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PubMedDate not supplied

Bias in visual attention behavior in a normal school-aged population.

Hemi-field visual-spatial attention was studied on a timed letter cancellation task in proficient readers from 7th to 9th grades. Participants maintained greater accuracy in identifying targets in the left quadrants (top/bottom) when compared with the right quadrants (top/bottom), revealing a leftward bias in their responses. Effects of gender and age were evident on performance; females scored significantly higher than males, and 9th graders scored significantly higher than 7th and 8th graders. Thus, a substantial shift in brain maturation may take place from 8th to 9th grades or from the ages of 13.0 to 14.11. Discriminative characteristics of the task are analyzed by assigning greater value to targets located in the top left quadrant. The 9th graders, as compared to the younger students, and the girls, as compared to the boys, evidenced a reading-direction-related bias toward systematic preference for the upper-left to lower-right quadrants.

Age Factors↗

PubMed1975

Septal lesions facilitate the shift from conditioned escape to conditioned avoidance behavior in the rat.

Normal rats were given 1000 training trials in a discriminated lever-press avoidance task. Those animals which exhibited consistent escape behavior but minimal avoidance responding were subjected to either septal lesions or control operations. One week later they were retested in the avoidance apparatus for an additional 1000 trials. Rats with large septal lesions exhibited an immediate increase in avoidance performance relative to the control rats. This increase occurred without a concomitant increase in number of lever-press responses. The performance of 3 out of 4 rats with smaller more dorsal septal lesions was unaffected by the surgery.

Animals↗

PubMed1981

Relation between pitch shifts and MMF shifts in forward masking.

Thresholds for brief sinusoidal signals were determined as a function of signal frequency for fixed sinusoidal maskers in a forward masking task. In some cases the frequency at which maximum masking occurred (MMF) was slightly above or below the masker frequency. In a second experiment subjects were required to adjust the frequency of the signals that its pitch matched that of the "masker." It was found that the frequency required for equal pitch correspond closely to the MMF. A possible explanation is that differences in quality between signal and masker (such as pitch differences) provide a cue for detection in forward masking which is not available when the signal and masker are very similar in quality. Thus maximum masking occurs when the signal and masker are most similar in quality.

Acoustics↗

PubMed2002

Horizontal space misrepresentation in unilateral brain damage. I. Visual and proprioceptive-motor influences in left unilateral neglect.

Patients with unilateral neglect can misperceive horizontal distances in the contralesional space as being shorter than equivalent ipsilesional ones. We evaluated the visual and motor-proprioceptive components of space misrepresentation through a distance reproduction task performed both with and without visual guidance. Four groups of right brain damaged patients (neglect with hemianopia (N+H+), neglect with inferior quandrantanopia (N+Q+), neglect without hemianopia (N+H-) and patients without neglect or hemianopia (N-H-)) and one group of healthy controls (C) performed the line bisection task and reproduced horizontal distances either by setting the endpoints or by doubling the length of a line in the contralesional or ipsilesional space. The doubling length task was administered in three different conditions: (a) visuomotor (the patient draws the line in free vision); (b) visual (by sight the patient guides the examiner drawing the line); (c) proprioceptive-motor (the patient is blindfolded and manually inspects and extends the horizontal distance subtended by the line). Compared to C and N-H- patients, only N+H+ patients exhibited a significant ipsilesional shift in line bisection. N+H+ patients showed the most severe contralesional-overextension/ipsilesional-underextension asymmetry in the endpoint, visuomotor and visual line extension task. In the proprioceptive-motor condition no asymmetry was found and N+H- showed greater overextension on both sides of space. In N+H-, brain damage was mainly centered in central-frontal cortex and basal ganglia. These findings re-emphasize the relevance of damage to visual retinotopically organized representations of space in the genesis of horizontal space misrepresentation of neglect patients and suggest the possible association of a non-lateralized defective processing of proprioceptive-motor information with unilateral neglect.

Adult↗

PubMed2006

Event-related potential studies of language and emotion: words, phrases, and task effects.

This chapter reviews research that focuses on the effects of emotionality of single words, and of simple phrases, on event-related brain potentials when these are presented visually in various tasks. In these studies, presentation of emotionally evocative language material has consistently elicited a late (c. 300-600 ms post-onset) positive-going, largely frontal-central shift in the event-related potentials (ERPs), relative to neutral materials. Overall, affectively pleasant and unpleasant words or phrases are quite similar in their neuroelectric profiles and rarely differ substantively. This emotionality effect is enhanced in both amplitude and latency when emotional content is task relevant, but is also reliably observed when the task involves other semantically engaging tasks. On the other hand, it can be attenuated or eliminated when the task does not involve semantic evaluation (e.g., lexical decisions to words or orthographic judgments to the spelling patterns) or when comprehension of phrases requires integration of the connotative meaning of several words (e.g., compare dead puppy and dead tyrant). Taken together, these studies suggest that the emotionality of written language has a rapid and robust impact on ERPs, which can be modulated by specific task demands as well as the linguistic context in which the affective stimulus occurs.

Brain↗

PubMed1996

Resolving a therapeutic impasse between parents and adolescents in multidimensional family therapy.

This study explored the process of resolving an in-session impasse between a parent and an adolescent in family therapy. Focusing on altering the content and affective tone of a discussion, the "shift intervention" was used to direct a family's conversation away from trying to solve behavior management problems and toward a discussion of fundamental relationship problems. Task analysis was used to specify problematic family interactions, the intervention strategy, and successful and unsuccessful outcomes. Descriptive analyses of 5 successful and 5 unsuccessful interventions yielded a detailed performance model of therapist and family behaviors involved in breaking the impasse. The Beavers Timberlawn Family Evaluation Scale was used to verify the presence of the shift intervention in the data set and to embellish the performance model. The model suggested that adolescents became more cooperative and engaged in treatment when parents shifted from trying to control them to trying to understand them. A detailed performance map for accomplishing this shift is offered.

Adolescent↗

PubMed2001

Comparative electrophysiological and hemodynamic measures of neural activation during memory-retrieval.

The spatial and temporal characteristics of the brain processes underlying memory retrieval were studied with both event-related potentials (ERP) and positron emission tomography (PET) techniques. Subjects studied lists of 20 words and then performed episodic (old/new judgment) or semantic (living/nonliving decision) retrieval tasks on multiple four-item test lists, each lasting 10 sec. The PET and ERP measurements at test were assessed in relation to both the task (episodic vs. semantic) and the item (old vs. new or living vs. nonliving). Episodic retrieval was associated with increased blood flow in the right frontal lobe (Brodmann Area 10) and a sustained, slowly developing positive ERP shift recorded from the right frontopolar scalp. Semantic retrieval was associated with increased blood flow in the left frontal (Area 45) and temporal (Area 21) lobes but no clear ERP concomitant. The two retrieval tasks also differed from each other in the ERPs to single items in an early (300-500 ms) time window. Item-related comparisons yielded convergent results mainly if the retrieved information was relevant to the given task (e.g., old/new items during episodic retrieval and living/nonliving items during semantic retrieval). Episodically retrieved old items were associated with increased blood flow in the left medial temporal lobe and a transient increase in the amplitude of the late positive component (500-700 ms) of the ERP. Semantically retrieved living items were associated with increased blood flow in the left frontal cortex and anterior cingulate and a transient late frontal slow wave (700-1,500 ms) in the ERPs. These results indicate that the brain regions engaged in memory retrieval are active in either a sustained or transient manner. They map task-related processes to sustained and item-related processes to transient neural activity. But they also suggest that task-related factors can transiently affect early stages of item processing.

Adult↗

PubMed2002

Hemispheric asymmetry in human lateral prefrontal cortex during cognitive set shifting.

Functional organization of human cerebral hemispheres is asymmetrically specialized, most typically along a verbal/nonverbal axis. In this event-related functional MRI study, we report another example of the asymmetrical specialization. Set-shifting paradigms derived from the Wisconsin card sorting test were used, where subjects update one behavior to another on the basis of environmental feedback. The cognitive requirements constituting the paradigms were decomposed into two components according to temporal stages of task events. Double dissociation of the component brain activity was found in the three bilateral pairs of regions in the lateral frontal cortex, the right regions being activated during exposure to negative feedback and the corresponding left regions being activated during updating of behavior, to suggest that both hemispheres contribute to cognitive set shifting but in different ways. The asymmetrical hemispheric specialization within the same paradigms further implies an interhemispheric interaction of these task components that achieve a common goal.

Adult↗

PubMed2004

[One-week variation of cotton dust and endotoxin levels in a cotton mill. Relation with the daily variation of the expiratory flow rates].

UNLABELLED: The prevalence of respiratory occupational diseases in the textile industry depends on environmental factors such cotton dust (CTD) levels and gram negative bacteria endotoxin (EDX) contamination. OBJECTIVE: To assess the environmental conditions (CTD and EDX) during one week in a cotton mill with respect to FEV1 variation throughout the work shift. POPULATION AND METHODS: 47 cotton mill workers (24F, 23M); average age: 42 +/- 11 years; average exposure to cotton dust: 22.5 +/- 9.4 years; Asthma: 15 (32%), Byssinosis: 11 (23%) and Asymptomatics: 21 (45%); a past history of respiratory symptoms: 13.1 +/- 11.7 years. Clinical evaluation, skin prick tests, a metacholine challenge, lung function tests and a work-place evaluation were performed. FEV1 Shift-variation (Delta-Shift) = end-shift FEV1 - start-shift FEV1, was calculated during one week. CTD and EDX levels were measured daily for each work place throughout this week and everyday during different operation tasks (work, cleaning, maintenance). The average values of CTD and EDX were calculated according to the time spent on each of these tasks for every worker who was exposed. RESULTS: Great variability of the environment conditions was observed throughout the week with the highest levels of CTD and EDX on Friday, even in comparison with Monday (CTD = 1.01 +/- 0.31 mg/m3 vs 0.68 +/- 0.65 mg/m3; p < 0.0005 e EDX = 33.1 +/- 8.9 ng/m3 vs 20.8 +/- 9.4 ng/m3; p < 0.0001). The shift variation was -129 +/- 97 ml for all the workers. The workers with asthma had the greatest reduction in expiratory flow rates, highest BHR and Delta-Shift but there were no differences in the levels of CTD and EDX among the three groups. Delta-Shift showed an association with the levels of EDX, specially in individuals with BHR but not with CTD levels. CONCLUSION: The environmental conditions that textile workers are exposed to, varies throughout the week and are associated with variations in flow rates and so lung function tests should be performed in a serial manner for the evaluation of respiratory occupational disease. The highest levels of EDX were recorded on Friday and this confirms the low reliability of the diagnostic criteria of byssinosis and points to the necessity of more objective measures.

Adult↗

PubMed2006

Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads.

Despite the well-recognized role of lifting in back injuries, the relative biomechanical merits of squat versus stoop lifting remain controversial. In vivo kinematics measurements and model studies are combined to estimate trunk muscle forces and internal spinal loads under dynamic squat and stoop lifts with and without load in hands. Measurements were performed on healthy subjects to collect segmental rotations during lifts needed as input data in subsequent model studies. The model accounted for nonlinear properties of the ligamentous spine, wrapping of thoracic extensor muscles to take curved paths in flexion and trunk dynamic characteristics (inertia and damping) while subject to measured kinematics and gravity/external loads. A dynamic kinematics-driven approach was employed accounting for the spinal synergy by simultaneous consideration of passive structures and muscle forces under given posture and loads. Results satisfied kinematics and dynamic equilibrium conditions at all levels and directions. Net moments, muscle forces at different levels, passive (muscle or ligamentous) forces and internal compression/shear forces were larger in stoop lifts than in squat ones. These were due to significantly larger thorax, lumbar and pelvis rotations in stoop lifts. For the relatively slow lifting tasks performed in this study with the lowering and lifting phases each lasting approximately 2 s, the effect of inertia and damping was not, in general, important. Moreover, posterior shift in the position of the external load in stoop lift reaching the same lever arm with respect to the S1 as that in squat lift did not influence the conclusion of this study on the merits of squat lifts over stoop ones. Results, for the tasks considered, advocate squat lifting over stoop lifting as the technique of choice in reducing net moments, muscle forces and internal spinal loads (i.e., moment, compression and shear force).

Adult↗

PubMed1998

Impact of nocturnal hypoglycemia on hypoglycemic cognitive dysfunction in type 1 diabetes.

To test the hypothesis that glycemic thresholds for cognitive dysfunction during hypoglycemia, like those for autonomic and symptomatic responses, shift to lower plasma glucose concentrations after recent antecedent hypoglycemia in patients with type 1 diabetes mellitus (T1DM), 15 patients were studied on two occasions. Cognitive functions were assessed during morning hyperinsulinemic stepped hypoglycemic clamps (85, 75, 65, 55, and 45 mg/dl steps) after, in random sequence, nocturnal (2330-0300) hypoglycemia (48 +/- 2 mg/dl) on one occasion and nocturnal euglycemia (109 +/- 1 mg/dl) on the other. Compared with nondiabetic control subjects (n = 12), patients with T1DM had absent glucagon (P = 0.0009) and reduced epinephrine (P = 0.0010), norepinephrine (P = 0.0001), and neurogenic symptom (P = 0.0480) responses to hypoglycemia; the epinephrine (P = 0.0460) and neurogenic symptom (P = 0.0480) responses were reduced further after nocturnal hypoglycemia. After nocturnal hypoglycemia, in contrast to nocturnal euglycemia, there was less deterioration of cognitive function overall (P = 0.0065) during hypoglycemia based on analysis of the sum of standardized scores (z-scores). There was relative preservation of measures of pattern recognition and memory (the delayed non-match to sample task, P = 0.0371) and of attention (the Stroop arrow-word task, P = 0.0395), but not of measures of information processing (the paced serial addition task) or declarative memory (the delayed paragraph recall task), after nocturnal hypoglycemia. Thus, glycemic thresholds for hypoglycemic cognitive dysfunction, like those for autonomic and symptomatic responses to hypoglycemia, shift to lower plasma glucose concentrations after recent antecedent hypoglycemia in patients with T1DM.

Adult↗

PubMed1995

Menstrual cycle affects functional cerebral asymmetries.

Cerebral lateralization in females is probably modulated by the menstrual cycle such that a part of hemispheric asymmetries are diminished with an increase of the steroids estrogen and progesterone during the follicular and luteal phase and enhanced with steroid decreases during the menstrual phase. However, previous data were contradictory with regard to the hemispheric side of modulation and could not analyze which steroid is mainly responsible for cycle dependent lateralization shifts. Therefore, in the present study estrogen and progesterone changes were assessed separately and related to changes in cerebral asymmetry. Plasma levels of estrogen and progesterone were measured once during luteal and once during menstrual cycle phase while 20 females subjects performed a verbal and a figural lateralized matching task. The results showed a significant cycle phase x lateralization interaction for the right hemisphere dominated figural comparison task but not for the left hemispheric lexical condition. Although the lateralization was modulated by the menstrual cycle, a within-subject regression analysis demonstrated that the asymmetry shift was not under direct influence of estrogen or progesterone. Thus, the present study provides further empirical support for cycle dependent alterations in lateralization but makes it unlikely that this effect is directly caused by estrogen or progesterone plasma level variations.

Adult↗

PubMed1998

Effects of sleep deprivation and user interface on complex performance: a multilevel analysis of compensatory control.

This study was carried out to test the compensatory control model, which predicts performance maintenance under stress at the expense of effort and increased selectivity. It examined the effects of sleep deprivation on performance in an automated process control task based on a simplified life support system with two types of operator control panel interface: machine centered (M-C), in which access to the system was scheduled by the computer, and human-centered (H-C), in which access was ad-lib. The task environment also permitted the analysis of changes in strategy and in subsidiary activities (alarm reaction time, prospective memory). In a 2 x 2 repeated-measures design, 16 participants carried out the task with each interface after both normal sleep and one night of sleep deprivation (SD). No effects of SD were observed on primary task performance. As predicted, SD effects were confined to strategy changes and subsidiary task impairment and occurred only under the (low control) M-C interface. Subjective effort was increased under SD, with greater increases of effort associated with high levels of performance protection. The findings provide strong evidence in favor of the compensatory control model and argue for the use of complex, multilevel tasks in the analysis of performance under stress. Actual or potential applications include the development of more sensitive performance-testing systems based on multilevel analysis of decrement, and the design of interfaces for shift work and other suboptimal work conditions.

Adult↗

PubMed1996

Exposure of contractors to chemical pollutants during the maintenance shut-down of a chemical plant.

The exposure of employees of different contracting firms to chemical pollutants was assessed during the five-week biennial maintenance shut-down of an isocyanate (TDI) synthesis plant. This assessment was mainly based on personal sampling, but work-related constraints occasionally required that area samples be used instead. Many tasks were carried out during the shut-down procedure (dismantling of reactors, installation of insulation, refection of kilns, cleaning, painting, electricity, etc.), thereby causing the employees of the contracting firms to be exposed to different kinds of pollutants, including products used or manufactured in the process (solvents, TDI and its synthesis intermediates), and products specific to the contractors' activity (welding fumes, crystalline silica, mineral fibers of heat insulation). The highest level of exposure (mainly to TDI) was found for the mechanical engineering activities undertaken during the dismantling of reactors and for cleaning activities. It was demonstrated that there was much variability in day-to-day exposure levels, and occasionally in the exposure levels encountered during a given shift. Cases of concomitant exposure to TDI (mainly short-term exposures) and other pollutants due to simultaneous activities from different tasks in the same area (co-activity) were also observed. Both the need for, and limitations of personal protective equipment (mainly respiratory) are stressed. Special emphasis is put on the responsibility of the owner of the facilities in helping the contractors in the organization of a health and safety policy.

Air Pollutants, Occupational↗

PubMed2006

Decision making and set shifting impairments are associated with distinct symptom dimensions in obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is clinically heterogeneous. The authors examined how specific OCD symptom dimensions were related to neuropsychological functions using multiple regression analyses. A total of 39 OCD patients and 40 controls completed the Iowa Gambling Task (IGT; A. Bechara, A. R. Damasio, H. Damasio, & S. W. Anderson, 1994), which is a test of decision making, and the Wisconsin Card Sorting Test (R. K. Heaton, 1981), which is a test of set shifting. OCD patients and controls showed comparable decision making. However, patients with prominent hoarding symptoms showed impaired decision making on the IGT as well as reduced skin conductance responses. OCD patients had poorer set shifting abilities than controls, and symmetry/ordering symptoms were negatively associated with set shifting. These results help explain previous inconsistent findings in neuropsychological research in OCD and support recent neuroimaging data showing dissociable neural mechanisms involved in mediating the different OCD symptom dimensions.

Adolescent↗

PubMed2005

Are the cognitive deficits associated with impaired insight in schizophrenia specific to executive task performance?

Although impaired insight in schizophrenia has been associated with deficits in executive task performance, the relationship remains unclear. We aimed to clarify this relationship by fractionating executive functioning into the theoretically derived functions of inhibition, working memory, set shifting, and sustained attention. We compared the performance of patients showing impaired insight, patients showing good insight, and a matched control group on measures of each of these executive functions, along with measures of current cognitive functioning and memory. We found that while patients with impaired insight performed significantly below those with good insight on our working memory task, they also performed poorly on measures of general cognitive functioning and memory. We conclude that while impaired insight does appear to be associated with executive deficits, this association may not be specific but may instead relate to cognitive deficits more generally.

Adult↗

PubMed2005

Efficient decoding algorithms for generalized hidden Markov model gene finders.

BACKGROUND: The Generalized Hidden Markov Model (GHMM) has proven a useful framework for the task of computational gene prediction in eukaryotic genomes, due to its flexibility and probabilistic underpinnings. As the focus of the gene finding community shifts toward the use of homology information to improve prediction accuracy, extensions to the basic GHMM model are being explored as possible ways to integrate this homology information into the prediction process. Particularly prominent among these extensions are those techniques which call for the simultaneous prediction of genes in two or more genomes at once, thereby increasing significantly the computational cost of prediction and highlighting the importance of speed and memory efficiency in the implementation of the underlying GHMM algorithms. Unfortunately, the task of implementing an efficient GHMM-based gene finder is already a nontrivial one, and it can be expected that this task will only grow more onerous as our models increase in complexity. RESULTS: As a first step toward addressing the implementation challenges of these next-generation systems, we describe in detail two software architectures for GHMM-based gene finders, one comprising the common array-based approach, and the other a highly optimized algorithm which requires significantly less memory while achieving virtually identical speed. We then show how both of these architectures can be accelerated by a factor of two by optimizing their content sensors. We finish with a brief illustration of the impact these optimizations have had on the feasibility of our new homology-based gene finder, TWAIN. CONCLUSIONS: In describing a number of optimizations for GHMM-based gene finders and making available two complete open-source software systems embodying these methods, it is our hope that others will be more enabled to explore promising extensions to the GHMM framework, thereby improving the state-of-the-art in gene prediction techniques.

Algorithms↗

PubMed1988

An investigation of the phenomenon of "set" in Parkinson's disease.

It has been suggested that patients with Parkinson's disease have a basic deficit in shifting "set." Previous authors have used this hypothesis as an explanation for deficits on a range of cognitive tasks. An experiment was conducted to investigate this phenomenon. A reaction time paradigm was used in which the subject had to make left-right decisions under two stimulus conditions. Both patients and controls showed a facilitation in performance with repetition within each block of trials, followed by a deterioration in performance when the stimulus type switched. Furthermore, the shapes of the reaction-time functions were equivalent in both groups, suggesting that the patients had no deficit in either switching or establishing set in this task. In contrast, they were impaired on the Wisconsin Card Sorting Test. This dissociation suggests that patients with Parkinson's disease do not have a generalized deficit in switching set. It is suggested that patients with Parkinson's disease are impaired on tasks where they have to rely upon internal control for the regulation of behaviour, but are relatively unimpaired on tasks where external cues are available.

Aged↗