Biomedical subjects

Elliot Hirshman

Publications and source records attributed to Elliot Hirshman.

13 recordsLinked to original sources

PubMed2006

Lower blood pressure correlates with poorer performance on visuospatial attention tasks in younger individuals.

The relationship between low blood pressure and cognitive function among younger individuals is not fully understood. While a number of studies have examined hypertensive and hypotensive individuals, particularly in older populations, little attention has been devoted to healthy, young populations. We tested 105 healthy young individuals whose blood pressure levels naturally fell in the below normal-to-normal range. Our primary finding was a positive relation between blood pressure and cognition, as measured by two visuospatial attention tasks. This relation appears to be specific to visuospatial skills, as no relationship was observed between recognition memory and blood pressure. We discuss possible explanations for this positive relationship, such as structural neural mechanisms, and how they apply to the overall blood pressure-cognition relationship.

Adolescent↗

PubMed2006

Combined pharmacological and electrophysiological dissociation of familiarity and recollection.

Dual-process theories of recognition memory hypothesize separate underlying familiarity and recollection processes, but the necessity of multiple processes is debated. Previous research has suggested that scalp-recorded event-related brain potentials (ERPs) may index the activity of separate familiarity and recollection processes. Other research indicates that the amnestic drug midazolam impairs recollection more than familiarity. Here, we used a convergent pharmacological and electrophysiological approach to manipulate and monitor human brain activity and provide evidence for separate processes. Midazolam selectively influenced the putative ERP-correlate of recollection but not the putative ERP-correlate of familiarity. Under control conditions (saline), subjects' accuracy correlated with the recollection-related but not the familiarity-related ERP component, suggesting that recollection was dominant in driving memory. The opposite pattern was observed under midazolam administration, suggesting that when recollection fails, subjects may leverage familiarity to compensate. Thus, in contrast to perspectives holding that familiarity represents the default process, these results suggest that recollection was dominant until its impairment unveiled the influence of familiarity.

Adult↗

PubMed2006

Episodic representations support early semantic learning: evidence from midazolam induced amnesia.

Current controversy exists regarding the role of episodic representations in the formation of long-term semantic memories. Using the drug midazolam to induce temporary amnesia we tested participants' memories for newly learned facts in a semantic cue condition or an episodic and semantic cue condition. Following midazolam administration, memory performance was superior in the episodic and semantic condition, suggesting early semantic learning is supported by episodic representations.

Adult↗

PubMed2006

Midazolam amnesia and short-term/working memory processes.

We examined whether midazolam impairs short-term/working memory processes. We hypothesize that prior dissociations in midazolam's effects on short-term/working memory tasks and episodic memory tasks arise because midazolam has a larger effect on episodic memory processes than on short-term/working memory processes. To examine these issues, .03 mg/kg of participant's bodyweight of midazolam was administered in a double-blind placebo-controlled within-participant design. Performance on the digit span and category generation/recall tasks was examined. The results of Experiment 1 demonstrated that: (1) midazolam impaired performance on the digit span task; (2) midazolam did not impair performance on the category generation task; (3) midazolam impaired performance on the category recall task; and (4) midazolam's effect on category recall was four times as large as its effect on digit span. The results of Experiment 2 demonstrated that midazolam did not impair digit span performance when the digit span task was administered at a later time. These results suggest that midazolam can impair short-term/working memory processes, but these effects are substantially smaller than midazolam's effect on episodic memory processes. Moreover, they demonstrate that conscious awareness of materials during study is not sufficient to produce episodic memory.

Adult↗

PubMed2004

Metamemory without the memory: are people aware of midazolam-induced amnesia?

RATIONALE: Midazolam is a benzodiazepine which produces a dense anterograde amnesia, while permitting relatively well-preserved short-term memory, semantic retrieval, and other higher cognitive functions. Given these preserved abilities, we were interested in whether or not participants given midazolam would be aware of this anterograde amnesia. METHOD: In the present experiment, participants were given midazolam in one testing session and a saline placebo in another. Participants provided judgments-of-learning (JOLs) immediately following study of cue-target pairs. During the test phase of the experiment, confidence levels and feeling-of-knowing (FOK) judgments were collected. RESULTS: Although cued recall performance was substantially impaired in the midazolam condition, mean JOLs were unaffected, indicating participants had little insight into their impairment during the study phase. Participants were relatively accurate in confidence levels and FOK judgments in the midazolam condition. CONCLUSION: When studying items under the influence of midazolam, participants are unaware that their memory will be impaired. Implications for clinical practice and pharmacological studies of amnesia are discussed.

Adult↗

PubMed2004

Evidence that androgenic and estrogenic metabolites contribute to the effects of dehydroepiandrosterone on cognition in postmenopausal women.

Prior studies of the effects of dehydroepiandrosterone (DHEA) on cognition have produced complex and inconsistent results. We hypothesize that these results may arise, in part, because of DHEA's metabolism into estrogens and androgens that produce opposing effects on cognition. Our study administered 50 mg of oral DHEA daily for 4 weeks in a placebo-controlled crossover design to six postmenopausal women. We measured blood levels of androgens (total testosterone, free testosterone, DHEA, DHEAS), estrogens (estradiol, estrone), and cognitive performance on recognition memory, perceptual identification, digit span memory, and visual attentional vigilance under both drug and placebo conditions. Multiple regression models incorporating the factors of age and body mass index (BMI) were used to ascertain the relation between sex steroids and cognitive performance. Our results demonstrated that estrogens produced a positive effect on recognition memory, while androgens produced a negative effect. This pattern reversed in perceptual identification with estrogens producing a negative effect and androgens producing a positive effect. In addition, BMI produced a negative effect on digit span memory, age produced a negative effect on perceptual identification, and androgens produced a negative effect on visual attentional vigilance. These results help, in part, to explain DHEA's complex effects on cognition. The diverse effects of sex steroids across tasks underscore the importance of identifying the specific cognitive mechanisms influenced by sex steroids and emphasizes that one should not expect sex steroids to produce homogeneous effects across cognitive tasks.

Aged↗

PubMed2004

Ordinal process dissociation and the measurement of automatic and controlled processes.

The process-dissociation equations (L. Jacoby, 1991) have been applied to results from inclusion and exclusion tasks to derive quantitative estimates of the influence of controlled and automatic processes on memory. This research has provoked controversies (e.g., T. Curran & D. Hintzman, 1995) regarding the validity of specific assumptions underlying the process-dissociation equations. In this article, the author explores the conclusions one can draw about the ordinal relations between automatic and controlled processes across experimental conditions from results in the inclusion and exclusion tasks. Given relatively neutral assumptions, this article presents and proves 6 theorems that allow investigators to draw conclusions about the ordinal relations between automatic and/or controlled processes across experimental conditions. An illustrative example is presented, and the current approach is compared with the original process-dissociation framework.

Automatism↗

PubMed2004

The effect of tobacco abstinence on recognition memory, digit span recall, and attentional vigilance.

This article examines the effects of tobacco abstinence on recognition memory, digit span recall, and visual attentional vigilance. The results demonstrated that abstinence impaired recognition memory discrimination (ad libitum d' =.85, abstinent d' =.64), recognition memory hit rates (ad libitum =.60, abstinent =.54), accuracy of target detection in attentional vigilance (ad libitum =.99, abstinent =.97), and speed of target detection in attentional vigilance (ad libitum = 662 ms, abstinent = 687 ms). Abstinence did not impair digit span recall (ad libitum =.55, abstinent =.56). These results are consistent with the hypotheses that tobacco abstinence impairs episodic memory and sustained attention. They also suggest that some, but not necessarily all, short-term memory processes may not be influenced by tobacco abstinence.

Adult↗

PubMed2004

The effect of midazolam on implicit and explicit memory in category exemplar production and category cued recall.

Transfer-appropriate processing theory (Roediger, Weldon, & Challis, 1989) proposes that dissociations between performance on explicit and implicit memory tests arise because these tests often rely on different types of information processing (e.g., perceptual processing vs conceptual processing). This perspective predicts that implicit and explicit memory tasks that rely primarily on conceptual processing should show comparable results, not dissociations. Numerous studies have demonstrated such similarities. It is, however, possible that these results arise from explicit memory contamination of performance on implicit memory tasks. To address this issue, an experiment was conducted in which participants were administered the sedative midazolam prior to study. Midazolam is known to create a temporary, but dense, period of anterograde amnesia. The effects of blocking stimulus materials by semantic category at study and generation at study were investigated on category exemplar production and category-cued recall. The results of this study demonstrated a dissociation of the effects of midazolam on category exemplar production and category-cued recall. Specifically, midazolam reduced the effect of blocking stimulus materials in category-cued recall, but not in category exemplar production. The differential effect of midazolam on explicit and implicit memory is at odds with transfer-appropriate processing theory and suggests that theories of memory must distinguish the roles of different types of conceptual processing on implicit and explicit memory tests.

Analysis of Variance↗

PubMed2003

Midazolam amnesia and retrieval from semantic memory: Developing methods to test theories of implicit memory.

Studies of organic anterograde amnesia have been central to the development of theories of implicit memory. Pharmacological amnesia provides an additional method for exploring implicit memory, allowing for the experimental manipulation of amnesia and the testing of more participants. A significant concern with pharmacological amnesia is whether its cognitive effects are specific to explicit memory. The current research examines the effects of the benzodiazepine, midazolam, on retrieval from semantic memory and encoding in explicit memory. We focus on midazolam because it holds significant advantages over other benzodiazepines in inducing pharmacological amnesia and prior research suggests it may be useful for testing theories of implicit memory. Our results demonstrate that midazolam does not impair accuracy of retrieval from semantic categories, even when it produces anterograde amnesia for retrieved category items on a later recall test. These results suggest ways midazolam can be used to help test theories of implicit memory.

Adult↗

PubMed2003

The effect of midazolam on conscious, controlled processing: evidence from the process-dissociation procedure.

The benzodiazepine midazolam produces a dense anterograde amnesia. Recent findings (see, e.g., Hirshman, Passannante, & Arndt, 2001) have demonstrated that midazolam produces larger impairments on explicit memory tests such as free recall and recognition memory than on implicit memory tests such as perceptual identification and free association. Such findings suggest that midazolam impairs conscious, controlled memory processes. In the present experiments, we used Jacoby's (1991, 1998) process-dissociation procedure to examine this hypothesis. Our results demonstrate that midazolam increases the production of old items on the exclusion task and reduces the production of old items on the inclusion task. Moreover, generation effects, hypothesized to arise from conscious processes, are reduced by midazolam on both tasks. Analyses using both independence and redundancy models of the process-dissociation procedure confirm the conclusion that midazolam impairs conscious memory processes.

Consciousness↗

PubMed2003

The effect of dehydroepiandrosterone (DHEA) on recognition memory decision processes and discrimination in postmenopausal women.

In this article, the theoretical distinction between recognition memory decision and discrimination processes is used to explore the effect of dehydroepiandrosterone (DHEA) in postmenopausal women. DHEA is an adrenal steroid that diminishes with aging. It has enhanced memory in laboratory animals. An 8-week placebo-controlled, double-blind experiment in which 30 women (ages 39-70) received a 50-mg/day oral dose of DHEA for 4 weeks demonstrated that DHEA made subjects more conservative (i.e., less likely to call test items "old") in their recognition memory decisions and enhanced recognition memory discrimination for items presented briefly. The former result may reflect an empirical regularity (Hirshman, 1995) in which recent strong memory experiences make participants more conservative. The latter result may reflect the effect of DHEA on visual perception, with consequent effects on memory. These results suggest the methodological importance of focusing on decision processes when examining the effects of hormones on memory.

Administration, Oral↗

PubMed2003

A paradoxical dissociation in the effects of midazolam on recollection and automatic processes in the process dissociation procedure.

This study used midazolam-induced amnesia to explore the plausibility of the estimates provided by the process dissociation procedure (PDP), which is designed to estimate the contributions of recollection (R) and automatic (A) processes to implicit memory performance. In a double-blind, placebo-controlled, within-subject design with 24 participants, single midazolam doses were administered intravenously, and word stem completion performance was used to calculate PDP estimates. A dissociation was observed such that midazolam decreased R but increased A estimates relative to placebo. Given that a manipulation that induces amnesia would not be expected to facilitate a memory process, these results add to the accumulating body of evidence suggesting that PDP estimates are not always theoretically plausible. Such evidence raises important questions about the use of the PDP.

Adult↗