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Biomedical subjects

D A Rosenbaum

Publications and source records attributed to D A Rosenbaum.

At least 19 recordsLinked to original sources
PubMed1999

Remembered positions: stored locations or stored postures?

Many recent studies indicate that memory for final position is superior to memory for movement. There is ambiguity about what is meant by the term final position, however. Is it final spatial location or final posture? According to a recently proposed theory by Rosenbaum et al., which maintains that stored postures form the basis for movement planning, when people try to return to recently reached positions, they should try to adopt the postures they just occupied. An alternative view, which holds that movements are primarily planned with respect to spatial locations, predicts that subjects should tend to return to places in external space. We describe an experiment that tested these opposing predictions. The experiment relied on the notion that if people store and use postures, they should "copy" the posture adopted with one arm to the other arm when possible. The results support this hypothesis. In this article, we review previous work that bears on the question of what is learned when people move repeatedly to a given position. Then we present two theoretical perspectives which make diverging predictions about what should be learned in repositioning tasks. One perspective predicts that final positions are remembered as postures; the other predicts that final positions are remembered as locations. We describe an experiment designed to distinguish between these two predictions. The experiment indicates that final postures are remembered and are "copied" from one arm to the other when subjects try to reach repeatedly to the same location in the midsagittal plane with alternating arms or when subjects try to reach repeatedly to the same location anywhere in the workspace with the same arm. In the last section of the article, we discuss the implications of our findings.

Adult↗
PubMed1999

Coordination of reaching and grasping by capitalizing on obstacle avoidance and other constraints.

Reaching and grasping an object can be viewed as the solution of a multiple-constraint satisfaction problem. The constraints include contact with the object with the appropriate effectors in the correct positions as well as generation of a collision-free trajectory. We have developed a computational model that simulates reaching and grasping based on these notions. The model, rendered as an animation program, reproduces many basic features of the kinematics of human reaching and grasping behavior. The core assumptions of the model are: (1) tasks are defined by flexibly organized constraint hierarchies; (2) manual positioning acts, including prehension acts, are first specified with respect to goal postures and then are specified with respect to movements towards those goal postures; (3) goal postures are found by identifying the stored posture that is most promising for the task, as determined by the constraint hierarchy, and then by generating postures that are more and more dissimilar to the most-promising stored posture until a deadline is reached, at which time the best posture that was found during the search is defined as the goal posture; (4) depending on when the best posture was encountered in the search, the deadline for the search in the next trial is either increased or decreased; (5) specification of a movement to the goal posture begins with straight-line interpolation in joint space between the starting posture and goal posture; (6) if an internal simulation of this default movement suggests that it will result in collision with an obstacle, the movement can be reshaped until an acceptable movement is found or until time runs out; (7) movement reshaping occurs by identifying a via posture that serves as a body position to which the actor moves from the starting posture and then back to the starting posture, while simultaneously making the main movement from the starting posture to the goal posture; (8) the via posture is identified using the same posture-generating algorithm as used to identify the goal posture. These processes are used both for arm positioning and, with some elaboration, for prehension. The model solves a number of problems with an earlier model, although it leaves some other problems unresolved.

Avoidance Learning↗
PubMed1998

Is dynamical systems modeling just curve fitting?

The development of mathematical tools for describing dynamical systems has made it possible to characterize forms of behavior that could not be characterized before. This represents progress, but the enterprise runs the risk of being nothing more than curve fitting if investigators fail to identify the physical, biological, or psychological mechanisms which are common to systems that follow the same dynamical regime and which are not common to systems that do not follow the same dynamical regime.

Biomechanical Phenomena↗
PubMed1997

Speed and sequential effects in reaching.

To investigate the impact of future task demands on reaching, participants performed repetitive sagittal-plane reaches at low and high speeds. In a control condition, they reached from a start location to a target and back. In the experimental conditions, they reached from the start to the target, then to a second target (the location of which varied between trials), then back to the first target, and finally back to the start. Contributions of the hip, shoulder, and elbow to reaches made to the first target depended on the second target's location, on movement speed, and on repetition. Participants combined sustained and transient postural adjustments to minimize effort. The results support the knowledge model of movement selection (D. A. Rosenbaum, L. D. Loukopoulos, R. G. M. Meulenbroek, J. Vaughan, & S. E. Engelbrecht, 1995) but also call for its elaboration. Variants of the model are explored through simulations of the above study.

Adult↗
PubMed1996

Adaptation of a reaching model to handwriting: how different effectors can produce the same written output, and other results.

This report shows how a model initially developed for the control of reaching can be adapted for the control of handwriting. The main problem addressed by the model is how people can produce essentially the same written output with different effectors (e.g., the preferred or nonpreferred hand, the foot, or even the mouth). The model is based on the assumption that writers strive for invariant graphic outputs when they write with different effectors, when they write on surfaces with different orientations, or when they write large or small script; such output invariance is an essential requirement for later recognition of the written result. Given this assumption, the question is how the motor system enables the relevant effectors to generate the necessary pen strokes. The adapted model provides one possible answer to this question. It is first fully working model of multijoint activity underlying writing and related graphic tasks. We describe how the model differs from other models developed in the past, and we review the model's strengths and weaknesses.

Female↗
PubMed1996

Cooperative selection of movements: the optimal selection model.

How one selects a movement when faced with alternative ways of doing a task is a central problem in human motor control. Moving the fingertip a short distance can be achieved with any of an infinite number of combinations of knuckle, wrist, elbow, shoulder, and hip movements. The question therefore arises: how is a unique combination chosen? In our model, choice is achieved by consideration of the similarity between the task requirements and the optimal biomechanical performance of each limb segment. Two variants of the model account for the movements that are selected when subjects freely oscillate the fingertip and when they tap against an obstacle. An important feature of both is that the impulse of collision with an obstacle (as in drumming with the hand or tapping with the finger) is assumed to be controlled in part by aiming for a point beyond the surface being struck. Thus, a force-related control variable may be represented and controlled spatially.

Arm↗
PubMed1996

From cognition to biomechanics and back: the end-state comfort effect and the middle-is-faster effect.

Consistent preferences for particular types of movement suggest criteria for movement selection. These can be important when, as is usually the case, infinitely many movements allow a task to be achieved. The experiments reported here were designed to identify the source of a strong preference observed in earlier object-manipulation studies. In those earlier studies, subjects usually grabbed objects to be moved from one location to another in a way that afforded a comfortable final posture rather than a comfortable initial posture (the end-state comfort effect). The comfortable final state usually allowed the forearm to be at or near the middle of its range of motion on the pronation-supination dimension. The hypothesis tested here was that the end-state comfort effect stemmed from an expectation that movements can be made more quickly in the middle of the pronation-supination range than at either extreme. To test this hypothesis, we asked subjects, in the first experiment, to perform a handle rotation task that demanded little or no precision and so no need to make rapid to-and-fro homing-in movements near the end of the rotation. Half the subjects did not show the end-state comfort effect, in contrast to all previous studies, where all subjects showed the effect. An incidental finding of the first experiment was that handle rotations that ended at or near the end of the range of motion took longer than handle rotations that ended at or near the middle of the range of motion. To test the latter result more carefully, we asked subjects, in Experiments 2 and 3, to oscillate the forearm as quickly as possible, either in the supination part of the forearm rotation range, in the middle part of the range, or in the pronation part of the range. As predicted, oscillation frequencies were highest in midrange, and this was true for both hands. The results as a whole have implications for the relation between cognitive psychology and biomechanics, and for human factors.

Adult↗
PubMed1995

Planning reaches by evaluating stored postures.

This article describes a theory of the computations underlying the selection of coordinated motion patterns, especially in reaching tasks. The central idea is that when a spatial target is selected as an object to be reached, stored postures are evaluated for the contributions they can make to the task. Weights are assigned to the stored postures, and a single target posture is found by taking a weighted sum of the stored postures. Movement is achieved by reducing the distance between the starting angle and target angle of each joint. The model explains compensation for reduced joint mobility, tool use, practice effects, performance errors, and aspects of movement kinematics. Extensions of the model can account for anticipation and coarticulation effects, movement through via points, and hierarchical control of series of movements.

Biomechanical Phenomena↗
PubMed1994

Choosing between models of choosing between sequences: comments on Shidoji (1993)

Previous studies have used a sequence choice procedure to explore the cognitive representations of forthcoming response sequences. Subjects choose as quickly as possible between memorized sequences, and differences in the choice reaction time for a given sequence as a function of the other possible sequence are used to model the structures and processes underlying the choice. In 1993 Shidoji reported experiments to distinguish between two models of choice. One model assumes a hierarchical editing process. The other model assumes that choice. One model assumes a hierarchical editing process. The other model assumes that choice time depends only on the total number of responses in the sequences to be distinguished. Shidoji argued that his data supported both models. He also suggested boundary conditions for the applicability of each model. I argue that the hierarchical editor model can account successfully for Shidoji's results.

Attention↗
PubMed1993

A model for reaching control.

In this paper we propose that reaches are made to target postures which are selected by evaluating stored postures. Target postures are chosen by taking a weighted average of the stored postures, where the weights assigned to the stored postures depend on their effectiveness for the task. Movements from starting postures to target postures are achieved by reducing the distance, in joint space, between the two. The form of the movement depends on drive (assumed to decrease as less distance remains) and inertia. The model predicts the Power Law of learning, compensation for immobility of joints, changes in limb contributions depending on movement speed, asymmetric bell-shaped velocity profiles, velocity-amplitude relations, Fitts' Law, and position-dependent variations in hand-path curvature. Planned extensions of the model may broaden its application-for example, to handwriting.

Humans↗
PubMed1993

Production of polyrhythms.

Previous research has shown that there are strong constraints on the concurrent performance of nonharmonically related motor sequences such as polyrhythms. A model of polyrhythm production is proposed that involves a hierarchical timing system. The model assumes a single mechanism (a counter) for the timing and serial ordering of responses. Predictions derived from the model were tested in an experiment in which skilled (musically trained) and unskilled Ss attempted to reproduce polyrhythms of varying complexity. The results agreed with the model's predictions and showed that Ss adopted a hierarchical form of integrated motor organization in which movements of the slow hand were subordinate to movements of the fast hand. This strategy was consistent across S groups, polyrhythms, and hand arrangements.

Attention↗
PubMed1993

Limb-segment selection in drawing behaviour.

How do we select combinations of limb segments to carry out physical tasks? Three possible determinants of limb-segment selection are hypothesized here: (1) optimal amplitudes and frequencies of motion for the effectors; (2) preferred movement axes for the effectors; and (3) a tendency to continue using already-recruited limb-segments. We tested these factors in a graphic production task. Seven subjects produced back-and-forth drawing movements of gradually changing amplitude. The largest amplitude to be covered, trial duration, movement axis, and direction of amplitude change (from small to large or vice versa) were varied between trials. Selspot recordings were used to study the relative contributions of the fingers, hand, and arm to displacements of the pen. The temporal order of limb-segment involvement was also studied. The results confirmed the predicted effects of the three limb-segment selection factors. We conclude that limb-segment coordination is adaptively related to biomechanical features of the motor system and to the computational demands of movement selection itself.

Adult↗
PubMed1992

Time course of movement planning: selection of handgrips for object manipulation.

A goal of research on the cognitive control of movement is to determine how movements are chosen when many movements are possible. We addressed this issue by studying how subjects reached for a bar to be moved as quickly as possible from a home location to a target location. Ss generally grabbed the bar in a way that afforded a comfortable posture at the target location (the end-state comfort effect) and with the thumb toward the end of the bar that would be aligned with the target (the thumb-toward bias). The data suggested that subjects chose handgrips by retrieving instances of previous reaches, not by carrying out computations that treated candidate reaches as new behavioral events.

Acceleration↗
PubMed1990

Fine-needle aspiration biopsy of the pancreas complicated by pancreatic ascites.

A case is reported of a patient with pancreatic carcinoma who developed pancreatic ascites after intraoperative fine-needle aspiration cytology (FNAC) biopsy. This complication of FNAC has not previously been reported to the authors' knowledge. The literature is reviewed, and FNAC is shown to be the safest method of pancreatic biopsy, the present report not withstanding.

Ascites↗
PubMed1990

On choosing between movement sequences: comments on Rose (1988).

One method of investigating human motor programming is to determine how the choice reaction time for a memorized response sequence depends on the composition of that sequence as well as the other sequence that may be required. Using this method, Rose (1988) found that the total number of responses in the two possible response sequences predicts the choice reaction time to initiate either one. On the basis of this result, Rose claimed that the hierarchical editor (HED) model of motor programming, developed by Rosenbaum, Inhoff, and Gordon (1984), may have to be reevaluated. In this commentary I argue that Rose's results are inconsistent with a precursor of the HED model, not with the HED model itself, that the HED model actually provides a better fit to Rose's data than her total-number-of-responses model, that in general, choice reaction time does not increase with the total number of possible responses, and that structural relations between alternative movement sequences are the main determinants of choice reaction time. Taken as a whole, the results suggest that possible responses are not held in completely readied form before being selected for execution. A further implication is that the storage capacity of the motor output buffer (the MOB) is extremely limited.

Functional Laterality↗
PubMed1987

Scheduling and programming of rapid finger sequences: tests and elaborations of the hierarchical editor model.

Is a response sequence executed only after the sequence has been fully programmed, as discrete processing models predict, or does execution begin before programming has been completed, as continuous processing models predict? To address this issue, we tested a discrete processing model of human motor performance, the hierarchical editor model of Rosenbaum, Inhoff, and Gordon (1984). This model was developed to account for data from experiments in which people perform one of two possible finger sequences, depending on the identity of a choice signal. The model assumes a hierarchically organized motor program that is first "edited" to resolve any uncertainties and is then "executed" to produce the desired responses. Three experiments reported here show that, contrary to the model's predictions and some well-known motor programming results (Sternberg, Monsell, Knoll, & Wright, 1978), the reaction time to begin a response sequence actually decreases with the length of the sequence under some choice conditions. We account for these results with a model that allows execution to begin while editing is still in progress. A key assumption in the model is that subjects schedule execution so that means and variances of interresponse times are minimized.

Attention↗