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PubMed2006

Behavioural and electrophysiological measures of task switching during single and mixed-task conditions.

In order to understand how the brain prepares for and executes a switch in task demand, we measured reaction time (RT), accuracy, and event-related brain potentials associated with performance in single and mixed-task blocks using a cued design. Our results show that trials which repeat in a mixed-task block (repeat trials) were more demanding than trials which repeated in a single-task block, as reflected by the presence of a RT mixing cost and by the presence of a smaller target-locked positivity (P3b) on repeat trials. Within a mixed-task block, repeat and switch trials also differed, where repeat trials showed evidence of greater preparation (larger cue-locked negativity), more efficient target processing (larger target-locked P3b), and shorter RTs. In addition, the cue-locked negativity difference remained despite equating repeat and switch trials on RT, suggesting that this negativity difference is specific to the switching process. Our results are discussed in light of existing models of task switching.

Adult↗

PubMed1998

Lingual action in normal sequential swallowing.

Current knowledge about the flexibility in lingual motor control and performance during swallowing is incomplete. The present study aimed at gaining a better understanding of the tongue's motor flexibility and at identifying variable versus invariant lingual motor program parameters in light of changing swallowing task demands (discrete vs. sequential). Specifically, the timing and patterns of tongue-palate contact and the associated changes in tongue shape and action were examined in 5 normal adults using simultaneous electropalatography and ultrasound. Tasks for discrete swallowing included 5 and 30 cc of water; tasks for sequential swallowing involved drinking 200 cc of water at normal and fast rates. Results showed little variation in propulsive contact pattern as a function of task or subject. However, the tongue demonstrated shorter movement duration and overlapping gestures during sequential swallowing. Thus, continuous drinking was performed without changes in motor strategies per se but with changes in the timing coordination of the "drink" and "swallow" action sequences. These findings support the theory that the deglutitive lingual motor program has both invariant and variant parameters, and that movement pattern and action sequence reflect fixed elements within the structure of the motor program, but movement timing can be modified according to the demands of the task at hand.

Adult↗

PubMed1997

Attention and somatic awareness in chronic pain.

Empirical methods are used to explore the relationship between chronic pain, somatic awareness and attention. Using a primary task paradigm, 46 chronic pain patients performed an attentionally demanding task. Patients were classified according to self reported pain intensity and the extent of their reporting of the perception of bodily sensations (somatic awareness). Results showed that, as predicted, disruption of attentional performance was most pronounced in those who reported high pain intensity and high somatic awareness. Further analysis revealed that these patients also reported high negative affect. These findings are discussed in terms of their theoretical implications for the concept of hypervigilance and their clinical implications for chronic pain control.

Adult↗

PubMed2006

Revealing language deficits following stroke: the cost of doing two things at once.

The costs of doing two things were assessed for a group of healthy older adults and older adults who were tested at least 6 months after a stroke. A baseline language sample was compared to language samples collected while the participants were performing concurrent motor tasks or selective ignoring tasks. Whereas the healthy older adults showed few costs due to the concurrent task demands, the language samples from the stroke survivors were disrupted by the demands of doing two things at once. The dual task measures reveal long-lasting effects of strokes that were not evident when stroke survivors were assessed using standard clinical tools.

Aged↗

PubMed2002

Pushing and pulling in association with low back and shoulder complaints.

AIMS: To examine the association between exposure to pushing/pulling at work and low back and shoulder complaints. METHODS: A cross sectional questionnaire survey was carried out among 434 workers from several companies with mainly pushing/pulling tasks. From the same companies 188 workers without physically demanding tasks served as reference. The questionnaire was used to assess the exposure to pushing/pulling and other physical risk factors for low back and shoulder complaints. Mean scores at company level were used to classify groups into medium and high exposed to pushing/pulling and a reference group. Psychosocial factors at work were also assessed. Several pain related questionnaires were used to assess the 12 month prevalence of low back and shoulder complaints in three dimensions: trouble (ache, pain, discomfort), pain intensity, and disability. Prevalence rate ratios (PRs) were calculated using Cox's proportional hazards regression analysis. RESULTS: The 12 month prevalence of low back complaints was almost equal for all three groups. The prevalence of shoulder complaints increased with an increase in exposure level. Adjusted PRs showed that the high exposed group had an increased risk for low back complaints compared to the reference group. For all dimensions of shoulder complaints a clear tendency towards a dose-response relation was observed. The high exposed group had significant PRs for shoulder complaints, ranging from 2.09 to 6.37. Generally, psychosocial factors had a confounding effect for pain intensity and disability, but not for trouble. CONCLUSIONS: For shoulder complaints a dose-response relation was observed for exposure to pushing/pulling. Low back complaints were less consistently associated with pushing/pulling. Stronger associations were observed for more severe cases of low back and shoulder complaints. It is hypothesised that work related psychosocial factors affect these associations.

Adult↗

PubMed2002

Sustained mnemonic response in the human middle frontal gyrus during on-line storage of spatial memoranda.

The mapping of cognitive functions to neural systems is a central goal of cognitive neuroscience. On the basis of homology with lesion and physiological studies in nonhuman primates, Brodmann's area (BA) 46/9 in the middle frontal gyrus (MFG) has been proposed as the cortical focus for both the storage as well as processing components of working memory in the human brain, but the evidence on the segregation of these components and their exact areal localization has been inconsistent. In order to study this issue and increase the temporal resolution of functional mapping, we disambiguated the storage component of working memory from sensory and motor responses by employing functional magnetic resonance imaging (fMRI) in spatial delayed-response (DR) tasks with long delay intervals and different conditions of demand. We here show that BA 46 can support a sustained mnemonic response for as long as 24 sec in a high-demand task and the signal change in this area exceeded that in the other prefrontal areas examined. Our findings support a conservation of functional architecture between human and nonhuman primate in showing that the MFG is prominently engaged in the storage of spatial information.

Adult↗

PubMedDate not supplied

Neural basis of spontaneous thought processes.

Studies examining thought processes have focused upon the deliberate, goal-directed mental processes occurring during complex cognitive tasks. Spontaneously occurring thought processes have, on the other hand, received much less attention. Such spontaneous thought processes occur frequently when no task is present or when task demands are low. Although their existence has been recognised, their study has been difficult due to lack of direct behavioural measures. Nevertheless, a number of behavioural methods based on subjects' verbal reports have been developed. Findings derived using such behavioural methods suggest that spontaneous thought processes share common cognitive mechanisms with purposeful, task-related thought processes. Furthermore, evidence from neuroimaging observations is accumulating suggesting similar conclusions about the neural basis of spontaneous thought processes. These neuroimaging findings demonstrate an overlap in the pattern of activation between various cognitive tasks and rest, with a number of higher cortical regions activated in common, including visual areas, medial temporal lobe, and lateral cortical association areas. Many of these observations have, however, been based upon comparisons between rest and tasks posing relatively high cognitive demands. In contrast, here we report an fMRI study in which rest was compared to a simple left/right response task of minimal cognitive demands. Rest was associated with greater activation in temporopolar cortex, parahippocampus, rostrolateral prefrontal cortex, parietal and visual cortical areas. Activation of temporal lobe structures was particularly extensive and robust, suggesting that long-term memory processes may form the core of spontaneous thought. By considering such long-term memory processes as an essential part of thought mechanisms, it may be possible to gain better understanding into spontaneous thought phenomena that have remained unaccounted for until now.

Adolescent↗

PubMed1982

[Ergonomic strain measurement in text processing].

Text processing task demands are analysed by using an Ergonomic Job Description Questionnaire. The tasks are classified by cluster analysis. Tasks out of each cluster are examined with respect to performance and physiological strain by 8-h measurements. These reactions are assessed in terms of tolerance limits and the distribution of demands is discussed for non-tolerable work conditions.

Female↗

PubMed1988

Assessing the development of automatic processing: an application of dual-task and event-related brain potential methodologies.

Previous research has found that properties of automatic processing do not always co-occur, suggesting that the acquisition rates may differ. The present study investigated the acquisition rate of several of these properties by employing additive factors logic, dual task methodology, and event-related brain potentials. Seven subjects participated in a ten session experiment in which they performed two tasks, a visual/memory search task and a pursuit step tracking task, both together and separately. RT and P300 latency measures indicated that parallel processing of the display was achieved early in training in the consistent mapping condition. This processing was unaffected by dual task demands. An analysis of RT/P300 ratios suggests that another form of perceptual efficiency was achieved later in practice in both the varied and consistently mapped search tasks. This effect was larger in the consistent mapping condition. Reductions in the slope of the memory set function occurred significantly earlier for P300 latency than for RT, suggesting that the stimulus evaluation processes became automated more rapidly than the response selection components of memory search. Consistent with an analysis of the processing demands of the two tasks, the introduction of the tracking task and an increase in tracking difficulty produced equivalent interference during consistent and varied mapping conditions. Results are discussed in terms of models of skill, skill acquisition and component task automaticity.

Adult↗

PubMed1990

Phonological and motoric demands in handwriting: evidence for discrete transmission of information.

In an experiment with handwriting tasks effects of phonological and motoric task factors upon reaction time and movement time were measured to test implications of a discrete information processing account of the task. The model is built up of serially organized stages, each of which monitors one specific type of operation, necessary to generate a message. The serial structure of the model is defined as the limitation that higher levels of the model provide their output to the next lower processor in the hierarchy, and receive their input from the next higher stage. The parallel character of the model is exemplified through the assumption that all processors are active at the same time and concurrently with the real time production of writing movements. The study adds evidence that a serial architecture of processors can be compatible with the parallel processing of a message as long as more abstract operations are prepared more in advance to real-time movements than operations lower in the hierarchy. In the experiment the prediction was tested that the time course of the manifestation of phonological and motoric task demands reflects the discrete and serial structure of the model.

Adult↗

PubMed1995

Chronic pain and distraction: an experimental investigation into the role of sustained and shifting attention in the processing of chronic persistent pain.

Although there is anecdotal evidence for the psychoanalgesic properties of distraction, research evidence is equivocal. Drawing on the clinical and experimental studies of attention-based coping strategies for pain control, and the theoretically driven 'cognitive' models of the human attention system, two experiments are reported. Experiment One demonstrates that chronic pain patients suffering high intensity pain show significantly impaired performance on an attentionally demanding task when compared to low pain patients and normal controls. Experiment Two tests the hypothesis that the low intensity pain patients in Experiment One are coping with the dual demand of processing the pain and processing the task by switching quickly between these attentional demands. The results of both experiments are discussed in terms of the evidence for the analgesic properties attention based coping strategies with clinical pain populations and re-addresses the literature on coping with pain in terms of cognitive theories of attention.

Adaptation, Psychological↗

PubMed1995

Favor referential representations.

Avrutin and Hickok (1993) argue that agrammatic patients have the ability to represent nonreferential or "government" chains ("who ... e") but not referential or "binding" chains ("which girl ... e"). By contrast, we propose the "referential representation hypothesis," which suggests that agrammatics attempt to cope with their well-known capacity limitations by favoring referential or content-based representations. This predicts that agrammatic patients' performance should degrade noticeably as task demands increase, and referential demands should take priority over computational ones. In a semantic task, referential phrases should lead to better or more accurate performances. In syntactic tasks, the availability of a referential or content-based representation will interfere with the development of a syntactic representation, resulting in worse syntactic performance on the referential phrases than on nonreferential ones. This predicts that agrammatic patients should incorrectly accept (resumptive) pronoun sentences with a referential wh-phrase because the pronouns will find the semantic or discourse referent of the referential wh-phrase and take it as an antecedent for the pronoun. However, they should reject a (resumptive) pronoun in a sentence with the nonreferential question constituent "who" or "what." "Who" and "what" will remain in syntactic form, since they have only grammatical content and therefore will have only a "nonreferential" syntactic representation. Consequently, they cannot serve as the antecedent of the pronoun. These predictions were largely confirmed by the results of a grammaticality judgement study. Agrammatics performed well on questions with pragmatic biases but failed to distinguish reliably between grammatical and ungrammatical questions where pragmatic biases were neutralized. They assigned especially low ratings to object gap sentences with referential wh-constituents, as predicted. They assigned relatively high ratings to ungrammatical subject pronoun sentences with either type of wh- constituent. The agrammatics accepted ungrammatical reflexive sentences even though syntactic number and gender features alone could have been used to correctly judge the sentences. We attribute this, too, to the unavailability of a reliable syntactic representation of those phrases with referential or extragrammatical semantic content.

Adult↗

PubMed2006

Age-related differences in spatiotemporal markers of gait stability during dual task walking.

Increased stride-to-stride variability during walking characterizes gait instability and predicts falling in older adults. Walking while performing cognitive tasks (dual task walking) is also associated with increased risk of falling. The purpose of the study was to examine whether gait velocity and stride-to-stride variability in gait velocity differ in older adults compared with middle-aged and younger adults during normal and dual task walking conditions. Sixty older (n=20, mean age=81 years), middle-aged (n=20, mean age=48 years), and young adults (n=20, mean age=25 years) participated in the study. Gait parameters were quantified with GAITRite instrumentation. In the dual task condition, participants spelled five-letter words in reverse while walking across the walkway. Across groups, gait velocity was slower (p<0.001) and stride-to-stride variability in gait velocity was greater (p=0.001) in dual task walking. Older subjects walked more slowly than did middle-aged and younger subjects and the difference in gait velocity was greatest in the dual task condition (p<0.05). Variability in stride velocity was increased in older subjects compared with middle-aged and younger subjects (p<0.05). Additionally, in older subjects, impaired walking performance was associated with impaired cognitive performance in dual task walking. The gait changes observed in dual task walking characterize decreased gait stability and indicate that cognitively demanding tasks during walking have a destabilizing effect on gait and may place older people at a greater risk of falling.

Adult↗

PubMed2005

Attention impairment in electrooculographic control of computer functions.

Previous work has demonstrated that computer functions can be controlled by eye movements recorded with the use of vertical and horizontal electrooculography (EOG). In the present study, an attempt was made to show that this newly developed task could be disrupted by dual-task demands and, therefore, would follow conventional principles of multiple-task performance. Fifteen participants performed the eye movement task under two conditions-control and divided attention. It was found that the time to process letters was significantly longer in the divided attention condition than in the control condition and that males and females showed comparable performance decrements in the divided attention condition. A task that utilizes eye movements to control computer operations for syntax construction follows the same principles of limited resource allocation of attention as more conventional perceptual-motor tasks such as reaction time and manual control of computer functions.

Adult↗

PubMed1996

Orthographic processing in visual word recognition: a multiple read-out model.

A model of orthographic processing is described that postulates read-out from different information dimensions, determined by variable response criteria set on these dimensions. Performance in a perceptual identification task is simulated as the percentage of trials on which a noisy criterion set on the dimension of single word detector activity is reached. Two additional criteria set on the dimensions of total lexical activity and time from stimulus onset are hypothesized to be operational in the lexical decision task. These additional criteria flexibly adjust to changes in stimulus material and task demands, thus accounting for strategic influences on performance in this task. The model unifies results obtained in response-limited and data-limited paradigms and helps resolve a number of inconsistencies in the experimental literature that cannot be accommodated by other current models of visual word recognition.

Adult↗

PubMed2004

Memory self-awareness and memory self-monitoring following severe closed-head injury.

OBJECTIVE: To examine the accuracy of memory self-awareness and memory self-monitoring abilities in participants with severe closed-head injury (CHI). DESIGN AND METHODS: A performance-prediction paradigm was used to evaluate meta-memory abilities in 31 participants with severe CHI (>1 year post-injury) and 31 controls. To assess memory self-awareness, before completing story recall, visual reproduction and list learning memory tasks, participants predicted the amount of information they would remember for each task. Memory self-monitoring was evaluated by examining participants' ability to increase the accuracy of their predictions following experience with each memory task. RESULTS: Although participants with CHI exhibited poorer recall than controls, they were equally aware of how differing task demands influence recall. They also successfully modified their predictions following task exposure. CONCLUSIONS: Meta-memory was better preserved than actual memory performance. It may be possible to build on meta-memory skills to help patients with CHI more consistently use strategies that aid memory performance.

Adult↗

PubMed2004

Effects of an indoor plant on creative task performance and mood.

In this study, we investigated the effect of an indoor plant on task performance and on mood. Three room arrangements were used as independent variables: a room with (1) a plant, or (2) a magazine rack with magazines placed in front of the participants, or (3) a room with neither of these objects. Undergraduate students (M= 35, F= 55) performed a task of associating up to 30 words with each of 20 specified words in a room with one of the three room arrangements. Task performance scores showed that female participants performed better in view of the plant in comparison to the magazine rack (p < 0.05). Moreover, mood was better with the plant or the magazine rack in the room compared to the no object condition (p < 0.05). However, the difference in task performance was highly influenced by the evaluation about the plant or the magazine rack. It is suggested that the compatibility between task demand and the environment is an important factor in facilitating task performances.

Adult↗

PubMedDate not supplied

Assessment of three-and-a-half-year-old children's emerging phonological awareness in a computer animation context.

Four computer-animated tasks were created to analyze the underlying structure of emerging phonological awareness at 3.5 years of age and to explore the factors that influence children's (N = 91) performance on the tasks. Our findings indicated that already at this young age, children are able to master tasks demanding identification, blending, and continuation of phonological units when the tasks are presented in a motivating assessment context. In line with earlier research, children showed higher mastery in dealing with words and syllables than in dealing with phonemes. Targets in the initial position of a word were easier for children to identify than those in the final position. Our analysis provided support for two major dimensions of emerging phonological awareness based on the cognitive operations of the tasks: identification and blending of phonological units.

Awareness↗