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Biomedical subjects

J Mates

Publications and source records attributed to J Mates.

At least 19 recordsLinked to original sources
PubMed2000

Sensorimotor synchronization: the impact of temporally displaced auditory feedback.

When subjects are asked to tap in synchrony to a regular sequence of stimulus events (e.g., clicks), performance is not perfect in that, usually, an anticipation of the tap is observed. The present study examines the influence of temporally displaced auditory feedback on the size of this anticipatory error. Whereas earlier studies have shown that this asynchrony exhibits a linear increase in size as a function of an increasing delay in such additional auditory feedback, this study compared the impact of shifting feedback forward in time (i.e., feedback presented before the tap) with that of delayed auditory feedback. Results showed that the impact of feedback displacement on the amount of asynchrony differed for positive and negative displacements. Delayed feedback led to an increase in asynchrony, whereas negative displacements had (almost) no effect. This finding is related to a model assuming that the various feedback components arising from the tap (tactile, kinesthetic, auditory) are integrated to form one central representation, and that the timing of this central representation arises from a linear combination of the components involved.

Acoustic Stimulation↗
PubMed1995

The perceptual centre of a stimulus as the cue for synchronization to a metronome: evidence from asynchronies.

In tasks where subjects are required to tap in synchrony to a sequence of evenly spaced uniform auditory stimuli (a metronome), tap onsets typically tend to anticipate the metronome's stimulus onsets. We investigated this phenomenon, called "negative asynchrony", as a function of (1) the duration of the stimuli (1 or 2, 50, 100, and 300 msec), (2) the rise time of the stimuli (0%, 40%, and 80% of stimulus duration), and (3) the interstimulus onset interval duration (500, 700, and 900 msec). The results from three experiments with 28 different subjects showed a significant reduction of the negative asynchrony with longer stimulus durations, and the reduction was not significantly affected by the tempo of the stimulus sequence. Also, a prolongation of the rise time of the stimuli caused an analogous reduction of the negative asynchrony. Findings were taken to suggest that subjects use the perceptual centre rather than physical onset of stimulus as the cue with which to synchronize their responses to metronome stimuli. It is concluded that perceptual processes play an important role in synchronization.

Adult↗
PubMed1994

A program for measuring timing and accuracy in a complex motor reaction task.

A program was developed to explore a subject's accuracy and response timing in a reaction-time paradigm, which involves a multiple choice along with a complex response. The program can be run on an IBM-PC or compatible computers. The subject's task is: (1) to react to a stimulus (task) pattern by releasing a go-key (release time); the pattern is displayed on a keyboard as a combination of up to five light-emitting diodes associated with five answer keys; (2) then to press correctly the key combination indicated (response completion time). The keys are located at positions corresponding to finger tips. The response is complete at the moment all keys of the required combination are held down simultaneously, the order in response completion is not important. Responses are classified according to possible errors: whenever a key is pressed that does not belong to the required combination or the full key combination is not held until a (preset) waiting time period, the response is classified as incorrect. Various task patterns representing the required response combination of any subset of the five keys can be designed. Both the left and the right hand can be tested separately. In this way, possible distortions in performance caused, for instance, by apraxia can be analyzed. Basic statistical characteristics of the release times and completion times for correct responses are computed from the data and stored. The program is written in MODULA-2, the output files are in the ASCII format, which enables further processing of the data by standard statistical packages.

Apraxias↗
PubMed1994

A model of synchronization of motor acts to a stimulus sequence. I. Timing and error corrections.

A closed-loop timing model is proposed that accounts for several phenomena observed in tasks which require production of a sequence of motor acts in synchrony with a sequence of stimuli. In contrast to the previous models, variables available to the central nervous system of a subject (internal variables) and externally measurable variables are distinguished, and several physiologically justifiable internal variables are included. The model assumes the existence of (a) an internal timekeeper producing a reference interval that is used in a motor-control unit for timing of the next motor command; (b) an intrinsic (subjective) synchrony that relies on some a posteriori (feedback) information about the already executed onset of the motor act. A two-way error-corrective mechanism is hypothesized: (1) period (inverted frequency) corrections--the reference interval (period) is set at the beginning of the task according to the interstimulus-onset interval(s) and later corrected for differences between its duration and the actual duration of s; (2) phase corrections--internal synchronization errors (i.e., time gaps between the central temporal availability of internal representations of stimuli and of some feedback aspect of responses) are corrected for directly in the motor-control unit. Objectively measured systematic asynchrony of responses and stimuli is determined by the internal delays in information transduction. Finally, the model is used for making predictions of a subject's performance in some other experimental settings of the synchronization task.

Acoustic Stimulation↗
PubMed1994

A model of synchronization of motor acts to a stimulus sequence. II. Stability analysis, error estimation and simulations.

In Part I (Mates 1994), a linear model of timing and error-corrections was constructed that aims at an explanation of the mechanisms underlying a subject's performance in an experimental paradigm, in which the task is to synchronize a sequence of motor acts to a sequence of stimuli. The model consists of two error-corrective mechanisms: (1) corrections of period (inverted frequency) of the sequence of responses; (2) corrections of phase shift of that sequence (synchronization error). In this paper, the influence of the physiologically justifiable model variables and of initial conditions on the steady-state response sequence as well as the stability of performance of the model are analyzed. The model is stable for error-correction gains in the range from 0 to 2. Comparison with known empirical data supports the assumption that reasonable values are less than 1. Furthermore, an alternative to the basic linear model is introduced in which the possible character of the process of subjective acquisition of the synchronization error is discussed. On the basis of findings from other experimental paradigms (fusion and order threshold) it can be assumed that the subjective estimate is a nonlinear function of the difference between the temporal central availability of internal representations of the stimulus and response-feedback events. Some other known synchronization data are simulated by the nonlinear modification of the model in this paper. A good fit of the simulation results achieved further justifies the model structure proposed. Finally, the possible effect of the subjective synchronization-error estimation on empirical data is discussed.

Humans↗
PubMed1994

Sensorimotor synchronization: motor responses to pseudoregular auditory patterns.

Musically trained and untrained subjects (N = 30) were asked to synchronize their finger tapping with stimuli in auditory patterns. Each pattern comprised six successive tonal stimuli of the same duration, the first of which was accented by a different frequency. The duration of inter-stimulus onset intervals (ISIs) gradually increased or decreased in constant steps toward the end of the patterns. Four values of such steps were used in different trials: 20, 30, 45, and 60 msec. Various time-control mechanisms are hypothesized as being simultaneously responsible for subjects' incorrect reproduction of the internal temporal ratios of the stimulus patterns. The mechanism of assimilation (of a central tendency) led subjects to enforce a regular (isochronous) structure on the patterns. The influence of other time-control mechanisms (distinction, subjective expression of an accent, sequential transfer) was expressed mainly in differences between intertap onset intervals (ITIs) and the corresponding ISIs at the beginning of the patterns. The duration of the first two ITIs was in the majority of the trials in an inverse ratio to the ratio of the respective ISIs. The distortions resulting from the timing mechanisms concerned were more pronounced in the performance of nonmusicians than in that of musicians.

Acoustic Stimulation↗
PubMed1992

Two-dimensional manual tracking of periodic movements: event and time interval analyses.

Human visuo-motor functions were analysed by means of two-dimensional manual tracking tasks. A computer-based system for visual target generation, its movement control and real-time evaluation of the subjects' performance was developed. Various types of two-dimensional periodic target movements (over circular and square trajectories with different velocities) and various settings of tracking spot-joystick relation (normal and reversed direction) were used. Tracking success was expressed in terms of: (a) incidence of tracking errors; and (b) time spent within target. Results from the experiments performed with healthy non-trained subjects have demonstrated that tracking success is lower for a square target trajectory than for the circular one, and for higher target velocity than for the lower one. Reversed two-dimensional tracking was found to be very difficult. The results based upon the two criteria of tracking success (a,b) were different for the majority of tracking variants adopted. Quantitative and qualitative differences among subjects in tracking success were found. Two-dimensional target movements were substantially more difficult than one-dimensional ones with comparable parameters (analyzed in a previous paper).

Adult↗
PubMed1992

A model of the perception of area.

A psychophysical experiment was performed to measure the ability of human observers to compare the areas of two geometrical figures (squares and rectangles). The results show a systematic overestimation of rectangle area with respect to that of the squares. A formal model of area perception and its consequent estimation is proposed, which is based on the concept of an 'image function'. It assumes that not the original figure but some specific isocline defined on the image function surface determines area perception. The systematic error observed in the experiment is explained by the model. We discuss the role of different definitions of the image function as well as its parameters on the model performance.

Adult↗
PubMed1992

Cooperative tapping: time control under different feedback conditions.

The same isochronous tone sequence was presented simultaneously to two mutually isolated subjects. In half the trials, accentuation in this sequence was accomplished by doubling the duration of the first and then of every fourth tone; in the other half, by doubling the frequency of those tones. The subjects' task was to follow the rhythm of the resulting four-tone patterns by finger tapping to tone onsets. There were four auditory feedback (FB) conditions: (1) no FB; (2) FB from the subject's own motor responses; (3) "alien" FB from the motor responses of the other pair member who, in turn, was listening to FB from his/her own tapping; (4) mutually "crossed" FB, where each pair member listened to FB from the tapping of the other. Tap onsets regularly preceded stimulus onsets. The observed order of the amount of this anticipation (from least to greatest) was: (1) own FB, (2) no FB, (3) alien FB, and (4) crossed FB. No mutual dynamic influence between simultaneously performing subjects was detected. Anticipation was more pronounced for sequences that were accentuated by frequency rather than by duration changes. The type of accent also influenced timing of intertap intervals in the rhythmic patterns. For the frequency accent, regular timing was produced, whereas for the durational accent, shortening of the second and lengthening of the fourth (the last) intertap interval were observed. The presence and source of feedback as well as the character of accentuation are therefore relevant factors in the timing of auditorally controlled rhythmic motor behavior.

Adult↗
PubMed1991

Finger tapping in musicians and nonmusicians.

Timing plays an important role in perceiving and performing music. Finger tapping has been successfully used for analyzing timing processes (Fraisse, 1966, Franĕk et al., 1987, 1988). The aim of this study is to determine differences between musically trained and untrained subjects in their ability to follow repetitive rhythmic tonal patterns by finger tapping. It has been found previously (Povel, 1981; Smith, 1983) that time estimation differs among musicians and nonmusicians under certain conditions. The results presented here show that motor timing revealed by tapping is more accurate in musicians than in nonmusicians.

Fingers↗
PubMed1991

Matching the orientation of dot patterns with real, interpolated, and extrapolated lines.

The perception of the orientation of random-dot patterns was studied using four different matching tasks. Homogeneous, elongated patterns and patterns containing Moiré effects were used. One of the tasks implied linear extrapolation and two others implied linear interpolation of the matching line. The fourth task was identical with those used in previous studies by the authors on this topic. Systematic deviations from the axes of orientation of the patterns were observed for the latter task when compared with the former ones. When a short matching line, implying linear extrapolation, was used performance by subjects tended to be more inaccurate than in the other matching tasks. The linear interpolation tasks, in which the matching line was determined by either two collinear distant short lines or by two distant dots, provided more accurate and stable performance than the other two tasks. The results are discussed from the point of view of global orientation perception derived from an image function of the stimuli.

Adult↗
PubMed1991

Sensorimotor synchronization: motor responses to regular auditory patterns.

Subjects (N = 32) were asked to synchronize a motor response with tones in auditory patterns. These patterns were created from six tones and six intertone intervals of equal duration. The pitch of the first tone differed from the others. It was found that subjects used three types of timing in their motor response: (1) the first intertone interval was prolonged and the second interval was shortened, (2) the second intertone interval was prolonged and the first interval was shortened, and/or (3) the first interval and the second interval were of approximately the same length. The prolongation of the fifth interval was observed during all three types of timing. The results are explained using the concept of suprasegmental control of timing, which explains a prolongation of intervals at critical control point of the patterns. The occurrence of three different strategies of timing is discussed in connection with similar principles in musical performance.

Acoustic Stimulation↗
PubMed1990

Stimulus anticipation in following rhythmic acoustical patterns by tapping.

Subjects followed rhythmic acoustical sequences by finger-tapping. Tapping onset preceded stimulus onset by a value close to 30 ms. It is suggested that this temporal difference might correspond to one cycle of a hypothetical timing mechanism in the brain which has been observed with other experimental paradigms.

Auditory Perception↗
PubMed1990

Models for the perception of orientation in random dot patterns.

The aim of this paper is to summarize and to compare some known mathematical models of orientation perception in random dot patterns and to propose new solutions of this question. The model adequacy is judged from the previously obtained experimental results. Apart from the models based on some simple function of the coordinates of dots forming a pattern, also models derived from the so-called image function of the pattern are analysed. The latter ones were found more flexible to render the different features of experimentally obtained data, mainly in the case of orientation ambiguity for some special patterns. The stochastic variants of the deterministic models are introduced.

Form Perception↗
PubMed1990

A system of personal computer control programs for tapping experiments.

A system of control and measuring programs on IBM-PC or compatible computers was developed to explore the precision and accuracy of a subject's timing mechanisms in sensorimotor behavior. Various rhythmic patterns composed of several accentuated and non-accentuated tones which the subject has to follow or to reproduce by finger tapping can be designed. All parameters of the stimulus tones, i.e., duration, pitch and inter-tone pause, in a pattern are variable. Two parallel, independent responses can be monitored simultaneously as well. In this way, the mutual influence of responses of two subjects or two responses of one subject can be analyzed. The programs are written in MODULA-2, the output data are in the ASCII format and can be processed by any common statistical package.

Data Interpretation, Statistical↗