Age-related asymmetry in anticipatory postural movements during unilateral arm movement and imagery.

Reaching movements of the arms are accompanied by anticipatory (APM) and compensatory postural motion (CPM) that counteract the resulting perturbations to body stability. Recent research has shown that these postural actions are also observable in the context of imagined arm movements. As motor imagery (MI) shares many neurophysiological and behavioral characteristics with physical movements, and MI training can affect subsequent performance, MI tasks provide a good setting for studying the anticipatory aspects of postural control. This study investigated APMs and CPMs of the head and hip of healthy young and older adults in the temporal vicinity of physical and imagined forward raises of the dominant and non-dominant arm. When MI of the dominant arm was self-initiated, both age groups showed APM in the anteroposterior plane. When the self-initiated MI was of the non-dominant arm, only the older group showed anteroposterior APM. The older group did not show APM when an expected arm movement (or MI) was made to an external signal. This suggests an age-related deficit in coordinating postural preparation with external events. Only the older group showed mediolateral APM, and only for dominant arm MI, indicating sensitivity to potential perturbation to the weaker, non-dominant side of the body. Overall, the older group showed more anticipatory postural motion at the head. Systematic APM for manual MI suggests that MI training may be an effective intervention for anticipatory postural control. An integrated model of postural support for executed and imagined limb movements is suggested.

The role of spatial alignment in posture-cognition dual task interaction.

BACKGROUND: A range of cognitive tasks can interfere with postural control, particularly in older adults. In the case of spatial tasks, the spatial alignment between the task and postural control can incur dual-task costs separately from task load. It has been suggested that spatial tasks incur dual-task costs because accessing the visuospatial sketchpad component of working memory reduces the capacity to utilize external visual information for postural control. RESEARCH QUESTION: We investigated whether the spatial alignment between a cognitive and a postural control task can affect postural stability even when visual perception is not involved in either task and task load does not differ between aligned and non-aligned conditions. We predicted that any such effect would be greater in older people and in a more challenging stance. METHODS: Fifty healthy adults (27 aged 20-35, 23 aged 59-88) with no history of balance or cognitive difficulties performed a mental navigation task while standing in open or closed stance with eyes closed. The mental navigation task was presented in a reference plane that was either aligned or non-aligned to the horizontal reference plane in which the posture control system controlled the position of the body's center of gravity. Task performance was measured as accuracy and response time and postural sway as anteroposterior (AP) and mediolateral (ML) sway velocity. RESULTS: The older group were less accurate in the mental navigation task, and both groups had higher AP and ML sway velocity in closed stance. When standing in the more challenging stance, the older group had higher AP sway velocity while performing the mental navigation task in the non-aligned than the aligned reference plane condition. SIGNIFICANCE: The spatial configuration compatibility between a cognitive task and postural control can affect postural stability even when visual information is not being used for either task and task load is unchanged.

Age-related differences in postural adjustments during limb movement and motor imagery in young and older adults.

Recent research has shown that systematic postural adjustments occur during periods of manual motor imagery (MI), but the timing (anticipatory or reactive) and directionality (against or in the direction of arm extension) of these postural motions relative to individual manual actions or imagery are not well understood. This study analyzed the anteroposterior hip and head motion of healthy young and older participants, while they imagined bilateral arm raises under self-initiated or environmentally triggered performance conditions. When MI was self-initiated, both age groups showed significant forward postural motion during the second prior to MI initiation. When MI (or physical arm movement) was environmentally triggered, however, older people did not show anticipatory forward postural motion, but did show compensatory backward head motion. These results suggest that manual MI is indeed accompanied by anticipatory postural motion, but this anticipation is attenuated in older people when they do not have control over the timing of manual movement onset.

Low-Frequency Repetitive Transcranial Magnetic Stimulation to Right Parietal Cortex Disrupts Perception of Briefly Presented Stimuli.

Right parietal cortex has recently been linked to the temporal resolution of attention. We therefore sought to investigate whether disruption to right parietal cortex would affect attention to visual stimuli presented for brief durations. Participants performed a visual discrimination task before and after 10 minutes repetitive transcranial magnetic stimulation (1 Hz) to right or central parietal cortex as well as 20 minutes after the second block of trials. Participants reported the spatial frequency of a masked Gabor patch presented for a brief duration of 60, 120, or 240 ms. We calculated error magnitudes by comparing accuracy to a guessing model. We then compared error magnitudes to blocks with no stimulation, producing a measure of baselined performance. Baselined performance was poorer at longer stimulus durations after right parietal than central parietal stimulation, suggesting that right parietal cortex is involved in attention to briefly presented stimuli, particularly in situations where rapid accumulation of visual evidence is needed.

Engagement of the motor system in position monitoring: reduced distractor suppression and effects of internal representation quality on motor kinematics.

The position monitoring task is a measure of divided spatial attention in which participants track the changing positions of one or more objects, attempting to represent positions with as much precision as possible. Typically precision of representations declines with each target object added to participants' attention load. Since the motor system requires precise representations of changing target positions, we investigated whether position monitoring would be facilitated by increasing engagement of the motor system. Using motion capture, we recorded the positions of participants' index finger during pointing responses. Participants attempted to monitor the changing positions of between one and four target discs as they moved randomly around a large projected display. After a period of disc motion, all discs disappeared and participants were prompted to report the final position of one of the targets, either by mouse click or by pointing to the final perceived position on the screen. For mouse click responses, precision declined with attentional load. For pointing responses, precision declined only up to three targets and remained at the same level for four targets, suggesting obligatory attention to all four objects for loads above two targets. Kinematic profiles for pointing responses for highest and lowest loads showed greater motor adjustments during the point, demonstrating that, like external environmental task demands, the quality of internal representations affects motor kinematics. Specifically, these adjustments reflect the difficulty of both pointing to very precisely represented locations as well as keeping representations distinct from one another.

Age-related reversal of postural adjustment characteristics during motor imagery.

Physical and imagined movements show similar behavioral constraints and neurophysiological activation patterns. An inhibition mechanism is thought to suppress overt movement during motor imagery, but it does not effectively suppress autonomic or postural adjustments. Inhibitory processes and postural stability both deteriorate with age. Thus, older people's balance is potentially vulnerable to interference from postural adjustments induced by thoughts about past or future actions. Here, young and older adults stood upright and executed or imagined manual reaching movements. Reported arm movement time (MT) of all participants increased with target distance. Older participants reported longer MT than young participants when executing arm movements, but not when imagining them. Older adults' anteroposterior (AP) and mediolateral (ML) postural sway was higher than young adults' at baseline, but their AP sway fell below their baseline level during manual imagery. In contrast, young adults' AP sway increased during imagery relative to their baseline. A similar tendency to reduce sway in the ML direction was also observed in older adults during imagery in a challenging stance. These results suggest that postural response during manual motor imagery reverses direction with age. Motor imagery and action planning are ubiquitous tasks, and older people are likely to spend more time engaged in them. The shift toward restricting body sway during these tasks is akin to a postural threat response, with the potential to interfere with balance during activities of daily living. (PsycINFO Database Record

Incomplete inhibition of central postural commands during manual motor imagery.

Imagined movements exhibit many of the behavioral and neurophysiological characteristics of executed actions. As a result, they are considered simulations of physical actions with an inhibition mechanism that suppresses overt movement. This inhibition is incomplete, as it does not block autonomic preparation, and it also does not effectively suppress postural adjustments planned in support of imagined movements. It has been suggested that a central inhibition command may fail to suppress postural adjustments because it may not have access to afference-based elaborations of the postural response that occur downstream of central motor planning. Here, we measured changes in the postural response associated with imagining manual reaching movements under varying levels of imagined loading of the arm. We also manipulated stance stability, and found that postural sway reduced with increased (imagined) arm loading when imagining reaching movements from the less stable stance. As there were no afferent signals associated with the loading constraint, these results suggest that postural adjustments can leak during motor imagery because the postural component of the central motor plan is itself not inhibited effectively.

Nonpharmacological Treatments of Insomnia for Long-Term Painful Conditions: A Systematic Review and Meta-analysis of Patient-Reported Outcomes in Randomized Controlled Trials.

STUDY OBJECTIVES: Insomnia is a debilitating comorbidity of chronic pain. This study evaluated the effect of nonpharmacological sleep treatments on patient-reported sleep quality, pain, and well-being in people with long-term cancer and non-cancer (e.g., back pain, arthritis, fibromyalgia) pain conditions. DESIGN: We systematically searched Cochrane CENTRAL, MEDLINE, Embase, and PsychINFO for relevant studies. Search period was set to inception of these databases to March 2014. Studies were included if they were: original randomized controlled trials (RCTs); testing a nonpharmacological intervention; that targets sleep; in adults; with painful health conditions; that has a control group; includes a measure of sleep quality; and at least one other health and well-being outcome. MEASUREMENT AND FINDINGS: Means and standard deviations of sleep quality, pain, fatigue, depression, anxiety, physical and psychological functioning were extracted for the sleep treatment and control groups at baseline, posttreatment and final follow-up. Methodological details concerning the treatment, participants, and study design were abstracted to guide heterogeneity and subgroup analyses. Eleven RCTs involving 1,066 participants (mean age 45-61 years) met the criteria for the meta-analysis. There was no systematic evidence of publication bias. Nonpharmacological sleep treatments in chronic pain patients were associated with a large improvement in sleep quality (standardized mean difference = 0.78, 95% Confidence Interval [0.42, 1.13]; P < 0.001), small reduction in pain (0.18 [0, 0.36] P < 0.05), and moderate improvement in fatigue (0.38 [0.08, 0.69]; P < 0.01) at posttreatment. The effects on sleep quality and fatigue were maintained at follow-up (up to 1 year) when a moderate reduction in depression (0.31, [0.09, 0.53]; P < 0.01) was also observed. Both cancer and non-cancer pain patients benefited from nonpharmacological sleep treatments. Face-to-face treatments achieved better outcomes than those delivered over the phone/internet. CONCLUSIONS: Although the body of evidence was small, nonpharmacological sleep interventions may represent a fruitful avenue for optimizing treatment outcomes in patients with chronic pain. REGISTRATION: PROSPERO registration: CRD42013004131.

Body posture modulates imagined arm movements and responds to them.

Imagined movements are thought to simulate physical ones, with similar behavioral constraints and neurophysiological activation patterns and with an inhibition mechanism that suppresses movement execution. When upper body movements such as reaching with the arm are made from an upright stance, lower body and trunk muscles are also activated to maintain body posture. It is not clear to what extent parameters of imagined manual movements are sensitive to the postural adjustments their execution would necessitate, nor whether such postural responses are as effectively inhibited as the imagined movements themselves. We asked healthy young participants to imagine reaching movements of the arm while in upright stance, and we measured their self-reported movement times and postural sway during imagined movements. We manipulated mediolateral stance stability and the direction of arm movement (mediolateral or anteroposterior). Imagined arm movements were reportedly slower when subjects were standing in a mediolaterally less stable stance, and the body swayed more when arm movements were imagined in the direction of postural vulnerability. The results suggest that the postural state of the whole body, not just the involved limbs, informs trajectory planning during motor imagery and that measurable adjustments to body posture accompany imagined manual actions. It has been suggested that movement is suppressed during motor imagery by a premotor inhibitory mechanism operating at brain stem or spinal level. Any such inhibition must be incomplete because, for example, it does not eliminate autonomic arousal. Our results suggest that it also does not effectively suppress postural adjustments planned in support of imagined movements.