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Biomedical subjects

Ulrich Mayr

Publications and source records attributed to Ulrich Mayr.

16 recordsLinked to original sources
PubMed2006

On how to be unpredictable: evidence from the voluntary task-switching paradigm.

The voluntary task-switching paradigm requires subjects to select randomly between tasks and promises to provide a window into executive task selection independent of exogenous influences present in standard task-switching situations. We show here that the degree to which subjects perseverate on tasks across trials captures unique individual differences variance, but also that the switch rate is under strong stimulus-driven control: "Voluntary" switches are much more frequent when the stimulus changes than when it repeats. Most important, we show that individuals whose no-switch trials are selectively slowed exhibit less perseveration and stimulus-driven effects (and thus more voluntary selection) than individuals whose no-switch trials do not show this slowing. We suggest that selective slowing indicates a strategy of treating trials as discrete events--possibly through inhibition of the preceding task set. These results not only demonstrate massive nonvoluntary influences on voluntary selection that are largely untapped by standard task-switching measures, but also show how such influences can be counteracted through strategic adaptations.

Adult↗
PubMed2006

Dissociating task-set selection from task-set inhibition in the prefrontal cortex.

Patients with focal lesions in the left (n=7) and right (n=4) prefrontal cortex were compared with controls (n=16) in a task-switching experiment using four different, simple spatial tasks. Each of these tasks involved a left-right decision, either regarding an arrow, the word "left" or "right," a circle position, or the direction of a moving line. We compared performance on trials that required rule switches versus rule repetitions (local switch costs) and we compared performance between blocks with bivalent stimuli (two dimensions present) and blocks with univalent stimuli (only one dimension present) to assess global switch costs. Patients with left prefrontal lesions, but not patients with right prefrontal lesions, exhibited increased costs on trials in which the relevant dimension switched (local switch costs), but also on no-switch trials with bivalent stimuli (global costs). We also assessed task-set inhibition in the form of the backward-inhibition effect [increased response times to recently abandoned tasks; Mayr, U., & Keele, S. Changing internal constraints on action: The role of backward inhibition. Journal of Experimental Psychology: General, 129, 4-26, 2000]. Although left frontal patients showed normal inhibition, right frontal patients showed no evidence for inhibition. These results suggest a neurocognitive dissociation between task-set selection and inhibition.

Acoustic Stimulation↗
PubMed2006

Psychological processes and neural mechanisms for action: the legacy of Steven W. Keele.

The recent untimely illness and death of Steven W. Keele is a great loss for psychology in general and for the field of motor control in particular. Steve Keele was a pioneer in the study of the psychological processes and neural mechanisms underlying attention and motor control. Steve was a Consulting Editor for the Journal of Motor Behavior from 1969 to 1974 and served on the Editorial Board from 1974 to 1977, and again from 1980 until his retirement in 1997. Steve served as head of the University of Oregon Psychology Department from 1992-1995, and, although he retired in 1997, he continued to perform important research until he became ill in early 2005.

History, 20th Century↗
PubMed2005

Outsourcing control to the environment: effects of stimulus/response locations on task selection.

Response-time and accuracy costs as assessed in the context of the task-switching paradigm are usually thought to represent processes involved in the selection of abstract task sets. However, task sets are also applied to specific stimulus and response constellations, which in turn may become associated with task-set representations. To explore the consequence of such associations, we used a task-switching paradigm in which subjects had to select between two tasks (color or orientation discrimination) that were either associated with shared or unique stimulus/response locations on a touchscreen. When each task was associated with unique locations, error switch costs, stimulus-response congruency effects, as well as the characteristic task-switch x repetition-priming interaction were eliminated, and global selection costs were substantially reduced. These results demonstrate that to understand standard task-switching phenomena it is critical to consider links between lower level stimulus/response parameters and task sets.

Choice Behavior↗
PubMed2005

Timing, sequencing, and executive control in repetitive movement production.

The authors demonstrate that the timing and sequencing of target durations require low-level timing and executive control. Sixteen young (M-sub(age) = 19 years) and 16 older (M-sub(age) = 70 years) adults participated in 2 experiments. In Experiment 1, individual mean-variance functions for low-level timing (isochronous tapping) and the sequencing of multiple targets (rhythm production) revealed (a) a dissociation of low-level timing and sequencing in both age groups, (b) negligible age differences for low-level timing, and (c) large age differences for sequencing. Experiment 2 supported the distinction between low-level timing and executive functions: Selection against a dominant rhythm and switching between rhythms impaired performances in both age groups and induced pronounced perseveration of the dominant pattern in older adults.

Adolescent↗
PubMed2005

Sticky rules: integration between abstract rules and specific actions.

The authors manipulated repetitions and/or changes of abstract response rules and the specific stimulus- response (S-R) associations used under these rules. Experiments 1 and 2, assessing trial-to-trial priming effects, showed that repetition of complete S-R couplings produced only benefits when the rule also repeated (i.e., rule-S-R conjunctions) but costs when identical S-R couplings repeated while rules changed. In Experiments 3 and 4, the authors manipulated amount of experience with specific rule-S-R conjunctions and demonstrated integration between rules and S-R couplings in terms of cumulative practice effects. However, unlike short-term priming effects, cumulative practice supported generalization of experience with specific S-R couplings across rule boundaries (Experiment 4). Results are discussed in terms of constraints on models of hierarchical control and in terms of qualitatively different ways in which people profit from very recent experiences (i.e., all-or-none access to working memory representations) versus cumulative experience (i.e., similarity-based retrieval from long-term memory).

Choice Behavior↗
PubMed2005

Cognitive change in aging: identifying gene-environment correlation and nonshared environment mechanisms.

We describe gene-environment processes that may help account for individual differences in successful aging. Our emphasis is on successful aging in the cognitive domain, wherein individuals come to use a variety of strategies to cope with changes in cognitive capacities. We focus on the role of executive control in particular and define gene-environment correlation and nonshared environmental mechanisms. The quantitative genetic methods used to identify these mechanisms are described, with examples from research in childhood, where such studies are now common. Future work will be most effective if it is guided by life-span development frameworks that address these processes, such as the developmental genotype-->environment theory of Scarr and McCartney and the selection/optimization/compensation theory of Baltes and Baltes.

Aging↗
PubMed2005

On the role of verbalization during task set selection: switching or serial order control?

Recent task-switching work in which paper-and-pencil administered single-task lists were compared with task-alternation lists has demonstrated large increases in task-switch costs with concurrent articulatory suppression (AS), implicating a crucial role for verbalization during switching (Baddeley, Chincotta, & Adlam, 2001; Emerson & Miyake, 2003). Experiment 1 replicated this result, using computerized assessment, albeit with much smaller effect sizes than in the original reports. In Experiment 2, AS interference was reduced when a sequential cue (spatial location) that indicated the current position in the sequence of task alternations was given. Finally, in Experiment 3, switch trials and no-switch trials were compared within a block of alternating runs of two tasks. Again, AS interference was obtained mainly when the endogenous sequencing demand was high, and it was comparable for no-switch and switch trials. These results suggest that verbalization may be critical for endogenous maintenance and updating of a sequential plan, rather than exclusively for the actual switching process.

Choice Behavior↗
PubMed2005

The power of a story: new, automatic associations from a single reading of a short scenario.

The implicit association test (IAT) is typically used to assess nonconscious categorization judgments that are "under control of automatically activated evaluation" (Greenwald, McGhee, & Schwartz, 1998, p. 1464) and that are usually considered independent of explicit judgments. The present study builds on recent work suggesting evidence of short-term modifiability of the IAT effect. Specifically, we show that reading a short text that describes a novel, fictional scenario, within which the to-be-evaluated categories are embedded, can produce substantial and immediate modulations of the IAT effect. This modulation effect does not occur when subjects are simply instructed to think about counterstereotypical associations (Experiment 1A and 1B). In Experiment 2, we use a variant of the IAT to show that scenario modulation cannot be explained in terms of strategic criterion shifts. These results suggest that a newly acquired knowledge structure targeting the abstract, category level can produce behavioral effects typically associated with automatic categorization.

Adult↗
PubMed2004

Conflict, consciousness, and control.

To what degree is executive conflict resolution dependent on conflict awareness? A recent study by Dehaene et al. compared neural responses to conflict elicited through either visible or subliminal primes. Despite behavioral conflict effects for both prime types, neural activity in a control network including the anterior cingulate cortex (ACC) was present only for visible primes. Along with other recent results, these findings have important implications for theories on the relationship between ACC, consciousness, and cognitive control.

Awareness↗
PubMed2003

The cognitive and neural architecture of sequence representation.

The authors theorize that 2 neurocognitive sequence-learning systems can be distinguished in serial reaction time experiments, one dorsal (parietal and supplementary motor cortex) and the other ventral (temporal and lateral prefrontal cortex). Dorsal system learning is implicit and associates noncategorized stimuli within dimensional modules. Ventral system learning can be implicit or explicit It also allows associating events across dimensions and therefore is the basis of cross-task integration or interference, depending on degree of cross-task correlation of signals. Accordingly, lack of correlation rather than limited capacity is responsible for dual-task effects on learning. The theory is relevant to issues of attentional effects on learning; the representational basis of complex, sequential skills; hippocampal-versus basal ganglia-based learning; procedural versus declarative memory; and implicit versus explicit memory.

Cognition↗
PubMed2003

Differential effects of cue changes and task changes on task-set selection costs.

A task-switching paradigm with a 2:1 mapping between cues and tasks was used to separate cue-switching processes (indexed through pure cue-switch costs) from actual task-switching processes (indexed through additional costs in case of cue and task changes). A large portion of total switch costs was due to cue changes (Experiments 1 and 2), and cue-switch costs but not task-switch costs were sensitive to effects of practice (Experiment 1) and preparation (Experiment 2). In contrast, task-switch costs were particularly sensitive to response-priming effects (Experiments 1 and 2) and task-set inhibition (Experiment 3). Results suggest two processing stages relevant during task-set selection: cue-driven retrieval of task rules from long-term memory and the automatic application of rules to a particular stimulus situation.

Choice Behavior↗
PubMed2002

On the dissociation between clustering and switching in verbal fluency: comment on Troyer, Moscovitch, Winocur, Alexander and Stuss.

Troyer, Moscovitch, Winocur, Alexander and Stuss (Neuropsychologia 36 (1998) 499) used a procedure originally introduced by Troyer, Moscovitch and Winocur (Neuropsychology 11 (1997) 138) for distinguishing two different components of verbal fluency-clustering and switching-in frontal and temporal-lobe patients. Application of this procedure yielded results that suggested a frontal-lobe switching deficit, but intact 'clustering'. I demonstrate here that the proposed procedure may lead to incorrect conclusions because it does not allow an unambiguous dissociation between a general reduction in processing speed and a selective switching deficit. Some implications of this critique for inferences about the neurocognitive components involved in verbal fluency tasks are discussed.

Adult↗
PubMed2002

Inhibition of action rules.

Inhibition is often proposed as an important executive-control process, but its existence is difficult to establish empirically. Recently, Mayr and Keele (2000) reported that it takes longer to switch to a recently disengaged task set (i.e., n - 2 task-set repetitions) than to a less recently disengaged task set. This set-alternation cost may indicate inhibition of the disengaged task set. The primary goal of the present study was to test the inhibition account of set-alternation costs against an important alternative account based on automatic episodic retrieval. The episodic retrieval account predicts reaction time facilitation instead of costs for the special case of complete n-2 repetitions of both task sets and all stimulus-response aspects. A new task-switching paradigm, in which action rules varied on a trial-by-trial basis while the relevant stimulus dimension remained invariant, allowed the implementation of a high proportion of complete n - 2 repetitions. Consistent with the inhibition view, set-alternation costs were obtained even for these constellations.

Humans↗
PubMed1990

[Tissue Culture Tests as an Alternative to the Uterotrophic Assay in the Detection of Estrogenic Active Compounds]

The bases for two biological systems which ascertain estrogenic activity were worked out. The primary aim was to assess animal foodstuff. The first system, the measurement of estrogen-specific proteins in MCF-7 cells (human breast cancer cells), has been used for a quantitative estimation of 17beta-estradiol, the mycoestrogen zearalenone and five phytoestrogens. Estimates of the relative estrogenic potentials of these substances using the MCF-7 test yields results similar to those of the uterotrophic assay. Analyses of cereal samples artificially contaminated with zearalenone showed that MCF-7 cells are suitable for examining not only purified compounds, but also biological material. A quantitative estimation of added zearalenone was possible in each case. In principle, then, the MCF-7 system can be suitably introduced into agronomic practice, for example in the examination of animal foodstuff. The second test system is based on genetically transformed mouse cell cultures. The synthesis of a bacterial enzyme (chloramphenicol-acetyltransferase, CAT) is used to measure hormone activity. This system was tested with zearalenone. Both test system are extremely sensitive and superior to the uterotrophic assay with mice and rats, concerning the accuracy of measurement and reproducibility. They can replace this commonly used bioassay in most cases - both in agronomic and in pharmaceutical research. Ways of simplifying the experimental procedures are discussed.

Journal Article↗