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PubMed2002

Attention to action in Parkinson's disease: impaired effective connectivity among frontal cortical regions.

The neural basis of attention to action was studied in 12 patients with Parkinson's disease (Hoehn and Yahr grades II and III) and 12 healthy age-matched controls. The subjects were studied by functional MRI (fMRI) during performance of a simple paced overlearned motor sequence task, with and without an additional attentional task. For the attentional task, subjects were instructed to attend either to their actions or to a visual distractor task. Statistical parametric mapping was used to implement a random effects analysis of the regional task-related activations in patient and control populations. Structural equation modelling of fMRI time series was used to measure effective connectivity among prefrontal and premotor areas. In both groups, the motor task was associated with activation of a distributed network including the premotor, motor and parietal cortex, striatum and cerebellum. In control subjects, but not patients, attention to action (relative to execution of an overlearned sequence) was associated with further activation of prefrontal, parietal and paracingulate cortex, and the supplementary motor area (SMA). Patients with Parkinson's disease showed greater than normal activation of the SMA during execution of the simple overlearned motor sequence, but less augmentation when attending to their actions. In control subjects, attention to action, but not attention to the visual distractor task, increased the effective connectivity between prefrontal cortex and both the lateral premotor cortex and the SMA. This represents a specific increase in effective connectivity. Attentional modulation of effective connectivity between the prefrontal, premotor cortex and SMA was not observed in patients. This deficit indicates a context-specific functional disconnection between the prefrontal cortex and the supplementary and premotor cortex in Parkinson's disease.

Aged↗
PubMed2002

Effects of monocular viewing and eye dominance on spatial attention.

Observations in primates and patients with unilateral spatial neglect have suggested that patching of the eye ipsilateral to the injury and contralateral to the neglected space can sometimes improve attention to the neglected space. Investigators have generally attributed the effects of monocular eye patching to activation of subcortical centers that interact with cortical attentional systems. Eye patching is thought to produce preferential activation of attentional systems contralateral to the viewing eye. In this study we examined the effect of monocular eye patching on attentional biases in normal subjects. When normal subjects bisect vertical (radial) lines using both eyes, they demonstrate a far attentional bias, misbisecting lines away from their body. In a monocular viewing experiment, we found that the majority of subjects, who were right eye dominant, had relatively nearer bisections and a diminished far bias when they used their right eye (left eye covered) compared with when they used their left eye (right eye covered). The smaller group of subjects who were left eye dominant had relatively nearer bisections and a diminished far bias when they used their left eye compared with when they used their right eye. In the hemispatial placement experiment, we directly manipulated hemispheric engagement by having subjects perform the same task in right and left hemispace. We found that right eye dominant subjects had a diminished far bias in right hemispace relative to left hemispace. Left eye dominant subjects showed the opposite pattern and had a diminished far bias in left hemispace. For both groups, spatial presentation affected performance more for the non-dominant eye. The results suggest that monocular viewing is associated with preferential activation of attentional systems in the contralateral hemisphere, and that the right hemisphere (at least in right eye dominant subjects) is biased towards far space. Finally, the results suggest that the poorly understood phenomenon of eye dominance may be related to hemispheric specialization for visual attention.

Adult↗
PubMed2005

Attentional modulation of SSVEP power depends on the network tagged by the flicker frequency.

Modulation of the steady-state visual evoked potential (SSVEP) by attention was studied in detail using 15 'tag' frequencies in the range of 2.5-20 Hz. The stimuli were two series of random disc search arrays superimposed on two concentric color-marked annuli respectively. Two series of arrays were updated independently; one updated at one fixed frequency (flicker) and the other updated randomly according to a white noise distribution (random broadband flicker, rbbf). On each trial, the observer was instructed to attend one annulus and to detect a target (a triangle) that occasionally appeared in a random disc array in the attended annulus. The SSVEP results show that the choice of flicker frequency selects which cortical network synchronizes to the flicker two distinct cortical networks showed different effects of attention. SSVEP power and the effects of attention on SSVEP power strongly depend on both flicker frequency and radial position of rbbf annulus. At flicker frequencies in the delta band (2-4 Hz), and in the upper alpha band (10-11 Hz), an occipital-frontal network appears to phase-lock to the flicker when attending to the flicker, increasing the magnitude of the SSVEP. At flicker frequencies in the lower alpha band (8-10 Hz), a global response to a peripheral flickering stimulus, that includes parietal cortex and posterior frontal cortex, has higher amplitude when attention is directed away from the flickering peripheral stimulus and towards a competing rbbf stimulus in the fovea. Increases in SSVEP power when attention is directed to peripheral flicker are always associated with increases in phase locking. By contrast, at frequencies in the lower alpha band, increases in SSVEP power when attention is directed away from the flicker and towards foveal stimuli are not associated with changes in phase-locking. Thus, whether attention to a flicker stimulus increases or decreases SSVEP amplitude and phase locking depends on which of two cortical networks, which have distinct spatial and dynamic properties, is selected by the flicker frequency.

Action Potentials↗
PubMed2006

Spatially selective representations of voluntary and stimulus-driven attentional priority in human occipital, parietal, and frontal cortex.

When multiple objects are present in a visual scene, they compete for cortical processing in the visual system; selective attention biases this competition so that representations of behaviorally relevant objects enter awareness and irrelevant objects do not. Deployments of selective attention can be voluntary (e.g., shift or attention to a target's expected spatial location) or stimulus driven (e.g., capture of attention by a target-defining feature such as color). Here we use functional magnetic resonance imaging to show that both of these factors induce spatially selective attentional modulations within regions of human occipital, parietal, and frontal cortex. In addition, the voluntary attentional modulations are temporally sustained, indicating that activity in these regions dynamically tracks the locus of attention. These data show that a convolution of factors, including prior knowledge of location and target-defining features, determines the relative competitive advantage of visual stimuli within multiple stages of the visual system.

Adult↗
PubMed1996

Stepping over obstacles: dividing attention impairs performance of old more than young adults.

BACKGROUND: Tripping over an obstacle is a common cause of falls in the elderly. An earlier study of abilities to avoid stepping on suddenly appearing obstacles found that, although healthy old adults had a lower rate-of-success than young adults, the magnitude of that difference was not large. The present study inquired whether dividing attention during such a task would differentially affect young and old healthy adults. METHODS: Rates-of-success were observed in 16 young and 16 old healthy adults (mean ages 24 and 72 years) in avoiding stepping on a band of light that was suddenly projected across their gait path while they walked at their comfortable gait speed. This virtual obstacle was placed at predicted next-footfall locations to give 350 or 450 msec available response times before footfall. During most of the trials the subjects were asked, in addition to trying not to step on the obstacle, simultaneously to respond vocally as quickly as possible when red lights near the end of the walkway turned on. These attention-dividing reaction time tests were of two types: synchronized, when only red lights lit at intervals synchronized with the appearance of the obstacle, and unsynchronized, when green or yellow lights lit in addition to the red lights, with lighting intervals not synchronized with the appearance of the obstacle. RESULTS: When synchronized and unsynchronized reaction time tests were conducted concurrently with the obstacle avoidance tasks, mean rates-of-success in avoidance decreased significantly in both young and old adults. With available response times of 350 msec, mean success rates decreased from their no-division values in the young adults by 14.7% for synchronized reaction and by 19.9% for unsynchronized reaction, attention-dividing tests. Corresponding mean decreases for the old adults were 32.0 and 35.7%. This age difference in the effects of dividing attention was significant. CONCLUSION: Both young and old adults had a significantly increased risk of obstacle contact while negotiating obstacles when their attention was divided, but dividing attention degraded obstacle avoidance abilities of the old significantly more than it did in the young. Diminished abilities to respond to physical hazards present in the environment when attention is directed elsewhere may partially account for high rates of falls among the elderly.

Accidental Falls↗
PubMed2003

Visual attention and driving behaviors among community-living older persons.

BACKGROUND: Older drivers have higher rates of crashes per mile driven compared with most other drivers, and these crashes result in greater morbidity and mortality. Various aspects of cognition, particularly visual attention, have been linked with crash risk among older individuals. The current study was designed to specify those cognitive variables associated with specific on-road driving behaviors in a sample of older, nonclinic-referred individuals. METHODS: 35 community-residing active drivers aged 72 years and older (M = 80) underwent a standardized, on-road driving evaluation involving parking lot maneuvers, and urban, suburban, and highway driving. They were also administered tests of visual attention, executive function, visuospatial cognition, and memory. RESULTS: Driving score was significantly correlated with visual attention, visual memory, and executive function. Visual attention was associated with 25 of 36 driving behaviors, including those involving scanning the environment, interaction with traffic or pedestrians, and distance judgments. Executive function and visual memory were associated with fewer maneuvers, most of which were a subset of maneuvers that correlated with visual attention. CONCLUSIONS: Visual attention, a cognitive function involving search, selection, and switching, plays an important role in driving risk among older drivers. In the current study, key driving maneuvers involving interaction with other vehicles/pedestrians, such as yielding right of way and negotiating safe turns or merges, have the greatest association with visual attention. Specification of both the cognitive risk factors and their impact on problematic driving maneuvers may provide guidelines for developing targeted interventions to reduce risk among older adults.

Accidents, Traffic↗
PubMed1994

Impaired attention, genetics, and the pathophysiology of schizophrenia.

Impaired attention is commonly observed among schizophrenia patients and those at genetic risk for the disease. This article reviews over 40 studies that used various versions of the Continuous Performance Test (CPT) as the primary measure of attention. These studies of normal subjects, affected patients, and various at-risk populations demonstrate that the CPT is a psychometrically sound procedure that consistently discriminates affected patients from controls. Sufficiently difficult versions of this task have also demonstrated that impaired attention is (1) evident in schizophrenia patients regardless of clinical state, (2) detectable before illness onset, (3) apparently heritable, (4) specific--in terms of distinct profile patterns--to schizophrenia, and (5) predictive of later behavioral disturbances in susceptible individuals. Selected studies are also discussed that examine the role of attentional deficit in the pathophysiology of schizophrenia and its potential consequences for personality development. With respect to pathophysiology, preliminary data suggest that subcortical brain dysfunction has an important role in the attentional deficits tapped by the CPT. With respect to personality, an association between chronically impaired attention and deficient social skills has been found. It is concluded that the CPT is a cost-effective measure of the attentional deficit commonly found in affected schizophrenia subjects and those at risk for the disorder, and is therefore a potentially valuable screening device for preventive intervention programs.

Attention↗
PubMed1997

Decreased attentional responsivity during sleep deprivation: orienting response latency, amplitude, and habituation.

Ever increasing societal demands for uninterrupted work are causing unparalleled amounts of sleep deprivation among workers. Sleep deprivation has been linked to safety problems ranging from medical misdiagnosis to industrial and vehicular accidents. Microsleeps (very brief intrusions of sleep into wakefulness) are usually cited as the cause of the performance decrements during sleep deprivation. Changes in a more basic physiological phenomenon, attentional shift, were hypothesized to be additional factors in performance declines. The current study examined the effects of 36 hours of sleep deprivation on the electrodermal-orienting response (OR), a measure of attentional shift or capture. Subjects were 71 male undergraduate students, who were divided into sleep deprivation and control (non-sleep deprivation) groups. The expected negative effects of sleep deprivation on performance were noted in increased reaction times and increased variability in the sleep-deprived group on attention-demanding cognitive tasks. OR latency was found to be significantly delayed after sleep deprivation, OR amplitude was significantly decreased, and habituation of the OR was significantly faster during sleep deprivation. These findings indicate impaired attention, the first revealing slowed shift of attention to novel stimuli, the second indicating decreased attentional allocation to stimuli, and the third revealing more rapid loss of attention to repeated stimuli. These phenomena may be factors in the impaired cognitive performance seen during sleep deprivation.

Attention↗
PubMed2006

Attention bias for sleep-related stimuli in primary insomnia and delayed sleep phase syndrome using the dot-probe task.

STUDY OBJECTIVES: Cognitive models of primary insomnia (PI) suggest attention bias as a maintaining process. This study used a hallmark measure of attention bias, the dot-probe task, to determine whether attention bias to sleep-related stimuli is present in individuals with PI. Control groups of good sleepers (GS) and individuals with delayed sleep phase syndrome (DSPS), a sleep disorder with no presumed cognitive pathway and, hence, no predicted association with attention bias, were included. DESIGN: A between-groups (PI, DSPS, GS) design was employed. Participants completed a dot-probe task with stimuli comprising sleep-related and neutral words, balanced for length and frequency of usage. It was predicted a priori that PI would show greater attention bias to sleep stimuli compared with GS and DSPS groups. No difference between GS and DSPS was predicted. PARTICIPANTS: Sixty-three individuals completed the study (PI = 21; DSPS = 22; GS = 20), with those in PI and DSPS classified by International Classification of Sleep Disorders criteria according to self-report sleep diaries and actigraphy. GS scored < 5 on the Pittsburgh Sleep Quality Index, reported being good sleepers, and met no criteria for a current or previous sleep disorder. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: As predicted, PI showed increased vigilance for sleep-related stimuli relative to GS and DSPS. No differences between GS and those with DSPS were found. The PI group showed shorter response latencies relative to the GS and DSPS groups. CONCLUSIONS: Results support an association between attention bias and PI. Further work must determine whether or not attention bias is a causal factor. Speeded responses in the PI group suggest heightened arousal, indicating that physiologic factors may play a related role.

Adolescent↗
PubMed1998

Functional neuroimaging of attention in the auditory modality.

Previous functional neuroimaging studies of attention have emphasized the visual modality. We developed an auditory version of the continuous performance test (CPT) that included simple, focused and divided attention conditions. Positron emission tomographic (PET) scans were acquired during CPT performance in normal young adults and then submitted to statistical parametric mapping. Simple attention brought about a large region of activation involving the anterior cingulate gyrus and the right anterior/mesial frontal lobe. Focused and divided attention CPT conditions were compared but there were few significant differences. The findings are consistent with activation of an anterior attention network during auditory attention, without involvement of posterior attention structures which are more likely to vary in accordance with sensory modality.

Acoustic Stimulation↗
PubMedDate not supplied

Effects of methylphenidate on attentional function after traumatic brain injury. A randomized, placebo-controlled trial.

Attention deficits after traumatic brain injury (TBI) are common and disabling. Many pharmacologic agents have been used to ameliorate attention deficits, and considerable interest has focused on methylphenidate (MP) because of its documented efficacy in attention deficit disorder. However, clinical studies of MP in subjects with TBI have yielded mixed results. We examined the effects of MP on attentional function in individuals with TBI referred specifically for attentional assessment and treatment. Subjects were studied in a double-blind, placebo-controlled, repeated crossover design, using five different tasks designed to measure various facets of attentional function. MP produced a significant improvement in the speed of mental processing. Orienting to distractions, most aspects of sustained attention, and measures of motor speed were unaffected. These results suggest that MP may be a useful treatment in TBI but is primarily useful for symptoms that can be attributed to slowed mental processing.

Adolescent↗
PubMed1997

The role of attention in a spatial memory task in Alzheimer disease patients.

Memory and attention are interrelated cognitive processes that most likely influence the functioning of each other, yet they are often difficult to distinguish in psychological experiments. Young, aged adults, and patients with Alzheimer disease (AD) were tested on a delay response task measuring spatial memory that also placed high demands on attentional resources. Aged adults performed as well as young, suggesting that neither attentional nor memory abilities were exceeded in either group. However, AD subjects were severely impaired on this task. Two further experiments with AD patients examined the relative contribution of attentional and memory deficits in the performance of this population. Both memory and attentional impairments were found; however, errors due to memory factors were more closely related to severity of disease as measured on the Folstein Mini-Mental State Examination than were errors of attentional origin. These studies demonstrate the necessity of accounting for attentional components in studies examining memory, especially in patients with AD.

Adult↗
PubMed1996

Attention problems versus conduct problems as six-year predictors of problem scores in a national sample.

OBJECTIVE: To test the extent to which attention problems, the continuation of early comorbid conduct problems, and overall initial problems account for poor outcome scores on the Child Behavior Checklist and related measures 3 and 6 years after initial assessment. METHOD: The course of attention and conduct problems was investigated in a nationally representative US sample assessed three times over 6 years, using standardized ratings of attention, conduct, and other problems and gender-specific scores for defining deviance. RESULTS: Subjects deviant on both attention and conduct problems scored significantly higher on behavior problems at outcome than did those deviant on only attention problems or conduct problems. After controlling for initial conduct problems, initial attention problems made little unique contribution to later conduct problems. Predictive patterns were similar across gender and age groups. CONCLUSIONS: Both boys and girls who show a combination of attention and conduct problems are at particular risk for the persistence of conduct problems.

Adolescent↗
PubMed1993

Neuropsychological assessment of attention problems in pathological gamblers.

Deficits in executive, frontally mediated attention processes have been observed in substance abusers. A significant rate of childhood histories of attention deficit hyperactivity disorder has also been reported in this population, creating the question of whether attention problems predated addiction or were secondary to neurological drug or alcohol effects in pathological gamblers. To address this issue, the current study compared 33 non-substance-abusing pathological gamblers with 33 nonaddicted controls on nine attention measures and childhood behavior questionnaires. Gamblers performed significantly worse than controls on higher order attention measures and reported more childhood behaviors consistent with attention deficits. Results suggest attention deficits may be a risk factor for development of addictive disorders.

Adult↗
PubMedDate not supplied

Adrenocorticotropin widens the focus of attention in humans. A nonliner electroencephalographic analysis.

OBJECTIVE: This study examined the effects of ACTH 4-10, a fragment of adrenocorticotropin (ACTH) with known central nervous system (CNS) activity, on the dimensional complexity of the ongoing electroencephalographic (EEG) activity. Stressful stimuli cause ACTH to be released from the pituitary, and as a neuropeptide ACTH may concurrently exert adaptive influences on the brain's processing of these stimuli. Previous studies have indicated an impairing influence of ACTH on selective attention. METHODS: Dimensional complexity of the EEG, which indexes the brain's way of stimulus processing, was evaluated while subjects performed tasks with different attention demands. Sixteen healthy men (23 to 33 years) were tested once after placebo and another time after administration of ACTH 4-10 (1.25 mg intravenously (i.v.), 30 minutes before testing). The EEG was recorded while subjects were presented with a dichotic listening task (consisting of the concurrent presentation of tone pips to the left and right ear). Subjects either a) listened to pips in both ears (divided attention), or b) listened selectively to pips in one ear (selective attention), or c) ignored all pips. RESULTS: Dimensional complexity of the EEG was higher during divided than selective attention. ACTH significantly increased the EEG complexity during selective attention, in particular over the midfrontal cortex (Fz, Cz). CONCLUSIONS: The effects support the view of a de-focusing action of ACTH during selective attention that could serve to improve the organism's adaptation to stress stimuli.

Adrenocorticotropic Hormone↗
PubMed2000

Moving out of the laboratory: does nicotine improve everyday attention?

The most robust demonstrations of the nicotine-related performance effects on human cognitive processes are seen in tasks that measure attention. If nicotine does have some potential for enhancing attention, the obvious question to ask is whether the effects demonstrated in the laboratory hold any significance for real-life performance. This paper describes three studies that compare the effects in smokers of a single own brand cigarette on laboratory tests of attention and on everyday analogues of these laboratory tasks. In the laboratory measures of sustained attention and in the everyday analogue, performance advantages were registered in the smoking condition. These benefits were observed in smokers who abstained for a self-determined period of not less than 2 h. The studies were unable to replicate previous research reporting positive effects of smoking on a laboratory task of selective attention, the Stroop task. Small but significant improvements in performance were registered in the everyday analogues, which involved sustaining attention in a dual task situation, a telephone directory search task and a map search task. In addition, smokers showed a significant colour-naming decrement for smoking-related stimuli in the Stroop task. This attentional bias towards smoking-related words occurred independent of whether they had abstained or recently smoked an own brand cigarette. The effect is discussed in terms of the two-component model of processing bias for emotionally valenced stimuli.

Adolescent↗
PubMed2005

Effects of prenatal alcohol exposure on attention and working memory at 7.5 years of age.

BACKGROUND: A broad range of attentional and neuropsychological impairments have been demonstrated in children with fetal alcohol exposure. This study was designed to investigate which specific aspects of attentional function are most directly affected by moderate to heavy doses of prenatal alcohol exposure. METHODS: A total of 337 black children who were aged 7.5 years and recruited prospectively to overrepresent prenatal alcohol exposure at moderate to heavy levels were assessed on a diverse battery of neuropsychological tests. Principal components analyses were used to replicate and extend Mirsky et al.'s (1991) four-component model of attention. The relation of prenatal alcohol exposure to empirically derived attentional constructs was examined. RESULTS: Both the replicated and the extended attentional models produced solutions similar to the original Mirsky et al. model, reflecting elements of encode (working memory), shift, and focused and sustained attention, as well as a distinct component reflecting impulsivity. Adverse effects of maternal drinking across pregnancy were found primarily for working memory, and these effects were exacerbated when mothers were aged 30 or older at the time of the child's birth. CONCLUSIONS: These data confirm previous studies using diverse methods that suggest that working memory may be the most important aspect of attention that is adversely affected by prenatal alcohol exposure.

Adult↗
PubMedDate not supplied

Cholinergic modulation of visual attention and working memory: dissociable effects of basal forebrain 192-IgG-saporin lesions and intraprefrontal infusions of scopolamine.

Two experiments examined the effects of reductions in cortical cholinergic function on performance of a novel task that allowed for the simultaneous assessment of attention to a visual stimulus and memory for that stimulus over a variable delay within the same test session. In the first experiment, infusions of the muscarinic receptor antagonist scopolamine into the medial prefrontal cortex (mPFC) produced many omissions but did not impair rats' ability to correctly detect a brief visual stimulus. However, these animals were highly impaired in remembering the location of that stimulus following a delay period, although in a delay-independent manner. In the second experiment, another group of animals with selective 192 IgG-saporin lesions of the nucleus basalis magnocellularis (nBM) were not impaired under conditions of low-attentional demand. However, when the stimulus duration was reduced, a significant memory impairment was observed, but similar to the results of the first experiment, the nBM-lesioned animals were not impaired in attentional accuracy, although aspects of attention were compromised (e.g., omissions). These findings demonstrate that (1) cortical cholinergic depletion produces dissociable deficits in attention and memory, depending on the task demands, (2) delay-independent mnemonic deficits produced by scopolamine are probably due to impairments other than simple inattention, and (3) working memory deficits are not simply dependent on attentional difficulties per se. Together, these findings implicate the nBM cortical cholinergic system in both attentional and mnemonic processing.

Acetylcholine↗