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PubMed2000

Increased distractibility by task-irrelevant sound changes in abstinent alcoholics.

BACKGROUND: Chronic alcoholism is accompanied by "frontal" neuropsychological deficits that include an inability to maintain focus of attention. This might be associated with pronounced involuntary attention shifting to task-irrelevant stimulus changes and, thereafter, an impaired reorienting to the relevant task. The neural abnormalities that underlie such deficits in alcoholics were explored with event-related potential (ERP) components that disclosed different phases of detection and orienting to stimulus changes. METHODS: Twenty consecutive abstinent male alcoholics (DSM-IV) and 20 age-matched male controls (healthy social drinkers) were instructed to discriminate equiprobable 100 and 200 msec tones in a reaction-time task (RT) and to ignore occasional, either slight (7%) or wide (70%), frequency changes (hypothesized to increase RT) during an ERP measurement. RESULTS: In the alcoholics, we found pronounced distractibility, evidenced by a RT lag (p < 0.01) caused by deviants, that correlated (Spearman p = 0.5) with a significantly enhanced (p < 0.01) amplitude of mismatch negativity (MMN) to deviants. Significantly increased RT lag for trials subsequent to deviants (slight p < 0.001, wide p < 0.05) in the alcoholics suggested impaired reorienting to the relevant task. The MMN enhancement also predicted poorer hit rates in the alcoholics (Spearman p = 0.6-0.7). Both the MMN enhancement and pronounced distractibility correlated (Spearman p = 0.4) with an early onset of alcoholism. CONCLUSIONS: Attentional deficits in the abstinent alcoholics were indicated by the increased distractibility by irrelevant sound changes. The MMN enhancement suggested that this reflects impaired neural inhibition of involuntary attention shifting, being most pronounced in early-onset alcoholics.

Adult↗
PubMed1993

Cognitive and memory deficits in untreated Parkinson's disease and amyotrophic lateral sclerosis patients: a comparative study.

We investigated the profile of cognitive and memory deficits of 22 Parkinson's disease (PD), 24 amyotrophic lateral sclerosis (ALS) patients and 26 age-matched controls. The patients were at the early phase of the disease and untreated. The ALS patients exhibited deficits in simple visuoperceptual functions and in complex visuoperceptual reasoning (Digit Symbol and Block Design tests), whereas the PD patients showed deficits only in simple visuoperceptual functions. Moreover, both ALS and PD patients had impairment in tasks requiring set shifting from one reaction to another that may suggest frontal lobe dysfunction. The ALS and PD patients also showed impairment in the task of learning a word list with effort-demanding organization of the material to be remembered. However, preserved delayed recall of logical passages suggests that memory, per se, is not impaired in ALS or in PD. The patterns of errors in a test of recognition of learned words imply, at least partially, different underlying deficits in the two diseases. An inability to inhibit irrelevant information may contribute to memory impairment in ALS patients, whereas the memory deficit in PD may derive from lowered motivation or initiating behaviour.

Aged↗
PubMed2006

The configuration and relaxation of motor task sets.

Often the performance of a task does not only require the processing of certain stimuli in certain ways, but also certain patterns of interlimb coordination. We studied shifts between different tasks involving different patterns of intermanual coupling by means of the timed-response procedure, which allows to trace state variables related to task sets. The tasks required the production of rapid bimanual reversal movements with symmetric or parallel directions. Symmetric movements are associated with symmetric coupling, as indicated by positive intermanual correlations between the directions of left-hand and right-hand movements, whereas parallel movements are associated with parallel coupling, as indicated by negative intermanual correlations. Task switches were associated with gradual changes of the intermanual correlations, which indicate the state of intermanual coupling as a major ingredient of a task set, in the course of action preparation. At short preparation intervals intermanual correlations were those appropriate for the preceding trial; with increasing preparation time they were replaced by those appropriate for the current trial, but the influence of the preceding trial did not disappear completely. In-between trials, intermanual coupling drifted toward a symmetric coupling, but not to uncoupled limbs. After a change of the task the specification of movement directions was slowed, but its initiation was not delayed. According to these results, task sets relax toward attractors which can be different from the absence of task sets. They are gradually configured during task preparation with a persistent influence of the preceding task, and the specification of response characteristics does not wait until the configuration of the new task set is completed.

Adult↗
PubMed1991

Attention tasks and EEG power spectra.

The authors attempted to observe differences in alpha and beta hemispheric asymmetry during a task in which attention was directed toward input from the environment (intake task) as opposed to tasks that required that environmental events be excluded from the focus of attention (rejection tasks). In comparison to resting, both attention tasks caused a shift in alpha asymmetry ratios toward increased power on the right, with the greatest effect at temporal leads. The only significant difference between attention tasks was a finding of higher alpha power during intake than during rejection. Some characteristics of the EEG during attention indicate potential clinical utility.

Adult↗
PubMed2005

[Investigation of set-shifting ability in patients with Parkinson's disease: influence of task sequence type].

INTRODUCTION: The aim of the present study was to investigate the origin of set-shifting deficits observed in Parkinson's disease (PD). METHODS: Seventeen patients diagnosed as having idiopathic PD were compared with 15 control subjects. We used a task-switching paradigm, including two tasks (task A and task B) so that subjects were required to switch either immediately after a switch-trial (i.e. alternating switch or ABA task sequence) or following one or two non-switch trials (ABBA or ABBBA task sequences). RESULTS: In both groups, switch cost (SC) in ABA task sequence was larger than SC in ABBA task sequence (p<0.05) and SC was larger in ABBA than ABBBA task sequence (p<0.05). PD patients demonstrated an increased SC compared to controls for alternating switch trials (p<0.01). Alternatively, when required to switch to a task abandoned two or three trials earlier (i.e. ABBA and ABBBA tasks sequences), patients did not demonstrate increased SC compared to controls. DISCUSSION AND CONCLUSION: The fact that SC associated with alternating switch trials was exacerbated in PD patients may reflect difficulties for switching to a recently inhibited task-set. In conclusion, our results indicate that set-shifting deficits in PD patients may depend of the type of task sequence.

Cognition Disorders↗
PubMed1985

Prior knowledge and memory: the influence of natural category size as a function of intention and distraction.

Words having larger numbers of related associates are more difficult to recall under conditions of intentional learning. This finding indicates that memory performance is inversely related to natural category size. The purpose of the experiments presented in this article was to evaluate the potential influence of orienting task and attention shifts associated with delayed testing on the natural category size effect. The results of Experiments 1 and 2 indicate that it is obtained regardless of task orientation. However, the results of Experiments 2 and 3 indicate that the effect is easily disrupted. Even after only 5 min of solving multiplication problems, words having larger sets of associates are no more difficult to recall than those having smaller sets. These findings suggest that related associates are automatically activated and encoded whenever a familiar concept is experienced in the absence of specific semantic cues. However, words having larger sets will be more difficult to recall only when these related associates are in a state of current activation.

Association Learning↗
PubMed1997

Functional localization of the system for visuospatial attention using positron emission tomography.

PET was used to image the neural system underlying visuospatial attention. Analysis of data at both the group and individual-subject level provided anatomical resolution superior to that described to date. Six right-handed male subjects were selected from a pilot behavioural study in which behavioural responses and eye movements were recorded. The attention tasks involved covert shifts of attention, where peripheral cues indicated the location of subsequent target stimuli to be discriminated. One attention condition emphasized reflexive aspects of spatial orientation, while the other required controlled shifts of attention. PET activations agreed closely with the cortical regions recently proposed to form the core of a neural network for spatial attention. The two attention tasks evoked largely overlapping patterns of neural activation, supporting the existence of a general neural system for visuospatial attention with regional functional specialization. Specifically, neocortical activations were observed in the right anterior cingulate gyrus (Brodmann area 24), in the intraparietal sulcus of right posterior parietal cortex, and in the mesial and lateral premotor cortices (Brodmann area 6).

Attention↗
PubMed2006

Dual-tasking postural control: aging and the effects of cognitive demand in conjunction with focus of attention.

Postural control in everyday life is generally accompanied by posture-unrelated cognitive activity. Thus, mild forms of dual-tasking postural control are the norm rather than the exception. Based on this consideration and available evidence, we propose and empirically examined, in young and old adults, a non-monotonic, U-shaped relation between the efficacy of postural control and concurrent cognitive demands that reflect opposing trends of the effects of attention focus and attentional resource competition. When instructed to perform an easy cognitive task that presumably shifted the focus of attention away from posture control, the center of body pressure (COP) excursions decreased both in young and older adults relative to a single-task baseline where the focus of attention was explicitly directed towards the postural control task itself. However, when performing more demanding cognitive tasks, older adults showed increased COP displacements, in line with the predicted U-shape function, whereas young adults did not. We outline mechanisms linking postural control to cognitive demand and suggest routes for future investigation.

Adult↗
PubMed2001

Characterization of TASK-4, a novel member of the pH-sensitive, two-pore domain potassium channel family.

We report the primary sequence of TASK-4, a novel member of the acid-sensitive subfamily of tandem pore K(+) channels. TASK-4 transcripts are widely expressed in humans, with highest levels in liver, lung, pancreas, placenta, aorta and heart. In Xenopus oocytes TASK-4 generated K(+) currents displaying a marked outward rectification which was lost by elevation of extracellular K(+). TASK-4 currents were efficiently blocked by barium (83% inhibition at 2 mM), only weakly inhibited by 1 mM concentrations of quinine, bupivacaine and lidocaine, but not blocked by tetraethylammonium, 4-aminopyridine and Cs(+). TASK-4 was sensitive to extracellular pH, but in contrast to other TASK channels, pH sensitivity was shifted to more alkaline pH. Thus, TASK-4 in concert with other TASK channels might regulate cellular membrane potential over a wide range of extracellular pH.

Amino Acid Sequence↗
PubMed1996

Shared neural control of attentional shifts and eye movements.

We are able to move visual attention away from the direction of gaze, fixating on one object while attending to something else at a different location, within the region of peripheral vision. It has been widely assumed that the attentional neural systems are separate from the motor systems, but some studies challenge this idea. It has now been suggested that the attentional system is part of the premotor processing in the brain. This model proposes that attentional processes evolved as part of the motor systems, with isolated attentional shifts representing an artificial separation of a natural linkage. Here we test how attentional shifts might be linked to the preparations for making saccadic eye movements. We studied the superior colliculus in monkeys as they shifted their attention during different tasks, and found that each attentional shift is associated with eye-movement preparation.

Animals↗
PubMed2000

Vocal control of acoustic information for sonar discriminations by the echolocating bat, Eptesicus fuscus.

This study aimed to determine whether bats using frequency modulated (FM) echolocation signals adapt the features of their vocalizations to the perceptual demands of a particular sonar task. Quantitative measures were obtained from the vocal signals produced by echolocating bats (Eptesicus fuscus) that were trained to perform in two distinct perceptual tasks, echo delay and Doppler-shift discriminations. In both perceptual tasks, the bats learned to discriminate electronically manipulated playback signals of their own echolocation sounds, which simulated echoes from sonar targets. Both tasks utilized a single-channel electronic target simulator and tested the bat's in a two-alternative forced choice procedure. The results of this study demonstrate changes in the features of the FM bats' sonar sounds with echolocation task demands, lending support to the notion that this animal actively controls the echo information that guides its behavior.

Animals↗
PubMed2006

Postural balance changes in on-duty firefighters: effect of gear and long work shifts.

OBJECTIVE: The objective of this study was to investigate the impact of long work shifts and turnout gear, including the self-contained breathing apparatus (SCBA) on firefighters' postural stability. METHODS: Sixteen firefighters were assessed using a portable forceplate system at the fire station. Postural sway parameters were recorded at the beginning of the work shift and repeated until the work shift ended. RESULTS: Task had the greatest impact on postural stability for all sway parameters. Turnout gear, with and without SCBA, improved postural stability. Postural stability decreased as firefighters spent more time on duty. CONCLUSIONS: Prolonged work shifts may be an important contributor to the high prevalence of slips and falls among firefighters. In all, the results indicate that many aspects of the firefighters' job may adversely impact their postural stability and potentially increase the risk of falling.

Adult↗
PubMed1996

Effects of single and repeated cognitive tasks on autonomic balance as observed by an analysis of R-R intervals.

The effects on sympathic-parasympathetic nervous system balance of single exposure and repeated exposures to a cognitively demanding task were examined by power spectrum analysis of cardiac R-R intervals. In the single task experiment, 32 healthy subjects engaged in a 90-min English language transcription task and in 90-min reading as a nontask control. In the repeated task experiment, 14 subjects experienced either intermittent exposure to the transcription task until late at night, or daytime exposure to the transcription task followed by relax wakefulness until sleep onset. The single task exposure significantly increased the normalized low frequency component (%LF; 0.05-0.15 Hz) of the R-R interval spectrum compared with the nontask control, but there was no significant task difference in the normalized high frequency component (0.15-0.50 Hz). The increased %LF values immediately returned to control levels after cessation of the task. Repeated exposure to the cognitive task until late at night produced a significantly greater %LF during the first nonrapid eye movement sleep period when compared to relaxed wakefulness. These results would suggest that a single exposure to a cognitive task may produce a shift to sympathetic nervous system dominance only during the period of the task, whereas repeated exposures to a cognitive task until late at night may produce a shift to sympathetic nervous system dominance which lasts into the subsequent sleep period.

Adult↗
PubMed2003

Coordination of eye and head movements during reading.

PURPOSE: There is little information regarding the characteristics of head movements during reading. This study was undertaken to investigate horizontal and vertical head movements during two different reading tasks. METHODS: Head and eye movements were monitored with an infrared pupil and head tracker in 15 subjects during repeated reading of text from an A4-sized card and a card 90 degrees wide. In addition, head and eye movements were recorded in 45 subjects to compare head movement propensity during an A4 text-reading task and a saccadic task of an equivalent gaze shift. RESULTS: During the A4 standard reading task, horizontal and vertical head movements accounted for 4.7% and 28.7% of the gaze shift, respectively. During the 90 degrees text reading, horizontal head movements accounted for 40.3% of the gaze amplitude, and vertical head movements accounted for 28.4%. Horizontal gaze velocities increased significantly on repeated A4 and 90 degrees text readings, as did horizontal head velocities and amplitudes. Reading head movement propensities were significantly smaller than saccadic head movement propensities (P < 0.001). CONCLUSIONS: Head movement strategies are rapidly switched between the A4 and 90 degrees text-reading paradigms. They are minimized during A4 text reading but actively assist the gaze strategy during 90 degrees text reading. Horizontal head movement is reduced during A4 reading compared to the equivalent saccadic task and may be suppressed to improve fixation stability. The results support the view that the head and eye movement system is a highly coupled but extremely flexible system.

Adult↗
PubMed1996

Searching for unknown feature targets on more than one dimension: investigating a "dimension-weighting" account.

Search for odd-one-out feature targets takes longer when the target can be present in one of several dimensions as opposed to only one dimension (Müller, Heller, & Ziegler, 1995; Treisman, 1988). Müller et al. attributed this cost to the need to discern the target dimension. They proposed a dimension-weighting account, in which master map units compute, in parallel, the weighted sum of dimension-specific saliency signals. If the target dimension is known in advance, signals from that dimension are amplified. But if the target dimension is unknown, it is determined in a process that shifts weight from the nontarget to the target dimension. The weight pattern thus generated persists across trials, producing intertrial facilitation for a target (trial n + 1) dimensionally identical to the preceding target (trial n). In the present study, we employed a set of new tasks in order to reexamine and extend this account. Targets were defined along two possible dimensions (color or orientation) and could take on one of two feature values (e.g., red or blue). Experiments 1 and 2 required absent/present and color/orientation discrimination of a single target, respectively. They showed that (1) both tasks involve weight shifting, though (explicitly) discerning the dimension of a target requires some process additional to simply detecting its presence; and (2) the intertrial facilitation is indeed (largely) dimension specific rather than feature specific in nature. In Experiment 3, the task was to count the number of targets in a display (either three or four), which could be either dimensionally the same (all color or all orientation) or mixed (some color and some orientation). As predicted by the dimension-weighting account, enumerating four targets all defined within the same dimension was faster than counting three such targets or mixed targets defined in two dimensions.

Adult↗
PubMed1997

An examination of the nature of attentional deficits in patients with Parkinson's disease: evidence from a spatial orienting task.

Endogenous and exogenous shifts of attention were examined in nondemented patients with Parkinson's disease (PD). In the endogenous condition, an arrow was used to cue participants' attention to the possible location of an impending target, whereas in the exogenous condition, a brightened box was used to cue attention. Cues were either valid (i.e., the target appeared in the cued location) or invalid (i.e., the target appeared in a noncued location). The time between cue onset and target onset (stimulus onset asynchrony or SOA) was varied in each condition. The results indicated that PD patients were not differentially impaired in shifting attention at the shorter SOAs relative to normal controls. However, at longer SOAs, the PD patients demonstrated less of an effect from cueing than did the normal control participants. PD patients' differential effect from cueing was evident in both exogenous and endogenous conditions. These results suggest that PD patients may experience a rapid decay of attentional inhibition and do not support the notion that a decrement in processing resources underlies their attentional deficits. Moreover, these findings further support the notion that the basal ganglia may play an important role in attentional functions.

Aged↗
PubMed2002

Differential effects of alcohol, cocaine, and opioid abuse on event-related potentials recorded during a response competition task.

The present study examined the abilities of cocaine-dependent and opioid-dependent patients and healthy, non-dependent volunteers to execute a task requiring rapid shifts in cognitive set. Sixty-six residential treatment program patients, characterized by a history of either cocaine (n=37) or opioid (n=29) dependence, and 18 non-drug-dependent community volunteers were evaluated. The task involved the execution of right- or left-hand button press responses that were either spatially-compatible or incompatible with a directional cue. Performance and event-related electroencephalographic (EEG) activity were recorded throughout the task. Analyses revealed that button press responses were significantly slower and less accurate for all of the groups when spatial conflict was introduced. The amplitude of a slow EEG potential (SP), emerging approximately 500 ms after stimulus onset, showed the normal effect of spatial conflict for the opioid-dependent and non-dependent groups, but not for subjects in the cocaine-dependent group. Correlational analyses restricted to data from the cocaine-dependent group showed that this abnormal SP amplitude was not related to the quantity, frequency, or recency of their cocaine use; it only correlated with their comorbid alcohol use. The results of the major analyses, in combination with the results of a neuroanatomical localization algorithm applied to the SP data, suggest that comorbid alcohol use disrupts normal task-related activation of the anterior cingulate, cerebellum, and prefrontal cortex. The present results have implications for the assessment of specific cognitive problems which could foster drug abuse.

Adult↗
PubMed1995

Set-shifting aptitude in Parkinson's disease: external versus internal cues.

A modified version of the odd-man-out test was used to investigate set-shifting aptitude in 12 patients with Parkinson's disease. We asked subjects to execute in alternation two different sorting rules over successive items. External and internal cueing conditions were employed. Patients with Parkinson's disease were impaired on the tasks with internal cues but were normal on the tasks with external cues. Moreover, the shift costs were consistently larger for the shift to the easier task than the shift to the more difficult task. These findings indicated that the model of 'Supervisory Attentional System' may not be sufficient to explain the data as Brown and Marsden (1988) originally suggested.

Aged↗