Decrements In Duration Research Articles

Biological Rhythms During Residence in Polar Regions

At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms. Thus, the status of the circadian system is of interest. Moreover, the relatively controlled artificial light conditions in winter are conducive to experimentation with different types of light treatment. The hormone melatonin and/or its metabolite 6-sulfatoxymelatonin (aMT6s) provide probably the best index of circadian (and seasonal) timing. A frequent observation has been a delay of the circadian system in winter. A skeleton photoperiod (2 × 1-h, bright white light, morning and evening) can restore summer timing. A single 1-h pulse of light in the morning may be sufficient. A few people desynchronize from the 24-h day (free-run) and show their intrinsic circadian period, usually >24 h. With regard to general health in polar regions, intermittent reports describe abnormalities in various physiological processes from the point of view of daily and seasonal rhythms, but positive health outcomes are also published. True winter depression (SAD) appears to be rare, although subsyndromal SAD is reported. Probably of most concern are the numerous reports of sleep problems. These have prompted investigations of the underlying mechanisms and treatment interventions. A delay of the circadian system with “normal” working hours implies sleep is attempted at a suboptimal phase. Decrements in sleep efficiency, latency, duration, and quality are also seen in winter. Increasing the intensity of ambient light exposure throughout the day advanced circadian phase and was associated with benefits for sleep: blue-enriched light was slightly more effective than standard white light. Effects on performance remain to be fully investigated. At 75°S, base personnel adapt the circadian system to night work within a week, in contrast to temperate zones where complete adaptation rarely occurs. A similar situation occurs on high-latitude North Sea oil installations, especially when working 18:00–06:00 h. Lack of conflicting light exposure (and “social obligations”) is the probable explanation. Many have problems returning to day work, showing circadian desynchrony. Timed light treatment again has helped to restore normal phase/sleep in a small number of people. Postprandial response to meals is compromised during periods of desynchrony with evidence of insulin resistance and elevated triglycerides, risk factors for heart disease. Only small numbers of subjects have been studied intensively in polar regions; however, these observations suggest that suboptimal light conditions are deleterious to health. They apply equally to people living in temperate zones with insufficient light exposure. (Author correspondence: arendtjo@gmail.com)

Effect of deviance direction and calculation method on duration and frequency mismatch negativity (MMN)

The mismatch negativity (MMN) component of the auditory event-related potential (ERP) reflects the process of change detection in the auditory system. The present study investigated the effect of deviance direction (increment vs. decrement) and calculation method (traditional vs. same-stimulus) on the amplitude of MMN. MMN was recorded for increments and decrements in frequency and duration in 20 adults. The stimuli (standard/deviant) were 250 Hz/350 Hz (frequency MMN) and 200 ms/300 ms (duration MMN) for increment MMN and vice versa for decrement MMN. Amplitude of MMN was calculated in two ways: the traditional method (subtracting ERP to the standard from the deviant presented in the same block) and the same-stimulus method (subtracting ERP to identical stimuli presented as standard in one block and deviant in another block). We found that increments in frequency produced higher MMN amplitudes compared to decrements for both methods of calculation. For duration deviance, the decrement MMN was absent in the traditional method, while the decrement and increment MMN did not differ for the same-stimulus method. These findings suggest that the brain processes frequency increments and decrements in different ways. The results also suggest the use of same-stimulus method for the calculation of duration MMN when long duration stimuli are used.

Sensory interaction on static balance: A comparison concerning the history of falls of community‐dwelling elderly

To determine whether elderly subjects with distinct histories of falls presented differences concerning the influence of sensory interaction on balance. Cross-sectional research. Ninety-six community-dwelling elderly subjects were divided into three groups, according to the history of falls within the past year (group 1, no falls; group 2, one fall; and group 3, recurrent falls). The Clinical Test of Sensory Interaction and Balance was used to evaluate the influence of sensory inputs on standing balance. The test required the subject to maintain stability during 30 s, under six conditions: (i) firm surface with eyes open; (ii) firm surface with eyes closed; (iii) firm surface with visual conflict; (iv) unstable surface with eyes open; (v) unstable surface with eyes closed; and (vi) unstable surface with visual conflict. The time expended on conditions and the number of abnormal cases were compared between groups. Each group was evaluated in relation to its performance in the progression of conditions. More abnormal cases occurred in group 3 compared to group 1 for conditions (iv) and (v); and compared to group 2 for condition (iv). Group 3 remained less time than group 1 under conditions (iv), (v) and (vi). Groups 1, 2 and 3 presented relevant decrements in trial duration from conditions (iv) to (v). For group 3, a significant decay was also noted from condition (i) to (ii). Sensorial interaction in the elderly varies according to their history of falls. Thus, it is possible to correctly guide the rehabilitation process and to prevent sensorial decays according to an individual's history of falls.

A Clinical Electrophysiological Study of Emotional Lability in Patients With Systemic Lupus Erythematosus

A Clinical Electrophysiological Study of Emotional Lability in Patients With Systemic Lupus Erythematosus

Three-dimensional kinematics and dynamics of the foot during walking: a model of central control mechanisms

The foot is a critical interface between the body and supporting surface during walking, but there is no coherent framework on which to model the dynamics of the stance and swing phases. To establish this framework, we studied the rotational and translational dynamics of foot movement in three dimensions with a motion detection system (OPTOTRAK), while subjects walked on a treadmill. Positions, velocities, and durations were normalized to leg-length and gravity. Foot position and rotation at toe-off were closely related to walking velocity. Foot pitch at toe clearance increased with walking velocity, but the medial-lateral and vertical toe positions were unaltered. Phase-plane trajectories along the fore-aft direction, i.e., plots of toe velocity versus position, were circular during the swing phases, with radii proportional to walking velocity. Peak forward, lateral, and upward velocities were linearly related to corresponding excursions, forming main sequences. A second order model predicted the changes in toe position and velocity, and the approximately hyperbolic decrements in duration as a function of walking velocity. The model indicates that the foot is controlled in an overdamped manner during the stance phase and as a feedback-controlled undamped pendulum during the swing. The data and model suggest that the state of the foot at toe-off, set by walking velocity during the stance phase, determines the dynamics of the swing phase. Thus, in addition to determining locomotion kinematics, walking velocity plays a critical role in determining the phase-plane trajectories and main sequence relationships of foot movements during the swing phases.

Sleep as a mediator of the relationship between socioeconomic status and health: a hypothesis.

This article discusses the hypothesis that the adverse impact of low socioeconomic status (SES) on health may be partly mediated by decrements in sleep duration and quality. Low SES is frequently associated with a diminished opportunity to obtain sufficient sleep or with environmental conditions that compromise sleep quality. In a recent study, we examined carbohydrate metabolism, endocrine function, and sympatho-vagal balance in young, healthy adults studied after restricting sleep to four hours per night for six nights as compared to a fully rested condition obtained by extending the bed-time period to 12 hours per night for six nights. The state of sleep debt was associated with decreased glucose tolerance, elevated evening cortisol levels, and increased sympathetic activity. The alterations in glucose tolerance and hypothalamo-pituitary-adrenal function were qualitatively and quantitatively similar to those observed in normal aging. These results indicate that sleep loss can increase the "allostatic load" and facilitate the development of chronic conditions, such as obesity, diabetes, and hypertension, which have an increased prevalence in low SES groups.

Haloperidol-induced decrements in force and duration of rats' tongue movements during licking are attenuated by concomitant anticholinergic treatment

To investigate the hypothesis that haloperidol's impairment of tongue protrusion in rats is Parkinson-like, the effects of centrally active scopolamine hydrochloride (0.1 or 0.2 mg/kg, SC) were evaluated in 36 rats that were also administered haloperidol (0.06, 0.12, or 0.24 mg/kg, IP). Rats were trained to lick water from a force-sensing disk, and the peak force and duration of each tongue contact were recorded along with the number of licks emitted in a 2-min session. Scopolamine hydrochloride significantly reversed haloperidol-induced deficits observed for peak force, duration, and number of licks. When given alone, scopolamine hydrochloride decreased peak force and duration. Fourier methods showed that the basic rhythm of licking was slowed by scopolamine hydrochloride but not by haloperidol. Taken together, the data suggest that central nervous system dopaminergic-cholinergic interactions importantly modulate tongue dynamics in the rat in a manner consistent with such interactions in neuroleptic-treated human patients.

Diabetes mellitus and male sexual function: a controlled study.

There is an extensive clinical literature on the erectile disorders of diabetic men but a paucity of controlled studies that have taken into account the effects of age, concurrent illnesses and medication on sexual function. This investigation was carried out on 40 diabetic men free from other illness or drugs that could affect sexual capacity and 40 age-matched healthy control subjects. Each subject and his female partner underwent semistructured interviews and the men had comprehensive medical evaluations and polygraphic assessment of sleep and nocturnal penile tumescence in the sleep laboratory during three nights. In comparison to control subjects, diabetic patients reported significant decreases in sexual desire, subjective arousal, erectile capacity, coital frequency and sexual satisfaction. The diabetic group also had significant decrements in duration of rapid eye movement sleep and in frequency, duration and degree of nocturnal penile tumescent episodes. There were no differences between Type 1 (insulin-dependent) and Type 2 (non-insulin dependent) diabetic patients in prevalence of sexual problems or in nocturnal tumescent measures. Significant relations were observed between lack of metabolic control, diabetic complications and impaired nocturnal tumescence. Sexually non-dysfunctional diabetic men had significant nocturnal penile tumescence abnormalities. Diabetic men without coital failures may have a subclinical impairment in erectile function which, although of not significant magnitude to interfere with penetration, is reflected in nocturnal penile tumescent measures. This result raises a note of caution in the interpretation of the nocturnal penile tumescence test for the differential diagnosis of diabetic erectile impotence.

Do event-related potentials to infrequent decrements in duration of auditory stimuli demonstrate a memory trace in man?

Sequences of identical acoustic stimuli were presented to normal subjects reading a book while event-related brain potentials (ERP) elicited by these stimuli were recorded. Occasional irrelevant decreases and increases in stimulus duration elicited an ERP component called the mismatch negativity (MMN). This component was larger over the right hemisphere irrespective of the ear stimulated. These data implicate memory representations which develop automatically and represent the physical features of the repetitive stimulus accurately. Further, when an input does not match with such a trace the MMN is generated. The memory traces involved appear to be those of the acoustic sensory memory, the ‘echoic’ memory.

An evaluation of hypnotic susceptibility and peripheral temperature elevation in the treatment of migraine.

Abstract The current study evaluated the various inter-relationships between hypnotic susceptibility, finger temperature elevation and symptom relief in the treatment of female migraine patients. Finger temperature measurements were taken during three thermal imagery training sessions with high susceptible Ss (n = 9) in hypnosis and low hypnotically susceptible Ss (n = 14) in simulated hypnosis. Subjects were also trained in autohypnosis or simulated autohypnosis for subsequent home practice. Daily records, kept by Ss, provided data for six outcome measures which were analyzed for the periods prior to training and for 6 months of follow-up. All Ss, regardless of susceptibility or peripheral temperature alteration, showed significant decrements in frequency, intensity, and duration of headaches, as well as in amount of medication ingested. The findings are discussed in terms of a potentially viable alternative to customary pharmacologic treatment.

Duration of Tonic Immobility In Lizards (Anolis Carolinensis) as a Function of Repeated Immobilization, Frequent Handling, and Laboratory Maintenance

Research has shown that chickens given repeated elicitations of the tonic immobility reaction, an habituation procedure, show larger decrements in duration of tonic immobility on a subsequent test trial than do either birds given simple handling or naive animals. The present study attempted to replicate this finding with another animal commonly used in studies of tonic immobility, the anole lizard (Anolis carolinensis). Experiment 1 employed the between-groups design used in previous studies and failed to detect differences among the three treatments (habituated, handled, and naive) in duration of immobility. A second experiment used a within-subjects measure of immobility duration to demonstrate that the habituation procedure and simple handling produce similar decrements in duration of immobility. The final experiment demonstrated that anoles maintained in a group-living situation, with some daily exposure to humans, also show reliable decrements in duration of immobility. These results are congruent with those obtained by Boice and Williams (1971) with frogs (Rana pipiens).