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PubMed1984

Detection of interaural phase shift between a subaudible and an audible tone.

Can a shift in interaural phase between a subthreshold signal and an audible contralateral probe tone affect perception of the probe? To obtain an answer, an 800-Hz tone was presented to both ears. The tone was presented continuously to one ear (-25 to + 10 dB SL) and in a sequence of four bursts per trial to the other ear (+ 10 dB SL). Interaural phase was reversed for either the second or the fourth burst in a 2 AFC task. Interaural phase-shift detection threshold (65% correct) varied with the intensity of the continuous signal; across subjects, this threshold varied from -21 to + 1 dB SL. When a 300-or 500-Hz masking tone was added to the ear with the continuous signal, phase-shift detection accuracy depended primarily upon the sensation level of the signal rather than its sound pressure level. These findings demonstrate temporal encoding at signal levels well below hearing threshold.

Adolescent↗

PubMed1997

Executive function in parents of children with autism.

BACKGROUND: Previous studies have shown that individuals with autism show impaired performance on tests of executive function (Ozonoff et al. 1991, 1993; Hughes & Russell, 1993; Hughes et al. 1994). There is also strong evidence for genetic involvement in autism (see Rutter, 1991 for review). If executive dysfunction is a core impairment in autism, then similar impairments are hypothesized to exist in a subtler form among the parents of autistic children. METHODS: Forty parents of autistic children were compared with 40 parents of learning disabled children and 36 adults from unaffected families on three computerized tests of executive function. These tasks tapped attentional-shifting skills, visuospatial planning and working memory. Participants also received a computerized control test of spatial memory-span. In addition, the interviewer's initial impressions of family members were coded using a new 33-item questionnaire. RESULTS: A significant proportion of parents of autistic children (especially fathers) showed impaired executive function. By contrast, parents did as well as both comparison groups on a control test of spatial span, and on other 'non-executive' measures from the tasks, indicating that the autism group were as able and motivated as comparison groups. Interestingly, impairment of executive function was significantly correlated with the interviewer's pre-test impression of social abnormality among parents of autistic children. CONCLUSIONS: The hypothesis that a significant proportion of parents of autistic children show impaired executive function was supported. Parents showed good memory ability, but relatively poor planning skills and attentional flexibility. The extent to which this is an inherent trait in family members, rather than a reflection of the difficulties involved in caring for an autistic child, remains to be examined.

Adolescent↗

PubMed2003

The Madrid card sorting test (MCST): a task switching paradigm to study executive attention with event-related potentials.

Event-related potentials (ERPs) provide valuable information about the fast brain dynamics subserving cognitive functions such as attention and working memory. Most ERP studies employ cognitive paradigms with a fixed task-set (i.e., press a button to coloured targets), but few have measured ERPs time-locked to shifts in set using a task-switching paradigm. The Madrid card sorting test (MCST) is a dual task protocol in which feedback cues signal unpredictable shifts in set (i.e., from 'sort cards by colour' to 'sort cards by shape'). This protocol allows for an integrated analysis of ERPs to both feedback cues and target card events, providing separate ERP features for the shifting, updating, and rehearsal of attention sets in working memory. Two of these ERP indices are the frontal and posterior aspects of the P300 response. Feedback cues that direct a shift in set also elicit a frontally distributed P3a potential (300-400 ms). Instead, target card events evoke increasingly larger posterior P3b (350-600 ms) activity as the new task set becomes gradually rehearsed. The observed modulations in the frontal and posterior aspects of the P300 response system are interpreted from current models of prefrontal cortex function in the executive control of attention.

Adolescent↗

PubMed1988

The effects of fornix section on win-stay/lose-shift and win-shift/lose-stay performance in the rat.

Two groups of rats were trained in 2-lever operant tasks that required them to follow either a Win-shift/Lose-stay rule, or else a Win-stay/Lose-shift rule. The rats in each testing condition attained a similar level of performance. Once the tasks had been learnt, half of the rats in each testing condition were given fornix lesions. These lesions produced a clear performance impairment at all inter-response retention intervals tested in those rats trained on the Win-shift/Lose-stay task, but impaired performance in rats trained on the Win-stay/Lose-shift condition only when the inter-response interval reached 10 s. The implications of these results for the working memory theory and for the temporal discontiguity theory are discussed.

Animals↗

PubMed2006

The role of temporal generalization in a temporal discrimination task.

Two experiments trained rats to discriminate two or three stimulus durations using a temporal discrimination task. A standard peak shift effect was observed when training was administered with short versus long signals in Experiment 1. Both discrimination accuracy scores and the generalization gradients revealed that shorter intervals were discriminated more accurately, which may be due to the scalar property of timing. In Experiment 2, three signals (short, medium, and long) were associated with three different responses, or two of the intervals were associated with one response (short and long or short and medium) and the other interval with a different response. Here, the short/medium versus long discrimination was learned most readily of the three tasks. The results of both experiments indicated a strong contribution of learning of individual durations combined with scalar generalization gradients, but Experiment 2 indicated that categorical encoding of durations may have also been operating.

Animals↗

PubMed2003

Working memory and executive functions in transient global amnesia.

Transient global amnesia (TGA) is usually considered to produce a profound impairment of long-term episodic memory, while at the same time sparing working memory. However, this neuropsychological dissociation has rarely been examined in detail. While a few studies have assessed some components of working memory in TGA, the results that have been obtained are far from conclusive. To clarify this issue, we carried out a comprehensive investigation of working memory in 10 patients during a TGA attack. In the first study, we report the results from three patients examined with a battery of neuropsychological tests designed to assess each of the three subcomponents of Baddeley's model of working memory. In a second study, seven different patients underwent neuropsychological investigations that focused specifically on the central executive system, using a protocol derived from a study by Miyake and colleagues. Our findings showed that subcomponents of working memory, such as the phonological loop and visuo-spatial sketch pad, were spared in TGA patients. Specific executive functions that entailed inhibitory control, dual task performance, updating and shifting mechanisms were also found to be normal. However, we found significantly impaired performance for the Brown-Peterson test, and that TGA patients were significantly impaired in the recollection of their episodic memories. They also made reduced numbers of 'remember' compared with 'know' judgments in the episodic memory test several days after TGA. On the basis of our findings, it would appear that the episodic memory deficit during TGA is not related to elementary aspects of executive functioning. Our data also highlight the nature of the cognitive mechanisms involved in the Brown-Peterson task, which may well depend on long-term memory (such as the process of semantic encoding). Lastly, the selective deficit in recollective episodic memories observed in TGA may be principally related to medial temporal lobe abnormalities that have been reported in this syndrome.

Aged↗

PubMed2001

Attention processes in children with shunted hydrocephalus versus attention deficit-hyperactivity disorder.

Children with congenital hydrocephalus, children with attention deficit-hyperactivity disorder, and normal controls were evaluated with measures of focused attention (Visual Orienting and Detection Task), sustained attention (continuous performance test), and attention shifting (Wisconsin Card Sorting Test). Components from these tasks have been linked to attention systems mediated by anterior or posterior brain networks. Children with congenital hydrocephalus showed an inability to focus and shift attention, which specifically implicated impairment of the disengage and move components of the posterior brain attention system. Children with attention deficit-hyperactivity disorder displayed the expected performance patterns on measures of focused attention once their difficulties with sustained attention were taken into account. However, they showed problems with shifting and sustaining attention, which are commonly associated with the anterior brain attention system.

Achievement↗

PubMed1994

Enhancement of memory processing in an inhibitory avoidance and radial maze task by post-training infusion of bombesin into the nucleus tractus solitarius.

Bombesin is a peptide known to modulate memory storage when given either systemically or intraventricularly immediately after training. Two experiments were conducted to determine whether the nucleus of the solitary tract (NTS) mediates the effects of bombesin on memory. In the first experiment male Sprague-Dawley rats were trained in an inhibitory avoidance task (0.35 mA, 0.5 s footshock) and bombesin or vehicle was infused unilaterally into the NTS through implanted cannulae immediately after training. Retention was assessed either 2 or 7 days later. Doses of 25 or 50 ng of bombesin significantly enhanced retention on the 2 day test (P < 0.05 and 0.01 compared with vehicle controls, respectively). There were no differences between the drug and control groups on the 7 day retention test. In the second experiment, bombesin (25, 50, or 250 ng) or vehicle was infused unilaterally into the NTS immediately after the animals were trained in a win-shift radial arm maze task. On retention tests given 18 h later, groups that received 25 ng or 50 ng of bombesin made a significantly greater percentage of correct choices on the retention test than did the vehicle-treated controls (P < 0.02 and P < 0.05, respectively). The findings indicating that bombesin influences retention by activating the NTS is consistent with recent evidence suggesting that the NTS is involved in regulating memory storage.

Analysis of Variance↗

PubMed1989

Stressful conditions of work: the participative ergonomics approach.

The nature of working stress requires a multi-disciplinary approach for its study. Ergonomics, by its nature multidisciplinary, takes a perspective in which the individual is central and the work and working environment represent the influences to be adjusted. This perspective considers human capacities to have a permissible range of values, within which work demands must be matched. Work demands are more than the physical or mental loads directly related to task performance, since the organisational structure imposes loads. These arise, inter alia, from the relative match between the organisation within the workplace and the structure of the society outside. What people expect from work, and what they get, are also important dimensions of matching the job to the person. The observed stresses, therefore, are not always directly linked to consequences, since there are interactions in what is a multi factor situation. Various aspects of stress are discussed in the paper. Physical stresses and their long and short term impacts are, in many cases, well studied and their effects are known. Work organisation factors such as shift work and repetitive tasks are other stressors, the repetitive work situation is discussed. The whole problem of mental stress is examined more fully than the earlier, perhaps more self evident, stress aspects. Mental stress syndromes are becoming more evident, and it is clear that the interventions are not always satisfactory. In investigations of these situations the involvement of the subjects is vital, the stress effects are often only demonstrated by the subjects' reports.(ABSTRACT TRUNCATED AT 250 WORDS)

Back Pain↗

PubMed2000

The objective structured clinical examination: a step in the direction of competency-based evaluation.

BACKGROUND: The Accreditation Council for Graduate Medical Education is embarking on the major task of a paradigm shift in graduate education in the direction of competency-based medical education and evaluation of outcomes. The Objective Structured Clinical Examination (OSCE), a measure of clinical competence that focuses on outcomes via observable behaviors, is gaining national recognition. OBJECTIVE: To review the pediatric literature relevant to the OSCE. METHOD: A MEDLINE search from the date of the original report of the OSCE (1975) to the present was performed. All English-language studies regarding the use of the OSCE in pediatric education published in the United States and Great Britain were reviewed. MAIN OUTCOME MEASURES: Reliability and validity of the OSCE were examined. Use of standardized pediatric patients was discussed. RESULTS: A greater number of stations and similarity between tasks at different stations increased the reliability of the OSCE. A greater number of stations increased sampling of material and content validity. Correlation between the OSCE and precertification examinations ranged between 0.59 and 0.71, with P< or =.01. Correlation between the OSCE and monthly clinical evaluations was much lower (0.39-0.57), but still statistically significant at P< or =.05. Gaps between expected and actual performance were documented. Overall, the experience of being a standardized patient was viewed as positive by children and their parents. CONCLUSIONS: With appropriate attention to design, acceptable reliability and validity can be achieved for the OSCE. Significant correlations between the OSCE and precertification examinations as well as monthly clinical evaluations were found, the former being stronger than the latter. We conclude that the combination of the OSCE, standardized board examinations, and direct observation in the clinical setting has the potential to become the "gold standard" for measuring physician competence.

Accreditation↗

PubMed2006

Preparatory adjustment of cognitive control in the task switching paradigm.

In this article, the authors investigate the assumption that preparation while switching between cognitive tasks is dynamically adjusted to the current task demands. Performance in high-shift blocks (75% shifts) was compared with performance in high-repetition blocks (75% repetitions). This probability information was given either at the beginning of a block (global condition) or by specific probability cues before every trial (local condition). The authors report strong preparation effects (activation of the probable task and inhibition of the improbable task) in high-shift blocks, especially when specific probability cues were provided. In high-repetition blocks, however, the preparation effects were less pronounced. The results support the assumption that preparation is dynamically adjusted to the expected task requirements.

Adolescent↗

PubMed2003

The subtype-selective nicotinic acetylcholine receptor agonist SIB-1553A improves both attention and memory components of a spatial working memory task in chronic low dose 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys.

Monkeys that receive chronic low dose (CLD) 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration develop deficits in spatial delayed-response task performance. The present study examined the extent to which SIB-1553A [(+/-)-4-[[2-(1-methyl-2-pyrrolidinyl)ethyl]thio]phenol hydrochloride], a novel neuronal nicotinic acetylcholine receptor (nAChR) agonist with selectivity for beta4 subunit-containing nAChRs, could counteract this cognitive deficit produced by CLD MPTP exposure. Prior to MPTP treatment, monkeys displayed a delay-dependent decrement in performance on a variable delayed response task. CLD MPTP treatment caused a shift to a delay-independent pattern of responding on this task, such that short-delay trials were performed as poorly as long-delay trials. At lower doses (e.g., 0.025 mg/kg), SIB-1553A significantly improved performance on short-delay trials but only at 24 h after drug administration. At higher doses (e.g., 0.50 mg/kg), SIB-1553A significantly improved performance on both short- and long-delay trials at both 20 min and 24 h after drug administration. When tested 24 h after drug administration, monkeys performed long-delay trials with greater accuracy than they did under normal (pre-MPTP) conditions. These results suggest that at lower doses, SIB-1553A may be more effective in improving attentional deficits associated with CLD MPTP exposure, whereas at higher doses, SIB-1553A may effectively improve both attentional and memory performance.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1984

Extinction-induced spatial dispersion in the radial arm maze: arrest by ethanol.

Adaptive changes in response to extinction can be observed if provisions are made that permit behavior to shift away from trained routine. In the present case, the baiting of four arms in the eight-arm radial maze increasingly restricted subject movements to those arms. The unbaited arms afforded a new direction for behavior to take during extinction. Withdrawal of reward was followed by an immediate and active expansion of sites visited. The previously unrewarded arms were now regularly sampled. This was one consequence of extinction. The other was the well-known decline in overall rate of arm entry, whether arms were previously baited or not. Ethanol, at doses of 1.5 or 2.0 g/kg, eliminated the spatial dispersion attendant upon nonreward. It did not affect the decline in overall responsiveness. Ethanol's deletion of extinction-induced spatial variability may account for its impairment on reversal and other kinds of tasks that require a shift away from old patterns of behavior.

Animals↗

PubMed1987

Hemispheric asymmetry of feedback-related potentials in a positioning task: comparison of right- and left-handed subjects.

Previous research has demonstrated that delayed nonverbal information feedback (IF) about the correctness of a positioning movement is preceded by a contingent negative variation (CNV) which is larger over the right hemisphere independent of movement side. It was hypothesized that this asymmetry is a manifestation of functional hemispheric specialization, and that, therefore, the distribution of the differences between CNV amplitude measures of the two hemispheres should be different in right-handed and left-handed subjects. The latter group should show a mean asymmetry score closer to zero, and a larger between-subject variance of the asymmetry scores. The present investigation was intended to test these assumptions in samples of rigorously defined right-handers (n = 12) and left-handers (n = 8). The results revealed the expected group differences of the CNV asymmetry scores. In addition, the P1-N1 peak-to-peak amplitude of the IF-evoked potentials was similarly lateralized as the pre-IF CNV and showed the same group differences. In contrast, the handedness groups did not differ in the contralateral lateralization of the movement-related potential shift in the same task.

Adult↗

PubMed1989

Temporal aspects of accommodative adaptation.

Pre- and post-task measures of dark focus (DF) were used to assess accommodative adaptation induced by brief near-vision tasks in 10 late-onset myopes (LOM's) and 10 emmetropes. The degree of adaptation was examined after tasks of 15, 30, and 45 s duration. Accommodation was measured after the task at 1 s intervals over a 90 s period using an objective infrared optometer. Emmetropic subjects showed a significant increase in DF during the first 10 s of post-task recording, which regressed to the pre-task value within a further 20 to 30 s. No significant difference in post-task accommodative regression was observed after the three task durations. Similar findings were observed for LOM's after the 15 and 30 s tasks. However, after the 45 s task, LOM's exhibited a marked negative shift in DF during the 10 to 50 s post-task period. Instillation of a beta adrenergic antagonist attenuated this negative shift, suggesting that it was mediated via beta adrenergic innervation to the ciliary muscle.

Accommodation, Ocular↗

PubMed2006

Eyes always attract attention but gaze orienting is task-dependent: evidence from eye movement monitoring.

Eyes and gaze are central to social cognition but whether they attract attention differently depending on the task is unknown. Here, the shift in attention towards the eye region and gaze direction of a perceived face was studied in two tasks by monitoring eye movements. The same face stimuli in front- or 3/4-view, with direct or averted gaze, were used in both tasks. In the Gaze task, subjects performed an explicit gaze direction judgment (gaze straight or averted) while in the Head task they performed a head orientation judgment (front- or 3/4-view). Gaze processing was evident in both tasks as shown by longer RTs and lower accuracy when head and gaze directions did not match. In both tasks the eye region was the most attended area but the amount of viewing was task-dependent. Most importantly, approximately 90% of the initial saccades landed in the eye region in the Gaze task but only approximately 50% of them did so in the Head task. These saccades were made in the direction signaled by gaze in the Gaze task but in the direction signaled by head orientation in the Head task. Altogether, these task-modulated behaviors argue against a purely exogenous and automatic orienting-to-gaze mechanism. Based on patient work and neuroimaging studies of gaze processing, we suggest that this task-dependent orienting behavior is rather endogenous and subtended by cortical areas amongst which frontal regions play a central role. We discuss the implications of this finding for clinical populations.

Adult↗

PubMed1998

Ocular vergence measurement in projected and collimated simulator displays.

The purpose of this study was to investigate electrooculography (EOG) as a measurement of ocular vergence in both collimated and projected simulator environments. The task required participants to shift their gaze between a central fixation point and a target appearing at one of three eccentricities. EOG was effective in recording ocular vergence. The EOG results were similar between collimated and projected displays, except for differences in vergence changes during lateral movement of the eyes, and ocular excursions downward elicited a greater EOG response than the reverse upward movement. The computer-based technique of recording vergence was found to produce measurable traces from a majority of participants. The technique has potential for further development as a tool for measuring ocular vergence in virtual environments where methods that require the wearing of head-mounted apparatus to track ocular structures (e.g., the pupil), which cannot be worn at the same time as a flight or flight-simulator helmet, are unsuitable.

Computer Simulation↗

PubMed2002

Role of the dorsomedial striatum in behavioral flexibility for response and visual cue discrimination learning.

These experiments examined the effects of dorsomedial striatal inactivation on the acquisition of a response and visual cue discrimination task, as well as a shift from a response to a visual cue discrimination, and vice versa. In Experiment 1, rats were tested on the response discrimination task followed by the visual cue discrimination task. In Experiment 2, the testing order was reversed. Infusions of 2% tetracaine did not impair acquisition of the response or visual cue discrimination but impaired performance when shifting from a response to a visual cue discrimination, and vice versa. Analysis of the errors revealed that the deficit was not due to perseveration of the previously learned strategy, but to an inability to maintain the new strategy. These results contrast with findings indicating that prelimbic inactivation impairs behavioral flexibility due to perseveration of a previously learned strategy. Thus, specific circuits in the prefrontal cortex and striatum may interact to enable behavioral flexibility, but each region may contribute to distinct processes that facilitate strategy switching.

Animals↗