No abstract

A cross-sectional sample of men (n = 177) tested in 1962-1964, and men (n = 188) and women (n = 113) tested in 1980-1984, and a longitudinal sample (n = 53) of men tested in 1962-1964 and 1980-1984, were used to investigate age differences and 18-year age changes on a 62-min sensory vigilance task that made virtually no demand on memory, the Mackworth Clock-Test. Age differences and changes in the vigilance decrement were also examined. No age differences or changes were obtained for detection accuracy. Target response time showed significant age-related 18-year longitudinal changes and one significant cross-sectional age difference; the overall age effect was of a U-shaped function with a minimum at middle age. Age differences and changes were obtained in a measure of arousal: skin potential response latency; the overall age effect was also consistent with a U-shaped function. There was little consistent evidence of a differential effect of age on the vigilance decrement. Outcomes contradictory to Surwillo and Quilter (1964) and Quilter, Giambra, and Benson (1983) are reconciled through additional statistical analyses.

In the public domain.

A consensus of critical reviews of single-process theories of vigilance or sustained attention has supported the view that the vigilance decrement must be the result of two or more coacting or interacting processes or systems. One theoretical position, as well as the ubiquity of exponential functions in characterizing the time course of biological processes, led to the hypothesis that the time course of sustained attention could be best modeled by the function A[e-T1-time 11(1 + eT2*time)]. An experimental test (n = 613) using 23 points showed that this function accounted for 96.7% of the variance of detection accuracy and was 1.2 times better than a previously proposed single-term model. All parameter estimates were highly statistically significant. Fits to data from three other studies also supported the two-term exponential model. The model fitted target response time less well, accounting for 75.6% of the variance.

No abstract

An 18-year longitudinal repeat of the Mackworth Clock vigilance experiment was conducted. Skin potential response latencies (SPRL) and reaction times were taken from 33 men during the vigilance task. The longitudinal change in this study reproduced the earlier cross-sectional relationship. The 51 to 69 year olds showed faster reaction times, the 70 to 88 year olds showed slower reaction times and, the 70 to 88 year olds detected significantly fewer targets than when 18 years younger. It was found that the greater the change noted in this study reflected previously determined cross-sectional SPRL effect. However, the SPRL outcome was equivocated by a time-of-measurement effect. It was concluded that at about age 70 years a noticeable reduction in vigilance performance occurs, and this is accompanied by a reduction in autonomic and central nervous system reactivity.

No abstract

The relationship between the external anal sphincter and the periurethral sphincter muscles is an unresolved issue. Recordings of the external anal sphincter (EAS) are commonly used to indicate the responses of the urethral sphincter during urodynamic evaluations and in biofeedback procedures for the treatment of urinary incontinence. This study examined the validity of using anal sphincter training to teach control of the external urethral sphincter. Subjects were 5 continent women, aged 37-51 years, who reported being free of all urologic symptoms. Using visual biofeedback of anal sphincter pressure, subjects were trained to voluntarily contract the sphincter to four amplitudes: 5 , 10, 15, and 20 mmHg (6.8. 13.6, 20.4, and 27.2 cmH,O). Then they were guided through a series of controlled anal sphincter contractions, while the response of the urethral sphincter was measured using surface electrodes embedded in a Foley catheter. At each of four bladder volumes, subjects performed 16 contractions (four contractions at each of the four amplitudes). The order of contractions was counterbalanccd, using a Latin square design. The results show a strong, statistically significant, monotonic relationship between the magnitude of anal sphincter contraction (pressure) and the level of urethral sphincter electromyographic (EMG) activity. The results support the usc of the external anal sphincter as an indicator of urethral sphincter activity for the purpose of conducting biofeedback in the treatment of urinary incontinence.