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Biomedical subjects

D E Meyer

Publications and source records attributed to D E Meyer.

At least 37 records · Page 2Linked to original sources
PubMed1989

Prescription drug use patterns of human immunodeficiency virus-infected patients taking zidovudine. Walter Reed Retrovirus Research Group.

Prescription drug profiles of 116 human immunodeficiency virus (HIV)-infected patients taking zidovudine in 1988 were surveyed. Patients received the drug an average of 236 days. About one-third (32 percent) required reduced dosage presumably because of hematologic toxicity and this was associated with length of time on the drug. Zidovudine dosage reduction was not associated with concurrent therapy with either acetaminophen or acyclovir. Concomitant drug therapy was common, especially with systemic antifungals (47 percent), antivirals (33 percent), nonsteroidal antiinflammatory drugs (23 percent), and antidepressants (20 percent), as well as topical fungicides (35 percent) and antiinflammatory agents (28 percent). Over three-fourths of patients on zidovudine were on chemoprophylaxis for Pneumocystis carinii pneumonia, most often with pentamidine inhalation therapy. This study showed that the HIV-infected patient population is being treated concomitantly with many pharmacologic agents prescribed by various medical specialties.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Impact of HIV infection on pharmaceutical services at Walter Reed Army Medical Center.

Services developed by the pharmacy department at Walter Reed Army Medical Center (WRAMC) relating to the treatment and study of patients infected with the human immunodeficiency virus (HIV) are described. The WRAMC pharmacy department closely monitored use of azidothymidine (renamed zidovudine) before and after its approval by FDA. It has also done pharmaceutical cost studies for HIV-infected patients by disease stage according to the Walter Reed Classification System. An Army pharmacist at the U.S. Army Centralized Allergen Extract Laboratory is involved with the development and distribution of delayed hypersensitivity skin tests used to determine the progression of the disease; the current test battery correlates with the CD4 T-lymphocyte count, low numbers of which indicate disease progression. The Walter Reed Retrovirus Research Group includes an Army pharmacist who not only is involved with the traditional distributive and clinical aspects of the position but also is involved in clinical pharmacy, pharmacoepidemiology, and social and behavioral research. This pharmacist is the principal investigator on protocols studying the relationship of various factors to the frequency and distribution of both beneficial and adverse pharmaceutical outcomes in this patient population. The pharmacy department at WRAMC has taken an active role in both the treatment of HIV-infected patients and HIV-associated research, as part of an aggressive overall Army effort to develop effective treatment and chemoprophylaxis or immunoprophylaxis for this disease.

Acquired Immunodeficiency Syndrome↗
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

Impulsivity and speed-accuracy tradeoffs in information processing.

Despite its theoretical importance for such areas of research as reflection-impulsivity (Kagan, 1966), there is little evidence to support the assumption that individual differences in the personality trait of impulsivity are associated with differences in the willingness to sacrifice accuracy for speed of information processing. The present studies explored this association further. In Experiment 1, high, medium, and low impulsives (identified by self-report) performed a visual-comparison task under conditions differing in the monetary payoff for speed relative to accuracy. High impulsives were consistently faster and less accurate than other subjects. However, an analysis based on Sternberg's (1969) additive-factor method indicated that high impulsives performed at least one stage of information processing as slowly and accurately as other subjects. In Experiment 2, it was found that high impulsives were actually more accurate than low impulsives when all subjects were required to process information extremely rapidly. Experiment 3 identified the response execution stage as one that high impulsives carry out just as slowly and accurately as other individuals. The data from these experiments pose problems for a simple speed-accuracy tradeoff model of impulsive cognitive functioning.

Adult↗
PubMed1988

Dynamics of activation in semantic and episodic memory.

Spreading-activation models for the structure of semantic and episodic memory postulate a network of interconnected nodes in which activation spreads from a source node to recipient nodes. These models account for a broad range of memory-related processes, including word recognition, sentence verification, prose comprehension, and sentence production. A fundamental question regarding this account concerns the nature of activation growth at each node in the network. Two mutually exclusive possibilities are (a) that activation grows in a discrete fashion, making abrupt transitions between two or more distinct states and (b) that activation grows continuously from a resting level to an asymptotic level. In the present article, we characterize this dichotomy with examples from the literature, and we apply an adaptive priming procedure for testing discrete versus continuous activation models. Our procedure involves the presentation of prime stimuli at various moments before a test stimulus; subjects are required to make a lexical (word/nonword) decision about the test stimulus. The duration of the interval between the prime and test stimuli is varied adaptively on the basis of subjects' performance. Reaction times are recorded as a function of this duration. According to discrete activation models, there is a unique reaction-time distribution associated with each possible state of node activation. The distribution of reaction times observed when the test stimulus appears near the moment of transition between discrete states should therefore constitute a finite mixture of the underlying basis distributions associated with the individual discrete activation states. The mixture proportion will depend on the relation between the priming interval and the distribution of state-transition times. Continuous activation models assert instead that activation grows continuously over time and that there is a unique reaction-time distribution associated with any given degree of intermediate priming. Such models predict that no finite mixture distribution will emerge when the priming interval has a fixed intermediate duration. Two experiments with the adaptive priming procedure are reported to test these alternative predictions. In Experiment 1, the prime and test stimuli were semantically associated words (e.g., bread-butter). In Experiment 2, episodic associations between the prime and test stimuli were established through paired associate learning. For both cases, the mixture prediction failed, and two-state discrete activation models were rejected.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1987

Structure and process in semantic memory: new evidence based on speed-accuracy decomposition.

Reaction-time and accuracy data obtained from studies of sentence verification have not been rich enough to answer certain important theoretical questions about structures and processes in human semantic memory. However, a new technique called speed-accuracy decomposition (Meyer, Irwin, Osman, & Kounios, 1986) may help solve this problem. The technique allows intermediate products of sentence verification to be analyzed more precisely. Three experiments with speed-accuracy decomposition indicate that verification processes produce useful partial information before they are completed. Such information appears to accumulate continuously at a rate whose magnitude depends on the degree of relatedness between semantic categories. This outcome is consistent with continuous computational (e.g., semantic-feature comparison) models of semantic memory. An analysis of reaction-time minima suggests that a discrete all-or-none search process may also contribute at least occasionally to sentence verification. Further details regarding the nature of these processes and the memory structures on which they operate can be inferred from additional results obtained through speed-accuracy decomposition.

Humans↗
PubMed1987

Activation and metacognition of inaccessible stored information: potential bases for incubation effects in problem solving.

Two experiments were conducted with a hybrid procedure that involved a battery of indirect criterion tests designed to study the activation and metacognition of inaccessible stored information. In each experiment, subjects first attempted to recall some rare target words in response to a series of definitions meant to cue retrieval from long-term semantic memory. For the words that could not be recalled initially, the subjects rated their feelings of knowing. They then performed a lexical-decision task in which the target words and other control words were presented. Reaction times were measured as a function of the feeling-of-knowing ratings and the length of the interval between the initial exposure to the definitions and the subsequent lexical decisions. Faster decisions occurred for the target words than for the controls, especially when strong feelings of knowing had been expressed about the targets. Similar facilitation was obtained in a subsequent old-new recognition task. It appears that unsuccessful attempts to retrieve inaccessible stored information prime the later recognition of the information through a process of spreading activation. Such activation may sensitize people to future occurrences of stimulus inputs needed for insightful solutions of semantically rich problems.

Cognition↗
PubMed1986

The point of no return in choice reaction time: controlled and ballistic stages of response preparation.

A countermanding procedure and race model are used to assess separately the effects of experimental factors before and after the "point of no return" in response preparation. The results reveal details about processes that so closely precede the initiation of movement that they cannot be inhibited. These processes appear to be affected by the repetition of stimulus-response pairs, but not by the physical or semantic properties of the stimuli. A model of response preparation is supported in which response inhibition depends upon the outcome of a race between independent excitatory and inhibitory processes, and reaction time is the sum of the durations of at least two stages, separated by the point of no return.

Choice Behavior↗
PubMed1984

Perceptual-motor processing of phonetic features in speech.

Some reaction time experiments are reported on the relation between the perception and production of phonetic features in speech. Subjects had to produce spoken consonant-vowel syllables rapidly in response to other consonant-vowel stimulus syllables. The stimulus syllables were presented auditorily in one condition and visually in another. Reaction time was measured as a function of the phonetic features shared by the consonants of the stimulus and response syllables. Responses to auditory stimulus syllables were faster when the response syllables started with consonants that had the same voicing feature as those of the stimulus syllables. A shared place-of-articulation feature did not affect the speed of responses to auditory stimulus syllables, even though the place feature was highly salient. For visual stimulus syllables, performance was independent of whether the consonants of the response syllables had the same voicing, same place of articulation, or no shared features. This pattern of results occurred in cases where the syllables contained stop consonants and where they contained fricatives. It held for natural auditory stimuli as well as artificially synthesized ones. The overall data reveal a close relation between the perception and production of voicing features in speech. It does not appear that such a relation exists between perceiving and producing places of articulation. The experiments are relevant to the motor theory of speech perception and to other models of perceptual-motor interactions.

Adaptation, Physiological↗
PubMed1976

Meaning, memory structure, and mental processes.

Although people experience little difficulty in recognizing printed words and comprehending sentences, they cannot do it instantaneously. Experimental psychologists have recently measured the speed of these mental processes by applying a reaction-time method. The method provides new data concerning the organization and retrieval of familiar semantic information in human memory. It has been found that close relations between the meanings of words help people to recognize and pronounce the words faster, especially when the words are hard to see because of visual distortions. Close relations between word meanings also facilitate the comprehension of some sentences, as indicated by how long a person takes to decide whether the sentences are true or false. The facilitation is not universal, however. When the relation between the meanings of two words must be analyzed carefully, their proximity may actually inhibit mental processing. These results, along with additional findings, support the hypothesis that human memory includes a semantic network that represents various categories of objects at distinct locations linked to specify their relations with each other. The memory structure probably influences a number of different mental processes that use it. One possible access route to the network is through a set of detectors designed to accumulate sensory information and signal the presence of particular words. There also appear to be processes for searching and comparing pieces of knowledge after a person finds the memory locations of designated categories. Further research using the reaction-time method may provide a more detailed inventory of what facts are retrieved directly from memory and what are computed from other stored information (36).

Humans↗
PubMed1976

Lexical ambiguity, semantic context, and visual word recognition.

Some alternative hypotheses about the recognition of ambiguous words are considered. According to the selective-access hypothesis, prior semantic context biases people to access one meaning of an ambiguous word rather than another in lexical memory during recognition. In contrast, the nonselectiveaccess hypothesis states that all meanings of the word are accessed regardless of the context. We tested certain versions of these hypotheses by having students decide whether selected strings of letters were English words. The stimuli included test sequnces of three words in which the second word had two distinct possible meanings, whereas the first and third words were related to these meanings in various ways. When the first and third words were related to the same meaning of the ambiguous second word (e.g., SAVE-BANK-MONEY), the reaction time to recognize the third word decreased. But when the first and third words were related to different meanings of the second word (e.g., RIVER-BANK-MONEY), the reaction time for the third word was not reliably different from a control sequence with unrelated words. These and other data favor the selective-access hypothesis. Selective access to lexical memory is discussed in relation to models of word recognition.

Adolescent↗