Bimanual Coordination Learning with Different Augmented Feedback Modalities and Information Types

Previous studies have shown that bimanual coordination learning is more resistant to the removal of augmented feedback when acquired with auditory than with visual channel. However, it is unclear whether this differential “guidance effect” between feedback modalities is due to enhanced sensorimotor integration via the non-dominant auditory channel or strengthened linkage to kinesthetic information under rhythmic input. The current study aimed to examine how modalities (visual vs. auditory) and information types (continuous visuospatial vs. discrete rhythmic) of concurrent augmented feedback influence bimanual coordination learning. Participants either learned a 90°-out-of-phase pattern for three consecutive days with Lissajous feedback indicating the integrated position of both arms, or with visual or auditory rhythmic feedback reflecting the relative timing of the movement. The results showed diverse performance change after practice when the feedback was removed between Lissajous and the other two rhythmic groups, indicating that the guidance effect may be modulated by the type of information provided during practice. Moreover, significant performance improvement in the dual-task condition where the irregular rhythm counting task was applied as a secondary task also suggested that lower involvement of conscious control may result in better performance in bimanual coordination.     

Auditory sensory support of complicated voluntary goal-aimed bimanual movements

The intrasensory and sensor-effector interactions between inter-spike intervals of acoustic stem-evoked potentials with parameters of hands coordination was found with the help of correlation analysis. Role of excitation of ascending fibres of rostral part of the pons and lateral loop in mechanisms of the auditory-motor coordination was determined. Sex-dependent differences in integration of elements of the sensor-motor system because of lateralization of incoming auditory information and complication of the motor task performed were revealed. In men, mechanisms of auditory-motor coordination have less determined character than in women. That probably determines higher level of bi-manual coordination in men. Optimal correct realization of motor program in men is performed prognostically, while in women--after a mistake has been done.     

Aging, visual information, and adaptation to task asymmetry in bimanual force coordination

This study investigated the coordination and control strategies that the elderly adopt during a redundant finger force coordination task and how the amount of visual information regulates the coordination patterns. Three age groups (20-24, 65-69, and 75-79 yr) performed a bimanual asymmetric force task. Task asymmetry was manipulated via imposing different coefficients on the finger forces such that the weighted sum of the two index finger forces equaled the total force. The amount of visual information was manipulated by changing the visual information gain of the total force output. Two hypotheses were tested: the reduced adaptability hypothesis predicts that the elderly show less degree of force asymmetry between hands compared with young adults in the asymmetric coefficient conditions, whereas the compensatory hypothesis predicts that the elderly exhibit more asymmetric force coordination patterns with asymmetric coefficients. Under the compensatory hypothesis, two contrasting directions of force sharing strategies (i.e., more efficient coordination strategy and minimum variance strategy) are expected. A deteriorated task performance (high performance error and force variability) was found in the two elderly groups, but enhanced visual information improved the task performance in all age groups. With low visual information gain, the elderly showed reduced adaptability (i.e., less asymmetric forces between hands) to the unequal weighting coefficients, which supported the reduced adaptability hypothesis; however, the elderly revealed the same degree of adaptation as the young group under high visual gain. The findings are consistent with the notion that the age-related reorganization of force coordination and control patterns is mediated by visual information and, more generally, the interactive influence of multiple categories of constraints.     

How do neural connectivity and time delays influence bimanual coordination?

Multilevel crosstalk as a neural basis for motor control has been widely discussed in the literature. Since no natural process is instantaneous, any crosstalk model should incorporate time delays, which are known to induce temporal coupling between functional elements and stabilize or destabilize a particular mode of coordination. In this article, we systematically study the dynamics of rhythmic bimanual coordination under the influence of varying connection topology as realized by callosal fibers, cortico-thalamic projections, and crossing peripheral fibers. Such connectivity contributes to various degrees of neural crosstalk between the effectors which we continuously parameterize in a mathematical model. We identify the stability regimes of bimanual coordination as a function of the degree of neural crosstalk, movement amplitude and the time delays involved due to signal processing. Prominent examples include explanations of the decreased stability of the antiphase mode of coordination in split brain patients and the role of coupling in mediating bimanual coordination.     

Effects of Neurofeedback Training on Performing Bimanual Coordination In-phase and Anti-phase Patterns in Children with ADHD

It is generally accepted that children with attention-deficit/hyperactivity disorder (ADHD) have poor motor control, especially in bimanual coordination tasks. Such children characteristically have impaired fine motor ability, problems with force control, and poor motor coordination. They are at particular risk of loss of motor control and reduced bimanual coordination. We tested whether, compared to a control condition, neurofeedback training (NFT) could improve bimanual coordination among children with ADHD. 20 Children with ADHD (mean age 7.9 years; SD 2.11) were randomly assigned either to NFT or to a control condition. All participants completed a bimanual coordination test at the following time points: baseline, assessment 1, assessment 2, assessment 3, and again 12 session later at posttest. NFT consisted of Sensory Motor Rhythm (SMR) training to achieve increased SMR in C3 and C4, while participants in the control condition were under mock NFT conditions. Bimanual coordination accuracy and consistency improved from baseline to completion of the intervention (significant Time effect), but in the NFT condition (significant time?×?group interaction). Compared to the control condition, the NFT group had fewer errors in both patterns of bimanual coordination (significant Group effect). Among children with ADHD, SMR neurofeedback training (NFT) led to significant improvements in a bimanual coordination task. The SMR NFT thus appears to have the potential to improve and enhance the motor control of ADHD patients.     

Intermanual coordination: from behavioural principles to neural-network interactions

Locomotion in vertebrates and invertebrates has a long history in research as the most prominent example of interlimb coordination. However, the evolution towards upright stance and gait has paved the way for a bewildering variety of functions in which the upper limbs interact with each other in a context-specific manner. The neural basis of these bimanual interactions has been investigated in recent years on different scales, ranging from the single-cell level to the analysis of neuronal assemblies. Although the prevailing viewpoint has been to assign bimanual coordination to a single brain locus, more recent evidence points to a distributed network that governs the processes of neural synchronization and desynchronization that underlie the rich variety of coordinated functions. The distributed nature of this network accounts for disruptions of interlimb coordination across various movement disorders.     

Evidence against a relationship between dermatoglyphic asymmetry and male sexual orientation

Hall and Kimura (1994) studied the relation between dermatoglyphic asymmetry and male sexual orientation in a sample of 66 homosexual and 182 heterosexual men. They found that more homosexual men possessed a leftward dermatoglyphic asymmetry than did heterosexual men. In this paper, we report a comparative study about the relationship between sexual orientation and dermatoglyphic characteristics, including 60 homosexual men, 76 heterosexual men, and 60 heterosexual women, recruited from the general population, and also from a gay-rights nongovernmental organization, in Salvador, Brazil. Ulnar loops were the most frequent dermatoglyphic pattern in all groups, followed by whorls, arches, and radial loops. A chi-square analysis comparing the frequencies of the patterns in the three groups only showed an excess of ulnar loops in women (p < 0.05) and arches in men (p < 0.01), but did not reveal significant differences between homosexuals and the other groups studied. There was no significant difference between gay and straight men on total ridge count. We found a preponderance of rightward asymmetry in homosexual and heterosexual men, as well as in heterosexual women. Our results do not agree with Hall and Kimura's data indicating that more gay men possessed the minority leftward asymmetry than did straight men. There was no significant difference in leftward asymmetry in the sample studied. The results reported in this paper do not support any relation between dermatoglyphic asymmetry and male sexual orientation, and, thus, any hypothesis concerning a biological intrauterine contribution to adult sexual orientation somehow associated with dermatoglyphic development.     

Neural activation and functional connectivity during motor imagery of bimanual everyday actions

Bimanual actions impose intermanual coordination demands not present during unimanual actions. We investigated the functional neuroanatomical correlates of these coordination demands in motor imagery (MI) of everyday actions using functional magnetic resonance imaging (fMRI). For this, 17 participants imagined unimanual actions with the left and right hand as well as bimanual actions while undergoing fMRI. A univariate fMRI analysis showed no reliable cortical activations specific to bimanual MI, indicating that intermanual coordination demands in MI are not associated with increased neural processing. A functional connectivity analysis based on psychophysiological interactions (PPI), however, revealed marked increases in connectivity between parietal and premotor areas within and between hemispheres. We conclude that in MI of everyday actions intermanual coordination demands are primarily met by changes in connectivity between areas and only moderately, if at all, by changes in the amount of neural activity. These results are the first characterization of the neuroanatomical correlates of bimanual coordination demands in MI. Our findings support the assumed equivalence of overt and imagined actions and highlight the differences between uni- and bimanual actions. The findings extent our understanding of the motor system and may aid the development of clinical neurorehabilitation approaches based on mental practice.     

Change in parameters of interhemispheric asymmetry during simulation of a destructive action

Interhemispheric EEG asymmetry was studied in 26 male subjects aged 8-23 with different behavioral destructiveness levels. Subjects with higher destructiveness level in the state of rest had the focus of interhemispheric asymmetry in the temporal and frontal areas of the left hemisphere, whereas in subjects with lower destructiveness level the asymmetry focus was found in the same areas of the right hemisphere. Simulation of aggressive activity led to displacement of the asymmetry focus to the right hemisphere in both groups. However, in the group with higher destructiveness the changes in the focus were observed in the EEG theta band, which suggested the involvement of mainly stem oscillators of EEG activity in the destructive behavior. In the group with lower destructiveness changes were observed mainly in the alpha3 and beta1 bands, which indicated that cortical oscillators of EEG activity were involved in the control of the destructive behavior. The results suggest better perception and assessment of stimuli by subjects with lower aggressiveness and their choice of more adequate models of behavior.     

Complex leaf-gathering skills of mountain gorillas (Gorilla g. beringei): Variability and standardization

The skills that mountain gorillas use to deal with the stings, tiny hooks, and spines protecting common plant leaves in their diet were examined for variation within and between animals. Many elements of uni- and bimanual performance were identified, often involving delicate precision and coordination, and varying idiosyncratically, erch individual having a different set of preferred elements. Many of these elements are functionally equivalent, and all but one weaned animals showed full processing capability; the history of the one exception suggests that early experience with the task may be important. Gorillas' idiosyncrasy in manual skill elements is entirely consistent with trial-and-error learning at this level. By contrast, each individual uses very few techniques (structured sequences of elements) for most processing, and these techniques are the same across the population. Where animals deviate from this generalization, they largely employ the simpler technique normally used for undefended leaves. Lateralization increases from start to finish, consistent with a logical structure in which each stage has a laterality bias and each stage is sequentially dependent on the last. Variations from their commonest, techniques occur in all animals (on average, about nine variant techniques were recorded from each animal). The repertoire of techniques increases significantly with age, whereas the repertoire of elements does not. This points to an initial reliance on a single logical structuring that is well established by weaning (about 3.5 years), with subsequent development of the ability to vary the technique used so as to take advantage of variations in the environment. Standardization of logical organization, despite variability between different animals in individual elements and behavioral laterality, suggests that the logical ordering of elements and the interrelationships of processing stages is copied by program-level imitation. © 1993 Wiley-Liss, Inc.     

Dynamics of interhemispheric asymmetry during perception of verbal information in men and women: EEG analysis

Neurophysiological basis of gender differences in the dynamics of asymmetry in retrieval of dychotically presented verbal information was studied by mapping of EEG power and coherence during a prolonged dychotical test. Right-handed students (20 men and 11 women) participated in the experiments. It was shown that gender differences in the EEG were absent at the initial stage of testing and appeared at the final stage. At this stage, the asymmetry of the theta 2 EEG power was lower in men than in women, while the interhemispheric coherence in the theta 2- and alpha 1-bands was more pronounced in women than in men, mainly, in the caudal cortical regions. Thus, different cortical electrophysiological processes underlie similar behavioral effects (the same values of asymmetry coefficients of retrieval of syllables at the final stage of dichotic testing) in men and women.     

A Performance Analysis of Public Expenditure on Maternal Health in Mexico

We explore the relationship between public expenditure, coverage of adequate ANC (including timing, frequent and content), and the maternal mortality ratio -adjusted by coverage of adequate ANC- observed in Mexico in 2012 at the State level. Additionally, we examine the inequalities and concentration of public expenditure between populations with and without Social Security. Results suggest that in the 2003–2011 period, the public expenditure gap between women with and without Social Security decreased 74%, however, the distribution is less equitable among women without Social Security, across the States. Despite high levels of coverage on each dimension of ANC explored, coverage of adequate ANC was lower among Social Security than non-Social Security women. This variability results in differences up to 1.5 times in State-adjusted maternal mortality rate at the same level of expense and maternal mortality rate, respectively. The increase in the economic resources is only a necessary condition for achieving improved health outcomes. Providing adequate health services and achieving efficient, effective and transparent use of resources in health, are critical elements for health systems performance. The attainment of universal effective coverage of maternal health and reducing maternal mortality in Mexico, requires the adjustment of policy innovations including the rules of allocation and execution of health resources. Health policies should be designed on a more holistic view promoting a balance between accessibility, effective implementation and rigorous stewardship.     

Simulating a neural cross-talk model for between-hand interference during bimanual circle drawing

Studies on drawing circles with both hands in the horizontal plane have shown that this task is easy to perform across a wide range of movement frequencies under the symmetrical mode of coordination, whereas under the asymmetrical mode (both limbs moving clockwise or counterclockwise) increases in movement frequency have a disruptive effect on trajectory control and hand coordination. To account for these interference effects, we propose a simplified computer model for bimanual circle drawing based on the assumptions that (1) circular trajectories are generated from two orthogonal oscillations coupled with a phase delay, (2) the trajectories are organized on two levels, “intention” and “motor execution”, and (3) the motor systems controlling each hand are prone to neural cross-talk. The neural cross-talk consists in dispatching some fraction of any force command sent to one limb as a mirror image to the other limb. Assuming predominating coupling influences from the dominant to the nondominant limb, the simulations successfully reproduced the main characteristics of performance during asymmetrical bimanual circle drawing with increasing movement frequencies, including disruption of the circular form drawn with the nondominant hand, increasing dephasing of the hand movements, increasing variability of the phase difference, and occasional reversals of the movement direction in the nondominant limb. The implications of these results for current theories of bimanual coordination are discussed. Received: 23 June 1998 / Accepted in revised form: 20 April 1999     

Facial attractiveness,developmental stability,and fluctuating asymmetry

Despite robust cross-cultural reliability of human facial attractiveness ratings, research on facial attractiveness has only superficially addressed the connection between facial attractiveness and the history of sexual selection in Homo sapiens. There are reasons to believe that developmental stability and phenotypic quality are related. Recent studies of nonhuman animals indicate that developmental stability, measured as fluctuating asymmetry in generally bilateral symmetrical traits, is predictive of performance in sexual selection: Relatively symmetrical males are advantaged under sexual selection. This pattern is suggested by our study of facial attractiveness and fluctuating asymmetry in seven bilateral body traits in a student population. Overall, facial attractiveness negatively correlated with fluctuating asymmetry; the relation for men, but not for women, was statistically reliable. Possible confounding factors were controlled for in the analysis.     

The discontinuous nature of motor execution

Human movement control requires adequate coordination of different movements, which is particularly important when different motor tasks are simultaneously executed by the same effector(s) (e.g. a muscle or a joint). The process of movement execution involves a series of highly nonlinear elements; for instance, a motor unit of a muscle produces force only in the direction of muscle shortening, thus representing a threshold operator that transforms the bipolar (i.e. excitatory or inhibitory) information at its spinal input into a purely unipolar signal (i.e. muscle force). This tripartite research report addresses the contribution of the nonlinearity of neuromuscular elements to the coordination of different motor tasks simultaneously executed by the same limb. In this first part of the series, a new hypothesis for such a single-muscle multiple-task coordination is presented which suggests an essentially threshold-linear coordination mechanism. Control signals generated by the central nervous system for each individual movement independently and feedback information from peripheral receptors are linearly superimposed. This compound control/feedback signal is processed by a nonlinear limiter element reflecting the discontinuous properties of the muscle and its reflex circuitry. It is shown that threshold-linear interaction of descending commands and afferent feedback information can lead to complex interdependent patterns of compound motor action. This includes the possibility of gating (i.e. the ability of one movement pattern to constrain or even impede the execution of another pattern) and of delayed response initiation when simultaneously performing more than one voluntary motor task. A theoretical analysis of the threshold-linear coordination mechanism and an extensive experimental validation of the model is provided in part II and part III of the report. Received: 6 October 1998 / Accepted in revised form: 2 June 1999     

Effects of age and gender on finger coordination in MVC and submaximal force-matching tasks.

The objective of the study is to examine the effects of age and gender on finger coordination. Twelve young (24 +/- 8 yr; 6 men and 6 women) and 12 elderly (75 +/- 5 yr; 6 men and 6 women) subjects performed single-finger maximal contraction [maximal voluntary contraction (MVC)], four-finger MVC, and four-finger ramp force production tasks by pressing on individual force transducers. A drop in the force of individual fingers during four-finger MVC tasks compared with single-finger MVC tasks (force deficit) was larger, whereas unintended force production by other fingers during single-finger MVC tasks (enslaving) was smaller, in elderly than in young subjects and in women than in men. Force deficit was smaller and enslaving was larger in subjects with higher peak force. During the ramp task, the difference between the variance of total force and the sum of variances of individual forces showed a logarithmic relation to the level of total force, across all subject groups. These findings suggest that indexes of finger coordination scale with force-generating capabilities across gender and age groups.     

The reorganization of bimanual movements during formation of a lateralized motor food skill in rats

After 48 h food deprivation adult Wistar rats were trained to obtain food from a narrow tube feeder using the forepaw under conditions of free choice of limb. At the initial stage of training animals use both paws: the grasping and extraction with one paw can be alternated with food grasping and extraction with another paw, and both paws can be alternately involved in movements preceding this grasping. Character of reorganization of bimanual movements was analyzed during training rats with different motor preference (right-handed and left-handed animals). It was shown that in the process of acquisition of both right- and left-hand skills, bimanual reactions in the anticipating attempts disappeared later than in the final successful movements. The disappearance of bimanual movements in the anticipating attempts is considered as an index of the maximum skill lateralization and acquisition of a novel lateralized movement coordination. The results suggest that left-handed rats more rapidly learn a novel movement coordination than right-handed animals.     

Does the Complexity of the Task Influence Manual Laterality in De Brazza’s Monkeys (Cercopithecus neglectus)?

We assessed the manual preferences of 12 De Brazza's monkeys ( Cercopithecus neglectus ) in spontaneous feeding situations and in two different coordinated bimanual tasks that were not visually guided. We recorded the hand used by each subject for 22 spontaneous activities, hand and digits use while extracting peanut butter from a hollow tube (tube task) and the hand used to extract candies from hanging plastic balls (ball task). Spontaneous activities revealed individual manual preferences but no population-level biases. For both experimental tasks, all subjects were lateralized in their hand use. We found a left bias at the group level for the tube task, but no group-level asymmetry for the ball task. Experimental tasks induced greater strength of laterality than did spontaneous activities. Although the size of our sample did not allow us to draw any conclusions concerning manual preference at the population level, this study stresses the importance of coordinated bimanual tasks to reveal manual laterality in non-human primates.     

Changes of Hand Switching Costs during Bimanual Sequential Learning

Many tasks in our daily life demand not only the use of different fingers of one hand in a serial fashion, but also to alternate from one hand to the other. Here, we investigated performance in a bimanual serial reaction time task (SRTT) with particular emphasis on learning-related changes in reaction time (RT) for consecutive button presses for homologous index- and middle fingers. The bimanual SRTT consisted of sequential button presses either with the left or right index- and middle-finger to a series of visual letters displayed on a computer screen. Each letter was assigned a specific button press with one of four fingers. Two outcome measures were investigated: (a) global sequence learning as defined by the time needed to complete a 15-letter SRTT sequence and (b) changes in hand switch costs across learning. We found that bimanual SRTT resulted in a global decrease in RT during the time course of learning that persisted for at least two weeks. Furthermore, RT to a button press showed an increase when the previous button press was associated with another hand as opposed to the same hand. This increase in RT was defined as switch costs. Hand switch costs significantly decreased during the time course of learning, and remained stable over a time of approximately two weeks. This study provides evidence for modulations of switch costs during bimanual sequence learning, a finding that might have important implications for theories of bimanual coordination and learning.