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PubMed2006

Are real-time displays of benefit in the singing studio? An exploratory study.

This article reports on an exploratory research project to evaluate the usefulness or otherwise of real-time visual feedback in the singing studio. The primary purpose of the work was not to optimize the technology for this application, but to work alongside teachers and students to study the impact of real-time visual feedback technology use on the students' learning experiences. An action research methodology was used to explore the benefit of real-time displays over an extended period. The experimental phase of the work was guided by a Liaison Panel of teachers and academics in the areas of singing, pedagogy, voice science, speech therapy, and linguistic science. Qualitative data were collected from eight students working with two professional singing teachers. The teachers and students acted as co-researchers under the action research paradigm. Teachers and students alike kept journals of their teaching and learning experiences. Singing lessons were observed regularly by the research team, coded for teacher and student behaviors, and all co-researchers were interviewed at the mid- and endpoint of the project. The use of technology had a positive impact on the learning process, and this is evidenced through case study data.

Equipment Design↗

PubMed1995

Age and gender effects on postural control measures.

OBJECTIVE: Identifying age-related changes in the postural control system is an important first step towards understanding the risk for falls in older adults. The purpose of this study was to determine whether age or gender had any effects on six relatively new postural control measures. DESIGN: Cross-sectional, 2 x 2 factorial design, representing two ages (younger [20 to 35 years], and older [60 to 75 years]) and both sexes. SETTING: University campus. PARTICIPANTS: Twenty-four community dwelling healthy adults (12 women, 12 men) participated in each of the younger and older groups. MAIN OUTCOME MEASURES: Outcome measures included five force platform measures and functional reach (cm). The force platform measures, obtained using the Balance Master system, included movement time and path length to targets, and sway area under conditions of eyes open, eyes closed, and with visual feedback. RESULTS: Although gender was not significant for any outcome measure, age was significant in all six outcome measures. Older adults demonstrated larger areas of sway regardless of condition (eyes open, eyes closed or with visual feedback). Older adults had longer movement times, longer path lengths, and shorter distances of functional reach when compared with younger adults. CONCLUSIONS: The results suggest that the measures studied are sensitive to age-related changes in healthy elderly.

Adult↗

PubMed1996

Visual influence on contact pressure of hemiplegic patients through photoelastic sole image.

OBJECTIVES: To assess the visual influence through photoelastic sole image on upright posture in hemiplegic patients. DESIGN: Before-during trial. SETTING: An academically based rehabilitation setting. PATIENTS: Nineteen hemiplegic patients 3 to 8 months after the stroke were designated as severe (n = 5), moderate I (n = 4), moderate II (n = 5), and mild groups (n = 5). The severe, moderate, and mild groups were in Brunnstrom's motor recovery stage II, IV, and V, respectively. Vibration sense in the paretic leg was intact in the moderate II and mild groups, but impaired in the severe and moderate I groups. INTERVENTION: Visual feedback therapy on standing before before and while watching his or her own photoelastic sole image on a television screen (before vs during). MAIN OUTCOME MEASURE: The body-weight-bearing ratio on the paretic sole was analyzed. RESULTS: The body-weight-bearing ratio on the paretic sole increased during visual feedback (before vs during, percentage, severe, 21.8 +/- 11.4 vs 38.7 +/- 13.7, p < .02; moderate I, 30.4 +/- 11.1 vs 39.3 +/- 6.4, not significant; moderate II, 32.8 +/- 10.3 vs 46.8 +/- 7.8, p < .05; mild, 29.7 +/- 7.0 vs 41.8 +/- 7.5, p < .005; mean +/- SD). CONCLUSION: As the only difference between the moderate I and II groups was impaired or intact vibration sense in the paretic limbs, vibration sense along with motor recovery is an important factor to increase body weight loading on the paretic sole in hemiplegic patients.

Adult↗

PubMed1995

Asymmetric control of bilateral isometric finger forces.

We examined the ability to match the voluntary isometric finger flexion forces of the dominant and nondominant hand in humans, as well as the influence of unilateral visual feedback during this task. Right- and left-handed subjects were trained to produce a "low" force level (50 +/- 25 g) and a "high" force level (200 +/- 50 g) with the right and left index finger, separately. Following the training session, subjects were instructed to match the isometric forces of both fingers simultaneously within the required range (either low or high) so that they were perceived to be identical. The results showed an asymmetry, whereby greater forces were exerted with the index finger of the dominant hand. The asymmetry was independent of the subjects' maximum finger flexion strength. When unilateral visual feedback represented the force output of the dominant hand, the asymmetry was no longer present. In contrast, when it represented the force output of the nondominant hand, the asymmetry was not compensated. We hypothesize that these findings are the result of anatomical or physiological asymmetries inherent in the motor system controlling the production of force.

Adult↗

PubMed1981

Cerebral potentials during skilled slow positioning movements.

Movement-related potentials recorded from the scalp of man were investigated in two skilled positioning tasks, requiring flexions at different joints of the upper extremities. The average response time was approximately 1 sec. Subjects paced their movements themselves and performed without visual control or other external cues. After each trial a delayed visual feedback was given. It was found that the negative potential shift prior to the EMG onset, the 'Bereitschaftpotential', is followed by a persisting negativity during the execution of the action until the target position is reached. Approximately at this point a positive-going deflection appears. This 'goal-directed movement potential' is composed of at least two components: (a) a widely distributed, centrally dominant negativity, and (b) a smaller negative wave over the sensorimotor cortex contralateral to the responding limb. Small variations in response force do not influence the amplitude of the potentials. A negative shift in anticipation of the visual feedback has a topography different from the movement-related potentials, being predominant over the right hemisphere independent of the hand used

Adult↗

PubMed2004

Body-centered visuomotor adaptation.

Previous research has shown that humans generalize distortions of visuomotor feedback in terms of egocentric rotations. We examined whether these rotations are linked to the orientation of the eyes or of the shoulder of the arm that was used. Subjects moved a hand-held cube between target locations in a sequence of adaptation and test phases. During adaptation phases, subjects received either veridical or distorted visual feedback about the location of the cube. The distortions were changes in azimuth either relative to the eyes or to the shoulder. During test phases subjects received no visual feedback. Test phases were performed either with the arm that was exposed to the distorted feedback or with the unexposed arm. We compared test movement endpoints after distorted feedback with ones after veridical feedback. For the exposed arm, the spatial layout of the changes in endpoints clearly reflected the small differences between a rotation around the shoulder and around the eyes. For the unexposed arm, the changes in endpoints were smaller for both types of distortions and were less consistent with the distortions. Thus although the adaptation closely matches the imposed distortion, it does not appear to be directly linked to the orientation of the eyes or of the exposed arm.

Adaptation, Physiological↗

PubMed2005

Bimanual adaptation: internal representations of bimanual rhythmic movements.

From tying your shoes and clipping your tie to the claps at the end of a fine seminar, bimanual coordination plays a major role in our daily activities. An important phenomenon in bimanual coordination is the predisposition toward mirror symmetry in the performance of bimanual rhythmic movements. Although learning and adaptation in bimanual coordination are phenomena that have been observed, they have not been studied in the context of adaptive control and internal representations-approaches that were successfully employed in the arena of reaching movements and adaptation to force perturbations. In this paper we examine the dynamics of the learning mechanisms involved when subjects are trained to perform a bimanual non-harmonic polyrhythm in a bimanual index finger tapping task. Subjects are trained in this task implicitly, using altered visual feedback, while their performance is continuously monitored throughout the experiment. Our experimental results indicate the existence of significant (p<<0.01) learning curves (i.e., error plots with significantly negative slopes) during training and aftereffects with a washout period after the visual feedback ceases to be altered. These results confirm the formation of internal representations in bimanual motor control. We present a simple, physiologically plausible, neural model that combines feedback and adaptation in the control process and which is able to reproduce key phenomena of bimanual coordination and adaptation.

Adaptation, Physiological↗

PubMed2004

Defective cone photoreceptor cytoskeleton, alignment, feedback, and energetics can lead to energy depletion in macular degeneration.

Macular degeneration (MD) is a puzzling disease characterized by disturbance, and then complete loss, of fine detailed vision in the central macular region of the human retina, as a result of disturbed function and then death of photoreceptor cells. This review describes a possible pathomechanism for MD that involves a causal relationship between mutated genes, altered photoreceptor cytoskeletal proteins, defective cone photoreceptor alignment, and disturbed visual feedback mechanisms that leads to energy depletion and apoptosis of macular cone photoreceptors. MD may be associated with mutations in genes encoding certain photoreceptor proteins (ATP-binding cassette transporter retina, retinitis pigmentosa GTPase regulator, retinal degeneration slow/peripherin) that are components of, or interact with, microtubule-containing cytoskeletal systems at the connecting cilium of rods and cones and at the multiple incisures of rod outer segments (OSs). Vertebrate photoreceptors are directionally sensitive: the longitudinal axis of each cell is actively aligned towards the entrance pupil of the eye, and the cells are most sensitive to light travelling along this axis (as in the Stiles-Crawford effect). The mechanisms responsible for photoreceptor alignment involve movements made by photoreceptors in response to the direction of incident light, using their cytoskeletons. A model is proposed for photoreceptor alignment whereby light absorption in the OS causes fast membrane and slower cytoplasmic changes that spread from the OS to the inner segment myoid, where they activate feedback-controlled motor functions by cytoskeletal elements (microtubules and microfilaments) to produce a differential local bending that adjusts photoreceptor orientation. The fovea at the center of the human macula has specialized features that enable it to provide uniquely high visual acuity, if its cones are accurately aligned. Accordingly, it is proposed that some gene defects in MD cause disturbances at photoreceptor connecting cilia that lead to gradual defects in photoreceptor alignment; misalignment of central macular cones will be initially perceived as blurring, distortions, and decreased acuity of central vision. Although photoreceptors throughout the retina use their cytoskeletons for alignment, the accurate alignment of foveal cones is particularly important because their signals contain fine resolution information that is used in visual feedback systems, e.g., for adjusting accommodation and eye movements. Vision involves multiple feedback loops that are interdependent, e.g., the accuracy of alignment of foveal cones influences how effectively changes in accommodation bring images into focus, and the state of accommodation in turn influences how light entering the eye is projected onto foveal cones. It is proposed that in MD gene defects that disturb the cytoskeleton and alignment of photoreceptors lead to a disturbance in the normal signalling within these feedback systems, causing the mechanisms controlling the alignment of cones in the center of the macula to become progressively more disturbed and the cells to unnecessarily expend energy. These disturbances can lead to local energy depletion within the metabolically fragile central macular cones that trigger them to die, producing central areas of blindness. If this line of reasoning is correct, it may be possible to treat the local energy depletion within macular cones in MD by energy supplementation.

Cytoskeleton↗

PubMed1989

Peripheral vision and simple catching: the screen paradigm revisited.

The importance of effector visual feedback has previously been indicated using an opaque screen to prevent sight of the catching hand for the final 150-200 ms of a flight path of 850 ms in total. Attention was drawn to the finding that the ability to position the arm correctly in the line of flight of the ball deteriorated as a consequence of the number of trials without visual feedback. However, the use of only 20 test trials allows a possibility that the proprioceptive system may be able to re-establish predominant control under conditions of prolonged visual decrement. In order to verify this notion, the number of experimental trials was quadrupled for 24 subjects of mixed sex in a replication of the initial paradigm. The results provided preliminary support for the view that the positioning of the catching arm is more seriously affected by visual occlusion than the timing of the grasp phase. However, increments in accuracy of limb orientation were evidenced in all screen conditions, as the number of trials increased. The grasp component of one-handed catching appeared to remain unaffected by the increase in experimental trials. The relative influence of skill level on catching errors was next addressed by comparing the performance of the six best and worst catchers in the group. The results did not support previous research which found a relation between skill level and error type. The number of position, but not grasp, errors decreased as a function of task practice for both subgroups. Future investigations should, perhaps, focus on the developmental nature of movement control in one-handed catching to obtain a clearer picture of this relation.

Adult↗

PubMed2005

Remapping hand movements in a novel geometrical environment.

The issue of how the Euclidean properties of space are represented in the nervous system is a main focus in the study of visual perception, but is equally relevant to motor learning. The goal of our experiments was to investigate how the properties of space guide the remapping of motor coordination. Subjects wore an instrumented data glove that recorded the finger motions. Signals generated by the glove operated a remotely controlled endpoint: a cursor on a computer monitor. The subjects were instructed to execute movements of this endpoint with controlled motions of the fingers. This required inverting a highly redundant map from fingers to cursor motions. We found that 1) after training with visual feedback of the final error (but not of the ongoing cursor motion), subjects learned to map cursor locations into configurations of the fingers; 2) extended practice of movement led to more rectilinear cursor movement, a trend facilitated by training under continuous visual feedback of cursor motions; 3) with practice, subjects reduced motion in the degrees of freedom that did not contribute to the movements of the cursor; 4) with practice, subjects reduced variability of both cursor and hand movements; and 5) the reduction of errors and the increase in linearity generalized beyond the set of movements used for training. These findings suggest that subjects not only learned to produce novel coordinated movement to control the placement of the cursor, but they also developed a representation of the Euclidean space on which hand movements were remapped.

Analysis of Variance↗

PubMed2005

The effect of visuo-motor transformations on hand-foot coordination: evidence in favor of the incongruency hypothesis.

Understanding how multiple constraints contribute to the emergence of coordinated behavior has been the topic of considerable debate in cognitive sciences. The present experiment addressed the issue of the effects of visual motion structures (iso- and non-isodirectionality) on the stability of hand-foot coordination patterns. Visuo-motor transformations--decorrelating the perceived movement direction from the actually generated direction--were applied to both in-phase and anti-phase patterns. Two mutually exclusive hypotheses--the "visual grouping hypothesis" and the "incongruency hypothesis"--were tested. The results indicated that both conditions of transformed visual feedback destabilized the actual performed coordination patterns. Thus, despite the existence of common underlying principles that govern both the perceived motion pattern and the generation of hand-foot coordination patterns, it appeared that perceptual grouping principles were not exploited to monitor the production of coordination. These results strongly suggest that the congruency between the performed pattern and the perceived visual feedback is the primary factor determining the (in)stability of hand-foot coordination patterns.

Adult↗

PubMed1989

Experiences of alien control in schizophrenia reflect a disorder in the central monitoring of action.

Twenty-three acute psychotic patients who were drug free at the time of testing performed a motor task designed to elicit many errors. Normal subjects and many of the psychotic patients were able to correct these errors in the absence of visual feedback. The ability to make such corrections depends on the subject knowing what response he has just made. Patients with experiences of alien control of their thoughts and actions who formed a subgroup of those classified as schizophrenic, were significantly less likely to make error corrections in the absence of visual feedback. This result is consistent with our previous suggestion (Frith, 1987) that these symptoms are a consequence of problems with the central monitoring of responses.

Affective Disorders, Psychotic↗

PubMed1998

Auditory and visual similarity of pitch contours.

It has been shown that visual display systems of intonation can be employed beneficially in teaching intonation to persons with deafness and in teaching the intonation of a foreign language. In this paper, the question is addressed whether important audible differences between two pitch contours correspond with visually conspicuous differences between displayed pitch contours. If visual feedback of intonation is to be effective in teaching situations, such correspondence must exist. In two experiments, phoneticians rated the dissimilarity of two pitch contours. In the first experiment they rated the two pitch contours auditorily (i.e., by listening to two resynthesized utterances). In the second, they rated the same two pitch contours visually (i.e., by looking at the two contours displayed on a computer screen). The results indicate why visual feedback may be very effective in intonation training if pitch contours are displayed in such a way that only auditorily relevant features are represented.

Deafness↗

PubMed1998

Role of feedback in formation of acute tolerance to alcohol.

OBJECTIVE: The contributions of feedback to formation of acute ethanol tolerance were studied during performance of a task that allowed practice in the absence of feedback about performance accuracy. METHOD: The perceptual instability of the seen environment during head movement (apparent concomitant motion, ACM) and the vestibulo-ocular reflex (VOR) were measured before and after alcohol ingestion. In separate conditions, eight (six female) subjects were either deprived or not deprived of normal vision of the laboratory during the portion of the experiment following onset of alcohol ingestion. RESULTS: Alcohol caused ACM in the direction opposite head rotation to increase in both sessions. The degree of ACM increase was greater during sessions in which visual feedback was prevented than in sessions in which subjects could see the surroundings. The increase in ACM was accompanied by a decrease in gain of the VOR which was relatively larger in the no-feedback condition. In addition, ACM returned to normal (pre-alcohol ingestion) values more rapidly during sessions in which subjects received visual feedback. CONCLUSIONS: The results suggest that feedback is an important component in forming acute tolerance to alcohol, independent of task practice.

Adult↗

PubMed2005

Experience and practice organization in learning a simulated high-velocity low-amplitude task.

OBJECTIVE: To evaluate the effect of practice schedule, type of feedback, and experience level on simulated force production accuracy in chiropractic students. METHODS: Thirty-three chiropractic students simulated a high-velocity low-amplitude prone thoracic spine manipulation. Three force goals based on percent of maximum thrusting ability were used in blocked and random variable practice. Participants received either visual feedback or knowledge of performance feedback regarding their force-time history. Serial retention tests without feedback followed blocked and random variable practice. Peak and average rates of thrust development, as well as the constant error, absolute constant error, and variable error of peak force production, were calculated. CONCLUSION: Familiarity and practice of high-velocity low-amplitude spinal manipulation resulted in greater accuracy of peak force production. Lower error scores were observed in acquisition with blocked variable practice. However, short-term accuracy was enhanced in retention when participants had used random variable practice. Random variable practice combined with visual feedback improved force production accuracy in retention. The variability of peak force production increased to 61% of maximum thrusting ability and then decreased. The greatest accuracy with least variability of peak force production was seen near 75% of maximum thrusting ability.

Adult↗

PubMed1981

The learning of programmed- and feedback- based processes controlling the production of a positioning response in two dimensions.

Two experiments were conducted to investigate the learning of the programmed- and feedback-based processes controlling the production of a slow, self-paced positioning response in two dimensions (direction and extent) in the horizontal plane. Both experiments had two phases: an acquisition phase of 60 trials with KR, followed by a KR withdrawal phase of 20 trials. In Experiment 1, one group (N=15) had visual feedback about the ongoing movement and the other group (N=15) did not. In Experiment 2, one group (N=15) practiced initiating the response in the criterion direction and moving the criterion extent, whereas, the other group (N=15) practiced initiating the response in the criterion direction and moving randomly varied extents. The results of Experiment 1 indicated that the learning of a programmed-based process is a gradually acquired freedom from visual feedback. Experiment 2 revealed that a programmed-based process can be learned independent of a feedback-based process.

Journal Article↗

PubMed1990

Timing and accuracy of visually directed movements in children: control of direction and amplitude components.

The reaction times (RTs), movement times (MTs), and final accuracy of hand movements directed towards visual goals were measured in 6-, 8-, and 10-year-old children, using tasks in which direction and amplitude components of movement were distinctly required. The tasks were performed with and without visual feedback of the limb. RTs decreased with age, and were shorter in directional than in amplitude task, in all ages. MTs were the longest at age 8 in both tasks, equally short at ages 6 and 10 in the directional task, the shortest at age 10, and intermediate at age 6, when amplitude had to be regulated. In the amplitude task, the target distance generally affected MTs under both visual conditions, but to a lower degree at age 10 than in the two younger groups. Movement accuracy, which was in all cases higher with visual feedback, showed different developmental trends among the two spatial components: directional accuracy was not different among the three groups of age, whereas amplitude accuracy showed a nonmonotonic development in the nonvisual condition, with an increase between age 6 and age 10, and the lowest level at age 8. In the visual condition, amplitude accuracy did not change with age. The specification of direction seems therefore to predominantly load the preparatory stage of the response. Amplitude specification seems to be more dependent on on-going regulations and to undergo a longer and more complex development, with a critical period around age 8 when a greater propensity for a feedback-based control appears on the two components. With increasing age, amplitude tends to be specific to a greater extent by a feedforward process.

Attention↗

PubMed1989

Complex oscillations in a human motor system.

Experiments were performed to investigate the oscillations arising in a human motor system with delayed visual feedback. Eight subjects were instructed to maintain a constant finger position relative to a stationary baseline. The finger displacement was measured using a microdisplacement transducer connected to the index finger, and was displayed on an oscilloscope. Time delays between 40 and 1,500 ms were inserted in the visual feedback loop for 100 s. Results show that, as the time delays increase, irregular rhythms appear with short intermittent periods of regular oscillations. These regular low-frequency oscillations have an amplitude that increases with the time delays and a period that is consistently about 2 to 4 times the time delay. Fast Fourier Transforms (FFT) show a peak between 8 and 12 Hz, corresponding to physiological tremor in half the subjects. No systematic variations in the FFT for the 2 to 15 Hz range were observed as time delay increased. In the 0 to 2 Hz range, the FFT show a consistent increase in power with the time delay. These results indicate that, under the conditions of this experiment, tremor is not affected by time delays in the visuomotor system, and time delays in the visuomotor feedback loop give rise to complex oscillatory behaviors.

Journal Article↗