The Relation of Articulatory and Vocal Auditory–Motor Control in Typical Speakers

Purpose The purpose of this study was to explore the relationship between feedback and feedforward control of articulation and voice by measuring reflexive and adaptive responses to first formant ( F 1 ) and fundamental frequency ( f o ) perturbations. In addition, perception of F 1 and f o perturbation was estimated using passive (listening) and active (speaking) just noticeable difference paradigms to assess the relation of auditory acuity to reflexive and adaptive responses. Method Twenty healthy women produced single words and sustained vowels while the F 1 or f o of their auditory feedback was suddenly and unpredictably perturbed to assess reflexive responses or gradually and predictably perturbed to assess adaptive responses. Results Typical speakers' reflexive responses to sudden perturbation of F 1 were related to their adaptive responses to gradual perturbation of F 1 . Specifically, speakers with larger reflexive responses to sudden perturbation of F 1 had larger adaptive responses to gradual perturbation of F 1 . Furthermore, their reflexive responses to sudden perturbation of F 1 were associated with their passive auditory acuity to F 1 such that speakers with better auditory acuity to F 1 produced larger reflexive responses to sudden perturbations of F 1 . Typical speakers' adaptive responses to gradual perturbation of F 1 were not associated with their auditory acuity to F 1 . Speakers' reflexive and adaptive responses to perturbation of f o were not related, nor were their responses related to either measure of auditory acuity to f o . Conclusion These findings indicate that there may be disparate feedback and feedforward control mechanisms for articulatory and vocal error correction based on auditory feedback.

Intermanual transfer of visuomotor adaptation is related to awareness

Previous studies compared the effects of gradual and sudden adaptation on intermanual transfer to find out whether transfer depends on awareness of the perturbation. Results from different groups were contradictory. Since results of our own study suggest that awareness depends on perturbation size, we hypothesize that awareness-related intermanual transfer will only appear after adaptation to a large, sudden perturbation but not after adaptation to a small sudden perturbation or a gradual perturbation, large or small. To confirm this, four groups (S30, G30, S75, G75) of subjects performed out-and-back reaching movements with their right arm. In a baseline block, they received veridical visual feedback of hand position. In the subsequent adaptation block, feedback was rotated by 30 deg (S30, G30) or 75 deg (S75, G75). This rotation was either introduced suddenly (S30, S75) or gradually in steps of 3 deg (G30, G75). After the adaptation block, subjects did an awareness test comprising exclusion and inclusion conditions. The experiment concluded with an intermanual transfer block, in which movements were performed with the left arm under rotated feedback, and a washout block again under veridical feedback. We used a hierarchical Bayesian model to estimate individual movement directions and group averages. The movement directions in different conditions were then used to calculate group and individual indexes of adaptation, awareness, unawareness, transfer and washout. Both awareness and transfer were larger in S75 than in other groups, while unawareness and washout were smaller in S75 than in other groups. Furthermore, the size of awareness indices correlated to intermanual transfer across subjects, even when transfer was normalized to final adaptation level. Thus, we show for the first time that the amount of intermanual transfer directly relates to the extent of awareness of the learned perturbation.

Evaluation of Total Ankle Arthroplasty Design Considered Motion Characteristics of Ankle Joint for Responding to Sudden Tilting Perturbation

Category: Ankle, Ankle Arthritis Introduction/Purpose: Total Ankle Arthroplasty (TAA) has been introduced as one of treatment methods for the arthritis of the ankle joint. Traditional TAAs have been generally designed considering the anatomical geometry and motion characteristics of the ankle joint for responding to general activities of daily living (ADLs). However, traditional TAA designs do not well consider the anatomical geometry and motion characteristics for responding to a sudden perturbation although the ankle joint contributes partially to human balance to prevent falling induced by a sudden perturbation. The aims of the current study were therefore to identify the anatomical geometry and motion characteristics of the ankle joint during sudden tilting perturbations, to reflect the motion characteristics in the design of TAA, and to evaluate the design. Methods: Following Institutional Review Board approval (IRB No SJU-2015-002), seven healthy participants with no sign of musculoskeletal pathology (gender: 7male, 25.5±1.7 years, height: 173.9±6.4 cm, weight: 71.3±6.5 kg) were tested to identify the motion characteristics of the ankle joint during sudden tilting perturbations. Eight sudden tilting perturbations were then implemented by the tilting perturbation simulator developed by our research group. The motion characteristics were measured by using a three-dimensional motion capture system with eight infrared cameras (T-10 s, VICON Motion System Ltd., UK). The motion characteristics, particular in the range of motion (ROM) and motion trajectory, were reflected in the design of TAA. The evaluation of the design of TAA was conducted using finite element (FE) analysis in accordance with the international testing standard ASTM F2665, F1223 and F1814. Results: Dorsi/plantar flexion, inversion/eversion and abduction/adduction were ranged from 11.2±1.5° to -9.3±3.5°, 7.0±4.0° to - 7.8±4.9°, and 0.7±0.2° to -1.0±0.2°, respectively, for the sudden tilting perturbations. Dorsi/plantar flexion of TAA designed newly were 1.5 times larger than that measured from the experiment above, with no interference. Inversion/eversion and internal/external rotation of TAA designed newly were favorably compared to those measured from the experiment above. The motion trajectories were different a little compared to those measured from the experiment above. Maximum von mises stresses predicted from FE analysis with the international test conditions were not exceed a yielding strength of the material used for TAA designed newly and no dislocations among the TAA components were identified. Conclusion: The results indicated that a realization of the natural ankle joint motion trajectory should be improved although TAA design suggested in the current study might well present ROMs for responding to sudden tilting perturbations and have a proper structural stability corresponded to the standard criterion recommended from the international testing standard. The TAA design will be, therefore, modified more considering advanced anatomical and biomechanical parameters, particular in the characteristics of the ankle joint motion trajectory, in our ongoing study. The current study may be, however, valuable to suggesting new TAA design for responding to a sudden perturbation to prevent falling.