MEG responses during rhythmic finger tapping in humans to phasic stimulation and their interpretation based on neural mechanisms

 The phase-resetting experiment was applied to human periodic finger tapping to understand how its rhythm is controlled by the internal neural clock that is assumed to exist. In the experiment, the right periodic tapping movement was disturbed transiently by a series of left finger taps in response to impulsive auditory cues presented randomly at various phases within the tapping cycle. After each left finger tap, the original periodic tapping was reestablished within several tapping cycles. Influences of the disturbance on the periodic right finger tapping varied depending on the phase of the periodic right finger tapping at which each left finger tap was made. It was confirmed that the periodic tapping was disturbed not by the auditory cues but by the left finger taps. Based on this fact, in this paper each single left tap was considered as the stimulus, and the phase of the periodic tapping of the right index finger when the left tap was executed as the phase of the stimulus. Responses of the neural activities (magnetoencephalography, MEG), the tapping movement, and the corresponding muscle activities (electromyography) were simultaneously measured. Phase-resetting curves (PRCs) representing the degree of phase reset as a function of the phase of the stimulus were obtained both for the left sensorimotor cortex MEG response and for the right index finger tapping response. The shapes of both PRCs were similar, suggesting that the phase reset of the left sensorimotor cortex activities and that of the finger tapping rhythm were the same. Four out of eight subjects showed type-0 reset in Winfree's definition, and the others showed type-1 reset. For general limit-cycle oscillators, type-0 reset is obtained for relatively strong perturbations and type 1 for weak perturbations. It was shown that the transient response of MEG to the single left tap stimuli in type-0 subjects, where the phase was progressively reset, were different from those in type-1 subjects. Based on detailed analysis of the differences, a neural network model for the phase reset of the tapping rhythm is proposed. Received: 10 February 2000 / Accepted in revised form: 15 January 2002     

Perception of the consequences of self-action is temporally tuned and event driven

It has been proposed that in order to increase the salience of sensations with an external cause, sensations that are predictable based on one's own actions are attenuated [1 and 2]. This may explain why self-imposed tickle [3 and 4] or constant forces [5] are perceived as less intense than the same stimuli externally imposed. Here, subjects used their right index finger to tap a force sensor mounted above their left index finger. When a motor generated a tap on the left finger synchronously with the right tap, simulating contact between the fingers, the perception of force in the left finger was attenuated compared to the same tap experienced during rest. Attenuation gradually reduced as the left tap was either delayed or advanced relative to the active right tap. However, no attenuation was seen to left taps triggered by right-finger movements that stopped above or passed wide of the sensor. We conclude that there is a window of sensory attenuation that is broadly temporally tuned and centered on the time at which the fingers would normally make contact. That is, predictive tactile sensory attenuation is linked to specific external events arising from movement rather than to the movement per se.     

Studies on human finger tapping neural networks by phase transition curves

Generally, the phase resetting experiments can be used to investigate the behaviors of the stable biological oscillators (e.g. circadian rhythms, biochemical oscillators, pacemaker neurons, bursting neurons). Winfree found that there are two types of phase transition curves (PTC) in the phase resetting experiments of biochemical oscillations. The one is the curve with an average slope of unity (Type 1) and is obtained for the small magnitude of perturbation. The other curve is that with a zero average slope (Type 0) and is obtained for the large magnitude of perturbation. Previously, we explained these results mathematically by the homotopy theory. In this paper, some properties of the human finger tapping neural network are studied psychologically using PTC on the basis of above theoretical results: assuming that an oscillatory neural network controls the human finger tapping, we performed two kinds of phase resetting experiments on the finger tapping. In the first experiment, we showed that the PTC was available to estimate the degree of functional interaction between the finger tapping neural network and that which controls another task. Three tasks (rapid key-pushing, rapid voicing and pattern discrimination) were chosen as the perturbation of the phase resetting experiment. Analyzing shapes of PTCs, it was found that the interaction with the key-pushing network was the largest, and that with the pattern recognition network was the smallest of the three. In the second experiment, we modified the first task as perturbation of the phase resetting experiments to investigate further the interactions between the left and the right hand motor systems. Consequently the following results were revealed. First, shapes of PTCs are very different according as subject's experiences of finger tapping. Second, the type of PTC for some subjects changes from Type 0 to Type 1 by learning. Third, the PTC tends to become Type 0 for shorter tapping periods. Fourth, neither changes of motor loads (the necessary force to push the key) nor an alternation of the tapping hand and the key-pushing hand affects the shape of PTCs.     

Digitomotography in Parkinson’s Disease: A Cross-Sectional and Longitudinal Study

Motor symptoms in Parkinson’s disease (PD) are usually assessed with semi-quantitative tests such as the Unified PD Rating Scale (UPDRS) which are limited by subjectivity, categorical design, and low sensitivity. Particularly bradykinesia as assessed e.g. with speeded index finger tapping exhibits low validity measures. This exploratory study set out to (i) assess whether force transducer-based objective and quantitative analysis of motor coordination in index finger tapping is able to distinguish between PD patients and controls, and (ii) assess longitudinal changes. Sixteen early-stage and 17 mid-stage PD patients as well as 18 controls were included in the cross-sectional part of the study; thirteen, 16 and 16 individuals of the respective groups agreed in a reassessment 12 months later. Frequency, force, rhythmicity, regularity and laterality of speeded and metronome paced tapping were recorded by digitomotography using a quantitative motor system ("Q-Motor"). Analysis of cross-sectional data revealed most consistent differences between PD patients and controls in variability of tap performance across modalities assessed. Among PD patients, variability of taps and the ability to keep a given rhythm were associated with UPDRS motor and finger tapping scores. After 12 months, laterality parameters were reduced but no other parameters changed significantly. This data suggests that digitomotography provides quantitative and objective measures capable to differentiate PD from non-PD in a small cohort, however, the value of the assessment to track PD progression has to be further evaluated in larger cohorts of patients.     

Two coupled oscillators as a model for the coordinated finger tapping by both hands

Recently, it was found that rhythmic movements (e.g. locomotion, swimmeret beating) are controlled by mutually coupled endogeneous neural oscillators (Kennedy and Davis, 1977; Pearson and Iles, 1973; Stein, 1974; Shik and Orlovsky, 1976; Grillner and Zangger, 1979). Meanwhile, it has been found out that the phase resetting experiment is useful to investigate the interaction of neural oscillators (Perkel et al., 1963; Stein, 1974). In the preceding paper (Yamanishi et al., 1979), we studied the functional interaction between the neural oscillator which is assumed to control finger tapping and the neural networks which control some tasks. The tasks were imposed on the subject as the perturbation of the phase resetting experiment. In this paper, we investigate the control mechanism of the coordinated finger tapping by both hands. First, the subjects were instructed to coordinate the finger tapping by both hands so as to keep the phase difference between two hands constant. The performance was evaluated by a systematic error and a standard deviation of phase differences. Second, we propose two coupled neural oscillators as a model for the coordinated finger tapping. Dynamical behavior of the model system is analyzed by using phase transition curves which were measured on one hand finger tapping in the previous experiment (Yamanishi et al., 1979). Prediction by the model is in good agreement with the results of the experiments. Therefore, it is suggested that the neural mechanism which controls the coordinated finger tapping may be composed of a coupled system of two neural oscillators each of which controls the right and the left finger tapping respectively.     

Temporal and Motor Representation of Rhythm in Fronto-Parietal Cortical Areas: An fMRI Study

When sounds occur with temporally structured patterns, we can feel a rhythm. To memorize a rhythm, perception of its temporal patterns and organization of them into a hierarchically structured sequence are necessary. On the other hand, rhythm perception can often cause unintentional body movements. Thus, we hypothesized that rhythm information can be manifested in two different ways; temporal and motor representations. The motor representation depends on effectors, such as the finger or foot, whereas the temporal representation is effector-independent. We tested our hypothesis with a working memory paradigm to elucidate neuronal correlates of temporal or motor representation of rhythm and to reveal the neural networks associated with these representations. We measured brain activity by fMRI while participants memorized rhythms and reproduced them by tapping with the right finger, left finger, or foot, or by articulation. The right inferior frontal gyrus and the inferior parietal lobule exhibited significant effector-independent activations during encoding and retrieval of rhythm information, whereas the left inferior parietal lobule and supplementary motor area (SMA) showed effector-dependent activations during retrieval. These results suggest that temporal sequences of rhythm are probably represented in the right fronto-parietal network, whereas motor sequences of rhythm can be represented in the SMA-parietal network.     

Finger joint impedance during tapping on a computer keyswitch

We studied the dynamic behavior of finger joints during the contact period of tapping on a computer keyswitch, to characterize and parameterize joint function with a lumped-parameter impedance model. We tested the hypothesis that the metacarpophalangeal (MCP) and interphalangeal (IP) joints act similarly in terms of kinematics, torque, and energy production when tapping. Fifteen human subjects tapped with the index finger of the right hand on a computer keyswitch mounted on a two-axis force sensor, which measured forces in the vertical and sagittal planes. Miniature fiber-optic goniometers mounted across the dorsal side of each joint measured joint kinematics. Joint torques were calculated from endpoint forces and joint kinematics using an inverse dynamic algorithm. For each joint, a linear spring and damper model was fitted to joint torque, position, and velocity during the contact period of each tap (22 per subject on average). The spring-damper model could account for over 90% of the variance in torque when loading and unloading portions of the contact were separated, with model parameters comparable to those previously measured during isometric loading of the finger. The finger joints functioned differently, as illustrated by energy production during the contact period. During the loading phase of contact the MCP joint flexed and produced energy, whereas the proximal and distal IP joints extended and absorbed energy. These results suggest that the MCP joint does work on the interphalangeal joints as well as on the keyswitch.     

Differing Dynamics of Intrapersonal and Interpersonal Coordination: Two-finger and Four-Finger Tapping Experiments

Finger-tapping experiments were conducted to examine whether the dynamics of intrapersonal and interpersonal coordination systems can be described equally by the Haken—Kelso—Bunz model, which describes inter-limb coordination dynamics. This article reports the results of finger-tapping experiments conducted in both systems. Two within-subject factors were investigated: the phase mode and the number of fingers. In the intrapersonal experiment (Experiment 1), the participants were asked to tap, paced by a gradually hastening auditory metronome, looking at their fingers moving, using the index finger in the two finger condition, or the index and middle finger in the four-finger condition. In the interpersonal experiment (Experiment 2), pairs of participants performed the task while each participant used the outside hand, tapping with the index finger in the two finger condition, or the index and middle finger in the four-finger condition. Some results did not agree with the HKB model predictions. First, from Experiment 1, no significant difference was observed in the movement stability between the in-phase and anti-phase modes in the two finger condition. Second, from Experiment 2, no significant difference was found in the movement stability between the in-phase and anti-phase mode in the four-finger condition. From these findings, different coordination dynamics were inferred between intrapersonal and interpersonal coordination systems against prediction from the previous studies. Results were discussed according to differences between intrapersonal and interpersonal coordination systems in the availability of perceptual information and the complexity in the interaction between limbs derived from a nested structure.     

Relationship between cerebral activity and movement frequency of maximal finger tapping

To examine the cerebral activity of the motor cortex during maximum movement, we measured regional cerebral blood flow (rCBF) in twelve normal volunteers, using near infrared spectroscopy (NIRS). Repetitive tapping of the right index finger was performed at 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5 Hz, and during maximum effort (ME). The relative increase rate of rCBF during movement beginning with a resting condition was calculated for each movement condition. The left primary sensorimotor cortex showed significant activation during ME compared to the other frequencies. The rapid increase of rCBF was seen immediately after the initiation of finger tapping at all the tested frequencies but showed no increase following that. However, the rCBF during ME continued to increase until the end of the task.Change of the integrated electromyogram (iEMG) for the frequency and change of rCBF for the frequency at all the tested frequencies showed similar tendencies.     

The contribution of the wrist, elbow and shoulder joints to single-finger tapping

We aimed to determine the role of the wrist, elbow and shoulder joints to single-finger tapping. Six human subjects tapped with their index finger at a rate of 3 taps/s on a keyswitch across five conditions, one freestyle (FS) and four instructed tapping strategies. The four instructed conditions were to tap on a keyswitch using the finger joint only (FO), the wrist joint only (WO), the elbow joint only (EO), and the shoulder joint only (SO). A single-axis force plate measured the fingertip force. An infra-red active-marker three-dimensional motion analysis system measured the movement of the fingertip, hand, forearm, upper arm and trunk. Inverse dynamics estimated joint torques for the metacarpal-phalangeal (MCP), wrist, elbow, and shoulder joints. For FS tapping 27%, 56%, and 18% of the vertical fingertip movement were a result of flexion of the MCP joint and wrist joint and extension of the elbow joint, respectively. During the FS movements the net joint powers between the MCP, wrist and elbow were positively correlated (correlation coefficients between 0.46 and 0.76) suggesting synergistic efforts. For the instructed tapping strategies (FO, WO, EO, and SO), correlations decreased to values below 0.35 suggesting relatively independent control of the different joints. For FS tapping, the kinematic and kinetic data indicate that the wrist and elbow contribute significantly, working in synergy with the finger joints to create the fingertip tapping task.     

Impairment of auditory-motor timing and compensatory reorganization after ventral premotor cortex stimulation

Integrating auditory and motor information often requires precise timing as in speech and music. In humans, the position of the ventral premotor cortex (PMv) in the dorsal auditory stream renders this area a node for auditory-motor integration. Yet, it remains unknown whether the PMv is critical for auditory-motor timing and which activity increases help to preserve task performance following its disruption. 16 healthy volunteers participated in two sessions with fMRI measured at baseline and following rTMS (rTMS) of either the left PMv or a control region. Subjects synchronized left or right finger tapping to sub-second beat rates of auditory rhythms in the experimental task, and produced self-paced tapping during spectrally matched auditory stimuli in the control task. Left PMv rTMS impaired auditory-motor synchronization accuracy in the first sub-block following stimulation (p<0.01, Bonferroni corrected), but spared motor timing and attention to task. Task-related activity increased in the homologue right PMv, but did not predict the behavioral effect of rTMS. In contrast, anterior midline cerebellum revealed most pronounced activity increase in less impaired subjects. The present findings suggest a critical role of the left PMv in feed-forward computations enabling accurate auditory-motor timing, which can be compensated by activity modulations in the cerebellum, but not in the homologue region contralateral to stimulation.     

Single tap identification for fast BCI control

One of the major aims of BCI research is devoted to achieving faster and more efficient control of external devices. The identification of individual tap events in a motor imagery BCI is therefore a desirable goal. EEG is recorded from subjects performing and imagining finger taps with their left and right hands. A Differential Evolution based feature selection wrapper is used in order to identify optimal features in the spatial and frequency domains for tap identification. Channel-frequency band combinations are found which allow differentiation of tap vs. no-tap control conditions for executed and imagined taps. Left vs. right hand taps may also be differentiated with features found in this manner. A sliding time window is then used to accurately identify individual taps in the executed tap and imagined tap conditions. Highly statistically significant classification accuracies are achieved with time windows of 0.5 s and more allowing taps to be identified on a single trial basis.     

Analysis of musculoskeletal loading in an index finger during tapping

Since musculoskeletal disorders of the upper extremities are believed to be associated with repetitive excessive muscle force production in the hands, understanding the time-dependent muscle forces during key tapping is essential for exploring the mechanisms of disease initiation and development. In the current study, we have simulated the time-dependent dynamic loading in the muscle/tendons in an index finger during tapping. The index finger model is developed using a commercial software package AnyBody, and it contains seven muscle/tendons that connect the three phalangeal finger sections. Our simulations indicate that the ratios of the maximal forces in flexor digitorum superficialis (FS) and flexor digitorum profundus (FP) tendons to the maximal force at the fingertip are 0.95 and 2.9, respectively, which agree well with recently published experimental data. The time sequence of the finger muscle activation predicted in the current study is consistent with the EMG data in the literature. The proposed model will be useful for bioengineers and ergonomic designers to improve keyboard design minimizing musculoskeletal loadings in the fingers.     

Comparative analysis of diadochokinetic movements.

Tests of diadochokinesia are an inherent part of a neurological examination. Various quantifying methods have been proposed to increase the objectivity, sensitivity, and reliability of such examinations. The methods used and analyses performed, however, differ substantially between tasks. We used a three-dimensional, ultrasound-based recording device to continuously record joint angles during three diadochokinetic movements, avoiding any external constraints of the movements. Alternate pronation and supination of the forearm, tapping with the whole hand and with the index finger in isolation were analyzed in a sample of 63 healthy control subjects. The most sensitive measure for capturing effects of gender, sex, and active hand was frequency. The right hand was faster than the left in all tasks, tapping performance declined with increasing age, and male subjects were faster than females in forearm diadochokinesia. Other measures that characterize speed of movement such as maximum angular velocities and accelerations did not yield comparable sensitivity in detecting the same statistical effects. However, angular velocity achieved the highest test-retest reliability for forearm diadochokinesia, while frequency was reproduced in the tapping tasks. Additional measures characterizing symmetry of the angular velocity profiles and intraindividual variability were shown to be largely independent of movement speed. Examples in neurological patients showed that the data define a valuable standard against which pathological performance can be precisely evaluated. In addition, the different measures captured dissociable aspects of motor performance that may further help to characterize the deficit and adjust therapy.     

Thumb motor performance varies with thumb and wrist posture during single-handed mobile phone use

Design features of mobile computing technology such as device size and key location may affect thumb motor performance during single-handed use. Since single-handed use requires the thumb posture to vary with key location, we hypothesize that motor performance is associated with thumb and wrist joint postures. A repeated measures laboratory experiment of 10 right-handed participants measured thumb and wrist joint postures during reciprocal tapping tasks between two keys for different key pairs among 12 emulated keys. Fitts' effective index of performance and joint postures at contact with each key were averaged across trials for each key. Thumb motor performance varied for different keys, with poorest performances being associated with excessive thumb flexion such as when tapping on keys closest to the base of the thumb in the bottom right corner of the phone. Motor performance was greatest when the thumb was in a typical resting posture, neither significantly flexed nor fully extended with slight CMC joint abduction and supination, such as when tapping on keys located in the top right and middle left areas on the phone. Grip was also significantly affected by key location, with the most extreme differences being between the top left and bottom right corners of the phone. These results suggest that keypad designs aimed at promoting performance for single-handed use should avoid placing frequently used functions and keys close to the base of the thumb and instead should consider key locations that require a thumb posture away from its limits in flexion/extension, as these postures promote motor performance.     

Mere expectation to move causes attenuation of sensory signals

When a part of the body moves, the sensation evoked by a probe stimulus to that body part is attenuated. Two mechanisms have been proposed to explain this robust and general effect. First, feedforward motor signals may modulate activity evoked by incoming sensory signals. Second, reafferent sensation from body movements may mask the stimulus. Here we delivered probe stimuli to the right index finger just before a cue which instructed subjects to make left or right index finger movements. When left and right cues were equiprobable, we found attenuation for stimuli to the right index finger just before this finger was cued (and subsequently moved). However, there was no attenuation in the right finger just before the left finger was cued. This result suggests that the movement made in response to the cue caused 'postdictive' attenuation of a sensation occurring prior to the cue. In a second experiment, the right cue was more frequent than the left. We now found attenuation in the right index finger even when the left finger was cued and moved. This attenuation linked to a movement that was likely but did not in fact occur, suggests a new expectation-based mechanism, distinct from both feedforward motor signals and postdiction. Our results suggest a new mechanism in motor-sensory interactions in which the motor system tunes the sensory inputs based on expectations about future possible actions that may not, in fact, be implemented.     

Hormone therapy in postmenopausal women affects hemispheric asymmetries in fine motor coordination

Evidence exists that the functional differences between the left and right cerebral hemispheres are affected by age. One prominent hypothesis proposes that frontal activity during cognitive task performance tends to be less lateralized in older than in younger adults, a pattern that has also been reported for motor functioning. Moreover, functional cerebral asymmetries (FCAs) have been shown to be affected by sex hormonal manipulations via hormone therapy (HT) in older women. Here, we investigate whether FCAs in fine motor coordination, as reflected by manual asymmetries (MAs), are susceptible to HT in older women. Therefore, sixty-two postmenopausal women who received hormone therapy either with estrogen (E) alone (n = 15), an E-gestagen combination (n = 21) or without HT (control group, n = 26) were tested. Saliva levels of free estradiol and progesterone (P) were analyzed using chemiluminescence assays. MAs were measured with a finger tapping paradigm consisting of two different tapping conditions. As expected, postmenopausal controls without HT showed reduced MAs in simple (repetitive) finger tapping. In a more demanding sequential condition involving four fingers, however, they revealed enhanced MAs in favour of the dominant hand. This finding suggests an insufficient recruitment of critical motor brain areas (especially when the nondominant hand is used), probably as a result of age-related changes in corticocortical connectivity between motor areas. In contrast, both HT groups revealed reduced MAs in sequential finger tapping but an asymmetrical tapping performance related to estradiol levels in simple finger tapping. A similar pattern has previously been found in younger participants. The results suggest that, HT, and E exposure in particular, exerts positive effects on the motor system thereby counteracting an age-related reorganization.     

Is the Brain's Inertia for Motor Movements Different for Acceleration and Deceleration?

The brain''s ability to synchronize movements with external cues is used daily, yet neuroscience is far from a full understanding of the brain mechanisms that facilitate and set behavioral limits on these sequential performances. This functional magnetic resonance imaging (fMRI) study was designed to help understand the neural basis of behavioral performance differences on a synchronizing movement task during increasing (acceleration) and decreasing (deceleration) metronome rates. In the MRI scanner, subjects were instructed to tap their right index finger on a response box in synchrony to visual cues presented on a display screen. The tapping rate varied either continuously or in discrete steps ranging from 0.5 Hz to 3 Hz. Subjects were able to synchronize better during continuously accelerating rhythms than in continuously or discretely decelerating rhythms. The fMRI data revealed that the precuneus was activated more during continuous deceleration than during acceleration with the hysteresis effect significant at rhythm rates above 1 Hz. From the behavioral data, two performance measures, tapping rate and synchrony index, were derived to further analyze the relative brain activity during acceleration and deceleration of rhythms. Tapping rate was associated with a greater brain activity during deceleration in the cerebellum, superior temporal gyrus and parahippocampal gyrus. Synchrony index was associated with a greater activity during the continuous acceleration phase than during the continuous deceleration or discrete acceleration phases in a distributed network of regions including the prefrontal cortex and precuneus. These results indicate that the brain''s inertia for movement is different for acceleration and deceleration, which may have implications in understanding the origin of our perceptual and behavioral limits.     

Comprehensive evaluation of corticospinal tract metabolites in amyotrophic lateral sclerosis using whole-brain 1H MR spectroscopy

Changes in the distribution of the proton magnetic resonance spectroscopy (MRS) observed metabolites N-acetyl aspartate (NAA), total-choline (Cho), and total-creatine (Cre) in the entire intracranial corticospinal tract (CST) including the primary motor cortex were evaluated in patients with amyotrophic lateral sclerosis (ALS). The study included 38 sporadic definite-ALS subjects and 70 age-matched control subjects. All received whole-brain MR imaging and spectroscopic imaging scans at 3T and clinical neurological assessments including percentage maximum forced vital capacity (FVC) and upper motor neuron (UMN) function. Differences in each individual metabolite and its ratio distributions were evaluated in the entire intracranial CST and in five segments along the length of the CST (at the levels of precentral gyrus (PCG), centrum semiovale (CS), corona radiata (CR), posterior limb of internal capsule (PLIC) and cerebral peduncle (CP)). Major findings included significantly decreased NAA and increased Cho and Cho/NAA in the entire intracranial CST, with the largest differences for Cho/NAA in all the groups. Significant correlations between Cho/NAA in the entire intracranial CST and the right finger tap rate were noted. Of the ten bilateral CST segments, significantly decreased NAA in 4 segments, increased Cho in 5 segments and increased Cho/NAA in all the segments were found. Significant left versus right CST asymmetries were found only in ALS for Cho/NAA in the CS. Among the significant correlations found between Cho/NAA and the clinical assessments included the left-PCG versus FVC and right finger tap rate, left -CR versus FVC and right finger tap rate, and left PLIC versus FVC and right foot tap rate. These results demonstrate that a significant and bilaterally asymmetric alteration of metabolites occurs along the length of the entire intracranial CST in ALS, and the MRS metrics in the segments correlate with measures of disease severity and UMN function.     

Functional magnetic resonance imaging of the primary motor cortex in humans: response to increased functional demands

Functional magnetic resonance imaging (fMRI) studies have been performed on 20 right handed volunteers at 1.5 Tesla using echo planar imaging (EPI) protocol. Index finger tapping invoked localized activation in the primary motor area. Consistent and highly reproducible activation in the primary motor area was observed in six different sessions of a volunteer over a period of one month. Increased tapping rate resulted in increase in the blood oxygenation level dependent (BOLD) signal intensity as well as the volume/area of activation (pixels) in the contra-lateral primary motor area up to tapping rate of 120 taps/min (2 Hz), beyond which it saturates. Activation in supplementary motor area was also observed. The obtained results are correlated to increased functional demands.