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PubMed2001

Location and attention.

A discrepancy exists in the literature concerning attention and visual localization accuracy. Prinzmetal, Amiri, Allen, and Edwards (1998), and Tsal and Bareket (1999a) found that localization accuracy increases with attention. Using an inattention paradigm, Rock, Linnett, Grant, and Mack (1992) found no difference between localization accuracy in three attention conditions: inattention, divided attention, and control. Using a similar inattention paradigm, the current study addressed this discrepancy. Subjects were instructed to perform a line judgement task, and attention for an additional location task was manipulated. In Experiment 1, location accuracy was worse in the inattention condition than in either the divided-attention or the control condition. There was no difference between the divided-attention and control conditions. Experiment 2 controlled for the possibility that improved location accuracy in the divided and control conditions was due to the expectation of performing a location response, rather than the manipulation of attention. Our results are in agreement with previous findings (Prinzmetal et al., 1998; Tsal & Bareket, 1999a) and suggest that the apparent discrepancy is due to coarse coding of the location responses in the study by Rock et al. (1992).

Adolescent↗
PubMed2006

Aging and the role of working memory resources in visuospatial attention.

Visuospatial attention has been shown to be robust to the effects of increasing age. Nonetheless, models linking individual differences in working memory capacity to attentional performance suggest that older adults may experience disruptions in visuospatial attention under conditions of resource load. Two experiments were conducted to investigate the effects of age and concurrent working memory load on two tasks that have been proposed to require posterior attentional processes. The findings suggest that loading working memory resources selectively disrupts performance on a nonintegrated Stroop task, whereas cue utilization remains intact. In addition, imposing a working memory load delays the deployment of visuospatial attention in both experiments. Regarding the effects of age, findings suggest that older adults can effectively perform both attentional tasks despite working memory load. Age differences did emerge in the time course of cue utilization. Findings point to the resilience of visuospatial attention in aging, even under conditions of significant cognitive load. We discuss these results and their implications for models postulating a role for working memory capacity in attentional behaviors.

Adolescent↗
PubMed2004

The status of empirical support for treatments of attention deficits.

Deficits in attention and self-regulation are common complaints associated with a number of disorders across the lifespan. The need to address attentional deficits is based on the premise that attention is a precursor and prerequisite to information processing and related cognitive tasks as well as a key factor in the success of other rehabilitation efforts. Many treatment programs have been developed with the intention of restoring or rehabilitating the impaired components of attention; the number and variety of attention programs is increasing rapidly. The purpose of this article is to evaluate available empirical support regarding the efficacy of treatments for remediation of attention deficits across disorders and age levels. The search of the major databases yielded 83 studies that included treatment of attentional deficits. Empirical studies were reviewed and categorized by the type of trial, whether or not the study included a control group, and the nature of the control group. The methodology and results of each study were then rated. For each treatment identified, the aggregated studies were then considered by the disorder of the samples included in the studies. Results indicated that, regardless of the treatment program or population, the existing research does not provide sufficient evidence to reach any conclusions about the efficacy of programs designed to address attention deficits. Before any conclusions, positive or negative, can be drawn, there is a need for more rigorous study of available treatment programs across age levels and disorders, with sufficient baseline and outcome data as well as control or alternative treatment conditions.

Attention Deficit Disorder with Hyperactivity↗
PubMed2006

EPS Mid-Career Award 2004: brain mechanisms of attention.

There are many varieties of "attention", to some extent separate yet working together to produce coherent perception, thought, and behaviour. Using data from human behaviour, functional neuroimaging, and single-cell recording in the behaving monkey, I consider different levels of attention and their basis in physiological mechanisms of biased competition. Beginning with visual attention, I suggest that processing is competitive in many brain systems that code visual input. Competition is biased towards stimuli that match task requirements and is integrated between systems coding different object properties. The result is flexible, object-based attentional selection. In the second part of the paper, I describe recent experiments on attentional competition within and between sensory modalities. Though competition is often modality specific, more global levels of interference are also easy to demonstrate. In the third part of the paper, I move to frontoparietal cortex and to a pattern of similar brain regions recruited by many different cognitive demands. This multiple-demand (MD) pattern, I suggest, reflects neurons with highly flexible response properties, adapting to represent the information and events of many different tasks. Biased competition in MD regions may play a central role in broad attentional capacity limits and attentional focusing. More generally, I suggest that biased competition is characteristic of many different cognitive domains and brain systems. Coherent "attention" develops as different systems converge to work on related cognitive content.

Attention↗
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↗
PubMed1998

The functional anatomy of attention to visual motion. A functional MRI study.

Attention can enhance or modulate neural responses to stimuli at early and late stages of sensory processing. We were interested in the modulatory effect of attention to visual motion on cortical responses as measured by functional MRI. Subjects were scanned during repeated presentations of identical stimuli (visual motion) while only the attentional component of the task was varied. Enhanced haemodynamic responses during attentive conditions defined an occipitoparietofrontal system, including sensory and association areas, as well as the medial thalamus and superior colliculus. Attentional modulation was not restricted to extrastriate areas (including V3a and the V5 complex) but was also evident, to a lesser degree, in early visual areas close to the calcarine fissure (V1/V2 border). Attention-related enhancement of cortical responsiveness is discussed in terms of data that implicate modulatory short-term changes in synaptic efficacy and reciprocal connections between striate, extrastriate, parietal and frontal areas. Given the similarity of our attentional network to that controlling eye movements, the results of this study are in accord with theories linking oculomotor control and attention.

Attention↗
PubMed2001

Attentional control in Alzheimer's disease.

Attentional control of executive function declines during the early stages of Alzheimer's disease. Controversy exists as to whether this decline results from a single global deficit or whether attentional control can be fractionated, with some aspects being more vulnerable than others. We investigated three proposed domains of attention, namely (i) focal attention, based on simple and choice reaction times; (ii) the capacity to resist distraction in a visual search task; and (iii) the capacity to divide attention between two simultaneous tasks. For each domain, two levels of difficulty were used to study Alzheimer's disease patients, who were compared with elderly and young control subjects. The unitary attentional hypothesis predicted that the impacts of level of difficulty, age and disease would be qualitatively similar across the three attentional domains. In fact we observed different patterns for each domain. We obtained no differential impairment for patients in the focal attentional task, whereas patients were somewhat more susceptible than control subjects to the similarity of the distractor items in visual search. Finally, we observed marked impairment in the capacity of Alzheimer's disease patients to combine performance on two simultaneous tasks, in contrast to preserved dual-task performance in the normal elderly group. These results suggest a need to fractionate executive processes, and reinforce earlier evidence for a specific dual-task processing deficit in Alzheimer's disease.

Adult↗
PubMed2005

Goal-driven selective attention in patients with right hemisphere lesions: how intact is the ipsilesional field?

Patients with right hemisphere (RH) lesions often display a spatial bias in attention towards the ipsilesional hemifield. The behavioural manifestations of this spatial bias are typically interpreted as reflecting increased or enhanced attention for stimuli within the 'intact' ipsilesional field, and impaired attentional functioning within the contralesional field. In the healthy brain, goal-driven and stimulus-driven attentional processes interact to determine which stimuli should be prioritized for selection. Although unilateral brain damage increases the relative attentional salience of stimuli within the ipsilesional field, it might also cause problems in filtering or attenuating task-irrelevant information. We examined whether goal-driven attention modulates the processing of ipsilesional and contralesional information in 6 patients with unilateral brain damage following RH stroke (5 male, 1 female; mean age 60.8 years) and a group of age and sex-matched controls. We used a flanker task in which participants made speeded judgements on a central target item (a coloured letter). On each trial the target was flanked by a coloured letter in the left and right hemifields. In separate blocks, participants were instructed to judge either the identity or the colour of the central target and to ignore the flankers. The flanker on one side could be congruent, incongruent or neutral with respect to the target, on either the letter or the colour dimension, whereas the flanker on the other side was always neutral on both dimensions. Healthy controls showed significant interference from incongruent flankers on either side. Crucially, however, this effect only occurred for the task-relevant dimension [F(2,10) = 24.60; P < 0.001]. For patients, however, both the task-relevant and task-irrelevant dimensions of ipsilesional flankers interfered with response times [task-relevant: F(2,10) = 7.50, P < 0.05; task-irrelevant: F(1,5) = 6.20, P < 0.05]. Conversely, contralesional flankers influenced response times only when the target and distractor were incongruent on the task-relevant dimension [F(2,10) = 4.85; P < 0.05]. Our findings demonstrate that following RH damage, goal-driven biases cannot constrain the processing of task-irrelevant features of ipsilesional stimuli. We speculate that a lateralized bias in spatial attention leads to unselective prioritization of all feature-based attributes of stimuli appearing within the ipsilesional hemifield, whether or not they are relevant to performance. Attentional selection for ipsilesional stimuli in disorders such as spatial neglect and extinction may not therefore be entirely normal, as previously assumed.

Aged↗
PubMedDate not supplied

Neurophysiological evidence for a role of posterior parietal cortex in redirecting visual attention.

Lesions of the posterior parietal cortex in humans and monkeys result in a spatial neglect syndrome characterized by defects in visual-spatial perception, oculomotor function, and directing visual attention. Although symptoms of spatial neglect can result from lesions to other cortical and subcortical areas, patients with posterior parietal lesions are particularly impaired in their ability to disengage and reorient visual attention. Neurophysiological experiments in area 7a of behaving monkeys reveal a large class of neurons that respond to visual stimuli and are powerfully modulated by states of attention. These cells respond better to passive visual stimuli presented during states of attentive fixation than to identical stimuli presented in nonattentive states. The responses of the majority of these cells are also influenced by covert shifts of attention away from the point of fixation; they respond to stimuli presented anywhere within their receptive fields except the covertly attended location. The combined effect of facilitation during attentive fixation and lack of response at the attended location results in a sensitivity for visual stimuli that appear at one location while attention is directed to another. The special sensitivity for unattended stimuli in this group of neurons in area 7a suggests that they may play a role in reorienting attention, possibly by providing signals of the spatial locations of novel stimuli.

Animals↗
PubMedDate not supplied

Tactile attention tasks enhance activation in somatosensory regions of parietal cortex: a positron emission tomography study.

We used positron emission tomography to study cortical regions mediating tactile attention. Cues selectively directed subjects to attend to the roughness or duration of contact with embossed gratings that rubbed against a single fingertip with controlled speed and force. The task required discriminating between paired gratings that differed in tactile features of roughness and/or length. For different blocks of trials, cues directed attention to one tactile feature or indicated a divided attention strategy to a change in either feature. All attention conditions unambiguously activated several somatosensory foci in the parietal cortex, including somatotopically appropriate portions of the primary somatosensory cortex in the postcentral gyrus (S1) and the secondary somatosensory region (S2) within parietal opercular regions. There was no evidence for separate processing foci for selective and divided attention strategies, or for selectively attending to roughness versus stimulus duration. We observed a greater magnitude blood flow change in S2 versus S1 during attention tasks, which suggests that S2 might actually influence S1 activity. Despite these differences, modulation of S1 and S2 supports concepts of early selection in tactile attention. There were also examples of non-sensory foci in frontal cortex, anterior cingulate gyrus and bilateral superior parietal regions at the fundus of the postcentral sulcus. Posterior parietal regions observed in this study did not overlap foci seen in studies of visual attention. Thus, the posterior parietal region may be subdivided into modality-specific subregions, each of which processes information needed to attend to a specific modality. These non-sensory areas may constitute a network that provides a source of modulating influences on the earlier stage, sensory areas.

Adolescent↗
PubMed2004

Control of object-based attention in human cortex.

Visual attention is a mechanism by which observers select relevant or important information from the current visual array. Previous investigations have focused primarily on the ability to select a region of space for further visual analysis. These studies have revealed a distributed frontoparietal circuit that is responsible for the control of spatial attention. However, vision must ultimately represent objects and in real scenes objects often overlap spatially; thus attention must be capable of selecting objects and their properties nonspatially. Little is known about the neural basis of object-based attentional control. In two experiments, human observers shifted attention between spatially superimposed faces and houses. Event-related functional magnetic resonance imaging (fMRI) revealed attentional modulation of activity in face- and house-selective cortical regions. Posterior parietal and frontal regions were transiently active when attention was shifted between spatially superimposed perceptual objects. The timecourse of activity provides insight into the functional role that these brain regions play in attentional control processes.

Acoustic Stimulation↗
PubMed2006

Dissociation of stimulus relevance and saliency factors during shifts of visuospatial attention.

The control of visuospatial attention entails multiple processes, including both voluntary (endogenous) factors and stimulus-driven (exogenous) factors. Exogenous processes can be triggered by visual targets presented at a previously unattended location, thus capturing attention in a stimulus-driven manner. However, little is known about the relative role of stimulus salience and behavioral relevance for this type of spatial reorienting. Here, we directly assessed how salience and relevance affect activation of the frontoparietal attentional system, using either low-salience but task-relevant target stimuli or salient but task-irrelevant flickering checkerboards. We compared event-related functional magnetic resonance imaging responses for stimuli presented at the unattended versus attended side (invalid minus valid trials), separately for the 2 categories of visual stimuli. We found that task-relevant invalid targets activated the frontoparietal attentional network, demonstrating that this system engages when target stimuli are presented at an unattended location, even when these have a low perceptual salience. Conversely, the presentation of high-salience checkerboards in one hemifield while endogenous attention was engaged elsewhere did not activate the attentional network. These findings indicate that task relevance is critical for stimulus-driven engagement of the attentional network when attentional resources are endogenously allocated somewhere else.

Adult↗
PubMed2006

Attentional modulation of receptive field structure in area 7a of the behaving monkey.

Spatial attention modulates the activity of inferior parietal neurons. A statistically rigorous approach to classical retinotopic mapping was used to quantify the receptive fields of area 7a neurons under 2 attentional conditions. Measurements were made with retinal stimulation held constant and the locus of attention manipulated covertly. Both tasks required central fixation but differed in the locus of covert attention (either on the center fixation point or on a peripheral square target in one of 25 locations). The neuron's identity over the recording session was confirmed using chaos theory to characterize unique temporal patterns. Sixty-six percent of the neurons changed prestimulus activity based on task state. Retinotopic mapping showed no evidence for foveal sparing. Attentional factors influenced visual responses for approximately 30% of the neurons. Two types of modulation were equally observed. One group of cells had a multiplicative scaling of response, with equal instances of enhancement and suppression. A second group of cells had a complex interaction of visual and attentional signals, such that spatial tuning was subject to a nonlinear modulation across the visual field based on attentional constraints. These 2 cell groups may have different roles in the shift of attention preceding motor behaviors and may underlie shifts in parietal retinotopic maps observed with intrinsic optical imaging.

Algorithms↗
PubMed1999

Attentional demands and postural recovery: the effects of aging.

BACKGROUND: Cognitive demands associated with balance and locomotion may contribute to the incidence of falling among older adults. This study addressed issues related to the effects of aging on the attentional demands of recovering from an external disturbance to balance. This research also investigated whether performing a secondary cognitive task differentially affects postural recovery in young versus older adults. METHOD: Fifteen young and 10 healthy older adults were exposed to a series of balance disturbances. Attentional demands were assessed using a dual task paradigm where postural recovery served as the primary task, and counting backwards served as a concurrent secondary cognitive task. The effect of the counting task was assessed by comparing kinematic variables related to feet-in-place and stepping recovery strategies. RESULTS: Recovering upright stance was found to be attentionally demanding in both age groups. The type of recovery strategy did not influence attentional demands in young adults; however, a hierarchy of increasing attentional demands between the ankle strategy and compensatory stepping was apparent among older adults. In addition, stepping appears to be more attentionally demanding for older adults than for younger adults. Counting backwards did not affect the type of strategy used; however, it did affect the kinematics of stepping. For both age groups, steps occurred when the center of mass was located in a more central location within the base of support when the secondary task was added. CONCLUSIONS: The ability to recover a stable posture following an external perturbation is more attentionally demanding for older adults than for younger adults. This would suggest that for some older adults, an increased risk for loss of balance and falls may result if sufficient attentional resources are not allocated to the task of postural recovery.

Accidental Falls↗
PubMed2003

Attentional abilities and functional outcomes following stroke.

Although stroke affects cognitive functioning as well as motor functioning, research on cognitive consequences has lagged behind that focused on motor function. The evidence that is accruing suggests that cognitive function is importantly related to successful rehabilitation. The present study examined two aspects of attentional functioning (divided attention and switching attention) in older adult stroke survivors and healthy older adults. In addition, the authors investigated the relation between attention and functional outcomes following stroke. Results revealed stroke-related deficits in both of the types of attention as well as significant associations between attentional functioning and both physical and social outcome measures. Poorer attentional performance was associated with a more negative impact of stroke on daily functioning. These findings suggest an important role for attention in post-stroke function and provide information that can contribute to improving outcomes following stroke.

Aged↗
PubMed2005

Independence of visual awareness from attention at early processing stages.

According to a widely accepted idea, only the results of attentional selection reach visual awareness. A competing model postulates that awareness is independent of attentional selection: contents of subjective visual experience may also exist without the contribution of attention. We tested these competing models by tracking the independent contributions of selective attention and awareness to electrophysiological brain responses. Our results showed that the earliest effects of visual awareness emerged earlier than the effects of attention and regardless of the presence or absence of attention. The early effects of attention were elicited regardless of the presence or absence of awareness. The results suggest that visual awareness and selective attention are initially independent of each other.

Adolescent↗
PubMed2003

An environmental intervention to restore attention in women with newly diagnosed breast cancer.

Earlier research indicated that attentional fatigue with reduced capacity to direct attention in women treated for breast cancer may be ameliorated by a theoretically based intervention involving regular exposure to the natural environment. This study tested the efficacy of a natural environment intervention aimed at restoring attention in 157 women with newly diagnosed breast cancer. Capacity to direct attention was assessed with a brief battery of objective measures at two time points: approximately 17 days before surgery (time 1) and 19 days after surgery (time 2). A randomly assigned intervention protocol was initiated after the first assessment and before any treatment. The intervention comprised a home-based program involving 120 minutes of exposure to the natural environment per week. The intervention group (n = 83) showed greater recovery of capacity to direct attention from the pretreatment (time 1) to the preadjuvant therapy period (time 2), as compared with the nonintervention group (n = 74). A significant effect of the natural environment intervention was observed even after control was used for the effects of age, education, attention scores at time 1, other health problems, symptom distress, and extent of surgery. The findings suggest therapeutic benefits for capacity to direct attention from early intervention aimed at restoring attention in women with newly diagnosed breast cancer.

Adaptation, Psychological↗
PubMed2000

Driving outcomes of young people with attentional difficulties in adolescence.

OBJECTIVE: To examine associations between attentional difficulties at age 13 and a range of adverse driving outcomes measured at 21 years. METHOD: Data were gathered over the course of a 21-year longitudinal study of a birth cohort of 1,265 New Zealand children. Data collection included the following: (1) parent and teacher report measures of attentional difficulties (13 years); (2) measures of driving behavior, including involvement in an accident, drinking and driving, and traffic violations (18-21 years); and (3) measures of a range of potentially confounding individual, sociofamilial, and driving-related factors. RESULTS: Young people with high levels of attentional difficulties were at greater risk of involvement in a motor vehicle accident, drinking and driving, and traffic violations. These associations were largely explained by the personal characteristics (gender, conduct problems) and driving experience (length of time respondent held a license, distance driven) of young people with attentional difficulties. Even after adjustment for the effects of confounding factors, adolescent attentional difficulties placed young people at increased risk of an injury accident, driving without a license, and other traffic violations. CONCLUSIONS: Associations between adolescent attentional difficulties and subsequent driving risks largely reflect the effects of confounding factors correlated with attentional difficulties and driving outcomes. However, even after adjustment for confounding, adolescent attentional difficulties contributed to later injury accident risk and possibly also to risky driving behavior.

Accidents, Traffic↗