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PubMed1985

Influence of task and input factors on hemispheric involvement in face processing.

Two experiments examined the respective role of the cerebral hemispheres in face perception and the nature of their contribution depending on task demands and on the spatial-frequency composition of the stimuli. Sixteen faces of members of the subjects' department were presented as stimuli, with men and women, and professors and nonprofessors being equally represented. In Experiment 1, high-resolution black-and-white photographs of faces were used in three reaction-time tasks: verbal identification, manual membership categorization, and manual male/female categorization, in a within-subject design. Identification and membership categorization were significantly better performed in right-visual-field presentations, whereas the male/female categorization yielded a nonsignificant left-visual-field superiority. In Experiment 2, two versions of the same faces were used: digitized low-pass (0 to 2 cycles/degree of visual angle) and digitized broad-pass (0 to 32 cycles/degree) faces. Broad-pass faces produced the same laterality pattern as in Experiment 1, while low-pass faces were better processed in left-visual-field presentations for all three tasks. The results suggest that the two hemispheres play a role in face perception, and their contribution may vary as a function of the task demands and of the spatial-frequency components of the incoming information.

Adult↗
PubMed1990

Asymmetries in hand movement during block design construction.

Changes in patterns of hand use were examined as a function of task demand characteristics. Using blocks, right- and left-handed male and female subjects were asked to simultaneously construct two replicas of presented patterns, one with each hand. With the presentation of visual-spatial patterns, a shift toward use of the left hand from baseline was observed. This change was least evident among right-handed females. The observed shift in hand use toward the left on a visuo-constructive block design task might suggest differential involvement of the right hemisphere with changes in task demand characteristics.

Adult↗
PubMed1991

Ecobehavioural analysis of stereotypic and adaptive behaviours: activities as setting events.

The effects of activities and task demands on the rate of stereotypic and adaptive behaviour were analysed within the conceptual framework of setting events. Data on 12 mentally retarded subjects were collected in real time using portable microcomputers during six activities: leisure, pre-vocational training, gym, academic instruction, home living, and lunch. Results showed that stereotypic and adaptive responses occurred in all settings, with the two behaviours occurring simultaneously across both subjects and activities some of the time. Micro-level analysis showed that teacher covert task demand provided the setting event for most of the stereotypic and adaptive responding during each activity. The importance of ecobehavioural analysis in understanding the nature of stereotypy and adaptive behaviour, and the contribution of such an analysis to appropriate and effective intervention were highlighted.

Adaptation, Psychological↗
PubMed1975

Cortical evoked potentials elicited by real speech words and human sounds.

Averaged evoked potentials were recorded from PZ and left and right temporo-parietal electodes to real speech words and human sounds in 8 right-handed subjects. Stimuli were presented in a "no task" condition where the subject was instructed to listen attentively, and a vigilance condition where the subject responded to a particular word or sound during a run of such stimuli. The vigilance condition produced two classes of stimuli:signals and non-signals. Evoked potentials to physically identical words or sounds were examined when they were "no task", non-signal and signal stimuli. P300 amplitude increased significantly as a function of increasing task demands going from "no task" to non-signal to signal. When a strict statistical criterion for multiple comparisons (Bonferroni test) was applied in looking for asymmetries between hemispheres, only 2 isolated left greater than right differences turned out to be significant. Review of the literature concerning evoked potential correlates of differential hemispheric processing pointed up flaws in design, statistical technique, and inconsistencies in reported findings which suggested that while evoked potentials may sometimes reflect differences in hemispheric functioning, this effect is marginal at best.

Adult↗
PubMed1990

Schizophrenic performance on line bisection: no simple lateralization defects.

Many studies have assessed the possible lateralization deficits of schizophrenics, and the results usually suggest left hemisphere dysfunction. Nevertheless, they have been variable. This may have been due to cognitive demand of the different tasks, not to changes in brain lateralization itself. In order to circumvent this problem, the present study evaluates the performance of schizophrenics on a simple but lateralized task, line bisection. Subjects bisected a line using either visual or tactile information, with the left or right hand, when it was placed in their left or right hemispace or directly in front of them. Schizophrenic subjects were not more erroneous than normals (variable error), nor were they biased differently from normals in either direction with either modality of sensory input (constant error). There were only two significant effects of group on the tactile line bisection, one of position x length x group and one of position x hand x end x length x group, both on constant error (directional bias). The lack of main effects and presence of interactions on these basic tasks suggests that apparent lateralization differences found in schizophrenic subjects are due not to a simple defect of brain lateralization but may stem from task demands and attention allocation.

Attention↗
PubMed1989

Spatial monitoring in visual working memory.

Three experiments examined the role of spatial monitoring in short-term visual memory. In the first experiment it was found that with consonants presented visually at one location articulatory suppression but not a concurrent tracking task disrupted performance. Experiment 2 demonstrated that tracking was disruptive when consonants were presented at three locations and more serial positions were affected when the locations of the consonants were random rather than highly predictable. Articulatory suppression was also disruptive in this study. The third experiment replicated the first two studies, without an articulatory suppression condition, using a within-subject design with a strictly forward serial recall constraint. The locus of the tracking effect was modified by this recall constraint suggesting that tracking disrupts a specific process that utilizes spatial monitoring. It was concluded that spatial monitoring depletes resources that can be used to encode visually presented consonants and these resources may be drawn from spatial working memory. The articulatory loop was also implicated given that articulatory suppression also disrupted performance. These results were explained in terms of working memory constellations. Morris (1986 b) suggested that such constellations consist of working memory components, in this instance the articulatory loop and spatial working memory, 'assembled' to meet task demands. This probably involves the activation, by the demand characteristics of the task, of modules in working memory that are similar to production system elements.

Adult↗
PubMed2026

The asymmetry of working memory training transfer: A systematic review and meta-analysis.

Working memory (WM) training is widely used to enhance cognitive performance; however, its transfer to untrained tasks remains controversial. Traditional theories emphasize task similarity as the primary determinant of training transfer, but they cannot fully explain emerging evidence of asymmetric transfer across tasks. Two directional transfer hypotheses are proposed here to explain this asymmetry: the resource-based transfer advantage hypothesis predicts stronger transfer from more to less cognitively demanding tasks, whereas the ability-based transfer advantage hypothesis predicts stronger transfer from tasks engaging broader task-general abilities to tasks engaging task-specific narrower abilities. The contrast between span and updating paradigms provides an informative framework for distinguishing these accounts, because updating tasks are generally more cognitively demanding, whereas span tasks involve broader abilities. Accordingly, we conducted a three-level meta-analysis of 55 studies (208 effect sizes; N = 3,492). The results showed that updating training transferred reliably to span tasks (g = 0.176, p < .001), whereas span training did not reliably transfer to updating tasks (g = 0.048, p = .453), supporting the resource-based account. This advantage of updating training also extended to non-WM outcomes and was more pronounced at lower training doses, in non-adult samples, and with verbal stimuli. Together, these findings extend WM transfer theory beyond task similarity by highlighting the importance of cognitive demand and offer guidance for WM training design.

Humans↗
PubMed1975

An alternative approach to dose reduction in dental radiography.

A responsible approach to dose reduction in dental radiography requires that relative exposure be related to the specific diagnostic task performed. All but the most demanding tasks can be performed when suitable film is used in conjunction with high-speed screens. Placing the source of radiation inside the mouth permits radiographic information to be recorded on an improved Polaroid cassette that has a relatively high quantum efficiency. As a result, the radiation dose can be significantly reduced in a versatile system which provides for instantaneous processing and interpretation from prints rather than negatives.

Radiation Dosage↗
PubMed1992

Verbal fluency and positron emission tomographic mapping of regional cerebral glucose metabolism.

Impairment in verbal fluency (VF) has been a consistently reported clinical feature of focal cerebral deficits in frontal and temporal regions. More recent behavioral activation studies with healthy control subjects using positron emission tomography (PET), however, have noted a negative correlation between performance on verbal fluency tasks and regional cortical activity. To see if this negative relationship extends to steady-state non-activation PET measures, thirty-three healthy adults were given a VF task within a day of their 18F-2-fluoro-2-deoxy-D-glucose PET scan. VF was found to correlate positively with left temporal cortical region metabolic activity but to correlate negatively with right and left frontal activity. VF was not correlated significantly with right temporal cortical metabolic activity. Some previous studies with normals using behavioral activation paradigms and PET have reported negative correlations between metabolic activity and cognitive performance similar to that reported here. An explanation for the disparate relationships that were observed between frontal and temporal brain areas and VF might be found in the mediation of different task demands by these separate locations, i.e., task planning and/or initiation by frontal regions and verbal memory by the left temporal area.

Adult↗
PubMed1990

Interhemispheric interaction: how do the hemispheres divide and conquer a task?

The present studies investigated how dividing processing between the hemispheres affects task performance. In particular, they examined whether dividing processing between the hemispheres leads to a performance advantage only when task demands exceed a certain threshold. In Experiment 1 processing demands were manipulated by varying the difficulty of the decision process. In the more difficult task, subjects decided as quickly as possible whether two of three letters had the same name (e.g. A a), whereas in the less difficult task they simply decided whether two of the three were physically identical (e.g. A A). As expected, dividing processing between the hemispheres aided performance for the more difficult name-identity task whereas it actually hindered performance for easier physical-identity task. In Experiment 2, subjects made a physical-identity decision about a different stimulus, digits. The pattern of results found in Experiment 1 for the physical-identity task was replicated; interhemispheric processing hindered task performance. These results indicate that the physical characteristics of a stimulus have minimal influence on the extent to which interhemispheric processing aids task performance. In Experiment 3, subjects were required to make more difficult decisions about digits. In one task, they decided whether the sum of two of the three digits was greater than or equal to 10, and in the other they decided if the value of a particular digit was less than either of the other two. Dividing processing between the hemispheres led to faster performance for both tasks, similar to the results for the name-identity condition. In sum, these experiments suggest that when task requirements are demanding, performance is enhanced by distributing processing across the hemispheres.

Adult↗
PubMed1990

Cognitive and affective disorders in elderly diabetics.

In non-insulin-dependent diabetes mellitus, performance of complex cognitive tasks requiring the storage and retrieval of new information is poorer than in age-matched controls. By contrast, performance of less demanding tasks such as immediate memory and simple reaction time is essentially equivalent for NIDDM patients and controls. This pattern parallels the cognitive change observed with normal aging, in which age differences are minimal on less demanding immediate memory tasks but older adults perform more poorly than young adults on secondary or long-term memory tasks. Age-related changes in cognitive performance have been attributed to a reduction in processing resources or working memory capacity. Although the explanation for NIDDM-related deficits remains to be identified, reduced glucose control and elevated levels of triglycerides appear to play some role in cognitive impairment. Non-insulin-dependent diabetes is associated not only with elevated levels of depression, but with an increased frequency of self-reported memory problems. Moreover, elevated levels of depression are associated with various indicators of neuropathy and with significant reductions in self-regulated control of glucose at the time of medical office visits. Diabetic patients may perceive less control over their lives as a result of the many restrictions associated with the disease. When provided with the opportunity to exercise control, however, performance on many cognitive tasks can be improved in NIDDM as well as in age-matched controls. This suggests that by providing NIDDM patients with opportunities to exercise increased control over their lives it may be possible to enhance motivation and to increase the likelihood of the patient's adopting more effective self-regulatory behaviors.

Aged↗
PubMed1991

Visual speech processing: word-decoding and word-discrimination related to sentence-based speechreading and hearing-impairment.

Two aspects of visual speech processing in speechreading (word decoding and word discrimination) were tested in a group of 24 normal hearing and a group of 20 hearing-impaired subjects. Word decoding and word discrimination performance were independent of factors related to the impairment, both in a quantitative and a qualitative sense. Decoding skill, but not discrimination skill, was associated with sentence-based speechreading. The results were interpreted such that, in order to represent a critical component process in sentence-based speechreading, the visual speech perception task must entail lexically induced processing as a task-demand. The theoretical status of the word decoding task as one operationalization of a speech decoding module was discussed (Fodor, 1983). An error analysis of performance in the word decoding/discrimination tasks suggested that the perception of heard stimuli, as well as the perception of lipped stimuli, were critically dependent on the same features; that is, the temporally initial phonetic segment of the word (cf. Marslen-Wilson, 1987). Implications for a theory of visual speech perception were discussed.

Adult↗
PubMed1991

Dual-task assessment of reorganization of postural control in persons with lower limb amputation.

Postural control in persons with lower limb amputation was studied using a cognitive approach to motor learning. The aim of this study was to show that an important characteristic of the central reorganization process after a lower limb amputation is the gradually decreasing need of attentional resources to perform a motor task. A dual-task procedure was developed to estimate the level of automaticity of a quiet, upright standing task. The effect of a concurrent attention-demanding task (Stroop task) on the efficiency of balance control was determined using force-platform measurements at the start and the end of the rehabilitation process. In contrast with a control group, the amputation group showed interference effects on body sway caused by the concurrent task both at the start (p less than .05) and, less severe, at the end of rehabilitation (p less than .05). Improvement of balance control was significant only for the dual-task condition (p less than .05). The results corroborated the hypothesis that dual tasks give information about the restoration of automaticity of postural control as an essential characteristic of the central reorganization process in persons with lower limb amputation. The role of dual-task procedures as a useful approach to skill assessment is discussed.

Adult↗
PubMed1990

Changes in spontaneous EEG activity indicate a special kind of information processing in concept learning.

Some findings in the literature suggest that a high amount of spectral power in spontaneous EEG alpha 1 band (7.5-10.0 Hz) may be associated with tasks demanding extensive monitoring of stimulus information and combining features for a match with internal concepts ("exploration"). EEG recordings were obtained from 9 subjects involved in a concept-learning task. They had to match visually presented objects with a concept built up by hypothesis and to respond by pressing a "yes" or "no" key. Epochs of EEG data were analyzed with epoch center-times at 500 and 250 ms before response execution. In the case of "yes" responses, when subjects could match their hypothesis positively with combined features of the presented object increased alpha 1 spectral power was found. Also alpha 1 power was larger immediately after disconfirming feedback than after confirming feedback. Additionally, alpha 2 spectral power (10.5-12.5 Hz) was found to be larger 250 ms after confirming feedback than after disconfirming feedback. It is argued that alpha 1 power seems to reflect those mental processes which are involving in combining features and matching them to a concept in mind. The increase in alpha 2 power after confirming feedback is interpreted in terms of general processing demands imposed during task performance.

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↗
PubMed1989

Human brainstem auditory evoked potentials fail to provide evidence of efferent modulation of auditory input during attentional tasks.

Efferent modulation of auditory input at the level of the brainstem during attention-demanding tasks has been described in animal studies. Attempts to demonstrate these effects in humans have produced conflicting results, however. These studies are reviewed with particular reference to those animal experiments that have demonstrated peripheral effects. The human experiments have used a number of attentional conditions which have not been related either to each other or to the successful animal work. Two of the most important conditions in these studies--the use of an intermodal attention task and the manipulation of attentional states--have been examined rarely or not at all in the human research. Two experiments were conducted to investigate the possibility of attention-related effects on the human brainstem auditory evoked potential. These experiments were designed to examine experimental conditions common to both successful and unsuccessful attempts to demonstrate attention-driven efferent modulation at the periphery in humans. Also examined was the gradation of attention effects on efferent modulation demonstrated in animals but never studied in humans. No significant changes in either the latency or the amplitude of the brainstem auditory evoked potential were found in any of the attention-demanding conditions. Results are discussed in terms of psychophysiological theories of attention. Also, the interpretation of the most recent animal work is questioned.

Adolescent↗