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Auditory system abnormalities in human albinos.

Auditory abnormalities were evaluated in human albinos using temporary threshold shift and dichotic listening tasks. Albinos exhibited a greater temporary threshold shift than did normally pigmented individuals after exposure to a fatiguing tone. In the dichotic listening task, albinos demonstrated a significantly larger right ear advantage than normally pigmented individuals. These results support earlier work indicating that hemispheric asymmetries are present in a albino auditory system and suggest that abnormalities may be present at the cochlear level as well.

Adult↗

A specific shifting deficit in Parkinson's disease: a reversal shift of consistent stimulus-response mappings.

Two experiments were designed to investigate effects of cueing upon aptitude for shifting by patients with Parkinson's disease. Subjects executed in alternation two different components of a task set over successive items in a list. We compared the costs of shifting when the stimulus ensemble remained constant from trial to trial ("uniform" lists), with the case in which a change of stimulus ensemble cued each shift of task ("mixed" lists). Shift costs with mixed lists were significantly smaller than those with uniform lists (Exp. 1, ns = 12). This suggests that patients with Parkinson's disease can benefit from cues about the stimulus ensemble in performing tasks. Patients' shifting performance was different from that of controls only in a reversal-shift condition of the previously consistent stimulus-response mappings (Exp. 2, ns = 12). This result suggests that patients with Parkinson's disease suffer from a specific but not a general deficit in ability to shift.

Basal Ganglia↗

Evidence that specific executive functions predict symptom variance among schizophrenia patients with a predominantly negative symptom profile.

INTRODUCTION: Although deficits in executive functioning in schizophrenia have been consistently reported, their precise relationship to symptomatology remains unclear. Recent approaches to executive functioning in nonschizophrenia studies have aimed to "fractionate" the individual cognitive processes involved. In this study, we hypothesised that if these processes are fractionable, then particular symptom syndromes may be selectively related to executive deficits. In particular, it was hoped that this approach could clarify whether negative and positive symptoms of schizophrenia are differentially related to particular aspects of executive/attentional functions. METHODS: A total of 32 patients with schizophrenia and 16 matched controls were assessed on a series of tasks designed to tap the theoretically derived executive functions of Inhibition, Shifting set, Working memory, and Sustained attention. RESULTS: Negative symptoms were significantly predicted by performance on an "Inhibition" task (Stroop), and not by performance on any other task. Furthermore, for a subgroup of patients with predominantly negative symptoms variance in positive symptoms was only significantly predicted by performance on a set-shifting task (Visual Elevator), and not by performance on other tasks, including inhibition. CONCLUSIONS: Our results support the contention that negative symptoms can, at least partly, be conceived of as cognitive behaviours expressing specific executive deficits. Specifically, we discuss the possibility that negative symptoms may, in part, express a failure in response monitoring. We further suggest that the disordered metacognition resulting in positive symptoms may be mediated by cognitive flexibility in patients with a predominantly negative symptom profile.

Adult↗

Selective extra-dimensional set shifting deficit in a knock-in mouse model of Huntington's disease.

People with early-stage Huntington's disease have been found to have a specific deficit in performing an extra-dimensional shift. To date no evidence of this deficit has been identified in transgenic or knock-in rodent models of the disease. The aim of the present paper then, was to test whether homozygous knock-in mice derived from the Hdh(CAG(150)) mouse line were impaired in any of five 2-choice discrimination tasks (simple, compound, compound reversal, intra-dimensional shift and extra-dimensional shift), and whether these mice were impaired at recalling these tasks on the following day. On the extra-dimensional shift task the Hdh(CAG(150)) homozygous mice required a greater number of trials to reach criteria than mice and the percentage of correct choices within the trials was also significantly reduced compared with the animals. For the recall tasks, a deficit for recalling the compound reversal test was found in the Hdh(CAG(150)) homozygous mice for both number of trials required to reach criteria and percentage of correct choices within the trials. Recall for the intra-dimensional shift task was also impaired in these animals when measured by the percentage of correct choices. Our results demonstrate a pronounced deficit in the Hdh(CAG(150)) mice not only on extra-dimensional shift performance in agreement with human studies, but also on recall tasks for both the compound reversal and the intra-dimensional shift tasks.

Animals↗

Fractionating the neural mechanisms of cognitive control.

Modifications of the Wisconsin Card Sorting Test were established. In these new task variants, participants were asked to exert sequential control over attentional sets or over intentional sets (task domain factor). Attentional set shifting requires changing the priorities by which sensory stimuli are selected, whereas intentional set shifting requires changing the priorities by which motor responses are selected. Auditory stimuli that signaled to maintain or shift set were presented immediately before (precuing) or after (postcuing) the selection of cards (cue timing factor). Twenty-four healthy young individuals participated. Performance data (response times, error percentages) indicated that intentional tasks were easier to perform than attentional tasks. The electroencephalogram was recorded during task performance, and the N1, medial frontal negativity (MFN), P3a, and sustained potential (SP) components of the cue event-related brain potentials (ERPs) were analyzed. Irrespective of the task domain, shift precues led to increased N1 amplitudes compared to shift postcues. When intentional sets had to be shifted, the MFNs in the postcuing condition were more pronounced than in the precuing condition. On the other hand, shifts of attentional sets resulted in a more prominent P3a in response to postcues compared to precues. Irrespective of the task domain, the shift effect that was evident in SPs was more pronounced in precue ERPs compared to postcue ERPs. We conclude that ERPs provide valid measures to empirically constrain theories about the neural mechanisms of cognitive control. The domain hypothesis of the fractionation of the neural mechanisms of cognitive control is introduced.

Adult↗

Rule shift under long-term PCP challenge in rats.

Performance of Long-Evans rats repeatedly treated with a high dose of phencyclidine (PCP) was compared with that of controls on two tasks involving rule shifts. Fifteen hours after receiving 12 daily doses of PCP (10mg/kg) or saline, rats were tested in the first task where a fixed or variable goal had to be recognized among four maze-arm locations. After receiving the last of 33 injections, rats were subjected to a second task: they had to discriminate the relevant perceptual dimension in a pair of stimuli and choose the appropriate stimulus in each problem. Results from both tasks revealed no difference between controls and rats injected with PCP either during acquisition using a constant rule or during testing with rule shifts. Consequently, PCP appears to lack consistency in disturbing frontal cognitive functions in animal models of schizophrenia.

Analysis of Variance↗

Place learning in scopolamine-treated rats: the roles of distal cues and catecholaminergic mediation.

Experiments 1 and 2 tested the hypothesis that cholinergic receptor antagonists impair place learning in a water maze by interfering with the processing of distal, visual cues. Extramaze cues were offered to rats in the form of geometrical patterns arranged on the inner circumference of a curtain surrounding the water maze. In Experiment 1 the animals were offered both the distal cues and proximal cues in the form of pingpong balls in fixed positions on the surface of the water while only distal cues were present in Experiment 2. Animals were injected with either scopolamine (0.5 mg/kg body wt) or saline 20 min prior to the daily place learning sessions. Upon reaching criterion level performance the animals were tested on "rotation" sessions on which the distal cues were displaced. The outcome of such "rotations" demonstrated that-regardless of the presence or absence of proximal cues-scopolamine-treated rats relied at least as much as normal animals on the distal cues. The acquisition phase of both Experiments 1 and 2 demonstrated an almost complete lack of scopolamine-associated impairment in acquisition and performance of the place learning task. In Experiment 3 (when scopolamine was no longer administered) the subjects of Experiment 2 were exposed to a series of pharmacological "challenges" of their place learning performance and eventually to surgical ablation of the anteromedial prefrontal cortex. The outcome of the pharmacological challenges and the postoperative test of task performance demonstrated that the place learning performance of animals which had acquired the task under scopolamine was mediated by a neural substrate dissimilar to the substrate of task performance in normal animals. Rats acquiring the task while deprived of the cholinergic system demonstrated above-normal contributions to task mediation from catecholaminergic-probably dopaminergic-mechanisms and tentative results pointed to a "shift" toward prefrontal task mediation.

Animals↗

Demand transitions and sustained attention.

A recent report by the National Research Council (Huey & Wickens, 1993) has identified transitions in task demand as an important dimension for study in vigilance research. This experiment tested the possibility that the effects of such transitions follow a relatively simple psychophysical rule--they are characterized by contrast effects. Transitions in task demand were achieved by shifting subjects from single-task to dual-task monitoring and vice versa. These transitions produced changes in subjects' sensing and decision-making functions that were far more intricate than simple contrast effects. The demand transition issue offers a complex research challenge on both basic and applied levels and warrants further investigation.

Adult↗

The impact of shift work on the risk and severity of injuries for hospital employees: an analysis using Oregon workers' compensation data.

BACKGROUND: While past research on health care workers has found that shift work can lead to negative physiological and psychological consequences, few studies have assessed the extent to which it increases the risk of specific work-related injuries, nor quantified and compared associated types, severity and costs. AIMS: This study aimed to derive and compare the rates, typologies, costs and disability time of injuries for various hospital worker occupations by day, evening and night shift. METHODS: This study used Oregon workers' compensation claim data from 1990 to 1997 to examine the differences in hospital employee claims (n = 7717) by shift and occupation. Oregon hospital employee claim data, hospital employment data from Oregon's Labor Market Information System and shift proportion estimates derived from the Current Population Survey (CPS) were used to calculate injury rate estimates. RESULTS: The injury rate for day shift per 10,000 employees was estimated to be 176 (95% CI 172-180), as compared with injury rate estimates of 324 (95% CI 311-337) for evening shift and 279 (95% CI 257-302), night shift workers. The average number of days taken off for injury disability was longer for injured night shift workers (46) than for day (38) or evening (39) shift workers. CONCLUSION: Evening and night shift hospital employees were found to be at greater risk of sustaining an occupational injury than day shift workers, with those on the night shift reporting injuries of the greatest severity as measured by disability leave. Staffing levels and task differences between shifts may also affect injury risk.

Adult↗

Impaired set-shifting and dissociable effects on tests of spatial working memory following the dopamine D2 receptor antagonist sulpiride in human volunteers.

RATIONALE: Dopamine (DA) D(2) receptor antagonists have been shown to produce similar impairments to those seen in Parkinson's disease. These include working memory and set-shifting deficits. Theories of DA function have predicted that distraction or impaired switching may be important determinants of such deficits. OBJECTIVES: In order to test these hypotheses, we have followed up our previous findings with more refined tests (1) that allow measurement of spatial working memory (SWM) and distraction, (2) that allow separation of executive and mnemonic components of SWM and (3) that allow isolation of set-shifting from learning deficits. METHODS: Thirty-six young healthy male volunteers were tested on two occasions after oral administration of either 400 mg sulpiride or placebo. All participants performed the delayed response task. Sixteen participants received task-irrelevant distractors during this task, and were also given a self-ordered SWM test. The remaining participants were given delayed response tasks with task-relevant distractors, and tests of attentional and task set-shifting. RESULTS: Sulpiride impaired performance of the delayed-response task both without distraction and with task-relevant distraction. By contrast, the drug protected against deficits from task-irrelevant distraction seen in the placebo group. Task set-switching was also impaired by sulpiride, with participants being slower to respond on switch trials compared with non-switch trials. There was also a trend for attentional set-shifting to be impaired following sulpiride. In contrast, self-ordered SWM performance was enhanced by sulpiride on the second test session only. CONCLUSIONS: These results support models of central DA function that postulate a role in switching behaviour, and in certain aspects of working memory.

Adult↗

Neural activity during attention shifts between object features.

To investigate the neural mechanisms involved in shifting attention we used positron emission tomography to examine regional cerebral blood flow (rCBF) during a task that demands shifting attention between color and shape. Significant activation was observed in the right dorsal prefrontal cortex and parieto-occipital cortex at all frequencies of attention shifts. The frequency of shifts between categories correlated significantly with rCBF in the rostral part of the supplementary motor area and the left precuneus, whereas the number of successive correct responses correlated with rCBF in the orbitofrontal cortex and the caudate nucleus. This study suggests that several prefrontal regions may participate in the processes of shifting attention in different ways.

Adult↗

Rapid tryptophan depletion improves decision-making cognition in healthy humans without affecting reversal learning or set shifting.

Rapid tryptophan (Trp) depletion (RTD) has been reported to cause deterioration in the quality of decision making and impaired reversal learning, while leaving attentional set shifting relatively unimpaired. These findings have been attributed to a more powerful neuromodulatory effect of reduced 5-HT on ventral prefrontal cortex (PFC) than on dorsolateral PFC. In view of the limited number of reports, the aim of this study was to independently replicate these findings using the same test paradigms. Healthy human subjects without a personal or family history of affective disorder were assessed using a computerized decision making/gambling task and the CANTAB ID/ED attentional set-shifting task under Trp-depleted (n=17; nine males and eight females) or control (n=15; seven males and eight females) conditions, in a double-blind, randomized, parallel-group design. There was no significant effect of RTD on set shifting, reversal learning, risk taking, impulsivity, or subjective mood. However, RTD significantly altered decision making such that depleted subjects chose the more likely of two possible outcomes significantly more often than controls. This is in direct contrast to the previous report that subjects chose the more likely outcome significantly less often following RTD. In the terminology of that report, our result may be interpreted as improvement in the quality of decision making following RTD. This contrast between studies highlights the variability in the cognitive effects of RTD between apparently similar groups of healthy subjects, and suggests the need for future RTD studies to control for a range of personality, family history, and genetic factors that may be associated with 5-HT function.

Adolescent↗

Brain slow potential changes elicited by missing stimuli and by externally paced voluntary responses.

Brain evoked potential changes were recorded from the scalp of 22 normal subjects and from the cortex of two patients in conditions where expected auditory stimuli were missing. It was found that such stimulus omissions could be used to initiate slow potential shifts (CNVs) in a warned foreperiod response task. Further slow potential shifts with durations of over 3 sec were recorded preceding self-initiated, but externally paced, responses made to one of a train of clicks. The experiments confirmed the cortical origins of the missing stimulus potentials, and illustrated the dependence of the CNV on endogenous factors rather than the physical properties of external stimuli. Contrary to most previous reports the negative component of the missing stimulus potential was in this study virtually identical in latency and amplitude to the N1 component of the click evoked potential. The slow potential shifts observed in the self-initiated condition contained elements of both the CNV and Bereitschaftspotential and appeared to reflect the steadily increasing cortical involvement during preparatory foreperiods.

Auditory Perception↗

Physical load as risk factor for musculoskeletal complaints among tank terminal workers.

In a cross-sectional study, the relationship between physical load and musculoskeletal complaints was examined among operators (n = 77), office workers (n = 52), and miscellaneous workers (n = 15) in a tank terminal company. Information about history of musculoskeletal complaints, individual characteristics, and working conditions in past and present was obtained by a standardized interview. Assessment of physical load was performed by direct observation of awkward postures and forceful exertions during normal activities. Workers filled out a diary regarding the executed tasks during one shift. Physical load was also modeled by linking the average physical load of workers performing a particular task with the task distribution of each worker. The modeling approach was beneficial to estimate infrequent characteristics of physical load, whereas the observations were better for assessing frequent exposure to awkward trunk postures. After adjustment for age and other confounders the observed work time with trunk flexion and rotation was associated with the occurrence of back pain. The modeled work time with arms raised above shoulder showed a relationship with elbow pain, and the modeled work time with forceful exertions over 100 N showed relationships with elbow pain and wrist pain. The described relationships demonstrate that the assessment strategy chosen in a particular study strongly influences random measurement error of physical load, and that inappropriate strategies may mask true associations between physical load and musculoskeletal complaints. Modeling strategies offer the opportunity to assess physical load in dynamic work environments.

Administrative Personnel↗

Ketanserin attenuates nicotine-induced working memory improvement in rats.

Nicotinic systems have been shown in numerous studies to be important for spatial working memory. Nicotinic systems are certainly not acting alone in the basis of memory function, but act in concert with a variety of other neural systems. Important for these interactions is nicotinic induced release of a variety of neurotransmitters involved in memory function including serotonin (5-HT). We have found that the 5-HT2 receptor antagonist, ketanserin, effectively attenuated nicotine-induced attentional improvement. The current study explored the interaction between nicotinic and serotonergic systems in the performance of a spatial working memory task in the radial-arm maze. Female Sprague-Dawley rats were trained on the win-shift working memory task on the 8-arm radial maze. After 18 sessions of acquisition training the rats were given acute doses of nicotine (0.2 and 0.4 mg/kg), ketanserin (0.5, 1 and 2 mg/kg) or combinations of the two. The vehicle served as the control. As seen in previous studies, nicotine caused a significant improvement in working memory performance as indexed by the number of correct arm entries before the first error (entries to repeat). Ketanserin at the doses tested did not cause a significant effect on choice accuracy, but it did significantly attenuate the improvement caused by the 0.2 mg/kg nicotine dose. The higher 0.4 mg/kg nicotine dose was nearly sufficient to overcome the ketanserin effect. This study shows that, as with attentional function, nicotine-induced working memory improvement is attenuated by the 5-HT2 antagonist ketanserin. Given that many antipsychotic drugs have substantial 5-HT2 antagonist effects, these atypical antipsychotic drugs may reduce the cognitive improvements caused by nicotinic treatments.

Animals↗

Determination of cognitive hemispheric dominance by "stereo" transcranial Doppler sonography.

BACKGROUND AND PURPOSE: Transcranial Doppler sonography (TCD) can assess blood flow velocity changes induced by focal brain activation. Therefore, TCD may have the potential to identify hemispheric dominance for cognitive tasks. METHODS: Using a system with two TCD probes ("stereo" TCD), we monitored simultaneously both middle cerebral arteries (MCAs) of 14 healthy right-handed volunteers while they performed cognitive tasks. The averaged blood flow velocity ratio of the two MCAs and the hemispheric blood flow velocity shift induced by the cognitive task were calculated. RESULTS: In every subject, language tasks resulted in blood flow velocity shift to the left compared with visuospatial tasks. Mean MCA blood flow velocity shift to the left was 1.67%, 2.01%, and 2.31% in three language tasks. Mean blood flow velocity shift to the right was 1.67% and 2.31% in two visuospatial tasks. CONCLUSIONS: Bilateral simultaneous MCA blood flow velocity monitoring and averaging during cognitive tasks can help to identify hemispheric dominance for cognitive tasks in individuals.

Adult↗

Impact of emergency department volume on registered nurse time at the bedside.

STUDY OBJECTIVE: We determine how emergency department (ED) registered nurses (RNs) allocate their time between various tasks and describe how RN task distribution changes as a function of various measures of ED patient volume and patient acuity. METHODS: This is a 3-year direct observational study using a convenience sample of 63 8-hour nurse shifts. Four RN task categories were defined: (1) direct patient care, (2) indirect patient care, (3) non-RN care, and (4) personal time. Two measures of nurse workload were used, the patient-to-nurse ratio and the ED acuity index (ED acuity index=(Sigma reverse order triage scores/half hour)/total number of nurses staffing). Trained observers classified RN activity at 1-minute intervals during 8-hour shifts daily for 7 nonconsecutive 24-hour periods. RN staffing data, ED patient census, and patient triage scores were collected every half hour. Summary statistics, correlation tables, and regression analysis were used to establish relationships between RN task allocation, patients per nurse, and the ED acuity index. RESULTS: For the 63 nursing shifts studied, on average RNs spent 25.6% of their time performing direct patient care, 48.4% on indirect patient care, 6.8% on non-RN care, and 19.1% on personal time. Regardless of the number of patients per RN, approximately twice as much time is spent on indirect patient care as direct patient care. The correlation between the ED acuity index and the patient-to-nurse ratio was 0.98. CONCLUSION: Regardless of workload, RNs spend the majority of their time performing indirect patient care. RNs spend little time performing tasks that could be performed by ancillary staff. The patient-to-nurse ratio performs just as well as a more complicated acuity index to measure the workload of RNs within an ED.

Emergency Nursing↗

Exposure to acid anhydrides in three resin and one cushioned flooring manufacturing plants.

Acid anhydrides are reactive organic chemicals of low molecular weight which cause occupational asthma. No previous research on the relationship between exposure to these chemicals and respiratory sensitization and development of occupational asthma has been reported. A retrospective cohort study was carried out in four factories (three alkyd resin factories and one cushioned flooring factory) to investigate the nature of exposure-response relationships for sensitization to phthalic anhydride (PA), trimellitic anhydride (TMA) and maleic anhydride (MA). This paper describes the results of full-shift and task-specific exposure measurements. Exposure to PA was low in relation to the Occupational Exposure Standard (OES). The highest full-shift PA exposures occurred among resin operators in the resin factory that used solid PA as compared to other resin factories where liquid PA was used. Arithmetic mean exposure levels to TMA and MA in the resin factories were well below their respective OESs. Short-term high exposures occurred during loading of acid anhydrides into the reactors and sampling and testing of the resin. Relatively high full-shift exposure to TMA occurred in the cushioned flooring factory, although no high peak exposures were detected.

Anhydrides↗