Contextual dependencies in motor skills

The development of contextual dependencies during motor skill acquisition was examined. Environmental context was varied along intentional and incidental dimensions. Intentional stimuli were defined as essential for achieving skilled performance, whereas incidental stimuli were defined as those that have the potential to become associated with specific tasks due to their selective presence in the learning environment. Experiment 1 demonstrated the occurrence of contextual dependencies for the learning of four-key typing sequences. Contextual dependencies were diminished in Experiment 2 when the number of keys used in the sequences was reduced. In Experiment 3, a retention condition was incorporated, in which both the intentional and the incidental stimuli were not available; this confirmed that task difficulty mediated the development of contextual dependencies. These findings are discussed with respect to the incorporation of environmental contextual stimuli with memorial representations of movement information.

Arterial pulse wave velocity, Fourier pulsatility index, and blood lipid profiles

Increased arterial pulse wave velocity (PWV) and decreased Doppler-shifted Fourier pulsatility index (PI) have been utilized clinically to diagnose the presence and severity of peripheral vascular disease. We have examined the relationships between these two diagnostic indices and several lipoprotein atherogenic risk factors, e.g., serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein-cholesterol (HDL-C), and low-density lipo-protein-cholesterol (LDL-C) among 74 healthy male volunteers, aged 20 to 56 yr. The Doppler signal from the radial artery was digitized and processed with the Hamming window and 512-point fast Fourier transform to obtain frequency power spectra and PI index by a desktop computer. PWV was determined on the computer by dividing the distance between two pressure transducers placed over the radial and carotid arteries by the transit time difference between the maximal first derivatives (dP/dt) of the recorded arterial pulse waves. The results indicated that PI was inversely related to TC, LDL-C, and TG (r = -0.50, -0.41, -0.54, respectively, P less than 0.001), but evidenced a positive relationship with the HDL-C/TC ratio (r = 0.69, P less than 0.001). PWV was also significantly correlated to TC (r = 0.40) and TG (r = 0.42), but was inversely associated with the HDL-C/TC ratio (r = -0.45, P less than 0.001). These findings are consistent with the current theory relating lipids to the pathology of atherosclerosis.

Augmented auditory information in the control of upper-limb prostheses

The present study compared the effects of augmented auditory information on the linear positioning performance of individuals with natural or prosthetic limbs. Subjects were ten male volunteers, five of whom had above-elbow amputations and had used their prosthetic devices for an average of 8.3 years. The other five subjects were selected from a volunteer pool. Movements were made and measured on a standard linear slide whose cursor had a pulsing infrared diode attached opposite the subject. An infrared camera and microprocessor translated diode movement into a corresponding change in voltage. The voltage was simultaneously applied to an audio device which supplied the augmented feedback. The movement of the cursor by the subject was paralleled by a linearly-related change in audible frequency (Hz). The subjects performed 15 trials at each of three retentions (immediate, 15-sec filled, and 15 sec unfilled), both with and without the augmented feedback, for a total of 90 trials. The results of group X feedback X retention intervals analysis of variance on absolute and variable error indicated both a group X retention and a group X feedback interaction. Subjects using a prosthetic limb to produce the movement were less accurate and more variable than the "normal" subjects when augmented feedback was not concurrent with response.

The effects of fatigue on the control of a coincident timing response

The present study investigated the extent to which fatigue influenced the usage of feedback by Ss to make corrections during coincident timing responses. Sixteen college males watched a .01-sec timer and attempted to knock over a barrier at the moment that the sweep hand reached 500 msec. All Ss were given 50 trials of practice on each of four consecutive days. The fatigue group's performance was immediately preceded by a response-specific local fatigue (dynamic exercise). To insure the maintenance of a high level of fatigue throughout practice, the fatiguing exercise was interspersed with the coincident timing task. The control group performed the same exercise as the fatigue group but without any resistance. Schmidt's (1972) index of preprogramming (IP) was calculated for each day in order to determine the level of feedback involvement in controlling the movement. Fatigue did not influence the accuracy with which Ss responded or the rate that they learned. However, the results indicated a relatively high and stable IP throughout all trials with the IP for the fatigue group higher than that of the control, suggesting a preference by these Ss for a programming mode of control.

Spatial-temporal structure of coincident-timing responses

The spatial temporal structure of coincident timing responses was investigated using an 86-cm movement from a microswitch to a barrier. The speed of the movement was monitored by a series of photocells placed at equal intervals along the movement line. Subjects (N = 24) watched a timer and attempted to displace the barrier at the precise moment that the timer sweep-hand reached a "target position" (250, 500, 1000 msec.) All subjects were given 100 trials of practice at a particular target position. The results indicate that rapid responses have similar spatial temporal structures but that this pattern is altered in slower movements.

Influence of movement activities on shape recognition and retention

Three groups of 4-yr.-old children were asked to complete a form perception assessment instrument prior to, 1 hr. after, and 1 wk. following a treatment. Group 1 participated in a movement-based form perception program, while Group 2 was instructed using a traditional classroom method. A third group which acted as control participated in unrelated movement activities. A repeated-measures analysis of variance gave a main effect of tests and an interaction of groups X tests. Group 2 displayed significantly higher performance on the posttest than Group 1; however, after 7 wk. the performance of Group 2 had decreased to a level below that of Groups 1 and 3, which remained stable.

Shifts in Attention Demands and Motor Program Utilization During Motor Learning

The relationship between changes in the level of motor program utilization and attention demand during the learning of a motor task was examined. The primary task involved an 86-cm horizontal arm movement which subjects attempted to complete coincident with the end of a 360 degrees sweep of a clock hand. A secondary task performed with the opposite limb required a rapid button press to an auditory probe stimulus presented at various temporal locations within each trial. Control subjects performed either the primary task or the secondary task alone, while experimental subjects performed both tasks in combination. Schmidt's (1972) index of preprogramming was used to measure the level of motor program utilization, while probe reaction time reflected the attention demand of the primary task. There was a stable level of motor programming over four consecutive days of practice (100 trials a day), but a general decrease in attention demand. Implications for an expansion of the concept of the motor program were discussed.