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Biomedical subjects

R J Jagacinski

Publications and source records attributed to R J Jagacinski.

15 recordsLinked to original sources
PubMed2000

Dynamic, stochastic, and topological aspects of polyrhythmic performance.

Previous research on polyrhythmic performance can be broadly summarized in terms of 2 classes of models: timekeeper models and nonlinear dynamical models. In the former approach, research has been focused on patterns of covariance among time intervals, and in the latter approach, the concentration has been on pattern (in)stability and the spatiotemporal properties of oscillating limbs. It is suggested that one can achieve a more comprehensive theory that incorporates the strengths of each of these approaches by endowing timekeeper models with nonlinear dynamics or by endowing nonlinear oscillator models with stochastic variability. Additionally, those models are complemented by a topological description of performance based on knot theory. Knot theory provides a new index of difficulty for polyrhythmic tapping, a spatial interpretation of transitions between different stable rhythms, and a possible instantiation of N. A. Bernstein's (1967a) notion of a topological motor program.

Attention↗
PubMed2000

A dynamical systems approach to manual tracking performance.

Manual tracking performance was investigated from the perspective of dynamical systems theory. The authors manipulated the type of visual display, the control system dynamics, and the frequency of the sinusoidal input signal to examine couplings with various phases between the visual signal and control movements. Analyses of the system output amplitude ratio and relative phase showed that participants (N = 24) performed poorly with 90 degrees relative phase coupling. All the couplings became less stable as the movement frequency increased. The authors developed an adaptive oscillator model with linear damping to describe the coupled system consisting of the human performer, the visual display, and the control system dynamics. A geometric account of the stability of performance at different relative phases is also presented.

Acceleration↗
PubMed1997

Quantifying the performance limitations of older and younger adults in a target acquisition task.

In a stationary target acquisition task, both 65-year-old and 20-year-old adults exhibited a negatively accelerated curvilinear relationship between the spatial variability of submovement endpoints and average submovement velocity. For high velocities, the variability was greater for the older adults. This elevated motor noise is considered a primary cause of their slower performance. Both age groups also exhibited a linear relationship between submovement duration and the logarithm of submovement relative accuracy. A stochastic model indicates that the two age groups were similar in the strategies they used to compose single movements from a variety of submovements. However, when performing sequences of movements containing varied target distances, older adults exhibited a repetition effect whereas younger adults exhibited a contrast effect. Older adults may plan movements individually, whereas younger adults plan sequences.

Acoustic Stimulation↗
PubMed1997

Tempo, Rhythm, and Aging in Golf.

Older (n = 12) and younger (n = 12) golfers attempted to hit a golf ball into a target net a short distance away. An accelerometer attached to the back of the clubhead measured the applied force. In contrast to the more typical finding of slower perceptual-motor performance by older adults, older golfers reached their peak downswing force earlier in the shot and also exhibited a trend toward a faster overall speed or tempo of the shot. Additionally, older golfers exhibited greater changes in applied force and greater variability. A pattern of divergence among the force-time histories from multiple shots suggested that the overall person-plus-golf-club dynamics were unstable during a part of the shot. Older adults may be slower in controlling this instability. Half of the participants heard a tone whose pitch was proportional to their force. These participants had a slower follow-through; however, they did not make significantly more or fewer shots than participants who had not been presented with the tone. Analyses of the temporal covariation among the backswing, downswing, and follow-through favored a chain-like temporal structure over a hierarchical, proportional structure. The pattern of covariation suggests that the tempo and rhythm of the shot are not independent and that changing one's tempo may disrupt rhythm.

aging↗
PubMed1995

Tests of attentional flexibility in listening to polyrhythmic patterns.

Four experiments examined attentional flexibility in listening to polyrhythmic patterns. Musically trained and untrained listeners detected changes in timing of 1 tone (the lower tone) in a 3:2 polyrhythm in which high and low tones varied in frequency separation. Experiment 1 encouraged integrative attending; all listeners performed significantly poorer in conditions with wide as opposed to narrow frequency separations. Experiment 2, which encouraged selective attending to low tones, reversed these results: Performance was poorer in the narrow frequency conditions. In neither experiment did skill interact with frequency separation. Experiments 3 and 4 extended these findings to moderate frequency separations. Over all experiments, musically trained listeners exhibited an enhanced ability to detect timing variations, but not flexibility of perceptual organization as it applies to detection of timing changes. Instead, pattern structure (e.g., frequency and time relation) decisively influenced perception for both levels of skill.

Attention↗
PubMed1995

Generalized slowing in sinusoidal tracking by older adults.

Older and younger adults manually tracked sinusoidal input signals. Older adults exhibited 2 forms of slowing. First, they lagged behind the target somewhat more than younger adults. Second, they made considerably smaller movements than the younger adults. Because the velocity of a sinusoidal pattern is proportional to its amplitude, these smaller movements were also slower. Both older and younger adults made smaller movements with a compensatory display and with higher frequency inputs. The high degree of proportionality among these effects was taken as evidence for generalized slowing by the older adults. This slowing may prevent older adults from successfully adjusting an internal pattern generator to match their motions to the sinusoidal input signal.

Acoustic Stimulation↗
PubMed1993

Manual performance of a repeated pattern by older and younger adults with supplementary auditory cues.

Ss performed the same M-shaped manual movement pattern on repeated trials using a visual display of instantaneous error. With practice, Ss' effective time delays were diminished by increased anticipation as evidenced by an increased correlation of their movement patterns with the input velocity. However, younger adults had lower error scores, performed larger movements, and had shorter effective time delays than did older adults. Supplementary auditory displays additionally contributed to greater anticipation. However, men exhibited this effect most with an auditory display of input velocity and women with an auditory display of input position. This benefit of the auditory displays did not carry over after these displays were withdrawn. When the visual display was additionally withdrawn, benefits of the auditory training were manifest among the older adults as relatively greater temporal modulation of movement.

Acoustic Stimulation↗
PubMed1988

Progression-regression effects in tracking repeated patterns.

Subjects used a position control system to perform compensatory tracking of a repeated input pattern. Tracking error was roughly proportional to the velocity of the input signal. Error magnitude decreased with practice and increased with the addition of a concurrent memory task. These effects can be modeled as progressive and regressive changes in how well subjects used control movement velocity and displayed error velocity to anticipate the input pattern and thereby reduce their effective time delay. The weighting of velocity cues in this model progressed with practice and regressed with the secondary task, even though the secondary task required no concurrent visual scanning or simultaneous motor response. This regression effect appears to indicate cognitive interference with the anticipation process. Stationary linear models provide a good approximation to the movement patterns; however, these models do not account for episodes of rapid pulse-like movements that were revealed in the ensemble-averaged trajectories.

Adult↗
PubMed1988

Tests of parallel versus integrated structure in polyrhythmic tapping.

Musically trained subjects tapped three beats with their right hand versus two beats with their left hand in synchrony with two corresponding tones. For independent groups of subjects, the pitch difference of the two tones was either small to encourage an integrated perceptual organization or large to encourage a streamed perceptual organization. Integrated versus parallel motor organization was tested by examining the pattern of covariances among intertap intervals. All subjects exhibited integrated motor organization. An integrated multiplicative hierarchical model of motor organization was superior to a serial chained model and to an independent hierarchical model in describing the pattern of covariances. The subjects who heard tones that encouraged an integrated percept performed with less variability than the subjects who heard tones that encouraged a streamed percept. This superior performance with an integrated motor organization and an integrated rather than a streamed perceptual organization is interpreted as evidence for temporal perceptual-motor compatibility.

Journal Article↗
PubMed1985

On marching to two different drummers: perceptual aspects of the difficulties.

People have remarkable difficulty generating two responses that must follow different temporal sequences, unless the temporal patterns are simply related (e.g., periods in 2:1, 3:1 relation). For example, it is hard to tap to two conflicting rhythms presented concurrently (i.e., a polyrhythm) using the right and left hands (Klapp, 1979), or to tap while articulating a conflicting speech utterance (Klapp, 1981). The present experiments indicate that difficulties in processing conflicting rhythms occur even when people must (a) merely monitor the stimuli and indicate the termination of one rhythmic sequence or (b) tap with a single hand. Responding to polyrhythms is thus difficult even without multiple limb coordination. Furthermore, the difficulty of two-handed tapping to polyrhythms that involve two different tones was found to decrease as the pitch difference between the tones was decreased. This result indicates that the difficulty of rhythmic coordination can be perceptually manipulated in a striking fashion. Polyrhythmic performance thus provides an excellent opportunity for examining possible interactions of perceptual and motor organizations.

Auditory Perception↗
PubMed1985

Fitts' Law in two dimensions with hand and head movements.

Subjects performed two-dimensional discrete movements either with a helmet-mounted sight or with a joystick. Fitts' Law was found to be a good predictor of the speed-accuracy tradeoff for both systems. The joystick produced faster movement times than the helmet-mounted sight. For both systems, horizontal and vertical movements were slightly faster than diagonal movements. Two dimensional generalizations of Fitts' Law were discussed in terms of multidimensional scaling. The obtained pattern of movement times was found to be intermediate to the predictions of Euclidean and City-block models of the movement space. Muscle coordination strategies were considered, and a strictly serial coordination model was rejected. A strictly parallel model was also rejected for the helmet-mounted sight, but not for the joystick.

Journal Article↗
PubMed1983

Quantifying the cognitive trajectories of extrapolated movements.

Subjects' extrapolations of a piecewise constant-velocity trajectory and a constant-acceleration trajectory were mapped out over a sequence of trials that required only a button-press response. Without any performance feedback, subjects' extrapolations of both trajectories approximated an acceleration segment followed by a constant-velocity segment. With performance feedback, subjects' extrapolations of the constant-acceleration trajectory approached optimal performance. Subsequent withdrawal of the feedback shifted the entire extrapolated trajectory. These feedback-related changes in the extrapolated trajectory can be interpreted as changes in two parameters of a cognitive representation of the movement pattern.

Cognition↗
PubMed1978

Fitts' law as a function of system dynamics and target uncertainty.

Fins' law was found to hold for discrete movements executed by subjects controlling the velocity of a cursor with a control stick The slope of movement time versus index of difficulty was approximately twice as large as for a comparable position control system. Target uncertainty also increased the slope of total time versus index of difficulty, and this effect is interpreted in terms of adaptive tuning of the human movement system.

Journal Article↗