Modulation of motor cortices on manual asymmetries

Differences between hands in motor performance are associated with differences in the interaction of inhibitory connections of homologous parts of the cerebral hemispheres. Modulation of these inhibitory connections in the right and left primary motor cortex (M1) may alter manual performance asymmetries. To investigate this assumption, eleven right-handed male university students performed a discrete aiming task in a digitizing tablet under three experimental conditions: dominant M1 inhibition, non-dominant M1 inhibition, and sham. The Transcranial Direct Current Stimulation technique was used to increase or decrease participants’ M1 excitability. We used a within-subject design, in which we counterbalanced the order of conditions and the order of the starting hand among participants. The performance-dependent variables were: reaction time, movement time, and radial error, while kinematic variables were: peak velocity, relative time to peak velocity, and number of discontinuities in acceleration in the final homing phase. Results showed changes in asymmetry related to reaction time, movement time, and relative time to peak velocity. The interaction between M1 modulation and hemispheric specialization produced specific changes in these variables. Taken together, these findings revealed that modulation of the dominant and non-dominant M1 affects manual performance asymmetries

Hemispheric asymmetries in goal-directed hand movements are independent of hand preference

Asymmetries  in  the  kinematics  and  neural  substrates  of  voluntary  right  and  left  eye-­hand coordinated   movements   have   been   accredited   to   differential   hemispheric specialization.  An  alternative  explanation  for  between-­hand  movement  differences  could result  from  hand-preference  related  effects.  To  test  both  assumptions,  an  experiment  was conducted   with   left-­   and   right-­handers   performing   goal-­directed   movements   with   either hand   paced   by   a   metronome.   Spatiotemporal   accuracy   was   comparable   between   hands, whereas   hand   peak   velocity   was   reached   earlier   when   moving   with   the   left   compared   to the  right  hand.  The  underlying  brain  activation  patterns  showed  that  both  left-­  and  right-­handers  activated  more  areas  involved  in  visuomotor  attention  and  saccadic  control  when using   their   left   compared   to   the   right   hand. Altogether, these results confirm a unique perceptuomotor processing specialization of the left brain/right hand system that is independent of hand preference.status: publishe

Orff-Based Music Training Enhances Children’s Manual Dexterity and Bimanual Coordination

How music training and expertise influence non-musical abilities is a widely researched topic. Most studies focus on the differences between adult professional musicians and non-musicians, or examine the effects of intensive instrumental training in childhood. However, the impact of music programs developed in regular school contexts for children from low-income communities is poorly explored. We conducted a longitudinal training study in such communities to examine if collective (Orff-based) music training enhances fine motor abilities, when compared to a homologous training program in sports (basketball), and to no specific training. The training programs in music and sports had the same duration, 24 weeks, and were homologous in structure. A pre-test, training, post-test and follow-up design was adopted. Children attending the 3rd grade (n = 74, 40 girls; mean age 8.31 years) were pseudorandomly divided into three groups, music, sports and control that were matched on demographic and intellectual characteristics. Fine motor abilities were assessed with the Purdue pegboard test (eye-hand coordination and motor speed, both subsumed under manual dexterity, and bimanual coordination) and with the Grooved pegboard (manipulative dexterity) test. All groups improved in manipulative dexterity that was not affected by type of training. On bimanual coordination and manual dexterity, however, a robust and stable advantage of music training emerged. At the end of training (post-test), children from the music group significantly outperformed children from the sports and control groups, an advantage that persisted at follow-up 4 months after training at the start of the following school year. Also, at follow-up none of the children from the music group were performing below the 20th percentile in the Purdue pegboard subtests and more than half were performing at the high end level (>80th percentile). Children from the sports group also improved significantly from pre- to post-test but their performance was not significantly different from that of the control group. These results show that an affordable, collective-based music practice impacts positively on fine-motor abilities, a finding that is relevant for a better understanding of the impact of music in childhood development, and that may have implications for education at the primary grade

Shared and Distinct Neural Bases of Large- and Small-Scale Spatial Ability: A Coordinate-Based Activation Likelihood Estimation Meta-Analysis

Background: Spatial ability is vital for human survival and development. However, the relationship between large-scale and small-scale spatial ability remains poorly understood. To address this issue from a novel perspective, we performed an activation likelihood estimation (ALE) meta-analysis of neuroimaging studies to determine the shared and distinct neural bases of these two forms of spatial ability.Methods: We searched Web of Science, PubMed, PsycINFO, and Google Scholar for studies regarding “spatial ability” published within the last 20 years (January 1988 through June 2018). A final total of 103 studies (Table 1) involving 2,085 participants (male = 1,116) and 2,586 foci were incorporated into the meta-analysis.Results: Large-scale spatial ability was associated with activation in the limbic lobe, posterior lobe, occipital lobe, parietal lobe, right anterior lobe, frontal lobe, and right sub-lobar area. Small-scale spatial ability was associated with activation in the parietal lobe, occipital lobe, frontal lobe, right posterior lobe, and left sub-lobar area. Furthermore, conjunction analysis revealed overlapping regions in the sub-gyrus, right superior frontal gyrus, right superior parietal lobule, right middle occipital gyrus, right superior occipital gyrus, left inferior occipital gyrus, and precuneus. The contrast analysis demonstrated that the parahippocampal gyrus, left lingual gyrus, culmen, right middle temporal gyrus, left declive, left superior occipital gyrus, and right lentiform nucleus were more strongly activated during large-scale spatial tasks. In contrast, the precuneus, right inferior frontal gyrus, right precentral gyrus, left inferior parietal lobule, left supramarginal gyrus, left superior parietal lobule, right inferior occipital gyrus, and left middle frontal gyrus were more strongly activated during small-scale spatial tasks. Our results further indicated that there is no absolute difference in the cognitive strategies associated with the two forms of spatial ability (egocentric/allocentric).Conclusion: The results of the present study verify and expand upon the theoretical model of spatial ability proposed by Hegarty et al. Our analysis revealed a shared neural basis between large- and small-scale spatial abilities, as well as specific yet independent neural bases underlying each. Based on these findings, we proposed a more comprehensive version of the behavioral model

Eye-Hand Coordination Varies According to Changes in Cognitive-Motor Load and Eye Movements Used

In this dissertation three studies were used to help improve the understanding of eye- hand coordination control of visuomotor reaching tasks with varying cognitive loads. Specifically, we considered potential performance differences based on eye-movements, postural influences, as well as fitness level of the young adult participants. A brief introduction in chapter 1 is followed by a detailed literature review in chapter 2. Results from the three studies presented in chapter’s 3-5 further advance our knowledge of the integrated control used for goal-directed visually-guided reaches. In the first study (chapter 3), the additional cost associated with the use of smooth pursuit slowed hand movement speed when the eyes and hand moved in distinct directions, yet improved accuracy over the use of saccadic eye movements and eye fixation. We concluded that eye-movement choice can influence various types of visually-guided reaching with different cognitive demands and that researchers should provide clear eye-movement instructions for participants and/or monitor the eyes when assessing similar upper limb control to account for possible differences. In the second study (chapter 4), results revealed slower speed and poor accuracy of hand movements along with less body sway for visually-guided reaching when the eyes and hand moved in opposite directions during eye-hand decoupling compared to when the eyes and hand moved in the same direction (eye-hand coupling). In contrast, standing up did not significantly influence reaching performance compared to sitting. We concluded that increases in cognitive demands for eye-hand coordination created a greater need for postural control to help improve the goal- directed control of reaching. In the third study (chapter 5), we found no evidence of eye-hand coordination differences between highly fit or sedentary participants, yet cerebral activation in the centro-parietal location differed between tasks involving eye-hand coupling/decoupling. We concluded that reaching performance declines accompanied increased sensorimotor demands during eye-hand decoupling that may link to prior/current athletic experience and not fitness level. Overall, alterations in visually-guided goal-directed reaching movements involving eye-hand coupling and decoupling depend on changes in eye-movements utilized and not on low threat postural changes or fitness levels of the young adults performing the task

Anticipatory planning in object manipulation: A cross-sectional investigation of children, young adults and older adults

Over a series of five studies, this work aimed to investigate anticipatory planning in object manipulation across the human lifespan. Main objectives were to: (a) understand the influence of the movement context; (b) delineate the role of handedness; (c) characterize the influence of familiarity with an object; (d) investigate independent and cooperative movements; and (e) outline similarities and differences across the lifespan. Chapter 2 established a foundation for the thesis with right and left handed young adults. Findings supported the hypothesis that manual asymmetries do not influence anticipatory planning. Furthermore, despite end-state comfort reaching ceiling, kinematic data provided evidence for an increase in cognitive demand in pantomime compared to actual object use. Chapter 2 therefore served as proof of concept for manipulating contextual information to alter the cognitive demands of the task. Chapter 3 compared data to a group of left and right handed older adults. Similar to Chapter 2, manual asymmetries were not influential. Evidence of end-state comfort did not differ in young and older adults; however, after separating older adults into two groups, those who did not display the effect spent a longer time in the final approach to the target in pure pantomime. This was attributed to the increased reliance on feedback-dependent corrective mechanisms with increasing age. To quantify similarities and differences among children, young and older adults, Chapters 4, 5 and 6 assessed anticipatory planning across the lifespan. The main findings of the thesis are highlighted in the results of Chapter 6. Object use involves the direct perception of affordances, and indirect selection of motor programs based on action intentions. The ability to interact with objects in the environment is thus rooted in learned knowledge. With cognitive development, improvements in multisensory integration, and familiarity with objects, children become more proficient in anticipatory planning. As such, behaviours emulate a gradual transition from a reliance on habitual actions executed successfully in the past, to the recognition of affordances and incorporation of intentions into actions. Likewise, with decline in cognitive and motor processes, the behaviour of older adults (ages 71+) reflects a gradual transition back to habitual behaviours. Actions thus reflect stimulus-driven responses, as opposed to those which consider affordances and intentions