Bimanual Tapping Research Articles

Manual Motor Function as a Classifier for Alzheimer’s Disease

AbstractBackgroundIn contrast to numerous reports of gross motor problems in Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD), fine motor function has been relatively understudied. We examined if performance on manual motor tasks can distinguish between cognitively normal (CN) subjects, and individuals with MCI or AD, and which fine motor features are most informative.Method47 CN, 25 MCI, and 16 AD participants completed computerized tests of unimanual (dominant and non‐dominant hand) tapping, synchronous bimanual tapping, and alternate bimanual tapping. Outcome measures included initial reaction time, tapping speed, and variance. We used imbalanced random forest learning for classification modeling. The model was trained on 70% of the data and tested on the remaining 30% using 5‐fold cross‐validation. To investigate the contribution of individual variables to the classification model, we conducted permutation feature importance analysis.ResultThe overall classification accuracy of the training data was 56%, while the overall classification accuracy of the test data was 70%. The group‐specific accuracy, defined as the proportion of subjects predicted to belong to a certain group who are truly a member of that group, was 76% for CN, 33% of amnestic MCI, and 86% for AD. In 50% of the cases amnestic MCI subjects were classified as control subjects, and in 17% of the cases as AD subjects. The group‐specific precision, defined as the proportion of subjects who received a certain group label who truly belonged to that group (i.e., ‘true positives’) was 76% for controls, 100% for amnestic MCI, and 45% for AD. The three most important features that were used for classification of the test hold‐out data were 1) variance in tapping speed during dominant hand finger tapping; 2) the number of dual tapping trials without gaps or onset delays; and 3) initial reaction time for non‐dominant hand finger tapping.ConclusionSupervised machine learning can discriminate CN and AD subjects based on finger tapping performance features, but is less effective for distinguishing MCI subjects from CN and AD subjects. Finger tapping performance could be a cost‐effective tool for augmenting existing AD biomarkers.

Correlation of the Karolinska sleepiness scale with performance variables of the monotonous bimanual psychomotor test

To assess the objectivity of measuring the level of sleepiness in the subjects using a monotonous psychomotor bimanual tapping test developed by us, performed on mobile devices running Android OS. Four hundred and ninety-four hour-long experiments with the performance of a psychomotor test were conducted on 102 students. Using the method of mixed linear models, correlations between the levels of sleepiness according to the Karolinska Sleepiness Scale (KSS) and the Epworth Sleepiness Scale (ESS) and the behavioral indicators of the test were evaluated. Statistically significant correlations between the increase in KSS scores and such indicators as a decrease in the total number of button taps and an increase in the frequency of «microsleep» episodes are shown. Statistically significant correlations of ESS score characteristics with the behavioral indicators of the test were not found. A large statistical material shows a reliable correlation of the parameters of the psychomotor test with the level of sleepiness on the Karolinska scale, which allows using the mobile application developed by us to determine the current level of sleepiness /alertness in the field.

Beta rhythmicity in human motor cortex reflects neural population coupling that modulates subsequent finger coordination stability

Human behavior is not performed completely as desired, but is influenced by the inherent rhythmicity of the brain. Here we show that anti-phase bimanual coordination stability is regulated by the dynamics of pre-movement neural oscillations in bi-hemispheric primary motor cortices (M1) and supplementary motor area (SMA). In experiment 1, pre-movement bi-hemispheric M1 phase synchrony in beta-band (M1-M1 phase synchrony) was online estimated from 129-channel scalp electroencephalograms. Anti-phase bimanual tapping preceded by lower M1-M1 phase synchrony exhibited significantly longer duration than tapping preceded by higher M1-M1 phase synchrony. Further, the inter-individual variability of duration was explained by the interaction of pre-movement activities within the motor network; lower M1-M1 phase synchrony and spectral power at SMA were associated with longer duration. The necessity of cortical interaction for anti-phase maintenance was revealed by sham-controlled repetitive transcranial magnetic stimulation over SMA in another experiment. Our results demonstrate that pre-movement cortical oscillatory coupling within the motor network unknowingly influences bimanual coordination performance in humans after consolidation, suggesting the feasibility of augmenting human motor ability by covertly monitoring preparatory neural dynamics.

A new screening test for idiopathic normal pressure hydrocephalus using bimanual coordination: A preliminary study.

The clinical spectrum of idiopathic normal pressure hydrocephalus (iNPH) comprises the triad of gait disturbance, cognitive impairment, and urinary incontinence. However, motor abnormalities involving the upper extremities in iNPH patients have few quantitative studies. The present study was designed to quantitatively assess bimanual tapping tasks in iNPH patients and to compare with the control groups. The subjects were divided into three groups: iNPH patients, older healthy group, and younger healthy group. The tasks were three synchronization finger-to-thumb tapping tasks with the auditory stimuli specified at 1 Hz by metronome: unilateral, bimanual simultaneous, and bimanual alternate. Two-way ANOVA was used to compare the outcomes of the three errors (absolute error: AE, variable error: VE, and constant error: CE) for tapping cycles. In the iNPH group, the absolute and variable errors increased in bimanual alternate tapping task with statistical significance (AE: p < 0.05 and VE: p < 0.05). There were no significant differences in errors between the older and young healthy groups (AE: p = 0.62, CE: p = 1.00 and VE: p = 0.31). We could quantitatively evaluate the bimanual coordination on iNPH patients using the bimanual alternate tapping task, potentially useful for evaluating patients unable to walk.

Amplitude setting and dopamine response of finger tapping and gait are related in Parkinson\u2019s disease

Movement amplitude setting is affected early in Parkinson’s disease (PD), clinically manifesting as bradykinesia. Our objective was to determine if amplitude setting of upper limb bimanual movements and bipedal gait are similarly modulated in PD. 27 PD and 24 control participants were enrolled. Participants performed a bimanual anti-phase finger tapping task wearing gloves with joint angular sensors, and an instrumented gait assessment. Participants performed normal and fast paced assessments to vary motor load. PD participants were evaluated OFF (PD-OFF) and ON (PD-ON) levodopa. PD-OFF participants had smaller tap amplitude, and greater tap amplitude variability than controls in the more affected hands (all p < 0.05). Tap amplitude and stride length (p = 0.030) were correlated in PD-OFF. Tap amplitude was also correlated with motor UPDRS (p < 0.005) and bradykinesia motor (p < 0.05) and ADL (p < 0.005) UPDRS subscores. The relative amount of improvement in tap amplitude and stride length with levodopa was correlated. In PD, upper limb and gait amplitude setting are similarly scaled with motor demand and dopamine supplementation. This suggests these automated motor functions are subserved by common functional networks.

Impact of interhemispheric inhibition on bimanual movement control in young and old

Interhemispheric interactions demonstrate a crucial role for directing bimanual movement control. In humans, a well-established paired-pulse transcranial magnetic stimulation paradigm enables to assess these interactions by means of interhemispheric inhibition (IHI). Previous studies have examined changes in IHI from the active to the resting primary motor cortex during unilateral muscle contractions; however, behavioral relevance of such changes is still inconclusive. In the present study, we evaluated two bimanual tasks, i.e., mirror activity and bimanual anti-phase tapping, to examine behavioral relevance of IHI for bimanual movement control within this behavioral framework. Two age groups (young and older) were evaluated as bimanual movement control demonstrates evident behavioral decline in older adults. Two types of IHI with differential underlying mechanisms were measured; IHI was tested at rest and during a motor task from the active to the resting primary motor cortex. Results demonstrate an association between behavior and short-latency IHI in the young group: larger short-latency IHI correlated with better bimanual movement control (i.e., less mirror activity and better bimanual anti-phase tapping). These results support the view that short-latency IHI represents a neurophysiological marker for the ability to suppress activity of the contralateral side, likely contributing to efficient bimanual movement control. This association was not observed in the older group, suggesting age-related functional changes of IHI. To determine underlying mechanisms of impaired bimanual movement control due to neurological disorders, it is crucial to have an in-depth understanding of age-related mechanisms to disentangle disorder-related mechanisms of impaired bimanual movement control from age-related ones.

Beat Patterns Determine Inter-Hand Differences in Synchronization Error in a Bimanual Coordination Tapping Task.

A previous study reported the unique finding that people tapping a beat pattern with the right hand produce larger negative synchronization error than when tapping with the left hand or other effectors, in contrast to previous studies that have shown that the hands tap patterns simultaneously without any synchronization errors. We examined whether the inter-hand difference in synchronization error occurred due to handedness or to a specificity of the beat pattern employed in that study. Two experiments manipulated the hand–beat assignments. A comparison between the identical beat to the pacing signal and a beat with a longer interval excluded the handedness hypothesis and demonstrated that beat patterns with relatively shorter intervals were tapped earlier (Experiment 1). These synchronization errors were not local but occurred consistently throughout the beat patterns. Experiment 2 excluded alternative explanations. These results indicate that the apparent inconsistency in previous studies was due to the specificity of the beat patterns, suggesting that a beat pattern with a relatively shorter interval between hands is tapped earlier than beats with longer intervals. Our finding that the bimanual tapping of different beat patterns produced different synchronization errors suggests that the notion of a central timing system may need to be revised.

Cross-frequency coupling explains the preference for simple ratios in rhythmic behaviour and the relative stability across non-synchronous patterns.

Rhythms are important for understanding coordinated behaviours in ecological systems. The repetitive nature of rhythms affords prediction, planning of movements and coordination of processes within and between individuals. A major challenge is to understand complex forms of coordination when they differ from complete synchronization. By expressing phase as ratio of a cycle, we adapted levels of the Farey tree as a metric of complexity mapped to the range between in-phase and anti-phase synchronization. In a bimanual tapping task, this revealed an increase of variability with ratio complexity, a range of hidden and unstable yet measurable modes, and a rank-frequency scaling law across these modes. We use the phase-attractive circle map to propose an interpretation of these findings in terms of hierarchical cross-frequency coupling (CFC). We also consider the tendency for small-integer attractors in the single-hand repeated tapping of three-interval rhythms reported in the literature. The phase-attractive circle map has wider basins of attractions for such ratios. This work motivates the question whether CFC intrinsic to neural dynamics implements low-level priors for timing and coordination and thus becomes involved in phenomena as diverse as attractor states in bimanual coordination and the cross-cultural tendency for musical rhythms to have simple interval ratios. This article is part of the theme issue 'Synchrony and rhythm interaction: from the brain to behavioural ecology'.

Distinct cortical activity patterns in Parkinson\u2019s disease and essential tremor during a bimanual tapping task

BackgroundParkinson’s disease (PD) and essential tremor (ET) are neurodegenerative diseases characterized by movement deficits. Especially in PD, maintaining cyclic movement can be significantly disturbed due to pathological changes in the basal ganglia and the cerebellum. Providing external cues improves timing of these movements in PD and also affects ET. The aim of this study is to determine differences in cortical activation patterns in PD and ET patients during externally and internally cued movements.MethodsEleven PD patients, twelve ET patients, OFF tremor suppressing medication, and nineteen age-matched healthy controls (HC) were included and asked to perform a bimanual tapping task at two predefined cue frequencies. The auditory cue, a metronome sound presented at 2 or 4 Hz, was alternately switched on and off every 30 s. Tapping at two different frequencies were used since it is expected that different brain networks are involved at different frequencies as has been shown in previous studies. Cortical activity was recorded using a 64-channel EEG cap. To establish the cortical activation pattern in each group, the task related power (TRP) was calculated for each subject. For inter-groups analysis, EEG electrodes for divided into 5 different areas.ResultsInter-group analysis revealed significant differences in areas responsible for motor planning, organization and regulation and involved in initiation, maintenance, coordination and planning of complex sequences of movements. Within the area of the primary motor cortex the ET group showed a significantly lower TRP than the HC group. In the area responsible for combining somatosensory, auditory and visual information both patient groups had a higher TRP than the HC group.ConclusionsDifferent neurological networks are involved during cued and non-cued movements in ET, PD and HC. Distinct cortical activation patterns were revealed using task related power calculations. Different activation patterns were revealed during the 2 and 4 Hz tapping task indicating different strategies to execute movements at these rates. The results suggest that a including a cued/non-cued tapping task during clinical decision making could be a valuable tool in an objective diagnostic protocol.

Rhythm-Motor Dual Task Intervention for Fall Prevention in Healthy Older Adults.

This study aimed to investigate the effects of a rhythm-motor dual task intervention on cognitive and gait control for older adults in relation to fall prevention. Ten healthy older adults participated in a rhythm-motor dual task intervention and 10 participated in the control group. The intervention group received 16 30-min intervention sessions for 8 weeks. During the intervention sessions, participants engaged in walking or bimanual tapping as a primary motor task with concurrent rhythm tasks including playing instruments and rhythmic chanting or singing. At pretest and post-test, measures of cognition, balance/mobility, and gait were administered. A significant difference between groups was found for part B of the Trail Making Test (TMT-B) measure that involved executive control of attention. Also, changes in the gait ratio in the dual task condition of walking while playing an instrument were significantly different between groups. The findings in this study support the use of the rhythm-motor dual task intervention for increasing available cognitive resources and improving gait control, which are critical factors in fall prevention.

Interpersonal and intrapersonal entrainment of self-paced tapping rate.

Entrainment is a ubiquitous property not only of interacting non-linear dynamical systems but also of human movements. In the study reported here, two premises of entrainment theory were investigated in a tapping task conducted in both interpersonal (i.e. between individuals) and intrapersonal (i.e. between effectors) conditions. Hypothesis 1 was that interacting oscillatory systems should demonstrate synchronisation, which was predicted to emerge as in-phase tapping behaviour in both inter- and intrapersonal conditions. Support for Hypothesis 1 was observed in the in-phase synchronisation of tapping in both individual bimanual trials and uni-manual and bimanual tapping in dyads. By contrast, Hypothesis 2 was that the oscillatory system with the faster initial rate would decelerate, whereas the one with the slower initial rate would accelerate, as manifest in increased self-paced tapping rates amongst participants with initially slower rates and decreased rates amongst ones who initially tapped at faster rates. However, that pattern predicted in Hypothesis 2 was not observed; on the contrary, all participants increased their tapping rates in interpersonal conditions, which occurred significantly amongst participants with the lowest preferred tapping rates. Such an outcome indicates a novel aspect of synchronised movement in humans that warrants further investigation.

Deficits in tapping accuracy and variability in tremor patients

BackgroundThe basal ganglia and cerebellum are brain structures involved in movement initiation, execution and termination. They are thought to be involved in the tremor generation and movement deficits in Parkinson’s disease (PD) and essential tremor (ET). Especially in PD, maintaining cyclic movement, such as walking or tapping can be significantly disturbed. Providing external cues improves timing of these movements in PD but its effect on ET has not yet been studied in depth. The aim of this study is to evaluate the usefulness of a bimanual tapping task as a tool during clinical decision making.MethodHand movements and tremor was recorded using accelerometers and EMG (m. extensor carpi ulnaris) from PD and ET patients and healthy controls during a bimanual tapping task as a way to distinguish PD from ET. All subjects performed the tapping task at two different frequencies, 2 Hz and 4 Hz, with and without the presence of auditory cues.ResultsNo significant intra-group differences were found in the patient groups. Acceleration data revealed significantly less accurate tapping and more variable tapping in PD than in ET and healthy controls. ET subjects tapped less accurate and with a greater variability than healthy controls during the 4 Hz tapping task. Most interestingly the tapping accuracy improved in PD patients when kinetic tremor was recorded with EMG during the task.ConclusionProviding ET and PD patients with an external cue results in different tapping performances between patient groups and healthy controls. Furthermore, the findings suggest that kinetic tremor in PD enables patients to perform the task with a greater accuracy. So far this has not been shown in other studies.

Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements

ABSTRACTBimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a “bimanual advantage” phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the “bimanual advantage”. However, the “bimanual advantage” was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the “bimanual advantage” may be dependent upon consistency of hand preference, as well as the direction of hand dominance.

Age-Related Changes in Bimanual Instrument Playing with Rhythmic Cueing.

Deficits in bimanual coordination of older adults have been demonstrated to significantly limit their functioning in daily life. As a bimanual sensorimotor task, instrument playing has great potential for motor and cognitive training in advanced age. While the process of matching a person’s repetitive movements to auditory rhythmic cueing during instrument playing was documented to involve motor and attentional control, investigation into whether the level of cognitive functioning influences the ability to rhythmically coordinate movement to an external beat in older populations is relatively limited. Therefore, the current study aimed to examine how timing accuracy during bimanual instrument playing with rhythmic cueing differed depending on the degree of participants’ cognitive aging. Twenty one young adults, 20 healthy older adults, and 17 older adults with mild dementia participated in this study. Each participant tapped an electronic drum in time to the rhythmic cueing provided using both hands simultaneously and in alternation. During bimanual instrument playing with rhythmic cueing, mean and variability of synchronization errors were measured and compared across the groups and the tempo of cueing during each type of tapping task. Correlations of such timing parameters with cognitive measures were also analyzed. The results showed that the group factor resulted in significant differences in the synchronization errors-related parameters. During bimanual tapping tasks, cognitive decline resulted in differences in synchronization errors between younger adults and older adults with mild dimentia. Also, in terms of variability of synchronization errors, younger adults showed significant differences in maintaining timing performance from older adults with and without mild dementia, which may be attributed to decreased processing time for bimanual coordination due to aging. Significant correlations were observed between variability of synchronization errors and performance of cognitive tasks involving executive control and cognitive flexibility when asked for bimanual coordination in response to external timing cues at adjusted tempi. Also, significant correlations with cognitive measures were more prevalent in variability of synchronization errors during alternative tapping compared to simultaneous tapping. The current study supports that bimanual tapping may be predictive of cognitive processing of older adults. Also, tempo and type of movement required for instrument playing both involve cognitive and motor loads at different levels, and such variables could be important factors for determining the complexity of the task and the involved task requirements for interventions using instrument playing.

Alteration of rhythmic unimanual tapping and anti-phase bimanual coordination in Alzheimer’s disease: A sign of inter-hemispheric disconnection?

Little attention is paid to motor control in Alzheimer’s disease (AD) although it is a relevant sign of central nervous system integrity and functioning. In particular, unimanual and bimanual tapping is a relevant paradigm because it requires intra- and inter-hemispheric transfer (IHT). Previous results indicate that both unimanual and anti-phase tapping requires more IHT than in-phase tapping, especially produced without external stimulation. The aim of the present study was to test the production of unimanual, bimanual in-phase and anti-phase tapping with a synchronization-continuation paradigm with and without visual stimulation in AD patients (N=9) and control participants (N=12). In accordance with our hypothesis, these results suggest that unimanual and anti-phase tapping is more altered in AD than in control participants. Moreover, performance is globally more variable in the AD group. These alterations are discussed in terms of possible IHT modulation, in line with functional and structural findings in AD, revealing changes in the connectivity of brain regions across hemispheres and white matter damage.

Bimanual tapping of a syncopated rhythm reveals hemispheric preferences for relative movement frequencies

In bimanual multifrequency tapping, right-handers commonly use the right hand to tap the relatively higher rate and the left hand to tap the relatively lower rate. This could be due to hemispheric specializations for the processing of relative frequencies. An extension of the double-filtering-by-frequency theory to motor control proposes a left hemispheric specialization for the control of relatively high and a right hemispheric specialization for the control of relatively low tapping rates. We investigated timing variability and rhythmic accentuation in right handers tapping mono- and multifrequent bimanual rhythms to test the predictions of the double-filtering-by-frequency theory. Yet, hemispheric specializations for the processing of relative tapping rates could be masked by a left hemispheric dominance for the control of known sequences. Tapping was thus either performed in an overlearned quadruple meter (tap of the slow rhythm on the first auditory beat) or in a syncopated quadruple meter (tap of the slow rhythm on the fourth auditory beat). Independent of syncopation, the right hand outperformed the left hand in timing accuracy for fast tapping. A left hand timing benefit for slow tapping rates as predicted by the double-filtering-by-frequency theory was only found in the syncopated tapping group. This suggests a right hemisphere preference for the control of slow tapping rates when rhythms are not overlearned. Error rates indicate that overlearned rhythms represent hierarchically structured meters that are controlled by a single timer that could potentially reside in the left hemisphere.

A Direct-Learning Approach to Acquiring a Bimanual Tapping Skill

ABSTRACTThe theory of direct learning (D. M. Jacobs & C. F. Michaels, 2007) has proven useful in understanding improvement in perception and exploratory action. Here the authors assess its usefulness for understanding the learning of a motor skill, bimanual tapping at a difficult phase relation. Twenty participants attempted to learn to tap with 2 index fingers at 2 Hz with a phase lag of 90° (i.e., with a right-right period of 500 ms and a right-left period of 125 ms). There were 30 trials, each with 50 tapping cycles. Computer-screen feedback informed of errors in both period and phase for each pair of taps. Participants differed dramatically in their success. Learning was assessed by identifying the succession of attractors capturing tapping over the experiment. A few participants’ attractors migrated from antiphase to 90° with an appropriate period; others became attracted to a fixed right-left interval, rather than phase, with or without attraction to period. Changes in attractor loci were explained with mixed success by direct learning, inviting elaboration of the theory. The transition to interval attractors was understood as a change in intention, and was remarkable for its indifference to typical bimanual interactions.

Manual asymmetries in bimanual isochronous tapping tasks in children

Tapping tasks have been investigated throughout the years, with variations in features such as the complexity of the task, the use of one or both hands, the employ of auditory or visual stimuli, and the characteristics of the subjects. The evaluation of lateral asymmetries in tapping tasks in children offers an insight into the structure of rhythmic movements and handedness at early stages of development. The current study aims to investigate the ability of children (aged six and seven years-old) to maintain a rhythm, in a bimanual tapping task at two different target frequencies, as well as the manual asymmetries displayed while doing so. The analyzed data in this work are the series of the time intervals between successive taps. We suggest several profiles of behavior, regarding the overall performance of children in both tempo conditions. We also propose a new method of quantifying the variability of the performance and the asymmetry of the hands, based on ellipses placed on scatter plots of the non-dominant–dominant series versus the dominant–non-dominant series. We then use running correlations to identify changes of coordination tendencies over time. The main results show that variability is larger in the task with the longer target interval. Furthermore, most children evidence lateral asymmetries, but in general they show the capacity to maintain the mean of consecutive intertap intervals of both hands close to the target interval. Finally, we try to interpret our findings in the light of existing models and timing modes.

EP 82. Lateralization of auditory-motor and somatosensory-motor loops during bimanual auditory-paced finger tapping

Introduction During asymmetric bimanual movements the right hand usually performs the faster movement compared to the left hand. This left hemisphere preference for processing of higher relative frequencies has been postulated in the sensory domain. The left hemisphere is thought to excel in analyzing higher relative stimulus frequencies while the right hemisphere is more engaged in processing lower relative frequencies ( Ivry and Robertson, 1998 ). The observed preference of right hand tapping the faster rhythm in 1:n bimanual tapping could potentially mirror this left hemisphere dominance for processing higher relative frequencies in the motor domain. The bimanual coordination of preferred movements has been related with activation of the left more than right supplementary motor area (SMA) ( Jancke et al., 2000 ). The intra- and interhemispheric interactions during asymmetric finger tapping and their relationship to hemispheric specialization for relative frequencies are not understood. We thus investigated the lateralization of neural networks engaged in bimanual coordination and explored the effect of tapping frequencies. Methods In an EEG-fMRI experiment, 32 right-handed subjects performed an auditory-paced finger tapping task during which the tapping frequency (low/high) and the executing hand (unimanual left/right and bimanual) were modulated. Auditory clicks were presented at 2.5 Hz. The ratio of low versus high tapping frequency was 1:4 clicks. Here, we report the fMRI results first. Conditions of interest were randomized, blocked, and contrasted against silent baseline. EPI images were standard pre-processed and analyzed using a general linear model in SPM 12. Results are presented at p . Results Right auditory association cortex activated more strongly in bimanual slow compared to fast tapping. The non-preferred asymmetric bimanual condition (left hand fast / right slow) activated the right SMA and right secondary somatosensory cortex (S2) more strongly than the preferred symmetric condition. This effect was independent of the left hand tapping frequency, as it was observed when tapping frequency was controlled for. Conclusion These findings indicate that the right auditory association cortex specifically engages for slow tapping when 1:4 tapping requires auditory processing of larger time windows in the absence of timing information from the motor system. Our results suggest processing during the non-preferred asymmetric bimanual tapping engages an additional right-hemispheric somatosensorimotor feedback loop (involving S2 and SMA).The left hemisphere does not require this loop to the same extent when performing the identical movement. We speculate that this is a consequence of a left hemispheric dominance in auditory-motor integration (4). We conclude that only the non-dominant right hemisphere uses more somatosensory feedback when it is forced to perform precisely timed finger tapping at higher relative frequencies. This could be taken as indirect evidence for a left hemispheric specialization for auditory-motor integration at higher relative frequencies.

EP 106. Contributions of alpha and beta oscillations to bimanual sequence tapping

Objective In 1:n bi-manual tapping studies participants intuitively choose their right hand for tapping the fast frequency. This preference is expressed in faster and more accurate performance compared to the opposite frequency mapping. This could be either due to a dominant role of the left hemisphere in planning and integration of movements ( Serrien et al., 2003 ) or due to a hemispheric specialization for relative frequencies [double filtering by frequency theory ( Robertson and Ivry, 2000 )]. In this framework, which has been proposed for sensory processing, the left hemisphere is optimized in processing higher relative frequencies while the right hemisphere excels in processing lower relative frequencies of a complex stimulus. We hypothesized comparable lateralization effects relative to movement frequencies. Since the strong tendency of the left hemisphere in controlling bi-manual learned sequences [pre-defined motor programs] would overlay a right hemisphere preference for lower frequencies, we expected to disclose frequency-related lateralization effects only in untrained sequences. Methods In 1:4 tapping paradigms, participants usually tap the first tone with both hands, continue tapping to every auditory tone with the fast hand, count until four and tap again with both hands. In our paradigm, participants were asked to wait for the fourth tone for the slow hand tapping, creating an unintuitive quadruple meter. We recorded magnetoencephalography (MEG) signals in 10 healthy right-handed subjects while performing optimal (left hand slow and right hand fast tapping) and non-optimal (opposite arrangement) bi-manual tapping conditions. As a control, uni-manual fast and slow conditions were performed with each hand alone and with both hands together. We reconstructed the timing signal in the alpha and beta bands of the underlying sources with beamforming. For comparing modulation of intra- and interhemispheric connectivity at different levels of the motor cortex hierarchy in optimal and non-optimal hand arrangements we used dynamic causal modeling. Results We found that the right hand benefit disappeared in all fast tapping conditions. Additionally, a left hand benefit for slow taps was found in the optimal bi-manual condition, which supports frequency-dependent lateralization effects. Comparing power spectra of the different positions in the sequence of four tones revealed two different effects in slow conditions. First and last position coincided with reduced alpha power while successive positions seem to be coded by a decrease in beta power. Changes in alpha power were found in right sensors, changes in beta power were found contralateral to the hand used for slow tapping. Conclusion Behavioral as well as spectral results fit the double filtering by frequency hypothesis. We therefore expected to find stronger intra-hemispheric connections in optimal hand arrangement indicating a local processing of information, whereas in non-optimal hand arrangement inter-hemispheric communication should be enhanced pointing to a higher amount of information exchange between the hemispheres.