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PubMed2006

Neurobiology of unilateral spatial neglect.

Hemispatial neglect is a common and disabling consequence of stroke. Earlier studies aimed to identify a single area of the brain where damage caused neglect and sought a single disrupted process that could account for the symptoms. Recent studies have shifted toward identifying component processes and representations underlying spatial attention required for various tasks and identifying areas of the brain responsible for each component that together constitute the network of regions responsible for neglect. This review focuses on recent insights into the mechanisms of neglect, regions of neural dysfunction that cause disruption of particular components or forms of neglect, and potential means of ameliorating neglect. Converging evidence supporting these insights comes from new imaging modalities in acute stroke, functional imaging, transcranial magnetic stimulation, electrophysiological studies in humans, and single-cell recording studies in nonhuman primates.

Animals↗

PubMed1997

An examination of the relationship between accountants' scores on field independence and use of and attitude toward computers.

This study examined the performance of 127 accountants on the Group Embedded Figures Test and assessed the accountants' use of and attitude toward using computers to complete job-related tasks. The data support Bernardi's (1993) finding that there has been a shift over time in scores on field independence among accountants. Comparison of field-independence scores by computer use and attitudes support Bernardi's (1993) hypothesis of an association between the shift in field independence and accountant's use of and attitude toward computers.

Accounting↗

PubMed2006

Change in the organization of degrees of freedom with learning.

The authors examined the effects of learning on the change in the organization of the mechanical and dynamical degrees of freedom in 5 men who performed a ski-simulator task. A 3-dimensional analysis of the motion of the total-body center of mass and the segmental centers of mass (head, torso, thighs, and shanks) over practice showed that the recruitment of mechanical degrees of freedom was strongly influenced by anatomical and task constraints. Principal components analysis of the body segments' motions revealed that practice shifted their relative contributions but did not change the number of principal components. The present findings show that there can be independence in the patterns of change in the mechanical and dynamical degrees of freedom that arise from practice.

Adolescent↗

PubMed2003

Using the observer to analyze learning in virtual worlds.

In this study, we describe and analyze the ways in which high school students explored a virtual solar system (VSS). VSS is a nonimmersive virtual environment that affords visual manipulations of space by altering its frame of reference. The Observer software was used to code and analyze the participants' real-time free-exploration task. Two basic behaviors were identified across participants: establishing several home bases, and shifting between a still mode and a dynamic mode. Moreover, three overall exploration patterns emerged: the butterfly pattern represents a superficial mode of learning; the bee pattern represents an in-depth mode of studying the various celestial objects; and the eagle pattern represents a global approach of studying the complex system. This virtual reality environment promises to provide a setting in which to further study consistent patterns and individual differences in exploration strategies.

Adolescent↗

PubMed2000

Divided attention, aging, and priming in exemplar generation and category verification.

Transfer-appropriate processing theories differentiate between conceptual- and perceptual-priming tasks. The former are said to be influenced by the nature of processing engaged in at study, but not by changes in modality between study and test; the latter are sensitive to changes in format between study and test, but not to variations in the extent of semantic processing at study. In the present experiments, we examined the effects of divided attention and aging on priming in exemplar generation and category verification, two tasks that require access to semantic information at test. Manipulations of attention during encoding affected the extent of priming in exemplar generation, but not in category verification. Priming effects were similar in young and older adults in exemplar generation following study in both full and divided attention. Although older adults did not demonstrate priming in category verification in one experiment, no effects of age or divided attention were observed in a second experiment. In addition, priming in category verification was unaffected by varying the level of processing at encoding. However, the absence of levels-of-processing and attention effects in category verification does not signal that priming in this task has a perceptual basis; priming in category verification was insensitive to modality shifts between study and test. The implications of these findings for theories of priming and cognitive aging are considered.

Adolescent↗

PubMed1999

Scale of attentional focus in visual search.

The effects of the spatial scale of attention on feature and conjunction search were examined in two experiments. Adult participants in three age groups--young, young-old, and old-old--were given precues of varying validity and precision in indicating the location of a target letter subsequently presented in a visual array. Systematic decreases in the size of a valid precue (toward the size of the target) progressively facilitated both feature and conjunction search, with a greater benefit accruing to conjunction search. Age-related slowing in conjunction search was mitigated by precise (small and valid) precues, presumably because they reduced the need for participants in the young-old group to focus and to shift attention. Nevertheless, this benefit was reduced in the old-old group. The effects of valid location precue size varied with cue-target stimulus onset asynchrony (SOA) in a manner that interacted with search difficulty: Effects of cue size developed more rapidly in feature search but more slowly in conjunction search. Finally, when precues were invalid for target location, search was faster with larger sized precues. Thus, in both easy feature search and hard conjunction search, the scale of visuospatial attention modulates the speed of visual search. Furthermore, when the SOA is sufficiently long for cue effects to develop, the ability to dynamically adjust the scale of visuospatial attention appears to decline in advanced age. These results go beyond current models in suggesting that visuospatial attention possesses two dynamic properties--shifting in space and varying in scale--that are deployed independently, depending on task demands.

Adolescent↗

PubMed2000

Cognitive dysfunction in obsessive-compulsive disorder.

OBJECTIVE: Assessment of cognitive functions among obsessive-compulsive disorder (OCD) patients would help in understanding the neurobiology and brain areas involved in that disorder. The objective of this work was to study the cognitive dysfunction in OCD patients and to identify its correlation with both the clinical picture and the severity of the disorder. METHOD: Neuropsychological and electrophysiological event-related potentials were tested in 30 OCD patients and compared with 30 normal volunteers of a matched gender, age and education. RESULTS: Results showed a defective visuospatial recognition, which worsens with chronicity, deteriorated set-shifting abilities, overfocused attention to irrelevant stimuli and delayed selective attention to relevant tasks. Mild cases showed better selective attention than severe cases. Obsessive cases had a defective visual memory, while compulsive cases had delayed perception of task relevant stimuli. Mixed cases showed disturbed information-processing both early and late. CONCLUSION: OCD patients have a characteristic pattern of cognitive dysfunction that differs among patients of varied severity, chronicity and symptom type. We suggest a striatofrontoparietal neural pathophysiology. OCD seems to be a heterogeneous disorder, both clinically and pathophysiologically.

Adolescent↗

PubMed1992

Anxiety and sport performance.

From the findings summarized in this review, it appears that there is little evidence in support of the inverted-U hypothesis. Available research indicates that there is considerable variability in the optimal precompetition anxiety responses among athletes, which does not conform to the inverted-U hypothesis. Many athletes appear to perform best when experiencing high levels of anxiety and interventions that act to produce quiescence may actually worsen the performance of this group. These findings indicate that there is a need to shift the research paradigm away from theories of anxiety and performance based on task characteristics or group effects and, instead, employ theoretical models that account for individual differences. Hanin's [39, 40] ZOF theory appears to be a good candidate for furthering our knowledge in this area. It was developed on the basis of research with athletes and it explicitly incorporates the concept of individual differences in the anxiety-performance relationship. Most important, because an individual's optimal range of anxiety is precisely defined, the validity of ZOF theory can be directly examined through hypothesis testing, whereas it has been argued that the inverted-U hypothesis is effectively shielded against falsification [84]. Although the findings of ZOF theory indicate that a significant percentage of athletes perform best at high levels of anxiety, Hanin's translated writings do not provide an explanation of why this is so. Further research is clearly indicated, but one explanation for this finding may involve how the athlete interprets or conceptualizes anxiety. For example, Mahoney and Avener [64] found that, although the absolute level of precompetition anxiety was similar between successful and unsuccessful Olympic gymnasts, there were differences in the way the athletes conceptualized the anxiety they were experiencing. The better performers viewed their anxiety as desirable, whereas anxiety was associated with self-doubts and catastrophizing in the unsuccessful gymnasts. Similar differences have been observed in the test anxiety literature where it has been found that poorer test takers perceive their anxiety to be more threatening and debilitating than do better performers [45]. Furthermore, temporal differences in the patterning of anxiety [64], fear responses, or cardiorespiratory measures [28] have been found between successful and unsuccessful performers; this may reflect a difference in the ability to regulate anxiety. It may also be the case that performance is not so much affected by the absolute level of precompetition anxiety as the consistency in the anxiety level across competitions. Athletes may also develop coping strategies that exploit consistent changes in attentional focus that result from elevated anxiety.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1979

The distance of rock test -- a preliminary report.

This paper is a preliminary report describing the development of a new clinical test for measuring the response time of the visual system to shift from distance to near and back to distance to a given discriminatory task. The new test is called Distance rock (Drk) and is calibrated in cycles per minute. Data from college students and survey results from 591 school children from the first to sixth grades were used to develop these preliminary results. Change in response time covariant with grade level was demonstrated which indicates this test may become clinically important for developmental vision.

Adolescent↗

PubMed1995

Peak exposure concentrations of dust and flour aeroallergen in flour mills and bakeries.

As part of an epidemiological study amongst workers exposed to flour we measured peak exposure levels to total dust and flour aeroallergen with personal samplers in bakeries, flour mills and packing stations. Short-term tasks which were expected to give rise to high concentrations of exposure (peaks) were identified. The frequency and duration of these tasks were estimated and their levels of exposure to dust and flour aeroallergen measured. In total 209 samples were taken. The highest exposure concentrations both for dust (geometric mean > 30 mg m-3) and for flour aeroallergen (geometric mean > 500 micrograms m-3) were measured during certain operations. Exposure concentrations for the tasks were often much higher than the levels we had measured over a shift in a previous study. This might be important for sensitization and for the development of asthma. Peak exposure concentrations could be used to explore the exposure-response relationship more comprehensively. In general average flour aeroallergen concentrations increased linearly with average dust concentrations, although there were some exceptions.

Allergens↗

PubMed1989

Visual cerebral lateralization over phases of the menstrual cycle: a preliminary investigation.

This study investigated whether visual cerebral asymmetries would change in phase with hormonal variations during the menstrual cycle. Lexical decision and line orientation tasks were administered during follicular, luteal, and menstrual phases of each woman's cycle. These tasks were also administered to a reference group of male subjects. Signal detection analyses indicated an unvarying RVF advantage in word/nonword discriminability (d') throughout the menstrual cycle, but a phase-dependent shift in left hemisphere response criterion (log beta). Gender differences were present for discriminability of line orientation, and female performance on this task varied over the cycle. The results imply that the neural systems subserving some cognitive functions are sensitive to fluctuations in gonadal steroids and suggest a hormonal basis for gender differences in some visual-spatial functions.

Adolescent↗

PubMed2004

Adaptation of performance during a week of simulated night work.

This study aimed to provide a comparative index of the performance impairment associated with the fatigue levels frequently experienced in workplaces that require night work. To do this, we equated fatigue-related impairment with the impairment resulting from varying levels of alcohol intoxication. Fifteen young individuals participated in two counterbalanced conditions which required them to (1). 'work' seven consecutive 8-h night shifts, and (2). consume an alcoholic beverage at hourly intervals until their blood alcohol concentration (BAC) reached 0.10%. In each condition, performance was measured at hourly intervals using a 10-min psychomotor vigilance task (PVT). Analysis indicated that as BAC increased, performance impairment significantly increased. Similarly, response times significantly increased during the first six simulated night-shifts, and lapse frequency significantly increased during the first two shifts. Equating the two conditions indicated that the first simulated night shift was associated with the greatest degree of performance impairment. In general, the impairment at the end of this shift was greater than that observed at a BAC of 0.10%. During the second and third simulated night shifts, the performance impairment was less than on the first night, but greater than that observed at a BAC of 0.05%. For the final four nights, the performance decrements generally did not exceed those observed at a BAC of 0.05%. This suggests that during a week of consecutive night shifts, adaptation of performance occurs.

Adolescent↗

PubMed2000

Inactivation of parietal and prefrontal cortex reveals interdependence of neural activity during memory-guided saccades.

Dorsolateral prefrontal and posterior parietal cortex share reciprocal projections. They also share nearly identical patterns of neuronal activation during performance of memory-guided saccades. To test the hypothesis that the reciprocal projections between parietal and prefrontal neurons may entrain their parallel activation, the present experiments have combined cortical cooling in one cortical area with single-unit recording in the other to more precisely determine the physiological interactions between the two during working memory performance. The activity of 105 cortical neurons during the performance of an oculomotor delayed response (ODR) task (43 parietal neurons during prefrontal cooling, 62 prefrontal neurons during parietal cooling) was compared across two blocks of trials collected while the distant cortical area either was maintained at normal body temperature or cooled. The mean firing rates of 71% of the prefrontal neurons during ODR performance changed significantly when parietal cortex was cooled. Prefrontal neurons the activity of which was modulated during the cue, delay, or saccade periods of the task were equally vulnerable to parietal inactivation. Further, both lower and higher firing rates relative to the precool period were seen with comparable frequency. Similar results were obtained from the converse experiment, in which the mean firing rates of 76% of the parietal neurons were significantly different while prefrontal cortex was cooled, specifically in those task epochs when the activity of each neuron was modulated during ODR performance. These effects again were seen equally in all epochs of the ODR task in the form of augmented or suppressed activity. Significant effects on the latency of neuronal activation during cue and saccade periods of the task were absent irrespective of the area cooled. Cooling was associated in some cases with a shift in the best direction of Gaussian tuning functions fit to neuronal activity, and these shifts were on average larger during parietal than prefrontal cooling. In view of the parallel between the similarity in activity patterns previously reported and the largely symmetrical cooling effects presently obtained, the data suggest that prefrontal and parietal neurons achieve matched activation during ODR performance through a symmetrical exchange of neuronal signals between them; in both cortical areas, neurons activated during the cue, delay, and also saccade epochs of the ODR task participate in reciprocal neurotransmission; and the output of each cortical area produces a mixture of excitatory and inhibitory drives within its target.

Animals↗

PubMed2001

The role of the striatum and hippocampus in planning: a PET activation study in Parkinson's disease.

Previous work has identified the prefrontal cortex (PFC) and striatum as participating in the planning and selection of movements. We compared the brain activation patterns during planning in Parkinson's disease patients and age-matched controls using H(2)(15)O-PET and the Tower of London (TOL) task. In this study, our mildly affected Parkinson's disease group performed as well as the control group but showed a different pattern of neuronal activation. In the two groups, overlapping areas of the PFC were activated but, whereas the right caudate nucleus was activated in the control group, this was not evident in the Parkinson's disease patients. This suggests that normal normal frontal lobe activation can occur in Parkinson's disease despite abnormal processing within the basal ganglia. Moreover, right hippocampus activity was suppressed in the controls and enhanced in the Parkinson's disease patients. This could represent a shift to the declarative memory system in Parkinson's disease during performance of the TOL task, possibly resulting from insufficient working memory capacity within the frontostriatal system.

Aged↗

PubMed2006

Now you see it, now you don't: on turning semantic interference into facilitation in a Stroop-like task.

We use a masked priming procedure to test two accounts of the picture-word interference (PWI) effect: the lexical selection by competition account (Levelt et al., 1999; Roelofs, 1992) and the response selection account (Lupker, 1979; Miozzo and Caramazza, 2003). In the visible (standard) condition, we replicated the often-observed semantic interference effect. In the masked condition, we observed semantic facilitation. We take the polarity shift as a function of masking to mean that the semantic interference and semantic facilitation in the PWI task should be attributed to two qualitatively different processes. We argue that this conclusion follows naturally from the response selection account, but only with great difficulty from the lexical selection by competition account.

Adolescent↗

PubMed1993

Decomposition of recognition memory event-related potentials yields target, repetition, and retrieval effects.

Task manipulations and a subtractive analytic strategy were combined to decompose the positive-going amplitude shift of the event-related potential (ERP) that is elicited by previously studied words during recognition memory testing. Target stimuli elicited a robust posterior P3b subcomponent, but this effect is shown to be independent of the effects of prior study. Two study-related subcomponents were also identified. The earlier study effect reached peak amplitude about 400 msec after word onset and was elicited by repeated words regardless of whether the task required retrieval of information from secondary memory. This effect might reflect a repetition-related decline in the amplitude of the N400 component. The other study-related effect reached peak amplitude around 600 msec post-stimulus onset. This later effect overlapped temporally with the P3b, but it was not related to targetness. Rather, it was specifically related to task conditions that required retrieval from secondary memory. The identification of this third effect helps to clarify the functional significance of the ERPs observed during recognition memory testing.

Analysis of Variance↗

PubMed2003

Parkin mutation associated parkinsonism and cognitive decline, comparison to early onset Parkinson's disease.

BACKGROUND: Patients with Parkinson's disease (PD) have cognitive changes resulting, presumably, from a progressive disruption of the functional integrity of frontostriatal circuitry. OBJECTIVE: To assess the cognitive state of two brothers with early onset autosomal recessive (EO-AR) parkinsonism and a large deletion in the parkin gene, and to compare it to that of patients with sporadic young onset PD (YOPD). METHOD: Two brothers with parkinsonism and deletion of axons 4-6 of the parkin gene (ages 51, 55 years; duration of symptoms, 22, 29 years respectively) and 4 randomly selected patients with YOPD (mean age 47.8+/-4.9 years; mean duration of symptoms, 11.5+/-1.9 years) were administered a neuropsychological battery at "on" state. We assessed global cognitive state using the Mini-Mental State Examination (MMSE), orientation, attention, memory, language, ideational praxis, constructive praxis and executive functions (shifting aptitude, verbal fluency, sequencing). RESULTS: The older of the two brothers with EO-AR parkinsonism had dementia according to DSM IV criteria, and MMSE score of 24, whereas the other had normal global cognitive status with mild cognitive changes (MMSE=29). The older brother had impaired memory tasks. Storage and retrieval capacities were defective on both immediate and delayed recalls, naming, constructional praxis, selective attention, shifting aptitude and phonemic and semantic fluency were also affected. The younger brother had difficulties in retrieval on delayed recall, selective attention, phonetic fluency, shifting aptitude and sequencing. This neuropsychological profile clearly differs from that of the YOPD patients, none of whom displayed cognitive dysfunction. CONCLUSIONS: Our patients with parkin mutation performed poorly on neuropsychological tests compared to those with YOPD. This difference could reflect the longer disease duration or the nature of the degenerative process.

Adult↗

PubMed1999

Vestibular stimulation affects dichotic lexical decision performance.

We report an experimental attempt to shift, by vestibular stimulation, healthy subjects' right ear advantage (REA) in a dichotic listening (DL) task with words and nonwords as stimuli. Forty right-handed men performed the task under two different conditions, once while sitting in a stationary turning chair (baseline) and once during sinusoidal rotation. In this latter condition, every other stimulation was received during maximal left-to-right (i.e., clockwise), every other during maximal right-to-left (i.e., counterclockwise) acceleration. There was a reliable REA for lexical decision accuracy in the baseline and right-to-left trials but not during left-to-right rotation. While right ear performance was unaffected by rotation, there were more correct lexical decisions to left ear targets exclusively during left-to-right turns (one-tailed P = 0.05). Since there were no parallel shifts in auditory thresholds under the different conditions, this effect is not due to any hypothetical auditory-vestibular interactions on a primary sensory level. The improvement in left ear DL performance, although small in our study, is comparable to the symptom-alleviating effect of caloric vestibular stimulation in patients with left-sided hemispatial neglect and interpreted as a consequence of a rotation-induced attentional shift towards the left hemispace.

Adult↗