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PubMed1998

Perceptions related to time in a qualitative study of informal carers of terminally ill cancer patients.

Caring for a terminally ill relative is a complex, time-consuming experience. Demands on carers' time stem from a variety of sources, notably the practical and emotional work they must perform. Carers should be helped to plan their time effectively. Carers need to come to terms with their perceptions about past, present and future. Achieving some sense of equilibrium in the caring role is important. Professionals working with families experiencing terminal illness have a duty to assess each family individually in order to provide appropriate help and support.

Adaptation, Psychological↗
PubMedDate not supplied

[Lateralization of perception of short time intervals and cortical evoked activity in man].

Recognition of short time intervals (10, 60, and 180 ms) between visual stimuli presented to the left or right hemisphere was studied in adult healthy people. The interval of 180 ms is recognized better than that of 10 or 60 ms. Learning with repeated tests with 180 ms intervals proceeds better than that with short intervals. The predominance of the left hemisphere has been revealed only for perception of 10 ms interval. The other time intervals asymmetry is not observed. It is suggested that the left hemisphere is predominant in estimation of short (less than 60 ms) time intervals. In formation of time nervous model a significant role is played by local activation of the cortical zone where the standard stimulus is addressed.

Adult↗
PubMed2002

The dose-response curve of the gravitropic reaction: a re-analysis.

The dose-response curve of the gravitropic reaction is often used to evaluate the gravisensing of plant organs. It has been proposed (Larsen 1957) that the response (curvature) varies linearly as a function of the logarithm of the dose of gravistimulus. As this model fitted correctly most of the data obtained in the literature, the presentation time (tp, minimal duration of stimulation in the gravitational field to induce a response) or the presentation dose (dp, minimal quantity in g.s of stimulation to induce a response) were estimated by extrapolating down to zero curvature the straight line representing the response as a function of the logarithm of the stimulus. This method was preferred to a direct measurement of dp or tp with minute stimulations, since very slight gravitropic response cannot be distinguished from the background oscillations of the extremity of the organs. In the present review, it is shown that generally the logarithmic model (L) does not fit the experimental data published in the literature as well as the hyperbolic model (H). The H model in its simplest form is related to a response in which a ligand-receptor system is the limiting phase in the cascade of events leading to the response (Weyers et al. 1987). However, it is demonstrated that the differential growth, responsible for the curvature (and the angle of curvature), would vary as a hyperbolic function of the dose of stimulation, even if several steps involving ligand-receptor systems are responsible for the gravitropic curvature. In the H model, there is theoretically no presentation time (or presentation dose) since the curve passes through the origin. The value of the derivative of the H function equals a/b and represents the slope of the cune at the origin. It could be therefore used to estimate gravisensitivity. This provides a measurement of graviresponsiveness for threshold doses of stimulation. These results imply that the presentation time (or presentation dose) derived from the L model cannot be used anymore as an estimate of gravisensitivity. On the contrary, the perception time (minimal duration of a repeated stimulation which induces a response), which is less than 1 s, should be related to the perception of gravity. The consequences of these results on the mode of action and the nature of graviperception are discussed.

Journal Article↗
PubMed2002

A tribute to John Gibbon.

This article provides an overview of the published research of John Gibbon. It describes his experimental research on scalar timing and his development of scalar timing theory. It also describes his methods of research which included mathematical analysis, conditioning methods, psychophysical methods and secondary data analysis. Finally, it describes his application of scalar timing theory to avoidance and punishment, autoshaping, temporal perception and timed behavior, foraging, circadian rhythms, human timing, and the effect of drugs on timed perception and timed performance of Parkinson's patients. The research of Gibbon has shown the essential role of timing in perception, classical conditioning, instrumental learning, behavior in natural environments and in neuropsychology.

Journal Article↗
PubMed2004

Adolescent girls perceptions of the timing of their sexual initiation: "too young" or "just right"?

PURPOSE: To examine variables associated with adolescent girls' perceptions of the timing of their first consensual intercourse. METHODS: One hundred seventy-four primarily African-American adolescent girls, aged 12 to 15 years participated in a 3-year longitudinal study of psychosexual development. Seventy-three percent reported being sexually experienced by the end of the study. They were asked whether they believed their age of initiation was "too young," "too old," or "just right." A generalized estimating equation (GEE) model was used to evaluate predictors of perception of timing of first consensual intercourse. RESULTS: Ninety-nine (78%) said that they were "too young" and 28 (22%) said that their age had been "just right." The results of the final GEE model indicated that variables associated with perceiving age of first consensual intercourse as "just right" included younger chronological age, an older age of first consensual intercourse, endorsement of being "in love" as a reason for first consensual intercourse, greater indirect parental monitoring (vs. "none" or "direct parental monitoring"), and a higher level of education for mothers. CONCLUSIONS: Most of these adolescents thought their age of initiation was too young. Factors associated with perceiving the timing of consensual intercourse as "just right" are similar to those reported in the literature to be associated with delaying the initiation of consensual intercourse.

Adolescent↗
PubMedDate not supplied

Attenuating effect of serotonin receptor antagonists on impairment of mealtime-associated activity rhythm in old rats.

In the present study, we examined attenuating effect of serotonin (5-HT) receptor antagonists on the impairment of the time perception presented by daily scheduled feeding in old rats. When feeding was restricted to a single meal at a fixed time of day (1300-1700 h) for six consecutive days, young rats exhibited intense locomotor activity from 1-3 h before feeding time. Intense locomotor activity was observed between 1200 adn 1700 h in young animals even on the fasting day (day 7) (mealtime-associated activity). However, this mealtime-associated activity was impaired in 24-mo-old rats. Daily injections of 5-HT2 receptor antagonists, mianserin or ritanserin, or a 5-HT3 receptor antagonist, Y25130, at 1700 h for 6 consecutive days significantly and dose-dependently attenuated the impairment of mealtime-associated activity on the fasting day in old rats without affecting the food intake. Our results suggest that the blockade of 5-HT2 and/or 5-HT3 receptors attenuates impairment of the manifestation of mealtime-associated anticipatory activity related to temporal learning in old rats.

Aging↗
PubMed2006

Differential effects of cocaine and ketamine on time estimation: implications for neurobiological models of interval timing.

The present experiment examined the effects of cocaine (0.0 and 15 mg/kg, i.p.) and ketamine (0.0, 10.0 and 15 mg/kg, i.p.) on timing behavior using a 12-s differential reinforcement of low rates (DRL) procedure and a 2- vs. 8-s bisection procedure in rats. DRL (time production) and bisection (time perception) procedures are sensitive to effects of dopaminergic drugs and provide an assessment of the accuracy and precision of interval timing as well as the subject's level of impulsivity. When administered to rats trained on either the DRL or the bisection procedure, cocaine shifted the psychophysical functions leftward relative to control conditions. In contrast, ketamine produced no change in the temporal control of behavior on either procedure. These differential effects of cocaine and ketamine are consistent with previous reports suggesting that dopamine levels in the dorsal striatum, but not in prefrontal cortex, ventral striatum or hippocampal regions, are crucial for the regulation of the speed of an internal clock.

Animals↗
PubMed2001

Colour, form, and movement are not perceived simultaneously.

Behavioural, neuro-anatomical and clinical evidence suggests that different aspects of the visual scene are processed separately, but the extent to which the processing is carried out along segregated and independent parallel pathways is still debated. Moreover, it is also unclear whether these aspects are processed at the same rate, and their neural correlates reach consciousness at the same time. An experiment investigated this issue in the case of three attributes of 2D displays: colour, form, and movement. There were three conditions, one for each possible pairing of these attributes. Stimuli were combinations of two values for each attribute (red/green, circle/square, fixed/moving). In each condition the stimuli changed twice in close temporal succession, each attribute switching asynchronously between the two possible values. The observer's task was to report which change had occurred first. Response probabilities were computed for 13 values of the asynchrony, and transformed into estimates of perception time with the help of a psychophysical model. The results showed that colour and form are processed almost simultaneously. By contrast, movement perception is delayed by about 50 ms. The implications of these findings vis à vis the so-called perceptual binding problem are discussed.

Analysis of Variance↗
PubMed2000

Conscious and preconscious adaptation to rhythmic auditory stimuli: a magnetoencephalographic study of human brain responses.

This study was triggered by the experimental evidence that subjects required to tap in synchrony with a heard rhythm spontaneously time their tapping to variations in rhythm frequency even when these variations are so small that they are not consciously detectable. We performed a series of magnetoencephalographic (MEG) measurements, aimed at investigating whether the response of the auditory cortex discriminates randomly administered series of brief tones differing from each other only by their interstimulus intervals (ISI). Moreover, by combining psychophysical measurements, conscious and preconscious adjustments of tapping to rhythm variations were compared with brain cortical responses. The ISIs were varied by 2% or 20% from a "central" value of 500 ms. Subjects always consciously detected the 20% ISI changes and easily adjusted their tapping accordingly, whereas they never consciously detected the 2% ISI changes, even though they always correctly adjusted their tapping to them. Analysis of the auditory evoked fields (AEFs) showed that the intensity of the M100 component decreased with decreasing ISI both for 20% and 2% variations in a statistically significant manner, despite the fact that the 2% variation was not consciously perceived. The M100 behavior indicated that connections between auditory and motor cortexes may exist that are able to use the information on rhythm variations in the stimuli even when these are not consciously identified by the subject. The ability of the auditory cortex to discriminate different time characteristics of the incoming rhythmic stimuli is discussed in this paper in relation to the theories regarding the physiology of time perception and discrimination.

Acoustic Stimulation↗
PubMed2003

Social capital in a changing society: cross sectional associations with middle aged female and male mortality rates.

OBJECTIVES: Social capital has been linked to self rated health and mortality rates. The authors examined the relations between measures of social capital and male/female mortality rates across counties in Hungary. DESIGN: Cross sectional, ecological study. SETTING: 20 counties of Hungary. PARTICIPANTS AND METHODS: 12,640 people were interviewed in 1995 (the "Hungarostudy II" survey), representing the Hungarian population according to sex, age, and county. Social capital was measured by three indicators: lack of social trust, reciprocity between citizens, and help received from civil organisations. Covariates included county GDP, personal income, education, unemployment, smoking, and alcohol spirit consumption. MAIN OUTCOME MEASURE: Gender specific mortality rates were calculated for the middle aged population (45-64 years) in the 20 counties of Hungary. RESULTS: All of the social capital variables were significantly associated with middle age mortality, but levels of mistrust showed the strongest association. Several gender differences were observed, namely male mortality rates were more closely associated with lack of help from civic organisations, while female mortality rates were more closely connected with perceptions of reciprocity. CONCLUSION: There are gender differences in the relations of specific social capital indicators to mortality rates. At the same time, perceptions of social capital within each sex were associated with mortality rates in the opposite sex.

Cross-Sectional Studies↗
PubMed1982

A nonspecific learning effect in the perception of random-dot stereograms?

An experiment is reported the object of which was to check whether a small amount of nonspecific experience in perceiving random-dot stereograms could facilitate the perception of a previously unseen stereogram. The mean stereopsis perception time of a group of totally naive subjects was found to be significantly slower than that of a group who had previously been shown two different stereograms. Closer inspection of the data showed that this difference was primarily due to approximately one third of the naive group who were much slower than the 'experienced' group. It is therefore suggested that nonspecific experience provides most initial help for relatively slow perceivers, since many naive subjects can perform as well as those with prior experience of other stereograms.

Depth Perception↗
PubMed1988

Dissociation of the lateral and medial cerebellum in movement timing and movement execution.

In a previous study (Ivry and Keele, in press), cerebellar patients were found to be impaired on both a motor and a perceptual task which required accurate timing. This report presents case study analyses of seven patients with focal lesions in the cerebellum. The lesions were predominantly in the lateral, hemispheric regions for four of the patients. For the remaining three patients, the lesions were centered near the medial zone of the cerebellum. The clinical evaluation of the patients also was in agreement with the different lesion foci: lateral lesions primarily impaired fine motor coordination, especially apparent in movements with the distal extremities and medial lesions primarily disturbed balance and gait. All of the patients were found to have increased variability in performing rhythmic tapping when tapping with an effector (finger or foot) ipsilateral to the lesion in comparison to their performance with a contralateral effector. Separable estimates of a central timekeeper component and an implementation component were derived from the total variability scores following a model developed by Wing and Kristofferson (1973). This analysis indicated that the poor performance of patients with lateral lesions can be attributed to a deficit in the central timing process. In contrast, patients with medial lesions are able to accurately determine when to make a response, but are unable to implement the response at the desired time. A similar dissociation between the lateral and medial regions has been observed on a time perception task in patients with cerebellar atrophy. It is concluded that the lateral regions of the cerebellum are critical for the accurate functioning of an internal timing system.

Adult↗
PubMed2007

Gender differences in social network characteristics and psychological well-being among Hong Kong Chinese: the role of future time perspective and adherence to Renqing.

Gender differences in social network characteristics are well documented in the literature. Socio-emotional selectivity theory emphasizes the importance of future time perception on selection of social partners whereas cultural studies stress the roles of Renqing (relationship orientation) on social interactions. This study examined the effects of future time perspective and adherence to Renqing on social network characteristics, and their associations with psychological well-being of 321 Chinese men and women, aged 28-91 years. Results showed that adherence to Renqing partially accounted for gender differences in the number of relatives, even after controlling for the effects of extraversion and structural factors. Moreover, women, but not men, with lower adherence to Renqing and more limited future time perspective were found to be happier when they had fewer close friends in their social networks.

Adult↗
PubMed2005

Chronometric evidence for entrained attention.

Recent theories of dynamic attention have renewed the interest in temporal context as a determinant of attention. The mechanism of dynamic attention remains unclear, and both stochastic time perception processes and deterministic oscillators are possible. The results of Experiment 1 demonstrate that attention can be guided by isochronous series of warning stimuli and that elapsed time cannot fully account for this effect. Experiment 2 indicates that temporal structure can be used over a limited range of time. The results of Experiment 3 indicate that temporal pattern, rather than variability, is a determinant of temporally focused attention. The results of Experiment 4 demonstrate that a coupled oscillator is a better predictor of reaction time than a stochastic timing mechanism is, under certain assumptions.

Adolescent↗
PubMed1983

Voice onset time production and perception in apraxic subjects.

This study explored the relationship between the perception and production of voice onset time (VOT) in apraxic subjects. Spectrograms of the words, "bees" and "peas" spoken by apraxic subjects were acoustically analyzed to obtain a measure of VOT. The subjects also identified the initial cognate ("b" or "p") from synthetically generated speech spanning a voiced to voiceless time continuum. The results suggest that apraxic subjects have production as well as perceptual errors in the voicing feature but no significant relationship was found between the two measures.

Adult↗
PubMed2000

Interaction of root gravitropism and phototropism in Arabidopsis wild-type and starchless mutants.

Root gravitropism in wild-type Arabidopsis and in two starchless mutants, pgm1-1 and adg1-1, was evaluated as a function of light position to determine the relative strengths of negative phototropism and of gravitropism and how much phototropism affects gravitropic measurements. Gravitropism was stronger than phototropism in some but not all light positions in wild-type roots grown for an extended period, indicating that the relationship between the two tropisms is more complex than previously reported. Root phototropism significantly influenced the time course of gravitropic curvature and the two measures of sensitivity. Light from above during horizontal exposure overestimated all three parameters for all three genotypes except the wild-type perception time. At the irradiance used (80 micromol m(-2) s(-1)), the shortest periods of illumination found to exaggerate gravitropism were 45 min of continuous illumination and 2-min doses of intermittent illumination. By growing roots in circumlateral light or by gravistimulating in the dark, corrected values were obtained for each gravitropic parameter. Roots of both starchless mutants were determined to be about three times less sensitive than prior estimates. This study demonstrates the importance of accounting for phototropism in the design of root gravitropism experiments in Arabidopsis.

Arabidopsis↗
PubMed2006

Parents with first time major depression: perceptions of social support for themselves and their children.

The aim of this study was to ascertain the perceptions of parents, with first time major depression, regarding the social support for themselves and their children. Eighteen parents, with children under the age of 19, were interviewed on admission to an inpatient unit and of these 16 were followed up 1 year later. In addition, the severity of parents' depression and their functional status was measured. The results showed that although the parents did regain their mental health and functional capacity to a certain extent, they nevertheless remained in a vulnerable position, increasing the strain on the whole family. The parents' and their children's social support was low and came mostly from outside the family. The parents were worried about their children, due to problems related to the depressive episode as well as ordinary teenage rebellion. Important questions concerned practical problems such as whether there was someone to take care of the children if the parent is incapable of doing so. There were also concerns pertaining to how the changed family situation might interfere with the child's natural development or whether depression was a question of heredity. This highlights the need to investigate the importance of social support for the family as a whole when one of them suffers from depression. There is a need for improved treatment of parental depression to reduce symptoms such as decreased functional status that may impair parenting. The study also emphasises the need for healthcare practitioners to assess multiple aspects of social support so that care planning will target all relevant domains.

Activities of Daily Living↗
PubMed1993

Defining excellence.

Excellence in the pharmacy profession, particularly pharmacy management, is defined. Several factors have a significant effect on the ability to reach a given level of excellence. The first is the economic and political climate in which pharmacists practice. Stricter controls, reduced resources, and the velocity of change all necessitate nurturing of values and a work ethic to maintain excellence. Excellence must be measured by the services provided with regard to the resources available; thus, the ability to achieve excellence is a true test of leadership and innovation. Excellence is also time dependent, and today's innovation becomes tomorrow's standard. Programs that raise the level of patient care, not those that aggrandize the profession, are the most important. In addition, basic services must be practiced at a level of excellence. Quality assessment is a way to improve care and bring medical treatment to a higher plane of excellence. For such assessment to be effective and not punitive, the philosophy of the program must be known, and the goal must be clear. Excellence in practice is dependent on factors such as political and social norms, standards of practice, available resources; perceptions, time, the motivation to progress to a higher level, and the continuous innovation required to reshape the profession to meet the needs of society.

Humans↗