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Biomedical subjects

J Mates

Publications and source records attributed to J Mates.

At least 19 recordsLinked to original sources
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↗
PubMed1989

On the visual orientation of random dot Moiré patterns.

We studied the orientation perception of dot patterns with Moiré effect. The Moiré effect was achieved by rotating the original patterns over small angles. When the angle was increased the effect disappeared while the characteristics of orientation estimation remained unchanged. For relatively small angles the subjects performance can be described by a model based on the concept of least squared distance axis. For large angles of rotation this model has began to be insufficient and a more refined model is proposed here.

Adult↗