy.

SIGNIFICANCE

This stepping SRTT is a feasible and efficacious way to measure motor learning, which could provide critical insights into anticipatory stepping, postural control, and fall risk. Future research is needed to determine feasibility, efficacy, and optimal practice dosages for older and impaired populations.

Neurotransmitters, Cell Types, and Circuit Mechanisms of Motor Skill Learning and Clinical Applications

Animals acquire motor skills to better survive and adapt to a changing environment. The ability to learn novel motor actions without disturbing learned ones is essential to maintaining a broad motor repertoire. During motor learning, the brain makes a series of adjustments to build novel sensory–motor relationships that are stored within specific circuits for long-term retention. The neural mechanism of learning novel motor actions and transforming them into long-term memory still remains unclear. Here we review the latest findings with regard to the contributions of various brain subregions, cell types, and neurotransmitters to motor learning. Aiming to seek therapeutic strategies to restore the motor memory in relative neurodegenerative disorders, we also briefly describe the common experimental tests and manipulations for motor memory in rodents.

Dopamine replacement improves motor learning of an upper extremity task in people with Parkinson disease

BACKGROUND

Dopamine replacement medication has positive effects on existing motor skills for people with Parkinson disease (PD), but may have detrimental effects on the learning of motor skills necessary for effective rehabilitation according to the dopamine overdose hypothesis.

OBJECTIVES

This study aimed to determine whether dopamine replacement medication (i.e. levodopa) affects: learning of a novel upper extremity task, decrements in skill following withdrawal of practice, the rate of learning, and the transfer of movement skill to untrained upper extremity tasks compared to training "off" medication, in people with PD.

METHODS

Participants with mild-moderate PD (Hoehn and Yahr stage 2) were randomized to train "on" (n = 12) or "off" (n = 11) levodopa medication. Participants practiced 10 blocks of five trials of a functional motor task with their non-dominant upper extremity over three consecutive days (acquisition period), followed by a single block of five trials two and nine days later. Participants were also assessed "on" levodopa with two transfer tasks (the nine-hole peg test and a functional dexterity task) prior to any practice and nine days after the end of the acquisition period.

RESULTS

Participants who practiced "on" levodopa medication learned the upper extremity task to a greater extent that those who practiced "off" medication, as determined by retained performance two days after practice. Skill decrement and skill transfer were not significantly different between groups. Rate of learning was unable to be modelled in this sample.

CONCLUSIONS

Levodopa medication improved the learning of an upper extremity task in people with mild-moderate PD.