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PubMed1981

Input and distractor modality effects upon the release from proactive interference in children.

Build-up of proactive interference (PI) with visual-picture and auditory-verbal input modalities and the subsequent release from Pi following a change in modality was investigated in three experiments with boys and girls, as follows: Experiment I (n=64) at two mean age levels, 7-6 and 10-5; Experiment II (n=64) at mean age 7-6; and Experiment III (n=48) at age 11-4. PI build-up occurred in both modalities for all ages tested. Release from PI occurred following a change from auditory to visual input by not from PI occurred following a change from auditory shift. In the final experiment, this asymmetrical improvement in performance was dependent upon an interaction between the modality of the input and distractor task on the final or release trial; changing to visual input produced a release effect regardless of the distractor task modality, while auditory input was associated with improvement in recall if a visual distractor task was employed whether or not a shift in input modality had occurred. This improvement was hypothesized to represent a decrease in retroactive interference rather than a release from proactive interference.

Child↗

PubMed2007

Gait initiation in children with cerebral palsy.

The task of gait initiation (GI), or taking a first step from a static standing position requires the development of forward momentum while maintaining dynamic balance as the body's center of mass (COM) moves forward and outside the base of support. The dynamics of GI in children (aged 7-12 years) with hemiplegic cerebral palsy (CP), diplegic CP and children with typical development (TD) were compared to characterize the mechanics and control of this task. Ground reaction forces (GRFs) and muscle activity were collected during GI at three different self-selected speeds (slow, moderate and fast). Movement of a sacral marker was also tracked to estimate downward shifting of the body during the GI task. Results demonstrate the presence of a motor sequence characterized by increased forward momentum development with increased GI speed for all groups of children. Anticipatory movements of children with CP were different when compared to children with TD. Children with hemiplegic CP demonstrated decreased lateral shifting while children with diplegic CP demonstrated a trend of decreased downward shifting of the body compared to children of TD. Analysis of the GI motor sequence in children provides a means to characterize coordination and motor control of a functional ambulatory task in children with CP compared to children with TD.

Analysis of Variance↗

PubMed1996

Brain potentials before and during memory scanning.

Brain potentials were recorded from 10 normal subjects engaged in a 3-item auditory verbal short-term memory task. A fixed interval (3 s) between the last memory item and the probe was compared to a random interval (1.8-4.2 s with a mean of 3 s). Subjects indicated by button press whether the probe was or was not a member of the memory-set. The same 3-item task was also presented as a counting task and required a button press to the "fourth stimulus' (the probe). The amplitudes of several slow potential shifts preceding and following the probe, and the amplitudes and latencies of the accompanying short duration components (N100, P200) were measured. When the probe appeared at a fixed interval, the amplitude of a slow negative potential in the 300 ms period preceding the probe was slightly larger in the memory than in the counting task. When the probe appeared at a random interval in the memory task, the slow negative shift preceding the probe was absent. Another slow negative shift that peaked at approximately 376 ms after the probe was present in the memory tasks but was absent in the counting task. The amplitude of a late positive shift that peaked at approximately 700 ms after the probe was not different within the memory tasks, or between the memory and counting tasks. N100 amplitude but not P200 amplitude was larger in the memory task when the probe occurred at a fixed than at a random interval. These results suggest that the amplitude of a slow negative shift preceding the probe was related primarily to a temporal expectancy for the appearance of the probe and to a lesser extent to memory processes. In contrast, a slow negative shift that followed the probe occurred only during the memory tasks.

Adult↗

PubMed1978

The role of frontal and parietal cortex in cognitive processing: tests of spatial and sequence functions.

Normal monkeys and monkeys with resection of anterior frontal or posterior parietal cortex were trained to press a panel next to a green panel as a test of extrapersonal spatial orientation and to press a panel next to their own prior press as a test of personal spatial orientation. All monkeys also learned two sets of sequence problems in which the solutions were made independent of spatial location by randomly shifting the locations of the stimuli after each response within a trial. The Parietal Group was significantly impaired on the extrapersonal 'next-to' task but not the more difficult personal 'next-to' task. The Frontal Group was impaired on both the personal and the extrapersonal 'next-to' tasks but only when the relevant cues shifted spatial locations from trial to trial. The performance of the Parietal Group completely overlapped that of the Normal Group on the sequence problems regardless of the level of testing sophistication the monkeys had attained. In contrast, the Frontal Group demonstrated a significant impairment in learning sequences but only when the monkeys were naive. Once they became sophisticated they learned each sequence at a normal rate. Their poor performance was attributed to the lack of stability in the spatial location of the stimuli. The data support the view that a distinction between personal and extrapersonal spatial orientation is relevant to posterior parietal function but indicate that neither sequencing per se nor personal spatial orientation or spatial memory per se is dependent on intact frontal functioning. Rather, the frontal cortex is involved with a higher-order control essential to allow the monkey to perceive the reliable aspects of stimuli contained in a stimulus context full of unreliable noise and to further allow for flexible response pattern appropriate to the demands of a variable context.

Animals↗

PubMed1989

The development of representation in young children.

The research summarized here shows that young children undergo an abrupt transition in their ability to understand the relation between a scale model and a larger space. Virtually none of our 2.5-year-old subjects seemed to understand the relationship between the model and the room; almost all of the 3-year-olds did understand it. The difference seems to be that the 2.5-year-olds do not respond to the model both as a real thing and as a representation of something else. Its status as a complex, meaningful real object prevents their apprehension of its abstract relation to the room. The resistance to instruction, abrupt developmental shift, and negligible individual differences in the model task suggest the possibility of a strong maturational underpinning (Espenschade & Eckert, 1967). Further research, including a longitudinal study and cross-cultural comparisons, will be addressed to the issue of the role of experience in the development of mastery of the model task. The primary contribution of this research lies in the revelation of a hitherto undocumented abrupt developmental shift in very young children's representational flexibility--in their ability to form and coordinate multiple representations. The ability to think of one thing in two ways is an important aspect of early symbolic development. In Western cultures, where so much of a child's learning occurs via various representational media, this is a crucial step. More generally, the cognitive advance that occurs between 2.5 and 3 years of age provides a foundation for further developments in the understanding of multiple representations.

Attention↗

PubMed2006

Proprioceptive guidance of saccades in eye-hand coordination.

The saccade generator updates memorized target representations for saccades during eye and head movements. Here, we tested if proprioceptive feedback from the arm can also update handheld object locations for saccades, and what intrinsic coordinate system(s) is used in this transformation. We measured radial saccades beginning from a central light-emitting diode to 16 target locations arranged peripherally in eight directions and two eccentricities on a horizontal plane in front of subjects. Target locations were either indicated 1) by a visual flash, 2) by the subject actively moving the handheld central target to a peripheral location, 3) by the experimenter passively moving the subject's hand, or 4) through a combination of the above proprioceptive and visual stimuli. Saccade direction was relatively accurate, but subjects showed task-dependent systematic overshoots and variable errors in radial amplitude. Visually guided saccades showed the smallest overshoot, followed by saccades guided by both vision and proprioception, whereas proprioceptively guided saccades showed the largest overshoot. In most tasks, the overall distribution of saccade endpoints was shifted and expanded in a gaze- or head-centered cardinal coordinate system. However, the active proprioception task produced a tilted pattern of errors, apparently weighted toward a limb-centered coordinate system. This suggests the saccade generator receives an efference copy of the arm movement command but fails to compensate for the arm's inertia-related directional anisotropy. Thus the saccade system is able to transform hand-centered somatosensory signals into oculomotor coordinates and combine somatosensory signals with visual inputs, but it seems to have a poorly calibrated internal model of limb properties.

Adult↗

PubMed2006

Chronic treatment with desipramine improves cognitive performance of rats in an attentional set-shifting test.

Alterations in central monoaminergic neurotransmission are important in the actions of many antidepressants. This study tested the hypothesis that tonic elevation of noradrenergic (NA) neurotransmission in medial prefrontal cortex (mPFC) by chronic treatment with the selective norepinephrine (NE) reuptake blocker desipramine (DMI) may contribute to the beneficial cognitive effects of this antidepressant drug (AD). Male Sprague-Dawley rats were treated with DMI acutely (15 mg/kg, i.p.) or chronically for 21 days (7.5 mg/kg/day via osmotic minipump) before assessing performance on an attentional set-shifting test. The extradimensional set-shifting component of this test reflects a process of cognitive flexibility that is dependent upon mPFC, and that we have shown previously to be facilitated by NA activity in mPFC. Microdialysis was performed to measure NE release in mPFC concurrently with behavioral testing. Acute DMI treatment produced an increase in extracellular NE levels in mPFC, and a modest improvement in overall performance across all task stages of the attentional set-shifting test, but failed to produce a significant improvement in any of the individual specific tasks comprising the test sequence. Chronic DMI treatment tonically elevated basal extracellular NE levels in mPFC, associated with a significant improvement in performance specifically on the extradimensional set-shifting component of the test. There was also a significant reduction in set loss errors in rats treated chronically with DMI. Hence, tonic elevation of NA transmission in mPFC by chronic DMI treatment was associated with a time-dependent facilitation of cognitive flexibility that may contribute to the mechanism whereby chronic treatment with ADs, specifically NE reuptake blockers, may exert a beneficial therapeutic effect on cognition in depressed patients.

Adrenergic Uptake Inhibitors↗

PubMed2001

Access to deductive logic depends on a right ventromedial prefrontal area devoted to emotion and feeling: evidence from a training paradigm.

Does the human capacity for access to deductive logic depend on emotion and feeling? With positron emission tomography, we compared the brain networks recruited by two groups of subjects who were either able or not able to shift from errors to logical responses in a deductive reasoning task. They were scanned twice while performing the same task, before and after a training session. The error-to-logical shift occurred in a group that underwent logicoemotional training but not in the other group, trained in logic only-a "cold" kind of training. The intergroup comparison pointed out that access to deductive logic involved a right ventromedial prefrontal area known to be devoted to emotion and feeling.

Adult↗

PubMed2002

The influence of "State" related factors on focused attention following whiplash associated disorder.

The modified Stroop task was presented to 48 patients with a Whiplash Associated Disorder (WAD) and 48 healthy matched controls to investigate possible attentional impairments in relation to state related factors (headache, neck pain, fatigue, tension and state-anxiety). It was expected that performance on the Stroop task is negatively influenced by these state related variables. Confirming the expectations, the results showed that response latencies increase for Subtasks 1 through 4, for both groups. In addition, WAD patients performed significantly worse on all subtasks. There was a significant interaction between the two groups and the four subtasks. The results revealed signs for interference susceptibility or reduced capacity to shift attention on the modified Stroop task. The results concerning the influence of state variables indicated that the intensity of headache was significantly related (demonstrating a worsening) to Stroop task performance in the WAD-group. It was concluded that WAD patients exhibit a general slowing of information processing, especially on tasks that require controlled attention. There are signs for subtle deficits in focused attention. The intensity of headache seems to play an important influence on attentional functioning. Clinical implications are discussed.

Adult↗

PubMed1996

Children's performance on "animal tests" of oddity: implications for cognitive processes required for tests of oddity and delayed nonmatch to sample.

To investigate the ontogenesis of oddity learning, children (16 to 102 months of age) and adults were tested on two versions of the oddity task using non-verbal procedures originally developed for monkeys. On the standard, "one-part" or "simultaneous" oddity task (Experiment 1), young children (16 to 74 months of age) performed more poorly than older children (81-102 months of age) who were as proficient as adults. The delayed mastery of one-part oddity contrasts to mastery, at much younger ages (3 to 4 years of age) of a similar, but two-part task, delayed non-match to sample (DNMS) (Overman, 1990). In Experiment 2, those children from the first experiment who had difficulty in learning the one-part oddity task were tested on a two-part oddity task, and a subset of the subjects was retested on the one-part oddity task, and, finally, given verbal instructions for the one-part oddity task. The two-part oddity task was mastered significantly more rapidly than the previous one-part task; however, children's performance dropped significantly when tested on the one-part oddity task, and finally, children rapidly mastered the one-part oddity task when given verbal instructions. The data suggested that (a) children used different strategies to solve the different versions of the oddity task, (b) the solution for the two-part-task appeared earlier in life than the solution for the one-part task and did not involve the use of the concept of "oddity relations", and (c) in tasks in which stimuli are shown twice, behavior may come under control of the absolute properties of the exemplar stimulus via a simple "win-shift" pattern of behavior. In contrast, in tasks in which all stimuli are presented simultaneously, behavior may be controlled by stimulus relations, the analysis of which has a protracted ontogenetic development.

Adult↗

PubMed2005

Disturbed overt but normal covert shifts of attention in adult cerebellar patients.

In an attempt to provide a common denominator for cognitive deficits observed in cerebellar patients, it has been suggested that they might be secondary to impaired control of attention, a 'dysmetria of attention', conceptually analogous to motor dysmetria. Albeit appealing and quite influential, the concept of attentional dysmetria as a consequence of cerebellar disease remains controversial. In an attempt to test this concept in a direct way, we compared the performance of patients with cerebellar disorders to that of normal controls on tasks requiring either overt or covert shifts of spatial attention. In the first experiment, visually guided saccades, i.e. overt shifts of spatial attention, were elicited. In the second experiment, covert shifts of attention were evoked by the need to discriminate the orientation of a Landolt C observed during controlled fixation and presented in the same locations as the saccade targets in the previous experiment. The allocation of attention was assessed by comparing acuity thresholds determined with and without spatial cueing. The patients exhibited dysmetric saccades as reflected by larger absolute position errors or a higher number of corrective saccades compared to controls. In contrast, the ability to shift attention covertly was unimpaired in the patients, as indicated by a robust improvement in visual acuity induced by spatial cueing which did not differ from the one observed in the controls and which was independent of the range of SOAs (stimulus onset asynchronies) tested. Finally, the individual amount of saccadic dysmetria did not correlate with the individual performance in the covert attentional paradigm. In summary, we conclude that the contributions of the cerebellum to attention are confined to overt manifestations based on goal-directed eye movements.

Adult↗

PubMed1994

Task-induced differential cortical activation pattern.

Measures of task-dependent cortical activation were assessed by bilateral EEG recordings from frontal, temporal, parietal and occipital areas. Two pictorial tests, the Raven Advanced Progressive Matrices and the Space Relations Test were used for verbal and spatial conditions, respectively. Recordings were obtained for 20 trials of each task from 22 right-handed adult males and 16 s. trial epochs were subjected to Fast Fourier analyses. Averaged intensity values for the alpha band were compared between verbal and spatial tasks for all subjects and between subgroups of verbalizers and visualizers, allotted on the basis of subject's performance index, derived from response speed and accuracy on the two tasks. The results were as follows: (1) The most pronounced EEG discriminators between the two performance subgroups are the left and right parietal and the right frontal area; (2) The left parietal zone provides the most pronounced discrimination between two groups; (3) There were significant interactions between the left parietal and the right frontal region; (4) The two parietal areas show characteristic frequency shifts in opposite directions for the task conditions. The findings imply complex interplay among the two parietal and right frontal areas, associated with sequential and holistic strategies. The results urge researchers to take into consideration subjectively preferred cognitive strategy, which along with objective task demands influences the process of problem solving and accompanying physiological changes.

Adult↗

PubMed2000

Asymmetry between encoding and retrieval processes: evidence from divided attention and a calibration analysis.

Two experiments provide further information on the effects of divided attention (DA) on encoding and retrieval processes. The first experiment examined the effects of decision and motor difficulty of a concurrent reaction time task. A calibration analysis was used in the second experiment to test the hypothesis that shifting attentional emphasis away from encoding to the secondary task reduces the level of processing the to-be-remembered items receive. Overall, the results confirm and extend the conclusions of Craik, Govoni, Naveh-Benjamin, and Anderson (1996) and Naveh-Benjamin, Craik, Guez, and Dori (1998), by pointing to clear differences between encoding and retrieval processes: Encoding is affected by simultaneous task demands, especially those associated with "central" resources involved in conscious decision making, whereas retrieval is obligatory in that it is largely immune to the effects of simultaneous demands. The results of the calibration analysis suggest that one reason for the poorer memory performance as a result of DA at encoding is a qualitative shift to less deep, elaborative strategies.

Attention↗

PubMed2004

A simultaneous job- and task-based exposure evaluation of petroleum tanker drivers to benzene and total hydrocarbons.

A simultaneous job- and task-based exposure study was conducted for tanker drivers delivering petroleum products from several bulk terminals and an agency to retail outlets. Full-shift (job-based) samples and job component tasks samples were collected simultaneously. The tasks sampled included loading, unloading, and travel. Three hundred sixty-six personal charcoal tube samples were collected. Full-shift visual observations of work practices and real-time monitoring using a data logging hydrocarbon analyzer were also conducted. Multiple measurements per worker were made, which permitted an assessment of sampling variability within and between workers. The highest exposures for drivers occurred during unloading at the agency. The mean benzene exposure for agency drivers was 0.88 ppm for full-shift time-weighted average, 2.86 ppm for unloading, and 0.54 ppm for loading. For bulk terminal drivers, the mean benzene level without vapor control was 0.12 ppm for time weighted average, 0.24 ppm for unloading, and 0.33 ppm for loading. The time-weighted average exposure of the agency and bulk terminal drivers based on the data collected and the lognormal model can be expected to exceed threshold limit value-time weighted average of 0.5 ppm for benzene about 70 and 2% of the time, respectively. Agency drivers' unloading and loading tasks accounted for approximately 30% and 7% of the total time, and 95% and 4% of total exposure, respectively. For the bulk terminal drivers, mean unloading and loading tasks constituted 24% and 12% of the total time, and 68% and 19% of the total exposure, respectively. Travel activity accounted for an average of 63% of the total time for agency and 64% for bulk terminal drivers, but only contributed < 1 and 13% of the total exposure, respectively. The actual job-based time-weighted average concentration and the calculated time-weighted average derived from the time-weighted summation of the components tasks are in very good agreement. Within-worker variability was generally higher than between-worker variability. Exposure control strategies are required primarily for unloading at the agencies. Vapor control technology at the terminal effectively reduces exposure (by almost 50%) and fugitive emissions.

Automobile Driving↗

PubMed1982

Explorations of individual differences relevant to high level skill.

Past research has uncovered few broad abilities that underlie high skill. In this paper, attempts to isolate three different abilities of potential relevance to skill are described. No evidence was found for a general time-sharing ability in common to different kinds of tasks. Modest evidence was found for a trait of attentional flexibility. That trait could potentially be of use in predicting success for skills that require rapid shifts of attention because of rapidly changing task demands. Finally, the rate of repetitive activity is correlated across different muscle groups. For example, finger tapping speed is correlated with foot tapping speed, suggesting a common rate limiting factor. In turn, those rates predict handwriting speed and, according to Book (1924), championship typing.

Journal Article↗

PubMed1995

[Effect of task difficulty on hemispheric differences in visual image processing].

Hemispheric specialization of visual imagery processes is a topic of recurrent debate. Recent theories have argued for a left postcentral center for the generation of visual images. Because of contradictory results the process of imaging has been divided into a left hemisphere component (visual imagery) and a right hemisphere component (supramodal spatial mental imagery). An alternative and more parsimonious account would be that the degree of difficulty of visual imagery tasks is responsible for hemispheric differences: easy tasks are solved faster within the left hemisphere because of a direct access to action control, whereas more difficult tasks rely on a right hemisphere specialization for spatial processing. In our experiment we varied the degree of difficulty by introducing concurrent tasks which were interspersed at random into the series of critical stimuli. Interspersing concurrent tasks prevents subjects from automatizing of critical processes and delays reaction times. For the critical visual imagery tasks we presented either upper or lower case letters to the different visual fields and asked for figural aspects of the corresponding lower or upper case letters, respectively. The interspersed stimuli concerned an estimation of the distance of the stimuli or the localization of the stimuli in the upper or lower part of the screen. We also presented upper and lower case letters in random order, thus forcing the subjects to shift between two different visual imagery tasks. In order to look for the effect of position-repetition priming upon visual field advantages we also analyzed the interaction of the position on the screen and its repetition with hemispheric advantages. In one of the visual imagery tasks, the experiments without concurrent tasks yielded a right visual field/left hemisphere advantage. On the other hand, interspersing other tasks resulted in a left visual field/right hemisphere advantage for visual imagery tasks, though none of the concurrent tasks showed a significant visual field advantage in itself. The same holds for combined and random presentation of the two different visual imagery tasks. The results therefore argue for a right hemisphere advantage for difficult visual imagery tasks, whereas easier tasks (monotonous presentation of only one visual imagery tasks) are processed faster in the left hemisphere. The random repetition of positions on the screen yielded a significant effect but had no influence on the visual field advantages found.

Adult↗

PubMed2005

Orienting and alerting: effect of 24 h of prolonged wakefulness.

It is well known that a decrease in vigilance can easily occur during 24 h of continuous wakefulness, but no study has assessed whether and in what way extended wakefulness might affect spatial orienting. In other words, it is not clear what happens when a subject has to orient his attention during a state of poor vigilance, resulting from sleep loss or sustained wakefulness. The aim of this study was to investigate this issue. Twelve right-handed male subjects participated in the experiment, which took place on two consecutive days. On the first day, in order to evaluate baseline orienting attention, the subjects performed a covert orienting task (in which the cue stimuli generated endogenous shifts of attention), lasting 20 min; on the second day, during 24 h of prolonged wakefulness, the same task was performed 12 times, about every 120 min, beginning at 10.00 a.m. Results showed an overall slowing of reaction time across the sessions, indicating a linear decrease of vigilance. However, this vigilance decrease did not seem to affect attention-orienting mechanisms, suggesting that the two systems are independent of each other.

Adult↗

PubMed2004

Spontaneous and imitated productions in Spanish-speaking children with phonological disorders.

PURPOSE: Research examining the relationship between spontaneous and imitated productions for phonological analysis has indicated that the inclusion of imitated productions may overestimate children's phonological abilities. Previous research in this area has included only English-speaking children. The purpose of this study was to determine what, if any, differences there were in the spontaneous and imitated productions of Spanish-speaking children with phonological disorders. METHOD: Twelve Spanish-speaking children with phonological disorders (5 boys and 7 girls), ranging in age from 3;1 (years;months) to 4;9 (M = 3;11), participated in the study. Their spontaneous and imitated productions, based on a sample of single words, were analyzed to determine which elicitation task yielded the more adult-like production. Differences in consonant accuracy between the two tasks were analyzed, as was the shift in error type from spontaneous to imitated productions. RESULTS: The results indicated that spontaneous and imitated productions were identical in 62% of the cases, an imitated production was more adult-like than a spontaneous one in 25% of the cases, and a spontaneous form was more adult-like than an imitated one in approximately 13% of the cases. Consonant accuracy for some children also varied as a function of elicitation task. CLINICAL IMPLICATIONS: For additional diagnostic and prognostic value, speech-language pathologists can incorporate imitated responses in their analyses.

Articulation Disorders↗