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Biomedical subjects

D E Irwin

Publications and source records attributed to D E Irwin.

At least 37 records · Page 2Linked to original sources
PubMed1997

Utilization and safety of oral acyclovir over an 8-year period.

The primary purpose of this project was to develop and implement surveillance systems to monitor the short- and long-term safety of acyclovir in oral dosage forms in a general population, the Kaiser Permanente Northwest (KPNW) region membership. KPNW is a group model HMO providing comprehensive care to over 390,000 members located primarily in the Portland, Oregon-Vancouver, Washington metropolitan area. Data were collected from the automated outpatient prescription, hospital discharge, tumor registry, KPNW membership information, and from medical record reviews, over an 8-year period. The findings showed oral acyclovir use increased substantially, and females were twice as likely to receive oral acyclovir as males. Most use was short-term. When the hospitalizations of oral acyclovir users with select serious morbidities conditions were examined following the receipt of acyclovir, no temporal association was observed between exposure to oral acyclovir and the hospitalizations. Similarly, where oral acyclovir was being used within a time frame possibly associated with serious life-threatening conditions, other morbidities rather than acyclovir were the likely cause of the condition, and no mention was made in the medical record that acyclovir might have been involved in the condition. In summary, oral acyclovir was a safe drug within the use patterns of the HMO population over an 8-year period.

Journal Article↗
PubMed1997

Self-treatment patterns among clients attending sexually transmitted disease clinics and the effects of self-treatment on STD symptom duration. The Study Group.

OBJECTIVE: To assess patterns of self-treatment and its effects on the duration of sexually transmitted disease (STD) symptoms before medical care. METHODS: A cross-sectional interview survey in public STD clinics (7 U.S. cities). Patients, seeking treatment for STD symptoms or having a known infected sexual contact, reported self-treatment behaviors and symptom duration. Additional data were abstracted from medical charts. RESULTS: Self-treatment, primarily over-the-counter topical medications (54.8%), was reported by 21.8% of 2,508 symptomatic patients. Self-treaters were significantly more likely to be African-American (odds ratio [OR] = 1.8), female (OR = 1.7), over age 30 (OR = 1.3), report > 1 symptom (OR = 1.4), and report a genital lesion (OR = 2.1). Symptom duration was 2 days longer among self-treaters (p < 0.01). African-Americans (OR = 1.5), men (OR = 1.2), and self-treaters of symptoms other than genital lesions (OR = 1.4) had a significantly longer time from symptom onset to receiving medical care. CONCLUSIONS: Self-treatment is common among patients with STDs. Self-treatment of a genital lesion, unlike certain demographic factors and self-treatment of other STD symptoms, did not prolong the time to medical treatment.

Adolescent↗
PubMed1996

Race, age, and cesarean delivery in a military population.

OBJECTIVE: To evaluate the relationship between race, age, and the risk of cesarean delivery. METHODS: This was a cohort study of 3603 nulliparous enlisted United States Navy women who were on active duty and had a singleton delivery between October 1987 and September 1989. Type of delivery and complications of pregnancy, labor, or delivery were identified through hospital discharge diagnoses codes. Demographic risk factors were obtained from military personnel files. RESULTS: Women over age 30 had a significantly increased risk of cesarean delivery (odds ratio [OR] 1.4, 95% confidence interval [CI] 1.1-1.9) compared with women under age 30. Multiple logistic regression modeling adjusted for education, marital status, military rank, type of hospital, and complications of pregnancy, labor and delivery showed African-American women over age 30 to have a significantly increased risk for cesarean delivery (OR 2.2, 95% CI 1.1-4.2) compared with white women over age 30. Among women under 30, African-Americans were not at a greater risk of cesarean delivery (OR 1.1; 95% CI 0.89-1.3). Other demographic factors were not related to the risk of cesarean delivery, but complications of pregnancy, labor, and delivery were strong predictors. CONCLUSION: We observed an increased risk in this unique population over age 30. Active duty military women serve as a useful population to examine demographic differences because of equitable access to medical care.

Adult↗
PubMed1996

What's in an object file? Evidence from priming studies.

Six experiments were conducted to investigate the nature of the contents of object files, temporary representations that store information about objects. Experiment 1 used a lexical priming paradigm with a lexical decision task, in which the prime and target could appear in either the same or different locations. The results indicated a greater priming effect when the prime and target appeared in the same location than when they appeared in different locations (object-or location-specific priming). Experiment 2 replicated these findings for objects that changed position during the display. Experiment 3 demonstrated that these findings reflected the inclusion of abstract identity information, rather than physical form, in object files. Three additional experiments tested for the presence of three types of semantic information (related concepts, semantic features, and category membership) in object files. No object-specific priming effects were found. Taken together, these experiments suggest that an object file includes identity information, but not semantic information. Implications of the results for object file theory are discussed.

Adult↗
PubMed1995

Uncertainty in estimating distances from memory.

Magnitude estimations involving spatial characteristics, such as distance, typically show a compressive function when estimates are made from memory. In particular, as the magnitude of a property grows larger and larger, estimates become more and more inaccurate, with increasing underestimates of the actual magnitude. Previous theories have attempted to explain this difference by supposing that magnitude estimation was accomplished through a reperceptual process, in which the errors of perception are magnified, or a transformation process, in which the memory trace undergoes a consistent alteration toward a more schematic form. The present experiments present evidence in support of an uncertainty hypothesis. When subjects are uncertain of the actual value of a distance, they are forced to guess on the basis of the mean distance they encountered, because they are unable to retrieve the information accurately. When they can retrieve the information, they are more certain and their estimates are more accurate. This hypothesis was also extended to integrative conditions in which the subjects were presented with the stimulus display in a piecemeal fashion. In these cases, distance estimates were derived by combining spatial representations. This method of presentation caused distance estimates to become less accurate.

Attention↗
PubMed1994

Study of occupational risk factors for pregnancy-induced hypertension among active duty enlisted Navy personnel.

The relationship between occupational exposures and the risk of pregnancy-induced hypertension (PIH) was investigated in a cohort of 5,605 enlisted active duty military women who gave birth during a 2-year period of time. A panel of experts, unaware of disease status, classified the women's job titles as "high," "medium," or "low" for a variety of occupational exposures. PIH was identified through hospital discharge ICD-9 diagnosis codes. Nulliparas were found to have a significantly increased risk ratio (RR) for PIH (RR = 2.3) compared with parous women. Nulliparas employed in jobs involving high levels of physical activity were at significantly decreased risk of PIH compared to nulliparas working at low levels of physical activity (construction craftsmen, RR = 0.37; unskilled laborers RR = 0.71). Occupational exposure to hazardous chemicals was not related to risk of PIH. Although the study results are limited by aggregate exposure classification, they suggest no adverse influence of occupational exertion and a possible beneficial role among nulliparas.

Adult↗
PubMed1994

The risk of pregnancy-induced hypertension: black and white differences in a military population.

The relationship between race and risk of pregnancy-induced hypertension was investigated in a cohort of active-duty military women who gave birth during the period 1987 through 1989. Cases were identified through hospital discharge diagnoses and included transient gestational hypertension, pre-eclampsia, eclampsia, and unspecified hypertension complicating pregnancy. Multivariate analysis showed nulliparous Black women to be at a slightly increased risk for all pregnancy-induced hypertension (risk ratio [RR] = 1.2) and for pre-eclampsia (RR = 1.3) compared with nulliparous White women. Black parous women were found to have a slightly reduced risk of all pregnancy-induced hypertension (RR = 0.77) and pre-eclampsia (RR = 0.38) compared with White parous women.

Adolescent↗
PubMed1993

Frames of reference in vision and language: where is above?

Spatial terms such as "above" must be used and interpreted with respect to some frame of reference. Perceptual cues for verticality were varied in four experiments to investigate whether the comprehension and production of "above" is based on a viewer-centered (deictic) frame, an environment-centered (extrinsic) frame, or an object-centered (intrinsic) frame of reference. "Above" was usually interpreted with respect to an environment-centered reference frame, but there was a significant contribution from object-centered reference frames as well; the viewer-centered reference frame made no independent contribution to "above". The meaning of "above" appears not to specify a particular reference frame; rather, selection of a reference frame during spatial assignment determines how spatial terms such as "above" and "below" will be used and interpreted.

Adult↗
PubMed1991

Information integration across saccadic eye movements.

The visual world contains more information than can be perceived in a single glance. Consequently, one's perceptual representation of the environment is built up via the integration of information across saccadic eye movements. The properties of transsaccadic integration were investigated in six experiments. Subjects viewed a random-dot pattern in one fixation, then judged whether a second dot pattern viewed in a subsequent fixation was identical to or different from the first. Interpattern interval, pattern complexity, and pattern displacement were varied in order to determined the duration, capacity, and representational format of transsaccadic memory. The experimental results indicated that transsaccadic memory is an undetailed, limited-capacity, long-lasting memory that is not strictly tied to absolute spatial position. In all these respects it is similar to, and perhaps identical with, visual short-term memory. The implication of these results for theories of perceptual stability across saccades are discussed.

Adult↗
PubMed1991

Duration of visible persistence in relation to stimulus complexity.

Visible persistence refers to the phenomenal impression that a stimulus is still present after its offset. A dispute exists whether visible persistence is due to temporal sluggishness in the visual pathway (neural hypothesis) or whether it is a byproduct of information-extraction processes under cognitive control (process hypothesis). This was investigated by manipulating stimulus complexity in five temporal integration experiments and one recognition memory experiment. According to the process hypothesis, complex stimuli should persist longer than simple stimuli because they require more information extraction. This prediction was not confirmed; in all six experiments, complexity was found to have no reliable effect on the duration of visible persistence. By contrast, and in accordance with earlier findings, complexity was shown to have a significant effect on a short-lived, nonvisible form of memory known as schematic persistenc. This pattern of results supports two major conclusions: First, that the effects of complexity reported in earlier research were probably on schematic--rather than visible--persistence; and second, that visible persistence must be regarded as a residual neural trace of an extinguished stimulus, rather than as a byproduct of information-extraction processes.

Adult↗
PubMed1990

Visual memory and the perception of a stable visual environment.

The visual world appears stable and continuous despite eye movements. One hypothesis about how this perception is achieved is that the contents of successive fixations are fused in memory according to environmental coordinates. Two experiments failed to support this hypothesis; they showed that one's ability to detect a grating presented after a saccade is unaffected by the presentation of a grating with the same spatial frequency in the same spatial location before the saccade. A third experiment tested an alternative explanation of perceptual stability that claims that the contents of successive fixations are compared, rather than fused, across saccades, allowing one to determine whether the world has remained stable. This hypothesis was supported: Experienced subjects could accurately determine whether two patterns viewed in successive fixations were identical or different, even when the two patterns appeared in different spatial positions across the saccade. Taken together, these results suggest that perceptual stability and information integration across saccades rely on memory for the relative positions of objects in the environment, rather than on the spatiotopic fusion of visual information from successive fixations.

Attention↗
PubMed1988

Modern mental chronometry.

Mental chronometry, in which conclusions about human information processing are reached through measures of subjects' reaction time, has contributed substantially to studies of cognition and action. During the evolution of the chronometric paradigm, several key issues have emerged. The issues concern (a) the existence of separable processing stages, (b) the degree to which various stages of processing produce partial outputs before they are completed, and (c) the discrete versus continuous form of the outputs. To obtain added temporal resolution, new reaction-time procedures have been developed, including special response-priming and speed-accuracy decomposition techniques that focus on quantitative patterns of reaction-time distributions and error rates. The present article summarizes these developments, starting with a historical review of chronometric research and proceeding to a survey of recent empirical and theoretical innovations. We also discuss the relevance and potential future impact of complementary work by cognitive psychophysiologists on event-related brain potentials and other physiological variables.

Cognition↗
PubMed1988

Visual masking and visual integration across saccadic eye movements.

The visual world appears unified, stable, and continuous despite rapid changes in eye position. How this is accomplished has puzzled psychologists for over a century. One possibility is that visual information from successive eye fixations is fused in memory according to environmental or spatiotopic coordinates. Evidence supporting this hypothesis was provided by Davidson, Fox, and Dick (1973). They presented a letter array in one fixation and a mask at one letter position in a subsequent fixation and found that the mask inhibited report of the letter that shared its retinal coordinates but appeared to occupy the same position as the letter that shared its spatial coordinates. This suggests the existence of a retinotopic visual persistence at which transsaccadic masking occurs and a spatiotopic visual persistence at which transsaccadic integration, or fusion, occurs. Using a similar procedure, we found retinotopic masking and retinotopic integration: The mask interfered with the letter that shared its retinal coordinates, but also appeared to cover that letter. In another experiment, instead of a mask we presented a bar marker over one letter position, and subjects reported the letter that appeared underneath the bar; subjects usually reported the letter with the same retinal coordinates as the bar, again suggesting retinotopic rather than spatiotopic integration across saccades. In Experiment 3 a bar marker was again presented over one letter position, but in addition a visual landmark was presented after the saccade so that subjects could localize the bar's spatial position; subjects still reported that the letter that shared the bar's retinal coordinates appeared to be under it, but they were also able to accurately specify the bar's spatial position. This ability could have been based on retinal information (the visual landmark) present in the second fixation only, however, rather than spatiotopic visual persistence. Because such a visual landmark was present in the Davidson et al. (1973) experiments, we conclude that their findings can be explained solely in retinotopic terms and provide no convincing evidence for spatiotopic visual persistence. But the exposure parameters that Davidson et al. (1973) and we used were biased in favor of retinotopic, rather than spatiotopic, coding: The stimuli were presented very briefly just before a saccadic eye movement, and subjects are poor at spatially localizing stimuli under these conditions. Thus, in Experiment 4 we presented the letter array about 200 ms before the saccade; then, subjects reported that the letter with the same spatial coordinates as the bar appeared under it.(ABSTRACT TRUNCATED AT 400 WORDS)

Attention↗
PubMed1987

Retinal masking during pursuit eye movements: implications for spatiotopic visual persistence.

White (1976) reported that presentation of a masking stimulus during a pursuit eye movement interfered with the perception of a target stimulus that shared the same spatial, rather than retinal, coordinates as the mask. This finding has been interpreted as evidence for the existence of spatiotopic visual persistence. We doubted White's results because they implied a high degree of position constancy during pursuit eye movements, contrary to previous research, and because White did not monitor subjects' eye position during pursuit; if White's subjects did not make continuous pursuit eye movements, it might appear that masking was spatial when in fact it was retinal. We attempted to replicate White's results and found that when eye position was monitored to ensure that subjects made continuous pursuit movements, masking was retinal rather than spatial. Subjects' phenomenal impressions also indicated that retinal, rather than spatial, factors underlay performance in this task. The implications of these and other results regarding the existence of spatiotopic visual persistence are discussed.

Discrimination Learning↗
PubMed1986

Sensory registration and informational persistence.

The traditional view of iconic memory as a precategorical, high-capacity, quickly decaying visible memory has recently come under attack (e.g., Coltheart, 1980). Specifically, distinctions have been drawn between visible persistence, or the phenomenal trace of an extinguished stimulus, and informational persistence, knowledge about the visual properties of the stimulus. In the present research we tested two alternative conceptions of informational persistence. One conception is that visual information persists in a visual memory that begins at stimulus offset and lasts for 150-300 ms, independently of exposure duration. The second is that informational persistence arises from a nonvisual memory that contains spatial coordinates for displayed items along with identity codes for those items. Three experiments were conducted in which 3 X 3 letter arrays were presented for durations ranging from 50 to 500 ms. A single character mask presented at varying intervals after array offset cued report of an entire row of the array. Comparison of the cued row's masked and unmasked letters revealed that spatially-specific visual (i.e., maskable) information persisted after stimulus offset, regardless of exposure duration. This result favors the visual conception of informational persistence. But there was also support for the nonvisual conception: Accuracy increased and item intrusion errors decreased as stimulus duration increased. The implications of these results for models of informational persistence and for transsaccadic integration during reading are discussed.

Cues↗