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At least 127 records · Page 7Linked to original sources
PubMed1996

Kinetics of desensitization induced by saturating flashes in toad and salamander rods.

1. The suction pipette technique was used to examine the effect of a conditioning pre-flash on the saturation time (tsat) of a bright test flash (intensity 10,000-250,000 isomerizations) delivered to intact salamander or toad rod outer segments. The conditioning flash was delivered 0-60 s before the test flash; its intensity was typically between six and sixty times dimmer than the test flash, and it was sufficient by itself to fully saturate the photocurrent. 2. A saturating pre-flash delivered before a saturating test flash reduced the tsat of the test flash. This was equivalent to a reduction in phototransduction gain (psi). 3. The pre-flash had little effect on tau zero the time constant of decay of the rate-limiting species in photoresponse inactivation (activated rhodopsin or the activated G-protein-phosphodiesterase complex). 4. The tsat declined exponentially as the separation time between a fixed intensity pre-flash and test flash was increased. The time constant (tau p) of decline in tsat was approximately 2.4s. The maximum reduction in tsat corresponded to a reduction in the apparent gain of phototransduction to approximately 0.10 of its original level. This exponential decline is consistent with a [Ca2+]i-mediated effect. 5. We conclude that the rate-limiting step in response inactivation and the step responsible for light-induced gain reduction constitute separate and distinct steps of the phototransduction cascade.

Animals↗
PubMed1998

The general kinetic model of electron transfer in photosynthetic reaction centers activated by multiple flashes.

A new general kinetic model for the functioning of photosynthetic reaction centers (RC) of purple bacteria, under multiple flash activation, has been developed. The model includes the primary electron donor (P870) as well as the primary (QA) and secondary (QB) acceptor quinones. The new features of this general model include: (1) consideration of four different states of the QB binding site (vacant, occupied by QB, by QB- and by QBH2), (2) incorporation of the dark relaxation of the RC between flashes, (3) the assumption of fast exchange of quinones between the RC and quinone pool in detergent micelles or chromatophore membrane, (4) description of the kinetics of electron transfer in both oxidized (no donor for P870+) and reduced (in the presence of donor for P870+) conditions simultaneously, (5) the consideration of both single and multiple flash activation of the RC of purple bacteria and (6) consideration of the cumulative effects of all previous flashes of the series in the response induced by the current flash. This model is used to calculate and predict (1) flash-induced binary oscillations of the secondary acceptor semiquinone (QB-), (2) flash-induced behavior of P870+ in the presence and absence of electron donor and (3) the apparent equilibrium constant of electron transfer between QA and QB and others. Different characteristics of RC are analyzed as a function of flash intensity, time between flashes, concentration of electron donor, redox-potential of the medium, concentration of pool quinone and quinol, association and dissociation equilibrium constants for quinone and quinol at the QB binding site, equilibrium constants of electron transfer between QA- and QB and between QA- and QB-, as well as the rate constants of oxidation of QA- and QB- by redox mediators. The proposed model can be used as a basis for assays of kinetic behavior of native and mutant RC of purple bacteria and for determination of the factors influencing the release of QH2 from RC. The latter is needed for analysis of factors controlling light-activated electron transport in the cytochrome bc1 complexes of purple bacteria by quinol molecules released from RC. The developed general approach for parallel consideration of flash-induced transitions of RC and its following dark relaxation between flashes can also be used for kinetic description of photosynthetic RC of oxygenic photosynthesis.

Electron Transport↗
PubMed2002

The attentional modulation of the flash-lag effect.

If a dot is flashed in perfect alignment with a pair of dots rotating around the visual fixation point, most observers perceive the rotating dots as being ahead of the flashing dot (flash-lag effect). This perceptual effect has been interpreted to result from the perceptual extrapolation of the moving dots, the differential visual latencies between flashing and moving stimuli, as well as the modulation of attentional mechanisms. Here we attempted to uncouple the attentional effects brought about by the spatial predictability of the flashing dot from the sensory effects dependent on its visual eccentricity. The stimulus was a pair of dots rotating clockwise around the fixation point. Another dot was flashed at either the upper right or the lower left of the visual field according to three separate blocked situations: fixed, alternate and random positions. Twenty-four participants had to judge, in all three situations, the location of the rotating dots in relation to the imaginary line connecting the flashing dot and the fixation point at the moment the dot was flashed. The flash-lag effect was observed in all three situations, and a clear influence of the spatial predictability of the flashing dot on the magnitude of the perceptual phenomenon was revealed, independently of sensory effects related to the eccentricity of the stimulus in the visual field. These findings are consistent with our proposal that, in addition to sensory factors, the attentional set modulates the magnitude of the differential latencies that give rise to the flash-lag phenomenon.

Adult↗
PubMed1994

Risk factors for menopausal hot flashes.

OBJECTIVE: To find predictors of hot flashes at natural menopause. METHODS: A cross-sectional sample of 334 black and white, naturally menopausal women was selected from a control group in a population-based study of reproductive cancers in central North Carolina. Women reported whether they had experienced hot flashes at the time of menopause. Life-style factors and reproductive histories of those with and without hot flashes were compared. RESULTS: Compared to women who were older at menopause, those reporting natural menopause before age 52 years had a significantly increased probability of having hot flashes (prevalence ratio 1.5, P = .04). Less than a high school education was significantly related to an increased probability of hot flashes (prevalence ratio 1.4, P = .20). There was significant interaction between cigarette smoking and body mass index (BMI), so that thin women who smoked in the premenopausal period were most likely to experience hot flashes (prevalence ratio 1.9, P = .03). Among non-smokers, BMI appeared to have no effect on the probability of hot flashes. Alcohol use, although not statistically significant, suggested a positive relation with hot flashes over and above that incurred from smoking. In addition, menarche before the age of 12 (prevalence ratio 0.6, P = .08) and a history of irregular menstrual cycles (prevalence ratio 0.6, P = .08) were marginally related to a decreased prevalence of hot flashes. Race, parity, and age at first and last pregnancy had no relation to hot flashes. CONCLUSION: Socioeconomic factors and those related to the decline of estrogen production are related to the occurrence of hot flashes at the time of menopause.

Adult↗
PubMed2004

Hot flashes and sleep in women.

Sleep disturbances during menopause are often attributed to nocturnal hot flashes and 'sweats' associated with changing hormone patterns. This paper is a comprehensive critical review of the research on the relationship between sleep disturbance and hot flashes in women. Numerous studies have found a relationship between self-reported hot flashes and sleep complaints. However, hot flash studies using objective sleep assessment techniques such as polysomnography, actigraphy, or quantitative analysis of the sleep EEG are surprisingly scarce and have yielded somewhat mixed results. Much of this limited evidence suggests that hot flashes are associated with objectively identified sleep disruption in at least some women. At least some of the negative data may be due to methodological issues such as reliance upon problematic self-reports of nocturnal hot flashes and a lack of concurrent measures of hot flashes and sleep. The recent development of a reliable and non-intrusive method for objectively identifying hot flashes during the night should help address the need for substantial additional research in this area. Several areas of clinical relevance are described, including the effects of discontinuing combined hormone therapy (estrogen plus progesterone) or estrogen-only therapy, the possibility of hot flashes continuing for many years after menopause, and the link between hot flashes and depression.

Climacteric↗
PubMed1999

Pilot evaluation of venlafaxine for the treatment of hot flashes in men undergoing androgen ablation therapy for prostate cancer.

PURPOSE: Hot flashes may be a significant clinical problem in men undergoing androgen deprivation therapy with gonadotropin releasing hormone analogues, oral antiandrogens and/or surgical bilateral orchiectomy. Anecdotal information suggests that a low dose of the relatively new antidepressant venlafaxine may abrogate this clinical problem. We developed the current pilot trial to investigate further whether venlafaxine alleviates hot flashes in such men. MATERIALS AND METHODS: The study included men in whom substantial hot flashes were associated with androgen deprivation therapy. Hot flash data were collected by daily diary questionnaires during a 1-week baseline period when no therapy was given for hot flashes, as well as for the next 4 weeks when study participants received 12.5 mg. venlafaxine orally twice daily. Questionnaires completed during the 4 weeks ofvenlafaxine therapy also documented data on potential drug toxicity. RESULTS: Of the 16 evaluable patients who completed the study 10 (63%) had a greater than 50% decrease in hot flash score, as determined using the formula, frequency x severity, by week 4 of treatment versus the baseline week. Median weekly hot flash scores decreased 54% from baseline during week 4 of venlafaxine therapy. Average incidence of severe and very severe hot flashes was reduced from 2.3 daily at baseline to 0.6 daily at study end (p = 0.003). Therapy was generally well tolerated. CONCLUSIONS: Venlafaxine hydrochloride appears to represent an efficacious new method for alleviating hot flashes in men undergoing androgen ablation therapy. Further evaluation of this compound for alleviating hot flashes is indicated.

Aged↗
PubMedDate not supplied

Circadian rhythm of objectively recorded hot flashes in postmenopausal breast cancer survivors.

OBJECTIVE: Similar to the circadian rhythm of core body temperature, hot flashes have been found to exhibit a circadian rhythm in healthy, naturally postmenopausal women, with a peak in frequency at 18:25 h. However, to date, no studies have evaluated whether this same pattern is found among breast cancer survivors reporting hot flashes. DESIGN: Daily hot flash frequencies were measured among 21 postmenopausal breast cancer survivors using validated 24-h sternal skin conductance monitoring. RESULTS: Hot flashes were noted in all women, ranging in frequency from 1 to 30 per 24-h period. A majority of the sample (86%) experienced > or = 1 nighttime hot flash, with 48% exhibiting > or = 3 but < or = 7 nighttime hot flashes. For the total sample, a modest circadian rhythm was noted with a peak in hot flash frequency occurring at 16:10 h. However, significant variability was observed across individual women, and, as a whole, breast cancer survivors demonstrated distorted to obliterated rhythms. CONCLUSIONS: Data suggest that hot flashes in postmenopausal breast cancer survivors do not follow the same circadian pattern as previously seen in healthy, naturally postmenopausal women. Findings have implications for (1) understanding the potential for sleep disturbances and fatigue in breast cancer survivors experiencing hot flashes, and (2) future research examining circadian rhythms of core body temperature and hot flashes in breast cancer survivors.

Body Temperature↗
PubMed2004

Sleep, fatigue, and depressive symptoms in breast cancer survivors and matched healthy women experiencing hot flashes.

PURPOSES/OBJECTIVES: To compare sleep quality and disturbance, fatigue, and depressive symptoms between breast cancer survivors and healthy women experiencing hot flashes and to examine relationships among sleep and remaining variables (fatigue, depressive symptoms, and frequency of hot flashes). DESIGN: Cross-sectional, descriptive, comparative pilot study. SETTING: University-based outpatient setting. SAMPLE: 15 breast cancer survivors and 15 healthy women matched on age, race, and menopausal status. All women had untreated hot flashes (no hormone replacement therapy or other hot flash treatments). METHODS: Questionnaires (sleep quality and disturbance, fatigue, and depression); two ambulatory, 24-hour sternal skin conductance monitoring sessions (hot flash frequency); and medical records review. MAIN RESEARCH VARIABLES: Sleep quality and disturbance, fatigue, depressive symptoms, and objective hot flash frequency. FINDINGS: The majority of participants evidenced poor sleep quality and high sleep disturbance (73% of breast cancer survivors and 67% of healthy women above a cutoff score of 5). Sleep duration was significantly shorter for breast cancer survivors in contrast to healthy women. Nighttime flashes were experienced by 67% of breast cancer survivors and 37% of healthy women. No group differences were found in fatigue, depressive symptoms, or objective hot flash frequency. Global sleep scores were significantly positively correlated with fatigue and depression but not with hot flash frequency. CONCLUSIONS: Findings suggest that sleep disturbance is common in menopausal breast cancer survivors and healthy women, is not necessarily related to hot flashes, and may stem from a multifactorial etiology. IMPLICATIONS FOR NURSING: Menopausal breast cancer survivors who present with any one of these symptoms should be screened for all symptoms both during and after treatment.

Breast Neoplasms↗
PubMed2002

Phase III evaluation of fluoxetine for treatment of hot flashes.

PURPOSE: Hot flashes can be a prominent problem in women with a history of breast cancer. Given concerns regarding the use of hormonal therapies in such patients, other nonhormonal means for treating hot flashes are required. Based on anecdotal information regarding the efficacy of fluoxetine and other newer antidepressants for treating hot flashes, the present trial was developed. PATIENTS AND METHODS: This trial used a double-blinded, randomized, two-period (4 weeks per period), cross-over methodology to study the efficacy of fluoxetine (20 mg/d) for treating hot flashes in women with a history of breast cancer or a concern regarding the use of estrogen (because of breast cancer risk). Eligible patients had to have reported that they averaged at least 14 hot flashes per week; they could have received tamoxifen or raloxifene as long as they were on a stable dose. The major outcome measure was a bivariate construct representing hot flash frequency and hot flash score, analyzed by a classic sums and differences cross-over analysis. RESULTS: Eighty-one randomized women began protocol therapy. By the end of the first treatment period, hot flash scores (frequency x average severity) decreased 50% in the fluoxetine arm versus 36% in the placebo arm. Cross-over analysis demonstrated a significantly greater marked hot flash score improvement with fluoxetine than placebo (P =.02). The results were not adjusted for potential confounding influences, including age and tamoxifen use. The fluoxetine was well tolerated. CONCLUSION: This dose of fluoxetine resulted in a modest improvement in hot flashes.

Adult↗
PubMed2006

Phase III trial of gabapentin alone or in conjunction with an antidepressant in the management of hot flashes in women who have inadequate control with an antidepressant alone: NCCTG N03C5.

PURPOSE: Despite the utility of newer antidepressants for alleviating hot flashes, antidepressants do not work adequately enough in many patients. Gabapentin is a nonhormonal agent that also can reduce hot flashes. No data have been available to address whether the combination of both agents would more effectively alleviate hot flashes, compared with gabapentin alone, in patients with inadequate hot flash control with an antidepressant alone. PATIENTS AND METHODS: This was a randomized trial in which 118 patients with inadequate hot flash control on an antidepressant were randomly assigned to receive both an antidepressant and gabapentin versus being weaned off the antidepressant and receiving gabapentin alone. Patients were observed for 5 weeks (including a baseline week in which patients continued on their current antidepressant without gabapentin) during which time they completed validated daily hot flash diaries. RESULTS: Ninety-one patients provided complete data at the 5-week assessment. Regardless of whether or not the antidepressant was continued when gabapentin was started, there was an approximately 50% median reduction in hot flash frequencies (54%; 95% CI, 34% to 70% for combined treatment v 49%; 95% CI, 26% to 58% for gabapentin alone) and scores (56%; 95% CI, 26% to 71% for combined treatment v 60%; 95% CI, 33% to 73% for gabapentin alone). CONCLUSION: Gabapentin seems to decrease hot flashes by approximately 50% in women with inadequate hot flash control who were using an antidepressant. This study saw no significant additional hot flash reduction from continuation of the antidepressant.

Adult↗
PubMed2006

Association of interleukin-8 with hot flashes in premenopausal, perimenopausal, and postmenopausal women and bilateral oophorectomized women.

OBJECTIVE: The purpose of this study was to identify serum cytokine concentrations in premenopausal, perimenopausal, and postmenopausal women and bilateral oophorectomized women with hot flashes. METHODS: Serum concentrations of 17 cytokines were simultaneously measured using a multiplexed human cytokine assay in 129 premenopausal, perimenopausal, and postmenopausal women and 50 bilateral oophorectomized women. RESULTS: Serum IL-8 concentrations in midlife women and bilateral oophorectomized women with severe hot flashes were significantly higher than the concentrations in women without hot flashes and women with mild and moderate hot flashes. Serum macrophage inflammatory protein-1beta concentration in women with severe hot flashes was significantly higher than those in women without hot flashes and women with mild and moderate hot flashes. CONCLUSION: Serum IL-8 concentrations in premenopausal, perimenopausal, and postmenopausal women and bilateral oophorectomized women with hot flashes were significantly higher than those in women without hot flashes. IL-8 may be associated with peripheral vasodilation in women with hot flashes.

Adult↗
PubMed2001

Momentary increase in plasma calcitonin gene-related peptide is involved in hot flashes in men treated with castration for carcinoma of the prostate.

PURPOSE: In women the vasodilatory neuropeptides calcitonin gene-related peptide and neuropeptide Y seem to be involved in menopausal hot flashes. We assessed whether plasma calcitonin gene-related peptide and neuropeptide Y change during hot flashes in men after castration. MATERIALS AND METHODS: We evaluated 10 men 61 to 81 years old who underwent castration due to cancer of the prostate and had frequent hot flashes for changes in plasma calcitonin gene-related peptide and neuropeptide Y during 1 day at the outpatient clinic. At least 5 blood samples were obtained between flashes and 4 were obtained during each flash. The samples were analyzed for calcitonin gene-related peptide and neuropeptide Y using radioimmunoassay technique. Hot flashes were objectively recorded by measuring peripheral skin temperature and skin conductance. RESULTS: Plasma calcitonin gene-related peptide increased 46% (95% confidence interval 21 to 71) during flashes in the 6 men in whom it was measurable. This change was statistically significant (p = 0.028). The concentration of neuropeptide Y was below the detection limit. Skin conductance and temperature increased significantly during flashes. CONCLUSIONS: Calcitonin gene-related peptide is involved in the mechanisms of hot flashes in men who underwent castration due to prostate carcinoma. Thus, there may be a similar mechanism of hot flashes in women and in men deprived of sex steroids.

Aged↗
PubMed1988

ATP formation onset lag and post-illumination phosphorylation initiated with single-turnover flashes. I. An assay using luciferin-luciferase luminescence.

The great sensitivity of the luciferin-luciferase ATP detection system allows direct observation of ATP formation derived from single-turnover flashes in a thylakoid reaction mixture. The method can measure the energization threshold--the number of flashes required for the initiation of ATP formation--as well as detect post-illumination ATP formation after the last flash of a flash sequence. We describe the characteristics of this post-illumination phosphorylation which can be observed after a series of phosphorylating flashes (PIP+) or when the assay for ATP formation was performed in a "traditional" manner where the ADP and Pi were added after the flash-energization period (PIP-). Comparing PIP+ yields and kinetics of the PIP+ decay under various treatments can give information about membrane energization events only if it is clearly established that different PIP+ yields and decay rates are not due to limitations of the luciferase-catalyzed reaction. Experiments showing that the PIP+ ATP yield and kinetics were due to membrane-limited deenergization events (proton efflux) rather than luciferase limitations include: (1) An uncoupler, nigericin, added after the last flash reduced the PIP+ yield, but had no effect on the luciferase reaction. (2) The kinetics of the luminescence after adding standard ATP were much faster than the PIP+ kinetics. (3) Valinomycin and K+ stimulated the PIP+ yield but had no influence on the luciferase reaction. (4) Lowering the pH from 8 to 7 increased both the PIP- (an assay independent of luciferase kinetics) and the PIP+ ATP yields, an expected result owing to the greater endogenous buffering power encountered by the proton gradient when the external pH is 7. In spite of the last-mentioned point, the threshold flash number for ATP formation onset was the same for pH 7 and 8 (valinomycin, K+ present) at slow flash frequencies. This is consistent with a membrane-localized rather than a delocalized gradient. The accompanying reports (W. A. Beard, G. Chiang and R. A. Dilley, and W. A. Beard and R. A. Dilley, J. Bioenerg. Biomembr.) show that different conditions can lead to observing either localized or delocalized proton gradient coupling in the PIP+ event and the ATP onset threshold flash number.

Adenosine Triphosphate↗
PubMed1978

Synthesis and hydrolysis of ATP by intact chloroplasts under flash illumination and in darkness.

ATP concentrations were measured in isolated intact spinach chloroplasts under various light and dark conditions. The following results were obtained: (1) Even in darkened chloroplasts and in the absence of exogenous substrates, ATP levels in the chloroplast stroma were significant. They decreased on addition of glycerate, phosphoglycerate or dihydroxyacetone phosphate. When dihydroxyacetone phosphate and oxaloacetate were added together, ATP levels increased in darkened chloroplasts owing to substrate level phosphorylation. (2) Under illumination with saturating single turnover flashes, oxygen evolution in the presence of phosphoglycerate, whose reduction requires ATP, was no lower on a unit flash basis at the low flash frequency of 2 Hz than at higher frequencies. Quenching of 9-aminoacridine fluorescence, which indicates the formation of a proton gradient in intact chloroplasts, decreased with decreasing flash frequencies, until there was no significant fluorescence quenching at a flash frequency of about 2 Hz. In contrast to intact chloroplasts, broken chloroplasts did not phosphorylate much ADP at the low flash frequency of 2 Hz. (3) Flashing at extremely low frequencies (0.2 Hz) caused ATP hydrolysis rather than ATP synthesis in intact chloroplasts. At higher flash frequencies, synthesis replaced hydrolysis. Still, even at high frequencies (10 Hz), the first flashes of a series of flashes given after a long dark time always decreased chloroplast ATP levels. From these results, it is concluded that the enzyme, which mediates ATP synthesis in the light, is inactive in darkened intact chloroplasts. Its light activation can be separated from the formation of the high energy condition, which results in ATP synthesis. After its activation, the enzyme catalyzes a reversible reaction.

Adenosine Diphosphate↗
PubMed1983

Postmenopausal flashes: studies of chronological organisation.

The times of occurrence of climacteric flashes were recorded by three women over a period of one month. The mean intervals between flashes were 130 +/- 5, 142 +/- 6 and 67 +/- 3 min (mean +/- S.E.) for the three women. The flashes did not occur simply randomly in time. Following a flash, a period of suppression of the ability to flash again was apparent. No mathematical model was derived which satisfactorily described the incidence of flashing in all three women. However, models assuming suppression of the ability to flash immediately following a flash gave the best fits to our data. This suggest that there is an inhibitory feedback mechanism mediating partial suppression of flashing for at least 30 min after a flash.

Aged↗
PubMed1984

Menopausal hot flashes: thermoregulatory, cardiovascular, and circulating catecholamine and LH changes.

Thermoregulatory, cardiovascular and endocrine changes were simultaneously monitored in 11 post-menopausal women with frequent hot flashes (catecholamine and LH levels were measured in 5 and 6 subjects respectively). Plasma samples were obtained at 1- and 5-min intervals. Hot flashes were accompanied by abrupt increases in plasma epinephrine (about 150%) and concomitant decreases in norepinephrine (about 40%). Increased luteinizing hormone was associated with most hot flashes. A detailed sequence of hot flash-associated changes was established. An aura preceded the onset of the hot flash by several seconds. HR and FBF increased just before the onset of the flash and reached peak levels of 10-20 beats/min and 30-fold respectively. Coincident with vasodilation and sweating, finger temperature increased an average of 3.9 degrees C and esophageal temperature fell 0.2-0.6 degrees C. Flashes of both discrete and prolonged intervals were observed. Sensation was a reliable index of flash occurrence and intensity as measured physiologically. Our observations are consistent with the hypothesis that hot flashes are due to a change in the thermoregulatory set point. Furthermore, the changes in catecholamine levels are consistent with the cardiovascular changes accompanying hot flashes.

Body Temperature Regulation↗
PubMed1993

[Visual compromise of automobile drivers by frontal photo-flash in mesoptic conditions].

The time for recovery of recognition of an optotype presented at a distance of 40 m subsequent to exposure to a flash gun (Eso company, Tettnang; flash energy 200 Ws, duration 1/1000 s; distance 10 m) was studied on 97 subjects aged 20 to 83 years. A Landolt-ring (contrast 1:5, diameter 29 cm), mounted on a disk (diameter 58 cm) which could be rotated in steps of 45 degrees served as a test target. The flash gun could be dimmed down by a red filter (Schott RG 665). The tests were performed at night without additional illumination except the low beam of the car. The flash gun was foveally fixated. After a white flash, a period of 93.1 s +/- 48.6 s (MEAN +/- SD) passed before the optotype could be recognized correctly again. By adding the red filter in front of the flash gun the recovery time could be shortened significantly (p < 0.0001; Wilcoxon signed-rank test) to 4.9 s +/- 1.7 s. "Time for re-adaptation" after dazzling by red flash is comparatively short and therefore strongly influenced by many variables (e.g. time for recognition and for verbalization). Because of that a final evaluation of dazzling by red flash seems to be impossible with this method. Subjects of advanced age and opacities of the ocular media showed an increase in the "time for re-adaptation" for the white as well as the red flash. In conclusion, a speed control using white flash guns at night can be considered as critical.

Adult↗
PubMed1982

The effect of forward and backward masking by flash on apparent size.

Subjects observed a briefly exposed square and set a variable square to match its size. In experiment 1 the square was black or white and was preceded or followed by a flash of light. The preceding adaptation field was complete darkness or an illuminated field. Marked underestimation of size occurred when flash followed the square in all conditions, compared with trials with no flash. Preceding flash produced a small reversal of this effect, the extent of which depended on whether the square was black or white. Absence of an illuminated adaptation field reduced estimates in all conditions except those where flash preceded the square. In experiment 2, a black square was used, and the stimulus duration and the interval between stimulus and flash were varied. No significant effects were found with preceding flash. When flash followed the square, apparent size increased linearly over the first 300 ms with the logarithm of the interval between onset of the square and onset of the flash, then levelled off. Experiment 3 demonstrated that the reduction in apparent size occurred with figure and interfering flash delivered to the same eye but not with dichoptic interference. The results are explained by reference to a suggestion of Georgeson that the optimum frequency of spatially tuned receptors decreases in impoverished viewing conditions. Hence the presented figures trigger receptors which normally are responsive to smaller figures, and the presented figures are therefore categorized as being smaller than they really are.

Female↗