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PubMed1989

Premotor programming and cortical processing in the cerebral cortex. Electrophysiological correlates of hemispheric dominance.

Slow brain potentials were averaged from 12-15 EEG records (t = DC or 5 s) before and during voluntary hand movements and writing, spatial vision, language, and calculation tasks without vocalization and with visual fixation. EOG and writing pressure or EMG were recorded simultaneously. Skilled actions caused largest negative potentials in the contralateral sensorimotor hand area. Left-sided lateralization or bilaterally equal surface-negative potential shifts appeared during language and calculation tasks in 90% of the right-handers and in 75% of the left-handers. Right-sided lateralizations occurred during the viewing of perspective Necker figures or random-dot stereograms in the large majority of all subjects.

Adolescent↗

PubMed1997

Random motor generation in a finger tapping task: influence of spatial contingency and of cortical and subcortical hemispheric brain lesions.

OBJECTIVE: To test the hypothesis that, during random motor generation, the spatial contingencies inherent to the task would induce additional preferences in normal subjects, shifting their performances farther from randomness. By contrast, perceptual or executive dysfunction could alter these task related biases in patients with brain damage. METHODS: Two groups of patients, with right and left focal brain lesions, as well as 25 right handed subjects matched for age and handedness were asked to execute a random choice motor task--namely, to generate a random series of 180 button presses from a set of 10 keys placed vertically in front of them. RESULTS: In the control group, as in the left brain lesion group, motor generation was subject to deviations from theoretical expected randomness, similar to those when numbers are generated mentally, as immediate repetitions (successive presses on the same key) are avoided. However, the distribution of button presses was also contingent on the topographic disposition of the keys: the central keys were chosen more often than those placed at extreme positions. Small distances were favoured, particularly with the left hand. These patterns were influenced by implicit strategies and task related contingencies. By contrast, right brain lesion patients with frontal involvement tended to show a more square distribution of key presses--that is, the number of key presses tended to be more equally distributed. The strategies were also altered by brain lesions: the number of immediate repetitions was more frequent when the lesion involved the right frontal areas yielding a random generation nearer to expected theoretical randomness. The frequency of adjacent key presses was increased by right anterior and left posterior cortical as well as by right subcortical lesions, but decreased by left subcortical lesions. CONCLUSIONS: Depending on the side of the lesion and the degree of cortical-subcortical involvement, the deficits take on a different aspect and direct repetions and adjacent key presses have different patterns of alterations. Motor random generation is therefore a complex task which seems to necessitate the participation of numerous cerebral structures, among which those situated in the right frontal, left posterior, and subcortical regions have a predominant role.

Adult↗

PubMed2002

Decision-making processes following damage to the prefrontal cortex.

Recent work has suggested an association between the orbitofrontal cortex in humans and practical decision making. The aim of this study was to investigate the profile of cognitive deficits, with particular emphasis on decision-making processes, following damage to different sectors of the human prefrontal cortex. Patients with discrete orbitofrontal (OBF) lesions, dorsolateral (DL) lesions, dorsomedial (DM) lesions and large frontal lesions (Large) were compared with matched controls on three different decision-making tasks: the Iowa Gambling Task and two recently developed tasks that attempt to fractionate some of the cognitive components of the Iowa task. A comprehensive battery including the assessment of recognition memory, working memory, planning ability and attentional set-shifting was also administered. Whilst combined frontal patients were impaired on several of the tasks employed, distinct profiles emerged for each patient group. In contrast to previous data, patients with focal OBF lesions performed at control levels on the three decision-making tasks (and the executive tasks), but showed some evidence of prolonged deliberation. DL patients showed pronounced impairment on working memory, planning, attentional shifting and the Iowa Gambling Task. DM patients were impaired at the Iowa Gambling Task and also at planning. The Large group displayed diffuse impairment, but were the only group to exhibit risky decision making. Methodological differences from previous studies of OBF patient groups are discussed, with particular attention to lesion laterality, lesion size and psychiatric presentation. Ventral and dorsal aspects of prefrontal cortex must interact in the maintenance of rational and 'non-risky' decision making.

Adult↗

PubMed2003

Spatio-temporal working-memory and short-term object-location tasks use different memory mechanisms.

Spatial short-term memory for objects' locations was investigated in a spatial relocation task. During maintenance, dynamic visual noise or spatial tapping were administered as visual or spatial secondary tasks, respectively. Because memory for location should tap the visual component of working memory, a visual but not a spatial secondary task should impair location memory. In fact, neither of the tasks impaired memory (Experiment 1), although the expected dissociation between visual and spatial components was clearly confirmed for a spatio-temporal main task (Corsi test) (Experiment 2). We then contrasted location memory for pictures of objects and of nonsense figures under visual interference. Real objects were relocated much better than nonsense figures, and visual noise was again ineffective (Experiment 3). When spatial tapping was combined with the same material (Experiment 3a), again no influence on memory for locations of objects was observed and only a small influence on remembering nonsense figures. We suggest that the Corsi and the relocation VSWM-tasks use different memory mechanisms. The configuration of objects is reconstructed from perceptual records in an episodic buffer, provided by the same structures that enable visual memory after longer intervals. Rehearsal is not necessary for the persistence of these traces. In contrast, in the Corsi task remembering, a temporal sequence across homogeneous locations needs spatio-temporal marking and therefore active rehearsal of the locations by shifting spatial attention. A spatially demanding secondary task during retention interrupts this rehearsal.

Adult↗

PubMed1989

Early-life undernutrition impairs the development of the learning and short-term memory processes mediating performance in a conditional-spatial discrimination task.

Previously undernourished and well-nourished control rats 23, 30, 40, and 90 days old were compared in a win-shift version of a conditional-spatial discrimination task. Control animals at each age were able to reach criterion on this problem. In contrast, the underfed rats were unable to solve this problem until they were at least 40 days old. The short-term memory of the 40- and 90-day-olds was further evaluated by increasing the interval between the forced run and choice run to 30, 60, and 180 s. Control animals could bridge all intervals; however, the undernourished animals' performance fell to chance when the interval was only 60 s. Thus, early-life undernutrition severely impaired the development of the ability of animals to solve spatial-conditional discrimination tasks and permanently impaired their short-term memory capacity. A simple threshold model relating undernutrition, brain development, and behavior is proposed to account for these data.

Animals↗

PubMed2001

Differential effects of 6-OHDA lesions of the frontal cortex and caudate nucleus on the ability to acquire an attentional set.

Evidence from both human and animal studies indicates that catecholamine (dopamine and noradrenaline) imbalances in the fronto-striatal circuitry are associated with deficits in higher- order cognitive functions. The present study examined how catecholamines within this circuitry modulate attentional function, specifically the ability to develop, maintain, and shift an attentional set. Catecholamine depletions within the frontal cortex of the common marmoset impaired the ability to acquire an attentional set, and increased susceptibility to distraction from task-irrelevant stimuli. Analysis of set-shifting performance with stimulus dimensions of varying salience suggested that frontal catecholamine depletion selectively disrupts "top-down", but not "bottom-up" attentional processing. In contrast, the ability to acquire and shift an attentional set remained intact following dopaminergic depletion from the caudate nucleus. However, the reduced susceptibility to distraction from task-irrelevant stimuli displayed by monkeys with dopaminergic depletions of the caudate nucleus suggests that responding was under more rigid control by the currently rewarded stimulus. The results demonstrate opposite behavioural effects of 6-hydroxydopamine (6-OHDA) lesions in the frontal cortex and caudate nucleus in tasks requiring selective attention. Frontal catecholamine depletion caused an increase in distractibility while caudate dopamine loss induced greater focusing of responding.

Adrenergic Agents↗

PubMedDate not supplied

Preserved performance by cerebellar patients on tests of word generation, discrimination learning, and attention.

Recent theories suggest that the human cerebellum may contribute to the performance of cognitive tasks. We tested a group of adult patients with cerebellar damage attributable to stroke, tumor, or atrophy on four experiments involving verbal learning or attention shifting. In experiment 1, a verb generation task, participants produced semantically related verbs when presented with a list of nouns. With successive blocks of practice responding to the same set of stimuli, both groups, including a subset of cerebellar patients with unilateral right hemisphere lesions, improved their response times. In experiment 2, a verbal discrimination task, participants learned by trial and error to pick the target words from a set of word pairs. When age was taken into account, there were no performance differences between cerebellar patients and control subjects. In experiment 3, measures of spatial attention shifting were obtained under both exogenous and endogenous cueing conditions. Cerebellar patients and control subjects showed similar costs and benefits in both cueing conditions and at all SOAs. In experiment 4, intra- and interdimensional shifts of nonspatial attention were elicited by presenting word cues before the appearance of a target. Performance was substantially similar for cerebellar patients and control subjects. These results are presented as a cautionary note. The experiments failed to provide support for current hypotheses regarding the role of the cerebellum in verbal learning or attention. Alternative interpretations of previous results are discussed.

Aged↗

PubMed1987

Shifting ear differences in melody recognition through strategy inducement.

In a previous study, the pattern of ear superiority displayed by nonmusicians in a task where dichotically presented target melodies have to be recognized among four probes was found to be correlated with subjects' descriptions of their operating modes: those who reported focusing on critical local differences in pitch tended to show right ear advantage (REA) and the others LEA. The purpose of the present study was to examine if laterality patterns can be affected by treatments designed to induce particular strategies. Treatments supposed to orient toward analytic processing, advising attention to critical notes, with (Experiment 2) or without (Experiment 1) the additional task of reporting their location, produced the expected shift toward REA. To the contrary, treatments supposed to orient toward holistic processing, advising attention to overall contour or requesting aesthetic judgments (Experiment 1), failed to produce the expected shift toward LEA. The result can be attributed either to a basic difference in susceptibility to strategic control between the different operating modes or, more simply, to ineffectiveness of the present holistically oriented treatments.

Adolescent↗

PubMed1995

Effect of computerized charting on nursing activity in intensive care.

OBJECTIVE: To measure the impact on nursing activity of introducing computerized medical records into intensive care units (ICUs). DESIGN: Prospective data collection monitoring the activity of ICU nurses before and after installation of a computerized charting system. SETTING: A six-bed coronary care unit and an eight-bed medical ICU at the Minneapolis VA Medical Center. SUBJECTS: Registered nurses providing intensive care services. INTERVENTIONS: Installation of a Clinical Information System that computerized the ICU medical records. MEASUREMENTS AND MAIN RESULTS: Before computer installation, nurses spent 24% of their time manipulating data (7% gathering and 17% charting). After installation, charting time decreased to 10%, and data gathering time decreased to 4%, while 10% of time was spent at computer terminals entering or reviewing data. The total time manipulating data post-installation was thus 24% (i.e., unchanged from previous). Computerized charting did not alter time spent in patients' rooms (43% pre- and 43% postinstallation) compared with time spent at the central station (37% pre- and 36% post-installation) or elsewhere (20% pre- and 21% postinstallation). Relative time spent at various tasks varied between units and from shift to shift, but the net effect of computerized charting was that nurses had more time available at the central station for monitoring, and that the computer terminals were used primarily in the patient rooms. CONCLUSIONS: Computerized charting will not necessarily provide ICU nurses with a net excess of time for tasks unrelated to manipulating data.

Computer Terminals↗

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↗

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↗

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↗

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↗