Early motor trajectories predict motor but not cognitive function in preterm- and term-born adults without pre-existing neurological conditions

Very preterm (VP; 0.05). Motor problems in childhood were homotypically associated with poorer motor competence in adulthood. Similarly, early cognitive problems were homotypically associated with adult cognitive outcomes. Thus, both motor and cognitive function should be assessed in routine follow-up during childhood

Triggering prepared actions by sudden sounds : reassessing the evidence for a single mechanism

Loud acoustic stimuli can unintentionally elicit volitional acts when a person is in a state of readiness to execute them (the StartReact effect). It has been assumed that the same subcortical pathways and brain regions underlie all instances of the StartReact effect. They are proposed to involve the startle reflex pathways, and the eliciting mechanism is distinct from other ways in which sound can affect the motor system. We present an integrative review which shows that there is no evidence to support these assumptions. We argue that motor command generation for learned, volitional orofacial, laryngeal and distal limb movements is cortical and the StartReact effect for such movements involves transcortical pathways. In contrast, command generation for saccades, locomotor corrections and postural adjustments is subcortical and subcortical pathways are implicated in the StartReact effect for these cases. We conclude that the StartReact effect is not a special phenomenon mediated by startle reflex pathways, but rather is a particular manifestation of the excitatory effects of intense stimulation on the central nervous system

Delayed inhibition of an anticipatory action during motion extrapolation

Background: Continuous visual information is important for movement initiation in a variety of motor tasks. However, even in the absence of visual information people are able to initiate their responses by using motion extrapolation processes. Initiation of actions based on these cognitive processes, however, can demand more attentional resources than that required in situations in which visual information is uninterrupted. In the experiment reported we sought to determine whether the absence of visual information would affect the latency to inhibit an anticipatory action. Methods: The participants performed an anticipatory timing task where they were instructed to move in synchrony with the arrival of a moving object at a determined contact point. On 50% of the trials, a stop sign appeared on the screen and it served as a signal for the participants to halt their movements. They performed the anticipatory task under two different viewing conditions: Full-View (uninterrupted) and Occluded-View (occlusion of the last 500 ms prior to the arrival at the contact point). Results: The results indicated that the absence of visual information prolonged the latency to suppress the anticipatory movement. Conclusion: We suggest that the absence of visual information requires additional cortical processing that creates competing demand for neural resources. Reduced neural resources potentially causes increased reaction time to the inhibitory input or increased time estimation variability, which in combination would account for prolonged latency

Grasping at laws:Speed-accuracy trade-offs in manual prehension

Most of human performance is subject to speed-accuracy trade-offs. For spatially constrained aiming, the trade-off is often said to take the specific form of Fitts' law, in which movement duration is predicted from a single factor combining target distance and target size. However, efforts to extend this law to the three-dimensional context of reaching to grasp (prehension) have had limited success. We suggest that there are potentially confounding influences in standard grasping, and we introduce a novel task to regularize the direction of approach and to eliminate the influences of nearby surfaces. In six participants, we examined speed-accuracy trade-offs for prehension, manipulating the depth (in the plane of the reach), height (orthogonal to the reach), and width (the grasped dimension) of the target object independently. We obtained lawful relationships that were consistent at the group and individual levels. It took longer to reach for more distant objects, and more time was allowed when placing the fingers on a contact surface smaller in either depth or height. More time was taken to grasp wider objects, but only beyond a critical width that varied between individuals. These speed-accuracy trade-offs showed substantial departures from Fitts' law, and were well described by a two-factor model in which reach distance and object size have separate influences on movement duration. We discuss empirical and theoretical reasons for preferring a two-factor model, and we propose that this may represent the most general form of speed-accuracy trade-off, not only for grasping but also for other spatially constrained aiming tasks. (PsycINFO Database Record [Abstract copyright: (c) 2018 APA, all rights reserved).

Predictors of early motor trajectories from birth to 5 years in neonatal at-risk and control children

Aim To describe motor development in preschool children, to identify perinatal, neonatal and social environmental risk factors of poor motor development, and to replicate results in a second cohort. Methods Two prospective samples in Germany (Bavarian Longitudinal Study, BLS) and Finland (Arvo Ylppo Longitudinal Study, AYLS) assessed 4741 and 1423 children from birth to 56 months, respectively. Motor functioning was evaluated at birth, and 5, 20 and 56 months. Perinatal, neonatal and social environmental information was collected at birth and 5 months. Results Two distinct motor trajectories were identified: low (BLS: n = 4486 (94.6%), AYLS: n = 1391 (97.8%)) and high (BLS: n = 255 (5.4%), AYLS: n = 32 (2.2%)) degree of motor difficulties. High degree of motor difficulties was predicted by neonatal complications, abnormal neonatal neurological status, duration of hospitalisation and poor parent-infant relationships. Although neonatal complications and poor parent-infant relationships did not significantly predict high degree of motor difficulties in the AYLS, the trends identified were similar to those obtained from the BLS. Conclusion Early identification of children at-risk of motor difficulties across infancy and toddlerhood may help referring those children to interventions earlier. Modifiable risk factors, such as parent-infant relationships, may be addressed by intervention strategies to prevent children from developing motor difficulties.Peer reviewe

Motor Sequence Learning in Healthy Older Adults Is Not Necessarily Facilitated by Transcranial Direct Current Stimulation (tDCS)

Background: Transcranial Direct Current Stimulation (tDCS) of the primary motor cortex (M1) can modulate neuronal activity, and improve performance of basic motor tasks. The possibility that tDCS could assist in rehabilitation (e.g., for paresis post-stroke) offers hope but the evidence base is incomplete, with some behavioural studies reporting no effect of tDCS on complex motor learning. Older adults who show age-related decline in movement and learning (skills which tDCS could potentially facilitate), are also under-represented within tDCS literature. To address these issues, we examined whether tDCS would improve motor sequence learning in healthy young and older adults. Methods: In Experiment One, young participants learned 32 aiming movements using their preferred (right) hand whilst receiving: (i) 30 min Anodal Stimulation of left M1; (ii) 30 min Cathodal Stimulation of right M1; or (iii) 30 min Sham. Experiment Two used a similar task, but with older adults receiving Anodal Stimulation or Sham. Results: Whilst motor learning occurred in all participants, tDCS did not improve the rate or accuracy of motor learning for either age group. Conclusion: Our results suggest that the effects of tDCS may be limited to motor performance with no clear beneficial effects for motor learning

Triggering Mechanisms for Motor Actions: The Effects of Expectation on Reaction Times to Intense Acoustic Stimuli

Motor actions can be released much sooner than normal when the go-signal is of very high intensity (>100 dBa). Although statistical evidence from individual studies has been mixed, it has been assumed that sternocleidomastoid (SCM) muscle activity could be used to distinguish between two neural circuits involved in movement triggering. We summarized meta-analytically the available evidence for this hypothesis, comparing the difference in premotor reaction time (RT) of actions where SCM activity was elicited (SCM+ trials) by loud acoustic stimuli against trials in which it was absent (SCM- trials). We found ten studies, all reporting comparisons between SCM+ and SCM- trials. Our mini meta-analysis showed that premotor RTs are faster in SCM+ than in SCM- trials, but the effect can be confounded by the variability of the foreperiods employed. We present experimental data showing that foreperiod predictability can induce differences in RT that would be of similar size to those attributed to the activation of different neurophysiological pathways to trigger prepared actions. We discuss plausible physiological mechanisms that would explain differences in premotor RTs between SCM+ and SCM- trials

Effects of infant motor problems and treatment with physiotherapy on child outcomes at school-age

Background: Early motor coordination problems have previously been associated with various developmental outcomes at school-age. Aims: Investigate whether and how treatment with physiotherapy may alter associations between early motor problems and subsequent developmental outcomes. Study design: A prospective whole-population study. Subjects: 1374 children were followed from birth to 8 years. Outcome measures: Early motor functioning was determined with standard neurological examinations at birth and at 5 months. Information on receipt of physiotherapy was collected through parent interviews at 5, 20 and 56 months. Developmental outcomes at 6 and 8 years included motor skills, mental health, cognitive function, and attention regulation and were determined through standard tests, parent reports and observed behavior ratings. Results: Early motor problems were associated with lower motor skills, cognitive function, and attention regulation at school-age, but not with mental health. In addition to early motor problems, receipt of physiotherapy was independently and negatively related to outcomes at school-age. Accounting for imbalances in covariates, including initial motor scores, via propensity score matching attenuated the adverse effects of receipt of physiotherapy on school-aged outcomes. Conclusions: Infant motor problems are associated with motor and cognitive outcomes at school-age. Early motor problems may represent a starting point of a trajectory of difficulties that may lead to a higher risk of problems in multiple developmental domains. No evidence for a beneficial effect of treatment with physiotherapy was found