Phase resetting with temporal template explains complexity matching in finger tapping to fractal rhythms.

The present study examined whether the elderly produced a hastened or delayed tap with a negative or positive constant intertap interval error more frequently in self-paced tapping than in the stimulus-synchronized tapping for the 2 N target force at 2 or 4 Hz frequency. The analysis showed that, at both frequencies, the percentage of the delayed tap was larger in the self-paced tapping than in the stimulus-synchronized tapping, whereas the hastened tap showed the opposite result. At the 4 Hz frequency, all age groups had more variable intertap intervals during the self-paced tapping than during the stimulus-synchronized tapping, and the variability of the intertap intervals increased with age. Thus, although the increase in the frequency of delayed taps and variable intertap intervals in the self-paced tapping perhaps resulted from a dysfunction of movement timing in the basal ganglia with age, the decline in timing accuracy was somewhat improved by an auditory cue. The force variability of tapping at 4 Hz further increased with age, indicating an effect of aging on the control of force.

Motor variability (MV) is an essential feature of the sensory motor system, and it plays an important role in sensory-motor learning. MV facilitates motor adaptation during auditory-motor synchronization (AMS). In AMS, individuals receive a series of similar auditory stimuli that come in a periodic manner at a fixed interval called an inter-stimulus interval (ISI). Peri-second ISI (1 second range) and supra-second ISI (>1 second) are differently processed, since these intervals involve different amount of cognitive resources. Supra-second ISI involves more top-down attention as compared to peri-second ISI. In this study we examined the effect of tone frequency (perceptual property of auditory stimuli) on predictive tapping and MV under peri-second and supra-second ranges. We examined the effect of tone frequency (a perceptual property of auditory stimuli) on predictive tapping and motor variability (MV) under short (peri-second) and long (supra-second) inter-stimulus intervals. Among 30 healthy participants (aged 18-35 years, M = 24.6 years), we randomly assigned equal numbers of these two inter-stimulus conditions to isochronous sound sequences. In their attempt to synchronize their motor responses with the tone, participants reproduced the ISI in their inter-tap intervals (ITIs). We analyzed their predictive tapping in terms of negative asynchrony (in which the tap occurs before the tone) and small positive asynchrony (0-100 ms), whereas we analyzed MV using the coefficient of variation (CV) of the ITI. We found that participants showed predictive tapping under short ISI, irrespective of the tone frequency. Moreover, their MV was unaffected by tone frequency. These findings imply that participants expressed MV in a predictive rather than reactive manner under short, but not long, ISI. Under long ISI, tone frequency had a significant effect on MV such that there was higher MV with the low-frequency than with the high-frequency tone. Thus, low-frequency tones are most suitable for auditory-motor learning in the supra-second range.

The relation between self-paced and synchronized tapping in 64 persons with mental retardation whose mental ages ranged from 2 to 11 years and chronological ages from 13 to 23 years was investigated. In a self-paced tapping task no stimulus was presented, and subjects' easy and spontaneous tapping was measured. In a synchronized tapping task their synchronous tapping with an auditory stimulus present at a quick or slow tempo was measured. Under both tempo conditions, the lower the subjects' mental age, the larger the errors in the intertap interval they made. The subjects of low mental age showed significantly larger errors in the intertap interval in the Slow than in the Quick Tempo condition and tended to tap at a rate near the self-paced tapping. These results may suggest that ability to adjust one's self pace is one of the key factors in the development of motor synchronization in persons with mental retardation.

The relation between self-paced and synchronized tapping in 64 persons with mental retardation whose mental ages ranged from 2 to 11 years and chronological ages from 13 to 23 years was investigated. In a self-paced tapping task no stimulus was presented, and subjects' easy and spontaneous tapping was measured. In a synchronized tapping task their synchronous tapping with an auditory stimulus present at a quick or slow tempo was measured. Under both tempo conditions, the lower the subjects' mental age, the larger the errors in the intertap interval they made. The subjects of low mental age showed significantly larger errors in the intertap interval in the Slow than in the Quick Tempo condition and tended to tap at a rate near the self-paced tapping. These results may suggest that ability to adjust one's self pace is one of the key factors in the development of motor synchronization in persons with mental retardation.

Financial and geophysical data, like many other low and high frequency time series, are known to exhibit some memory effects. These memory effects may be long or short, permanent or temporal depending on the event that is being modeled. The purpose of this study is to investigate the memory effects characterized by the financial market closing values and volcanic eruption time series as well as to investigate the relation between the self-similar models used and the Lévy process. This paper uses highly effective scaling methods including Lévy processes, Detrended Fluctuation Analysis (DFA) and Diffusion Entropy Analysis (DEA) to examine long-range persistence behavior in time series by estimating their respective parameters. We use the parameter of the Lévy process (α) characterizing the data and the scaling parameters of DFA (H) and DEA (δ) characterizing the self-similar property to generate a relationship between the three (3) aforementioned scaling methods. Findings from the numerical simulations confirm the existence of long-range persistence (long-memory behavior) in both the financial and geophysical time series. Furthermore, the numerical results from this study indicates an approximate inverse relationship between the parameter of the Lévy process and the scaling parameters of the DFA and DEA (i.e., H , δ ≈ 1 α ), which we prove analytically.

The phase reset hypothesis states that the phase of an ongoing neural oscillation, reflecting periodic fluctuations in neural activity between states of high and low excitability, can be shifted by the occurrence of a sensory stimulus so that the phase value become highly constant across trials (Schroeder et al., 2008). From EEG/MEG studies it has been hypothesized that coupled oscillatory activity in primary sensory cortices regulates multi sensory processing (Senkowski et al. 2008). We follow up on a study in which evidence of phase reset was found using a purely behavioral paradigm by including also EEG measures. In this paradigm, presentation of an auditory accessory stimulus was followed by a visual target with a stimulus-onset asynchrony (SOA) across a range from 0 to 404 ms in steps of 4 ms. This fine-grained stimulus presentation allowed us to do a spectral analysis on the mean SRT as a function of the SOA, which revealed distinct peak spectral components within a frequency range of 6 to 11 Hz with a modus of 7 Hz. The EEG analysis showed that the auditory stimulus caused a phase reset in 7-Hz brain oscillations in a widespread set of channels. Moreover, there was a significant difference in the average phase at which the visual target stimulus appeared between slow and fast SRT trials. This effect was evident in three different analyses, and occurred primarily in frontal and central electrodes.

Fine motor impairments are common in neurodegenerative disorders, yet standardized, quantitative measurements of motor abilities are uncommonly used in neurological practice. Thus, understanding and comparing fine motor abilities across disorders have been limited. The current study compared differences in finger tapping, inter-tap interval, and variability in Alzheimer's disease (AD), Parkinson's disease (PD), mild cognitive impairment (MCI), and healthy older adults (HOA). Finger tapping was measured using a highly sensitive light-diode finger tapper. Total number of finger taps, inter-tap interval, and intra-individual variability (IIV) of finger tapping was measured and compared in AD (n = 131), PD (n = 63), MCI (n = 46), and HOA (n = 62), controlling for age and sex. All patient groups had fine motor impairments relative to HOA. AD and MCI groups produced fewer taps with longer inter-tap interval and higher IIV compared to HOA. The PD group, however, produced more taps with shorter inter-tap interval and higher IIV compared to HOA. Disease-specific changes in fine motor function occur in the most common neurodegenerative diseases. The findings suggest that alterations in finger tapping patterns are common in AD, MCI, and PD. In addition, the present results underscore the importance of motor dysfunction even in neurodegenerative disorders without primary motor symptoms.

P2. Spatial and temporal changes of electrical cortical activity induced by self-initiated finger tapping

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.

At any given moment, we receive multiple signals from our different senses. Prior research has shown that signals in one sensory modality can influence neural activity and behavioural performance associated with another sensory modality. Recent human and nonhuman primate studies suggest that such cross-modal influences in sensory cortices are mediated by the synchronisation of ongoing neural oscillations. In this review, we consider two mechanisms proposed to facilitate cross-modal influences on sensory processing, namely cross-modal phase resetting and neural entrainment. We consider how top-down processes may further influence cross-modal processing in a flexible manner, and we highlight fruitful directions for further research.

Deficits in the processing of sensory reafferences have been suggested as accounting for age-related decline in motor coordination. Whether sensory reafferences are accurately processed can be assessed based on the bimanual advantage in tapping: because of tapping with an additional hand increases kinesthetic reafferences, bimanual tapping is characterized by a reduced inter-tap interval variability than unimanual tapping. A suppression of the bimanual advantage would thus indicate a deficit in sensory reafference. We tested whether elderly indeed show a reduced bimanual advantage by measuring unimanual (UM) and bimanual (BM) self-paced tapping performance in groups of young (n = 29) and old (n = 27) healthy adults. Electroencephalogram was recorded to assess the underlying patterns of oscillatory activity, a neurophysiological mechanism advanced to support the integration of sensory reafferences. Behaviorally, there was a significant interaction between the factors tapping condition and age group at the level of the inter-tap interval variability, driven by a lower variability in BM than UM tapping in the young, but not in the elderly group. This result indicates that in self-paced tapping, the bimanual advantage is absent in elderly. Electrophysiological results revealed an interaction between tapping condition and age group on low beta band (14-20 Hz) activity. Beta activity varied depending on the tapping condition in the elderly but not in the young group. Source estimations localized this effect within left superior parietal and left occipital areas. We interpret our results in terms of engagement of different mechanisms in the elderly depending on the tapping mode: a 'kinesthetic' mechanism for UM and a 'visual imagery' mechanism for BM tapping movement.

Chronic alcohol-dependent patients (ALC) exhibit neurocognitive impairments attributed to alcohol-induced fronto-cerebellar damage. Deficits are typically found in complex task performance, whereas simple tasks may not be significantly compromised, perhaps because of little understood compensatory changes. We compared finger tapping with either hand at externally paced (EP) or maximal self-paced (SP) rates and concomitant brain activation in ten pairs of right-hand dominant, age-, and gender-matched, severe, uncomplicated ALC and normal controls (NC) using functional magnetic resonance imaging (fMRI). Mean tapping rates were not significantly different in ALC and NC for either task, but SP tapping variances were greater in ALC for both hands. SP tapping was more rapid with dominant hand (DH) than non-dominant hand (NDH) for both groups. EP and SP tapping with the non-dominant hand demonstrated significantly more activation in ALC than NC in the pre and postcentral gyri, inferior frontal gyrus, inferior parietal lobule, and the middle temporal gyrus. Areas activated only by ALC (not at all by NC) during NDH tapping included the inferior frontal gyrus, middle temporal gyrus, and postcentral gyrus. There were no significant group activation differences with DH tapping. No brain regions activated more in NC than ALC. SP tapping in contrast to EP activated fronto-cerebellar networks in NC, including postcentral gyrus, anterior cingulate, and the anterior lobe and vermis of the cerebellum, but only parietal precuneus in ALC. These findings with NDH finger tapping support previous reports of neurocognitive inefficiencies in ALC. Inferior frontal activation with EP in ALC, but not in NC, suggests engagement of regions needed for planning, organization, and impulse regulation; greater contralateral parietal lobe activation with SP in ALC may reflect right hemispheric impairments in visuospatial performance. Contrasting brain activation during SP and EP suggests that ALC may not have enlisted a fronto-cerebellar network as did NC but rather employed a higher order planning mode by recruiting parietal lobe functions to attain normal mean finger tapping rates. Elucidation of the compensatory neural mechanisms that allow near normal performance by ALC on simple tasks can inform functional rehabilitation of patients in recovery.

when finger taps are synchronized with an isochronous click, it is known that tap-click asynchrony and its variability increase with the interonset interval (IOI). It remains unclear whether these results are due to the IOI or the intertap interval (ITI) duration. The present study examines how these two factors influence tapping performance by altering the tap-click ratio (i.e., 1:n tapping). It has been shown that holding the ITI constant while decreasing the IOI—so that extra clicks subdivide each tap—results in a reduction of tapping variability, described as a subdivision benefit (Repp, 2003). Two questions remain: Does asynchrony and variability increase with the ITI while holding the IOI constant? Does asynchrony decrease with the IOI while holding ITI constant? Using linear regression, both asynchrony and variability decreased with the IOI, with little additional effect of ITI. In contrast, when using ITI as a predictor, the contribution of IOI was significant, suggesting that IOI is the main determinant of tapping performance. In addition, an ANOVA revealed a disadvantage for 1:3 tapping, supporting a categorical distinction between duple and triple meters since 1:n tapping can engender the subjective feel of different metric structures.

Growing evidence from electrophysiological data in animal and human studies suggests that multisensory interaction is not exclusively a higher-order process, but also takes place in primary sensory cortices. Such early multisensory interaction is thought to be mediated by means of phase resetting. The presentation of a stimulus to one sensory modality resets the phase of ongoing oscillations in another modality such that processing in the latter modality is modulated. In humans, evidence for such a mechanism is still sparse. In the current study, the influence of an auditory stimulus on visual processing was investigated by measuring the electroencephalogram (EEG) and behavioral responses of humans to visual, auditory, and audiovisual stimulation with varying stimulus-onset asynchrony (SOA). We observed three distinct oscillatory EEG responses in our data. An initial gamma-band response around 50 Hz was followed by a beta-band response around 25 Hz, and a theta response around 6 Hz. The latter was enhanced in response to cross-modal stimuli as compared to either unimodal stimuli. Interestingly, the beta response to unimodal auditory stimuli was dominant in electrodes over visual areas. The SOA between auditory and visual stimuli--albeit not consciously perceived--had a modulatory impact on the multisensory evoked beta-band responses; i.e., the amplitude depended on SOA in a sinusoidal fashion, suggesting a phase reset. These findings further support the notion that parameters of brain oscillations such as amplitude and phase are essential predictors of subsequent brain responses and might be one of the mechanisms underlying multisensory integration.

BackgroundSynchronous finger tapping to external sensory stimuli is more stable for audiovisual combined stimuli than sole auditory or visual stimuli. In addition, piano players are superior in synchronous tapping and manipulating the ring and little fingers as compared to inexperienced individuals. However, it is currently unknown whether the ability to synchronize to external sensory stimuli with the ring finger is at the level of the index finger in piano players. The aim of this study was to compare the effect of piano experience on synchronization stability between the index and ring fingers using auditory, visual, and audiovisual combined stimuli.MethodsThirteen piano players and thirteen novices participated in this study. They were instructed to tap with their index or ring finger synchronously to auditory, visual, and audiovisual combined stimuli. The stimuli were presented from an electronic metronome at 1 Hz, and the tapping was performed 30 times in each condition. We analyzed standard deviation of intervals between the stimulus onset and the tap onset as synchronization stability.ResultsSynchronization stability for visual stimuli was lower during ring than index finger tapping in novices; however, this decline was absent in piano players. Also, piano players showed the higher synchronization stability for audiovisual combined stimuli than sole visual and auditory stimuli when tapping with the index finger. On the other hand, in novices, synchronization stability was higher for audiovisual combined stimuli than only visual stimuli.ConclusionsThese findings suggest that improvements of both sensorimotor processing and finger motor control by piano practice would contribute to superior synchronization stability.