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PubMed1990

Hot flashes: epidemiology and physiology.

A review of the literature illustrates the many questions about hot flashes that remain unanswered. My survey addresses some of these questions. The prospective and retrospective descriptions of hot flashes provide a more detailed profile of the hot flash than has previously been available. Further, data from this survey demonstrate that while the patterns of hot flashes may be varied, there are commonalities in hot flash physiology and subjective manifestation. The data indicate that hot flashes may start much earlier and continue far longer than is commonly recognized by physicians or acknowledged in textbooks of gynecology. Studies of hot flash duration must control for age or age at hot flash onset, since the older the subjects, the more potential years of hot flashes and the greater the probability of encompassing the entire period of hot flashes. Hot flashes are not static; patterns may change with time. For some women, hot flashes become less frequent and less intense; for others, hot flashes may continue at hourly intervals well into old age. How common these experiences are for women of all ages still needs to be discovered. As expounded by Kaufert, McKinlay, Goodman, and many others, a greater effort must be made to standardize definitions and question formats as well as to improve methodology in epidemiologic investigations to facilitate comparability between studies and insure that proffered conclusions indeed reflect the questions being asked. Physiological studies are critical counterparts to the epidemiology; yet such studies have been too few. My work, by examining the physiology and psychophysiology of hot flashes, has raised additional questions about central and peripheral inputs that may affect the subjective experience of hot flashes. A more complete understanding of the thermoregulatory, cardiovascular, and psychophysiology of women with hot flashes are compared to women without will facilitate the prediction of who is most likely to be affected and the identification of additional approaches to the management of hot flashes.

Adult↗
PubMedDate not supplied

Emotional antecedents of hot flashes during daily life.

OBJECTIVE: Hot flashes are among the most frequently reported menopausal symptoms. However, little is known about factors associated with their occurrence. Moreover, despite the wide use of self-report hot flash measures, little is known about their concordance with physiological flashes. This study evaluated emotional and behavioral antecedents of subjectively and objectively measured hot flashes during daily life. It also examined individual differences predicting concordance between objective and subjective hot flashes. METHODS: Forty-two perimenopausal or postmenopausal women (mean age = 50.5 +/- 4.8 years) reporting daily hot flashes completed 2 days of ambulatory sternal skin conductance monitoring, behavioral diaries 3 times an hour, and psychometric questionnaires. Hot flashes meeting objective physiological criteria and subjectively reported flashes not meeting physiological criteria were assessed. Likelihood of hot flashes following emotions and activities were examined in a case-crossover analysis. RESULTS: Relative to nonflash control times, objective hot flashes were more likely after increased happiness, relaxation, and feelings of control, and less likely after increased frustration, sadness, and stress. Conversely, subjective hot flashes not meeting physiological criteria were more likely after increased frustration and decreased feelings of control. Questionnaires revealed increased negative mood and negative attitudes were associated with fewer objective flashes and higher false-positive reporting rates. CONCLUSION: Increased positive and decreased negative emotions were associated with objective hot flashes, whereas increased negative and decreased positive emotions were associated with subjective flashes not meeting physiological criteria. The anecdotal association between negative emotions and hot flashes may be the result of self-reported flashes lacking physiological corroboration.

Activities of Daily Living↗
PubMed2002

Hot flashes and related outcomes in breast cancer survivors and matched comparison women.

PURPOSE/OBJECTIVES: To compare the hot flash symptom experience and related outcomes between breast cancer survivors and healthy women. DESIGN: Descriptive, cross-sectional, comparative study. SETTING: Southeastern university medical center. SAMPLE: 69 of 207 breast cancer survivors contacted via a tumor registry and 63 age-matched healthy female volunteers. Survivors were a mean of 57 years and a mean of 39 months postdiagnosis. METHODS: Mailed survey included a demographic, disease, and treatment information form; a gynecologic history form; a two-day, prospective, hot flash diary; a detailed hot flash questionnaire; mood and affect scales; and the Hot Flash-Related Daily Interference Scale. MAIN RESEARCH VARIABLES: Hot flashes, mood, affect, interference with daily activities, and overall quality of life. FINDINGS: Breast cancer survivors had hot flashes that were significantly more frequent, severe, distressing, and of greater duration. Breast cancer survivors were less likely to be using hormone replacement and more likely to have tried nonhormonal prescription interventions in the past, but reported significantly less effectiveness from hot flash treatments. Breast cancer survivors with severe hot flashes reported significantly greater mood disturbance; higher negative affect; more interference with daily activities, including sleep, concentration, and sexuality; and poorer overall quality of life in comparison to breast cancer survivors with no hot flashes to mild hot flashes. Hot flash quality and triggers were not significantly different between groups. No clear temporal pattern of hot flashes emerged. CONCLUSIONS: Hot flashes are a significant problem for breast cancer survivors, even for those who are naturally postmenopausal (i.e., did not undergo menopause as a result of surgery or the effects of chemotherapy). Hot flashes remained fairly stable over time and did not diminish in frequency, severity, or associated distress. IMPLICATIONS FOR NURSING: The findings guide the assessment of the uniqueness of the problem of hot flashes experienced by breast cancer survivors and help define outcomes to address in clinical practice or include in future hot flash intervention research.

Affect↗
PubMed1978

The initial stages of photophosphorylation. Studies using excitation by saturating, short flashes of light.

1. Photophosphorylation was studied in spinach chloroplasts on illumination, from the dark state, with saturating short ("single turnover") flashes of light. 2. At rapid flash rates (100 Hz), phosphorylation began within the first five flashes. The ATPase inhibitor protein appeared to be displaced from its inhibitory site on the ATPase also within five flashes, as deduced from the flash-induced ATPase activity. 3. At slower flash rates, or if the rate of electron transfer were reduced with 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), phosphorylation began only after a larger number (50--60) of flashes. The displacement of the ATPase inhibitior protein was similarly delayed. 4. Partial displacement of the inhibitor protein from its inhibitory site on the ATPase (by pretreatment with dithioerythritol) allowed phosphorylation to proceed without a perceptible lag, even in the presence of DCMU. It was concluded that the ATPase inhibitor protein must be displaced on the ATPase before phosphorylation can begin, and that this process is energy dependent. 5. During the flash regime used, release of inhibitor from its inhibitory site seemed to be governed largely by the membrane potential. The light-induced pH gradient seemed to have little effect under these conditions. Our results are not compatible with a direct conformational interaction between the electron transfer chain and the ATPase causing displacement of the inhibitor. 6. The maximal rate of photophosphorylation induced by less than 200 flashes was 0.12--0.15 mol ATP made/mol ATPase per flash. This rate seemed to be limited not be the supply of energy to the ATPase molecules, nor by the maximal turnover capacity of the ATP synthesising system, but by the number of ATPase molecules which were active in synthesis, i.e., which lacked the inhibitor protein. 7. The bound nucleotides of the coupling ATPase exchanged with added nucleotides during single turnover flashes. At high flash rates, exchange began within 5 flashes. The average amount of nucleotide exchanged per flash over 100 flashes was about one tenth the amount of ATP synthesised in each flash. 8. It is concluded that, during phosphorylation, a steady state level of active coupling ATPases is set up. The energy-dependent displacement of the inhibitor protein, and its (energy-independent) relaxation back on to the inhibitory site are the two opposing factors involved in this steady state.

Adenosine Triphosphatases↗
PubMedDate not supplied

Photoresponses of human rods in vivo derived from paired-flash electroretinograms.

In the human eye, domination of the electroretinogram (ERG) by the b-wave and other postreceptor components ordinarily obscures all but the first few milliseconds of the rod photoreceptor response to a stimulating flash. However, recovery of the rod response after a bright rest flash can be analyzed using a paired-flash paradigm in which the test flash, presented at time zero, is followed at time t by a bright probe flash that rapidly saturates the rods (Birch et al., 1995). In ERG experiments on normal subjects, the hypothesis that a similar method can be used to obtain the full time course of the rod response to test flashes of subsaturating intensity was tested. Rod-only responses to probe flashes presented at varying times t after the test flash were used to derive a family of amplitudes A(t) that represented the putative rod response to the test flash. These rod-only responses to the probe flash were obtained by computational subtraction of the cone-mediated component of each probe flash response. With relatively weak test flashes (11-15 scot-td-s), the time course of the rod response to the test flash derived in this manner was consistent with a four-stage impulse response function of time-to-peak approximately 170 ms. A(170), the amplitude of the derived response at 170 ms, increased with test flash intensity (Itest) to a maximum value Amv and exhibited a dependence on Itest given approximately by the relation, A(170)/Amo = 1 - exp(-kItest), where k = 0.092 (scot-td-s)-1. In steady background light, the falling (i.e. recovery) phase of the derived response began earlier, and the sensitivity parameter k was reduced several-fold from its dark-adapted value. As the sensitivity, sensitivity, kinetics, and light-adaptation properties of the derived response correspond closely with those of photocurrent flash responses previously obtained from isolated rods in vitro, it was concluded that the response derived here from the human ERG approximates the course of the massed in vivo rod response to a test flash.

Adaptation, Ocular↗
PubMed2007

Randomized, double-blind, placebo-controlled crossover trials of venlafaxine for hot flashes after breast cancer.

BACKGROUND: Although venlafaxine reduces self-reported hot flashes, no data have established the drug's impact on physiologically documented hot flashes. Two randomized, double-blind, placebo-controlled crossover trials examined the efficacy of two doses of venlafaxine in relation to physiological and self-reported hot flashes and other outcomes, including negative affect, fatigue, sleep, and quality of life. METHODS SAMPLE: 57 breast cancer survivors in the low-dose study; 20 in the high-dose study. SETTING: university cancer clinics in the Southeast and Midwest. INTERVENTION: 37.5 mg of venlafaxine (low-dose study) or 75 mg of venlafaxine (high-dose study). MEASURES: hot flash frequency (physiological monitor, diary, and event marker), hot flash severity (diary), hot flash bother (diary), and questionnaires for hot flash impact on daily life, negative affect, fatigue, sleep, and quality of life. RESULTS: Subjective but not physiological hot flash measures showed placebo effects. Venlafaxine resulted in modest decreases in hot flashes, but only hot flash interference improved differentially at the higher dose. The timing of venlafaxine's effects on hot flashes varied by dose. Only women with a > or =50% decrease in physiological hot flashes experienced significant improvement in fatigue, sleep quality, and quality of life. Although side effects were mild, most patients discontinued venlafaxine long-term. CONCLUSIONS: Although venlafaxine resulted in modest and acute reductions in hot flashes with few side effects, it may not be tolerable to some patients long-term. At least 50% relief in physiological hot flashes may be needed for patients to demonstrate improvement in other outcomes, including decreased fatigue, improved sleep, and improved quality of life.

Adult↗
PubMed2000

Tamoxifen-induced hot flashes.

Hot flashes are the most prominent side effect of tamoxifen, the most frequently prescribed antitumor agent in the world. Little detailed information is available to predict who will develop hot flashes on tamoxifen, to describe the natural history of these hot flashes, and/or to predict who will request therapy for such a side effect. This current trial was developed to address these items. Women who were about to begin adjuvant tamoxifen for locally treated breast cancer were approached for this trial. Before initiating tamoxifen, patients completed a short questionnaire designed to inquire about potential prognostic factors. Upon starting tamoxifen, women were asked to complete a hot flash diary daily for 3 months, and then daily for 1 week of each of the subsequent 9 months. Fifty patients, aged 51-83 years, provided data for this report. Approximately half of the women reported that they did not have any substantial hot flashes while the other half reported hot flashes of variable intensity. On average, these hot flashes gradually increased over 3 months and then plateaued. Baseline factors that appeared to predict for subsequent hot flash problems included a prior history of moderate to severe hot flashes with menopause and a history of prior estrogen therapy use. Overall, 16% of the women reported the desire for therapy for their hot flashes. Thirty-seven and one-half percent of the women (6/16) had a history of both prior estrogen use and moderate to severe hot flashes with menopause as compared to none (0/14) of the women without either of these factors. The data from this study can be utilized to better identify and educate women as to their probability of developing hot flashes after starting tamoxifen, to describe the average time frame for these hot flashes, and to predict the likelihood of whether resultant hot flashes will be substantial enough to have a woman request therapy for them.

Aged↗
PubMed1991

Menopausal hot flashes: Randomness or rhythmicity.

Menopausal hot flashes are episodes of flushing, increased heart rate, skin blood flow and skin temperature, and a sensation of heat. The thermoregulatory and cardiovascular concomitants of hot flashes are associated with peaks in the levels of various hormones and neurotransmitters in the peripheral circulation. Although hot flashes affect about 75% of women, and are the primary reason that women at menopause seek medical attention, the mechanism of hot flashes is still not understood. Hot flashes vary in frequency and intensity both within and between individuals, and have been thought of as occurring randomly. Yet, some women report that their hot flashes are worse at a particular time of day or year. Initial examination of subjects' recordings of their hot flashes showed diurnal patterns of hot flash occurrence. There also seems to be a diurnal rhythm of hot flash intensity. Continuous physiological monitoring of hot flashes is facilitating the analysis of these patterns, which is revealing circadian and ultradian periodicities. The occurrence of hot flashes can be modulated by external and internal factors, including ambient temperature and fever. Rhythms of thermoregulatory and endocrine functions also may influence hot flash patterns. Examination of the interrelationships between the various systems of the body involved in hot flashes, and a multidisciplinary approach to the analysis of hot flash patterns, will aid our understanding of this complex phenomenon.

Journal Article↗
PubMed2000

The role of attention in motion extrapolation: are moving objects 'corrected' or flashed objects attentionally delayed?

Objects flashed in alignment with moving objects appear to lag behind [Nijhawan, 1994 Nature (London) 370 256-257]. Could this 'flash-lag' effect be due to attentional delays in bringing flashed items to perceptual awareness [Titchener, 1908/1973 Lectures on the Elementary Psychology of Feeling and Attention first published 1908 (New York: Macmillan); reprinted 1973 (New York: Arno Press)]? We overtly manipulated attentional allocation in three experiments to address the following questions: Is the flash-lag effect affected when attention is (a) focused on a single event in the presence of multiple events, (b) distributed over multiple events, and (c) diverted from the flashed object? To address the first two questions, five rings, moving along a circular path, were presented while observers attentively tracked one or multiple rings under four conditions: the ring in which the disk was flashed was (i) known or (ii) unknown (randomly selected from the set of five); location of the flashed disk was (i) known or (ii) unknown (randomly selected from ten locations). The third question was investigated by using two moving objects in a cost-benefit cueing paradigm. An arrow cued, with 70% or 80% validity, the position of the flashed object. Observers performed two tasks: (a) reacted as quickly as possible to flash onset; (b) reported the flash-lag effect. We obtained a significant and unaltered flash-lag effect under all the attentional conditions we employed. Furthermore, though reaction times were significantly shorter for validly cued flashes, the flash-lag effect remained uninfluenced by cue validity, indicating that quicker responses to validly cued locations may be due to the shortening of post-perceptual delays in motor responses rather than the perceptual facilitation. We conclude that the computations that give rise to the flash-lag effect are independent of attentional deployment.

Attention↗
PubMed1985

Visual evoked potential correlates of laser flashblindness in rhesus monkeys I. Argon laser flashes.

The visual evoked potential (VEP) in four rhesus monkeys was used to assess the transient loss of visual function resulting from single 100-ms argon laser flashes (476.5 and 514.5 nm) whose energy levels did not exceed the maximum permissible exposure (MPE). VEP's were elicited by high-contrast square-wave test gratings which were phase-reversed at a frequency of 6 Hz, and were recorded using bipolar electrodes implanted in the foveal projection region of area 17. The parameters which were investigated included (1) flash size (focused vs. expanded), (2) position of the electrode's receptive field relative to the position of the flash (0, 1.5, 3.0, and 4.5-deg separation), (3) flash exposure level (50, 5.0, and 0.5% of the MPE), (4) peak wavelength of the test grating (454, 540, and 630 nm), and (5) spatial frequency of the test grating (1.0, 4.0, 6.0, and 12.0 c/deg). The results of the flash-size experiment revealed that the expanded flash, whose retinal diameter was approximately 750 microns, eliminated or severely attenuated the VEP for a longer duration than did the focused flash and also resulted in a more gradual recovery function. The combined results of the flash position and energy level experiments indicated that the effective energy of the focused flash declined rapidly beyond 1.5 deg, but still approximated 4% of its maximum value as far as 4.5 deg from its center. Few, if any, wavelength-specific effects were observed after exposure to either the 476.5- or 514.5-nm flashes, even when the energy of the flashes was reduced to a small fraction of the MPE. Finally, the flash effect was considerably longer in duration for the 12.0 c/deg grating relative to the low and intermediate frequency gratings. In general, the findings suggest that the focused and expanded argon laser flashes produce a VEP suppression whose time course and other characteristics correlate well with those associated with behaviorally observed flashblindness in humans after exposure to intense noncoherent flashes.

Animals↗
PubMed2005

Geographical distribution of hot flash frequencies: considering climatic influences.

Laboratory studies suggest that hot flashes are triggered by small elevations in core body temperature acting within a reduced thermoneutral zone, i.e., the temperature range in which a woman neither shivers nor sweats. In the present study, it was hypothesized that women in different populations develop climate-specific thermoneutral zones, and ultimately, population-specific frequencies of hot flashes at menopause. Correlations were predicted between hot flash frequencies and latitude, elevation, and annual temperatures. Data on hot flash frequencies were drawn from 54 studies. Pearson correlation analyses and simple linear regressions were applied, first using all studies, and second using a subset of studies that included participants only to age 60 (n = 36). Regressions were repeated with all studies, controlling for method of hot flash assessment. When analyses were restricted to studies that included women up to age 60, average temperature of the coldest month was a significant predictor of hot flash frequency (P < 0.01), explaining 29.2% of the variation in hot flash frequency. In a separate equation, the difference between hottest and coldest temperatures was also a significant predictor (P < 0.01), explaining 26.4% of the variation in hot flash frequency. When regressions used all studies but controlled for method of hot flash assessment, average temperature of the coldest month, difference between hottest and coldest temperatures, and mean annual temperature were significant predictors of hot flash frequency. Women reported fewer hot flashes in warmer temperatures, and more hot flashes with increasing seasonality. These results suggest that acclimatization to coldest temperatures or sensitivity to seasonality may explain part of the population variation in hot flash frequency.

Body Temperature Regulation↗
PubMed2000

Impact of hot flashes on quality of life among postmenopausal women being treated for breast cancer.

Hot flashes are among the most commonly reported symptoms among women who have completed treatment for breast cancer. Relatively little is known, however, about hot flashes among women while they are undergoing breast cancer treatment. The present study investigated the prevalence and severity of hot flashes of women during chemotherapy and radiotherapy for breast cancer. We also sought to identify the medical, demographic, and treatment correlates of hot flashes during treatment and to document the impact of hot flashes on quality of life. Seventy postmenopausal women with breast cancer completed a self-report questionnaire packet during chemotherapy and radiotherapy. Forty percent (n = 28) reported hot flashes during the week prior to assessment. Of the 28 women endorsing hot flashes, 25% (n = 7) rated them as severe, 39% (n = 11) rated them as moderate, and 36% (n = 10) rated them as mild. Women with hot flashes were significantly (p < 0.05) younger and reported significantly (p < 0.001) more fatigue, poorer sleep quality, and poorer physical health compared to women without hot flashes. Multivariate analyses revealed that, even after controlling for relevant medical, demographic, and treatment variables, the prevalence of hot flashes significantly (p < 0.05) predicted poorer sleep quality, more fatigue, and worse physical health. The results indicate that hot flashes are experienced by a sizable percentage of postmenopausal breast cancer patients as they undergo treatment. Hot flashes during cancer treatment appear to have a negative impact upon patient quality of life that may be due, in part, to fatigue and interference with sleep. Future research should seek to evaluate interventions to relieve hot flashes during breast cancer treatment as a means of improving patient quality of life.

Aged↗
PubMedDate not supplied

Ambulatory blood pressure and heart rate in relation to hot flash experience among women of menopausal age.

OBJECTIVE: The purpose of this study was to evaluate whether ambulatory blood pressure and heart rate varied with hot flash experience among women of menopausal age. SUBJECTS AND METHODS: A total of 1149 ambulatory blood pressure and heart rate measurements from 20 women aged 44-55 were examined. Women were categorized by hot flash experience as (1) having had hot flashes during the study period (Symptomatic during Study; n = 5; 302 measurements), (2) having a past history of hot flashes, but no hot flashes during the study period (Historically Symptomatic; n = 7; 385 measurements), and (3) never having had a hot flash (Asymptomatic; n = 8; 462 measurements). Using repeated measures, nested ANOVA models that also adjusted for posture, the variation in blood pressure and heart rate associated with hot flash experience over the whole day and by location of measurement (microenvironment) was evaluated. RESULTS: The results show that, overall, systolic pressure did not differ among the hot flash experience groups although the Symptomatic during Study group had higher pressures at work than the other two groups (p<0.01), and tended to have higher pressures during sleep (p<0.08). The sleep diastolic pressure of the Asymptomatic group was significantly lower than that of the women who had hot flashes on the study day (p<0.01), but women who had a past history of hot flashes had slightly lower diastolic pressure (p<0.01) than those in the other two groups overall. Heart rates of the Asymptomatic group, however, were significantly lower (4-6 b.p.m.; p<0.001) in each microenvironment and over the whole day than both groups who had hot flash experience. CONCLUSIONS: These data suggest first that there may be a relationship between the experience of hot flashes and accelerated heart rate, and second that women who do not experience hot flashes may have lower sleep blood pressures than women who do.

Adult↗
PubMedDate not supplied

The role of anxiety and hormonal changes in menopausal hot flashes.

OBJECTIVE: To estimate the association of anxiety with menopausal hot flashes in the early transition to menopause. DESIGN: A randomly identified, population-based cohort of midlife women followed up for 6 years to assess reproductive hormones and other physical, emotional, and behavioral factors. At enrollment, the women were premenopausal, aged 35 to 47 years, and had regular menstrual cycles in the normal range. Enrollment was stratified to obtain equal numbers of African American (n = 219) and white (n = 217) women. RESULTS: At the 6-year endpoint, 32% of the women were in the early transition stage and 20% reached the late menopausal transition or were postmenopausal. Reports of hot flashes increased with the transition stages, which were determined by bleeding patterns. At endpoint, hot flashes were reported by 37% of the premenopausal women, 48% of those in the early transition, 63% of women in the late transition, and 79% of the postmenopausal women. Anxiety scores were significantly associated with the occurrence of hot flashes and were also significantly associated with the severity and frequency of hot flashes (each outcome at P < 0.001). Compared with women in the normal anxiety range, women with moderate anxiety were nearly three times more likely to report hot flashes and women with high anxiety were nearly five times more likely to report hot flashes. Anxiety remained strongly associated with hot flashes after adjusting for menopause stage, depressive symptoms, smoking, body mass index, estradiol, race, age, and time. In a predictive model, anxiety levels at the previous assessment period and the change in anxiety from the previous assessment period significantly predicted hot flashes (P < 0.001). CONCLUSIONS: Anxiety is strongly associated with menopausal hot flashes after adjusting for other variables including menopause stage, smoking, and estradiol levels. Anxiety preceded hot flashes in this cohort. Additional studies are needed to examine the duration of menopausal hot flashes and to determine whether treatments that target anxiety effectively reduce menopausal hot flashes.

Adult↗
PubMed2002

Evidence for an attentional component of the perceptual misalignment between moving and flashing stimuli.

If a pair of dots, diametrically opposed to each other, is flashed in perfect alignment with another pair of dots rotating about the visual fixation point, most observers perceive the rotating dots as being ahead of the flashing dots (flash-lag effect). This psychophysical effect was first interpreted as the result of a perceptual extrapolation of the position of the moving dots. Also, it has been conceived as the result of differential visual latencies between flashing and moving stimuli, arising from purely sensory factors and/or expressing the contribution of attentional mechanisms as well. In a series of two experiments, we had observers judge the relative position between rotating and static dots at the moment a temporal marker was presented in the visual field. In experiment 1 we manipulated the nature of the temporal marker used to prompt the alignment judgment. This resulted in three main findings: (i) the flash-lag effect was observed to depend on the visual eccentricity of the flashing dots; (ii) the magnitude of the flash-lag effect was not dependent on the offset of the flashing dot; and (iii) the moving stimulus, when suddenly turned off, was perceived as lagging behind its disappearance location. Taken altogether, these results suggest that neither visible persistence nor motion extrapolation can account for the perceptual flash-lag phenomenon. The participation of attentional mechanisms was investigated in experiment 2, where the magnitude of the flash-lag effect was measured under both higher and lower predictability of the location of the flashing dot. Since the magnitude of the flash-lag effect significantly increased with decreasing predictability, we conclude that the observer's attentional set can modulate the differential latencies determining this perceptual effect. The flash-lag phenomenon can thus be conceived as arising from differential visual latencies which are determined not only by the physical attributes of the stimulus, such as its luminance or eccentricity, but also by attentional mechanisms influencing the delays involved in the perceptual processing.

Adult↗
PubMed2002

Spatial but not temporal cueing influences the mislocalisation of a target flashed during smooth pursuit.

Human subjects misjudge the position of a target that is flashed during a pursuit eye movement. Their judgments are biased in the direction in which the eyes are moving. We investigated whether this bias can be reduced by making the appearance of the flash more predictable. In the normal condition, subjects pursued a moving target that flashed somewhere along its trajectory. After the presentation, they indicated where they had seen the flash. The mislocalisations in this condition were compared to mislocalisations in conditions in which the subjects were given information about when or where the flash would come. This information consisted of giving two warning flashes spaced at equal intervals before the target flash, of giving two warning beeps spaced at equal intervals before the target flash, or of showing the same stimulus twice. Showing the same stimulus twice significantly reduced the mislocalisation. The other conditions did not. We interpret this as indicating that it is not predictability as such that influences the performance, but the fact that the target appears at a spatially cued position. This was supported by a second experiment, in which we examined whether subjects make smaller misjudgments when they have to determine the distance between a target flashed during pursuit and a reference seen previously, than when they have to determine the distance between the flashed target and a reference seen afterwards. This was indeed the case, presumably because the reference provided a spatial cue for the flash when it was presented first. We conclude that a spatial cue reduces the mislocalisation of targets that are flashed during pursuit eye movements. The cue does not have to be exactly at the same position as the flash.

Cues↗
PubMed1988

Pulsed photoacoustic detection of flash-induced oxygen evolution from intact leaves and its oscillations.

Photoacoustic signals from intact leaves, produced upon excitation with single-turnover flashes, were shown to be dependent on their position in the flash sequence. Compared to the signal obtained from the first flash, all the others were time-shifted and had increased amplitudes. The signal from the third flash had the largest deviation, whereas that from the second flash deviated only minimally. The amplitude difference of the signals relative to that from the first flash was measured at a convenient time point (5 ms) and showed oscillations of period 4, similar to the O(2)-evolution pattern from algae. These oscillations were strongly damped, tending to a steady state from about the seventh flash on. The extra photoacoustic signal (relative to the first flash) was shown to be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, heat treatment, or water infiltration. Its change with flash number, its saturation with increasing flash energy, and the above inhibition criteria indicate that it originates in pulsed O(2) evolution. The sound wave produced by the first flash, however, arose by a photothermal mechanism only, as shown by its linear dependence on the flash intensity and insensitivity to the above treatments. The above flash pattern demonstrates that the photocycle of the S states (i.e., positive charge accumulation before two water molecules can be oxidized in a concerted way to produce molecular oxygen) occurs in intact leaves. It proves the applicability of the photoacoustic method for mechanistic studies of O(2) evolution in leaves under physiological conditions. Water content of leaves is readily measured by this method.

Journal Article↗
PubMed2006

Association between race and hot flashes in midlife women.

OBJECTIVE: Studies suggest that African American women may have a greater risk of hot flashes compared to Caucasian women, but the reasons for this are unknown. This study tested the hypothesis that African American women have an increased risk of hot flashes due to racial differences in risk factors for hot flashes, including high body mass index (BMI) and lower estrogen levels. METHODS: A population-based study was conducted among women aged 45-54 years. Participants were divided into women who reported ever experiencing hot flashes (n=356) and women who reported never experiencing hot flashes (n=257). Participants provided a blood sample for hormone assays, were weighed and measured, and completed a questionnaire. RESULTS: Among peri-menopausal women, African American women were more likely than Caucasian women to report any hot flashes (RR=2.08), severe hot flashes (RR=2.19), and hot flashes for more than 5 years (RR=1.61). The risk ratios for the associations between race and the hot flash outcomes were attenuated after controlling for other important hot flash risk factors (i.e. obesity and low estrogen levels). CONCLUSIONS: African American women have an increased risk of hot flashes compared to Caucasian women due to racial differences in a number of risk factors for hot flashes, including advanced age, obesity, current smoking, less than 12 drinks in the past year, and lower estrogen levels.

Age Distribution↗