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Brandon Rohrer, Susan Fasoli, Hermano Igo Krebs, Bruce Volpe, Walter R Frontera, Joel Stein, and Neville Hogan

Submovements are hypothesized building blocks of human movement, discrete ballistic movements of which more complex movements are composed. Using a novel algorithm, submovements were extracted from the point-to-point movements of 41 persons recovering from stroke. Analysis of the extracted submovements showed that, over the course of therapy, patients' submovements tended to increase in peak speed and duration. The number of submovements employed to produce a given movement decreased. The time between the peaks of adjacent submovements decreased for inpatients (those less than 1 month post-stroke), but not for outpatients (those greater than 12 months post-stroke) as a group. Submovements became more overlapped for all patients, but more markedly for inpatients. The strength and consistency with which it quantified patients' recovery indicates that analysis of submovement overlap might be a useful tool for measuring learning or other changes in motor behavior in future human movement studies.

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Michael A. Khan, Trevor Hale, Michael I. Carry, and Ian M. Franks

The purpose of this research was to examine the role of distance and location information in the production of rapid aiming movements. Participants performed an aiming task consisting of horizontal left-handed elbow flexion movements that translated to movements of a cursor on an oscilloscope screen. The location of the home position and the target on the oscilloscope screen were fixed but me initial angle of the elbow was varied randomly. Participants were informed mat the required distance was always constant. Initial impulse and error correction phases were analyzed to examine whether separate spatial codes for distance and position were used in the control of these two movement phases. The results indicated mat initial impulse endpoints and the final positions of the limb overshot the target from the leftmost starting positions, while they undershot me target from me rightmost starting positions. Also, varying the initial angle of the elbow had a greater influence on me final position of the limb than initial impulse endpoints.

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Aaron England, Timothy Brusseau, Ryan Burns, Dirk Koester, Maria Newton, Matthew Thiese, and Benjamin Chase

states occurring during the successful execution of a movement task ( Schack & Mechsner, 2006 ). The BACs combine sensory features of submovements through a process termed chunking. Chunking involves linking related BACs to form clusters ( Schack & Mechsner, 2006 ). Clusters are more pronounced in the MR

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Wan-Xiang Yao and Mark G. Fischman

This study investigated, in aiming movements, the conditions needed to produce a single movement and those needed to produce secondary submovements. Using a 2 × 2 (Temporal Constraint × Spatial Constraint) factorial design with repeated measures on both factors, subjects moved a stylus from a starting position to a target position 12 cm away. They participated in two testing sessions on consecutive days. The first session involved two nonrestrictive target (a set of crosshairs) conditions, moving to the target either within a goal of 400 ms (temporal-accuracy procedure) or within a minimum time (time-minimization procedure). In the second session the subjects performed two strict-target (circle) conditions, moving to the target either within a goal of 400 ms or within a minimum time. The results showed that the two strict-target conditions had a greater percentage of trials containing multiple-submovements than the two nonrestrictive target conditions, regardless of temporal requirements. Therefore, whether an aiming movement contains a single movement or multiple submovements may be a function of spatial constraints regardless of temporal constraints. It appears that with respect to the nature of the speed-accuracy tradeoff, spatial constraints are an important factor.

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Elizabeth J. Bradshaw and W.A. Sparrow

The study examined adjustments to gait when positioning the foot within a narrow target area at the end of an approach or “run-up” similar to the take-off board in long jumping. In one task, participants (n = 24) sprinted toward and placed their foot within targets of four different lengths for 8-m and 12-m approach distances while “running through” the target. In a second task, participants (n = 12) sprinted toward and stopped with both feet in the target area. Infra-red timing lights were placed along the approach strip to measure movement times, with a camera positioned to view the whole approach to measure the total number of steps, and a second camera placed to view the final stride, which was analyzed using an in-house digitizing system to calculate the final stride characteristics. In the run-through task, a speed-accuracy trade-off showing a linear relationship (r = 0.976, p < .05) between target length and approach time was found for the 8-m amplitude. An accelerative sub-movement and a later targeting or “homing-in” sub-movement were found in the approach kinematics for both amplitudes. Final stride duration increased, and final stride velocity decreased with a decrease in target length.

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Werner F. Helsen, Janet L. Starkes, and Martinus J. Buekers

This experiment addresses the coordination of point of gaze (PG) and hand movements in a speeded aiming task to predictable targets of three different eccentricities (35, 40, and 45 cm). In each condition subjects moved the eyes, head, trunk, and hand freely. Performance was assessed on 5 blocks of 5 trials. Analyses were conducted for (a) frequencies for initiation order of PG and the hand, (b) correlation between initiation latencies of PG and the hand, and (c) initiation, movement, and response times of PG and the hand. PG always arrived on target in advance of the hand and at approximately 50% of the response time of the hand (proportional time).Varying eccentricity increased initiation time of PG but not of the hand. With learning there was an initial temporal improvement and decreased variability of response within the first 10 trials, and with additional practice response times were further reduced. The importance of proportional time and its relationship to the first submovement in aiming are discussed.

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Hedwig Bogaerts and Stephan P. Swinnen

Whereas previous bimanual coordination research has predominantly focused on the constraining role of timing, the present study addressed the role of spatial (i.e., directional) constraints during the simultaneous production of equilateral triangles with both upper limbs. In addition to coordination modes in which mirror-image and isodirectional movements were performed (compatible patterns), new modes were tested in which the left limb lagged with respect to the right by one triangle side (non-compatible patterns). This resulted in the experimental manipulation of directional compatibility between the limbs. In addition. triangles with either horizontal or vertical orientations were to be drawn in order to assess the role of static images on movement production. Results supported the important role of directional constraints in bimanual coordination. Furthermore, triangles in vertical orientations (with a vertical symmetry axis, i.e., one apex pointing up) were drawn more successfully than those in horizontal orientations (with a horizontal symmetry axis, i.e., one apex pointing left or right), suggesting that the static aspects of a geometric form may affect movement dynamics. Finally, evidence suggested that cognitive processes related to integration of the submovements into a unified plan mediate the performance of new coordination patterns. The implications of the present findings for clinical populations are discussed.

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Howard N. Zelaznik

acceleration portion of the movement should exhibit changes in negative acceleration associated with the execution of submovements. The comparison of the timing characteristics of the Schmidt task and the Fitts task as equal average velocity values as well as equal durations provides an excellent contrast of

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James W. Roberts

corroborating Woodworth’s early findings by measuring the primary and secondary submovement components between different feedback conditions (vision vs. no vision). However, despite the obvious advantages in endpoint accuracy for vision compared with no vision conditions, there was no such difference in the

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Yi-Ching Chen, I-Chen Lin, Yen-Ting Lin, Wei-Min Huang, Chien-Chun Huang, and Ing-Shiou Hwang

on perceived errors ( Merchant, Pérez, Zarco, & Gámez, 2013 ; Vanneste, Pouthas, & Wearden, 2001 ). According to the additive accuracy mechanism ( Miall, Weir, & Stein, 1986 ; Pasalar, Roitman, & Ebner, 2005 ), tracking deviations are remedied by superimposition of scaled submovements onto an a