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Biomedical subjects

J A Kelso

Publications and source records attributed to J A Kelso.

10 recordsLinked to original sources
PubMed1979

On the nature of human interlimb coordination.

Movement time varies as a function of amplitude and requirements for precision, according to Fitts' law, but when subjects perform two-handed movements to targets of widely disparate difficulty they do so simultaneously. The hand moving to an "easy" target moves more slowly to accommodate its "difficult" counterpart, yet both hands reach peak velocity and acceleration synchronously. This result suggests that the brain produces simultaneity of action not by controlling each limb independently, but by organizing functional groupings of muscles that are constrained to act as a single unit.

Adult↗
PubMed1979

On the coordination of two-handed movements.

In a set of three experiments, we show that after an auditory "go" signal, subjects simultaneously initiate and terminate two-handed movements to targets of widely disparate difficulty. This is the case when the movements required are (a) lateral and away from the midline of the body (Experiment 1), (b) toward the midline of the body (Experiment 2), and (c) in the forward direction away from the body midline (Experiment 3). Kinematic data obtained from high-speed cinematography (200 frames/sec) point to a tight coordinative coupling between the two hands. Although the hands move at entirely different speeds to different points in space, times to peak velocity and acceleration are almost perfectly synchronous. We believe that the brain produces simultaneity of action as the optimal solution for the two-handed task by organizing functional groupings of muscles (coordinative structures) that are constrained to act as a single unit.

Adolescent↗
PubMed1979

Movement coding and memory in retarded children.

Three experiments on the coding and retention of movement-generated information were performed on two groups of mildly retarded children varying in MA. The cue to be reproduced in each case was the terminal position of the limb that studies with adults have shown to require central processing activity for maintained performance. In Experiment 1, although the older MA group was superior, both groups showed similar decrements in performance over a 15-second retention interval. In Experiment 2 the procedures were adopted in an attempt to overcome performance deficits. Subjects were allowed to choose (preselect) their own movements voluntarily in addition to performing constrained, experimenter-defined movements. Preselected reproduction was superior to constrained at all three retention intervals (0, 7, and 15 seconds) but was not statistically different among age groups. Also, performance was maintained for both groups over 7 seconds but deteriorated over 15 seconds. These results were replicated in Experiment 3, which also showed that an interpolated motor task designed to block rehearsal processes interfered with reproduction at the 7- and 15-second retention-interval conditions. The findings indicated that mildly retarded children could maintain motor information over brief time periods and also illustrated the important contribution of the planning component in facilitating the coding of motoric information.

Adolescent↗
PubMed1975

Allocation of attention and the locus of adaptation to displaced vision.

Experimental subjects were exposed to prism-induced visual displacement of a target whose location was correctly given by proprioceptive-kinesthetic information. Control subjects were exposed alternately to visual displacement or proprioceptive-kinesthetic location information. During the adaptation period, experimental subjects in the visual attention condition performed a localization task that directed them to attend selectively to the visual modality; experimental subjects in the proprioceptive attention condition attended selectively to the proprioceptive modaltiy; control subjects performed the task on the basis of the available modality. Measures of adaptation and aftereffect were secured separately in each of the two modalities. These confirmed the predictions that the shifts in the experimental conditions would be confirmed to localization tests dependent on the unattended modality and that control subjects would not exhibit adaptation. We proposed that allocation of attention determines situational dominance and that dominance determines the locus of adaptation. The findings were compared to those reported by Canon (1970) and were applied to a reassessment of the "visual capture" phenomenon.

Adaptation, Physiological↗
PubMed1975

Preselection in short-term motor memory.

Recent studies by Jones (1974) have posited that accurate movements in short-term motor memory (STMM) are mediated by the subject's ability to preset effector mechanisms and monitor their efferent output. Three experiments were conducted to examine this hypothesis. Experiment 1 involved comparisons between the reproduction of the end-location and the reproduction of the distance of a preselected movement. The results revealed that preselected location was superior to preselected distance, indicating that the efference attached to movement extent was not primary. Experiment 2 examined whether location cues were primarily encoded independent of the movement presentation mode. The subjects recalled target locations under preselected, constrained, and passive movement conditions. Recall in the preselected condition was superior to that in the constrained and passive conditions, which showed no difference, suggesting that afferent location information per se was not totally responsible for recall accuracy. Experiment 3 examined the processing requirements of preselected, constrained, and passive location information by filling the retention interval with interpolated processing activity. While preselected location was clearly superior, the three conditions were not differentially affected by processing activity. These overall findings were interpreted as contrary to Jones (1974) and pointed to the importance of preselection in short-term motor memory.

Cues↗