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The point of no return in planar hand movements: an indication of the existence of high level motion primitives.

ABSTRACT: Previous psychophysical studies have sought to determine whether the processes of movement engagement and termination are dissociable, whether stopping an action is a generic process, and whether there is a point in time in which the generation of a planned action is inevitable ("point of no return"). It is not clear yet, however, whether the action of stopping is merely a manifestation of low level, dynamic constraints, or whether it is also subject to a high level, kinematic plan. In the present study, stopping performance was studied while nine subjects, who generated free scribbling movements looking for the location of an invisible circular target, were requested unexpectedly to impede movement. Temporal analysis of the data shows that in 87% of the movements subsequent to the 'stop' cue, the tangential motion velocity profile was not a decelerating function of the time but rather exhibited a complex pattern comprised of one or more velocity peaks, implying an unstoppable motion element. Furthermore, geometrical analysis shows that the figural properties of the path generated after the 'stop' cue were part of a repetitive geometrical pattern and that the probability of completing a pattern after the 'stop' cue was correlated with the relative advance in the geometrical plan rather than the amount of time that had elapsed from the pattern initiation. Altogether, these findings suggest that the "point of no return" phenomenon in humans may also reflect a high level kinematic plan and could serve as a new operative definition of motion primitives.

SUBMITTER: Sosnik R

PROVIDER: S-EPMC2289048 | biostudies-other | 2007 Dec

REPOSITORIES: biostudies-other

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Project description:ObjectivesAssessment of competence in technical skills, including point-of-care ultrasound (POCUS), is required before a novice can safely perform the skill independently. Ongoing assessment of competence is also required because technical skills degrade over time, especially when they are infrequently performed or complex. Hand-motion analysis (HMA) is an objective assessment tool that has been used to evaluate competency in many technical skills. The purpose of this study was to demonstrate the feasibility and validity of HMA as an assessment tool for competence in both simple and complex technical skills as well as skill degradation over time.MethodsThis prospective cohort study included 36 paramedics with no POCUS experience and six physicians who were fellowship trained in POCUS. The novices completed a 4-hour didactic and hands-on training program for cardiac and lung POCUS. HMA measurements, objective structured clinical examinations (OSCE), and written examinations were collected for novices immediately before and after training as well as 2 and 4 months after training. Expert HMA metrics were also recorded.ResultsExpert HMA metrics for cardiac and lung POCUS were significantly better than those of novices. After completion of the training program, the novices improved significantly in all HMA metrics, knowledge test scores, and OSCE scores. Novices showed skill degradation in cardiac POCUS based on HMA metrics and OSCE scores while lung POCUS image acquisition skills were preserved. Novices deemed competent by OSCE score performed significantly better in HMA metrics than those not deemed competent.ConclusionWe have demonstrated that HMA is a feasible and valid tool for assessment of competence in technical skills and can also evaluate skill degradation over time. Skill degradation appears more apparent in complex skills, such as cardiac POCUS. HMA may provide a more efficient and reliable assessment of technical skills, including POCUS, when compared to traditional assessment tools.

Project description:BACKGROUND:Subject motion is known to produce spurious covariance among time-series in functional connectivity that has been reported to induce distance-dependent spurious correlations. PURPOSE:To present a feasibility study for applying the extended Kalman filter (EKF) framework for high temporal resolution motion correction of resting state functional MRI (rs-fMRI) series using each simultaneous multi-slice (SMS) echo planar imaging (EPI) shot as its own navigator. STUDY TYPE:Prospective feasibility study. POPULATION/SUBJECTS:Three human volunteers. FIELD STRENGTH/SEQUENCE:3T GE DISCOVERY MR750 scanner using a 32-channel head coil. Simultaneous multi-slice rs-fMRI sequence with repetition time (TR)/echo time (TE) = 800/30 ms, and SMS factor 6. ASSESSMENT:Motion estimates were computed using two techniques: a conventional rigid-body volume-wise registration; and a high-temporal resolution motion estimation rigid-body approach. The reference image was resampled using the estimates obtained from both approaches and the difference between these predicted volumes and the original moving series was summarized using the normalized mean squared error (NMSE). STATISTICAL TESTS:Direct comparison of NMSE values. RESULTS:High-temporal motion estimation was always superior to volume-wise motion estimation for the sample presented. For staged continuous rotations, the NMSE using high-temporal resolution motion estimates ranged between [0.130, 0.150] for the first volunteer (in-plane rotations), between [0.060, 0.068] for the second volunteer (in-plane rotations), and between [0.063, 0.080] for the third volunteer (through-plane rotations). These values went up to [0.384, 0.464]; [0.136, 0.179]; and [0.080, 0.096], respectively, when using volume-wise motion estimates. DATA CONCLUSION:Accurate high-temporal rigid-body motion estimates can be obtained for rs-fMRI taking advantage of simultaneous multi-slice EPI sub-TR shots. LEVEL OF EVIDENCE:2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018.

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The point of no return in planar hand movements: an indication of the existence of high level motion primitives.

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