Attentional dysfunction is among the most consistent observations of autism spectrum disorders (ASD). However, the neural nature of this deficit in ASD is still unclear. In this study, we aimed to identify the neurobehavioral correlates of attentional dysfunction in ASD. We used the Attention Network Test-Revised and functional magnetic resonance imaging to examine alerting, orienting, and executive control functions, as well as the neural substrates underlying these attentional functions in unmedicated, high-functioning adults with ASD (n = 12) and matched healthy controls (HC, n = 12). Compared with HC, individuals with ASD showed increased error rates in alerting and executive control, accompanied by lower activity in the mid-frontal gyrus and the caudate nucleus for alerting, and by the absence of significant functional activation in the anterior cingulate cortex (ACC) for executive control. In addition, greater behavioral deficiency in executive control in ASD was correlated with less functional activation of the ACC. These findings of behavioral and neural abnormalities in alerting and executive control of attention in ASD may suggest core attentional deficits, which require further investigation.
Alerting; anterior cingulate cortex; attentional networks; autism; executive control
We compared the attention abilities of a group of first-episode schizophrenia (FES) patients and a group of healthy participants using the Attention Network Test (ANT), a standard procedure that estimates the functional state of three neural networks controlling the efficiency of three different attentional behaviors, i.e., alerting (achieving and maintaining a state of high sensitivity to incoming stimuli), orienting (ability to select information from sensory input), and executive attention (mechanisms for resolving conflict among thoughts, feelings, and actions).
We evaluated 22 FES patients from 17 to 29 years of age with a recent history of a single psychotic episode treated only with atypical neuroleptics, and 20 healthy persons matched with FES patients by sex, age, and educational level as the control group. Attention was estimated using the ANT in which participants indicate whether a central horizontal arrow is pointing to the left or the right. The central arrow may be preceded by spatial or temporal cues denoting where and when the arrow will appear, and may be flanked by other arrows (hereafter, flankers) pointing in the same or the opposite direction.
The efficiency of the alerting, orienting, and executive networks was estimated by measuring how reaction time was influenced by congruency between temporal, spatial, and flanker cues. We found that the control group only demonstrated significantly greater attention efficiency than FES patients in the executive attention network.
FES patients are impaired in executive attention but not in alerting or orienting attention, suggesting that executive attention deficit may be a primary impairment during the progression of the disease.
Schizophrenia; First-episode; Attention; ANT; Executive; Cognitive
Attention is impaired in schizophrenia. Early attention components include orienting and alerting, as well as executive control networks. Previous studies have shown mainly executive control deficits, while few of them found orienting and alerting abnormalities. Here we explore the different attentive networks, their modulation and interactions in patients with schizophrenia.
Twenty-one schizophrenic patients (DSMIV), compared to 21 controls, performed a modified version of the Attention Network Task, in which an orienting paradigm (with valid, invalid and no cues) was combined with a flanker task (congruent/incongruent) and an alerting signal (tone/no tone), to assess orienting, executive control and alerting networks independently.
Patients showed an abnormal alerting effect and slower overall reaction time compared to controls. Moreover, there was an interaction between orienting and alerting: patients are helped more than controls by the alerting signal in a valid orientation to solve the incongruent condition.
These results suggest that patients with schizophrenia have altered alerting abilities. However, the orienting and alerting cues interact to improve their attention performance in the resolution of conflict, creating possibilities for cognitive remediation strategies.
Very little is known about attention deficits in developmental dyscalculia, hence, this study was designed to provide the missing information. We examined attention abilities of participants suffering from developmental dyscalculia using the attention networks test - interactions. This test was designed to examine three different attention networks--executive function, orienting and alerting--and the interactions between them.
Fourteen university students that were diagnosed as suffering from developmental dyscalculia--intelligence and reading abilities in the normal range and no indication of attention-deficit hyperactivity disorder--and 14 matched controls were tested using the attention networks test - interactions. All participants were given preliminary tests to measure mathematical abilities, reading, attention and intelligence.
The results revealed deficits in the alerting network--a larger alerting effect--and in the executive function networks--a larger congruity effect in developmental dyscalculia participants. The interaction between the alerting and executive function networks was also modulated by group. In addition, developmental dyscalculia participants were slower to respond in the non-cued conditions.
These results imply specific attentional deficits in pure developmental dyscalculia. Namely, those with developmental dyscalculia seem to be deficient in the executive function and alertness networks. They suffer from difficulty in recruiting attention, in addition to the deficits in numerical processing.
Attention capacities, alerting responses, orienting to sensory stimulation, and executive monitoring of performance are considered independent yet interrelated systems. These operations play integral roles in regulating the behavior of diverse species along the evolutionary ladder. Each of the primary attention constructs—alerting, orienting, and executive monitoring—involves salient autonomic correlates as evidenced by changes in reactive pupil dilation (PD), heart rate, and skin conductance. Recent technological advances that use remote high-resolution recording may allow the discernment of temporo-spatial attributes of autonomic responses that characterize the alerting, orienting, and executive monitoring networks during free viewing, irrespective of voluntary performance. This may deepen the understanding of the roles of autonomic regulation in these mental operations and may deepen our understanding of behavioral changes in verbal as well as in non-verbal species. The aim of this study was to explore differences between psychosensory PD responses in alerting, orienting, and executive conflict monitoring tasks to generate estimates of concurrent locus coeruleus (LC) noradrenergic input trajectories in healthy human adults using the attention networks test (ANT). The analysis revealed a construct-specific pattern of pupil responses: alerting is characterized by an early component (Pa), its acceleration enables covert orienting, and executive control is evidenced by a prominent late component (Pe). PD characteristics seem to be task-sensitive, allowing exploration of mental operations irrespective of conscious voluntary responses. These data may facilitate development of studies designed to assess mental operations in diverse species using autonomic responses.
arousal; attention; autonomic response; pupil dilation; Norepinephrine; locus coeruleus
Reaction time (RT) and event-related potential (ERP) measures were used to examine the relationships between psychopathic symptoms and three major attention networks (alerting, orienting, and executive attention) among a community sample of youth. Antisocial Process Screening Device (APSD; Frick and Hare 2001) total and subscale scores were negatively correlated with ERP measures of attentional alerting, indicating that youth with psychopathic symptoms had difficulty using warning cues to prepare for upcoming targets. APSD total scores were not related to performance on measures of orienting or executive attention, although weaker executive attention was found among youth with higher scores on the Impulsivity subscale. These findings support attention-based models of psychopathy and provide evidence of specific deficits in attentional alerting among youth with psychopathic traits. Deficiencies in attentional alerting may be related to noradrenergic functioning and may have cascading effects on higher order cognitive and affective processing.
Attention; Psychopathy; Antisocial personality; ANT; Evoked potential
The attention network test (ANT) is a reliable tool to detect the efficiency of alerting, orienting, and executive control networks. However, studies using the ANT obtained inconsistent relationships between attention networks due to two reasons: on the one hand, the inter-network relationships of attention subsystems were far from clear; on the other hand, ANT scores in previous studies were disturbed by possible inter-network interactions. Here we proposed a new computing method by dissecting cue-target conditions to estimate ANT scores and relationships between attention networks as pure as possible. The method was tested in 36 participants. Comparing to the original method, the new method showed a larger alerting score and a smaller executive control score, and revealed interactions between alerting and executive control and between orienting and executive control. More interestingly, the new method revealed unidirectional influences from alerting to executive control and from executive control to orienting. These findings provided useful information for better understanding attention networks and their relationships in the ANT. Finally, the relationships of attention networks should be considered with more experimental paradigms and techniques.
Attention deficits belong to the main cognitive symptoms of schizophrenia and come along with altered neural activity in previously described cerebral networks. Given the high heritability of schizophrenia the question arises if impaired function of these networks is modulated by susceptibility genes and detectable in healthy risk allele carriers.
The present event-related fMRI study investigated the effect of the single nucleotide polymorphism (SNP) rs1018381 of the DTNBP1 (dystrobrevin-binding protein 1) gene on brain activity in 80 subjects while performing the attention network test (ANT). In this reaction time task three domains of attention are probed simultaneously: alerting, orienting and executive control of attention.
Risk allele carriers showed impaired performance in the executive control condition associated with reduced neural activity in the left superior frontal gyrus [Brodmann area (BA) 9]. Risk allele carriers did not show alterations in the alerting and orienting networks.
BA 9 is a key region of schizophrenia pathology and belongs to a network that has been shown previously to be involved in impaired executive control mechanisms in schizophrenia. Our results identified the impact of DTNBP1 on the development of a specific attention deficit via modulation of a left prefrontal network.
Previous studies have examined the influence of meditation on three functionally different components of attention: executive control, alerting, and orienting. These studies have consistently found that meditation training improves both executive attention and alerting, but there has not been a consistent and clear effect of meditation training on orienting. In addition, while previous studies have shown that the functional coupling of the alerting and executive networks increases the processing of task irrelevant stimuli, it is unknown if participating in a meditation retreat can decouple these components of attention and lead to improved performance. The current study investigated the influence of a week-long intensive meditation retreat on three components of attention by randomly assigning participants to either pre- or postretreat testing groups. A modified attention network test (ANT) was used. Executive attention was measured as the difference in response time (RT) between congruent and incongruent task irrelevant flankers (conflict effect). Reflexive and volitional orienting were measured by manipulating cue validity and stimulus onset asynchrony (SOA). The coupling of executive attention and alerting was measured by examining flanker interference as a function of the SOA of an alerting cue. The meditation retreat improved task based indices of executive attention, but not reflexive or volitional orienting. There was clear behavioral evidence of coupling between executive attention and alerting in the preretreat group, as the conflict effect peaked when an alerting cue was presented 300 ms before the target. Importantly, there was no increase in the conflict effect for the postretreat group. This is consistent with the notion that the retreat decoupled the executive and alerting networks. These results suggest that previously reported improvements in the executive and alerting networks after meditation training might be mediated by the same underlying mechanism.
meditation; attention network test; orienting; alerting; shamatha meditation; visual attention; executive attention
The Attention Network Test (ANT) assesses alerting, orienting, and executive attention. The current study was designed to achieve three main objectives. First, we determined the reliability, effects, and interactions of attention networks in a relatively large cohort of non-demented older adults (n = 184). Second, in the context of this aged cohort, we examined the effect of chronological age on attention networks. Third, the effect of blood pressure on ANT performance was evaluated. Results revealed high-reliability for the ANT as a whole, and for specific cue and flanker types. We found significant main effects for the three attention networks as well as diminished alerting but enhanced orienting effects during conflict resolution trials. Furthermore, increased chronological age and low blood pressure were both associated with significantly worse performance on the executive attention network. These findings are consistent with executive function decline in older adults and the plausible effect of reduced blood flow to the frontal lobes on individual differences in attention demanding tasks.
Aging; Attention; Executive function; Blood pressure; Processing speed
Attentional dysfunction is one of the most consistent findings in individuals with autism spectrum disorders (ASD). However, the significance of such findings for the pathophysiology of autism is unclear. In this study, we investigated cellular neurochemistry with proton magnetic resonance spectroscopy imaging (1H-MRS) in brain regions associated with networks subserving alerting, orienting, and executive control of attention in patients with ASD. Concentrations of cerebral N-acetyl-aspartate (NAA), creatinine + phosphocreatinine, choline-containing compounds, myo-inositol (Ins) and glutamate + glutamine (Glx) were determined by 3 T 1H-MRS examinations in 14 high-functioning medication-free adults with a diagnosis of ASD and 14 age- and IQ-matched healthy controls (HC) in the anterior cingulate cortex (ACC), thalamus, temporoparietal junction (TPJ), and areas near or along the intraparietal sulcus (IPS). Compared to HC group, the ASD group showed significantly lower Glx concentrations in right ACC and reduced Ins in left TPJ. This study provides evidence of abnormalities in neurotransmission related to networks subserving executive control and alerting of attention, functions which have been previously implicated in ASD pathogenesis.
autism; spectroscopy; glutamate; anterior cingulate cortex; intraparietal sulcus; myo-inositol
Although amnestic mild cognitive impairment (aMCI; often considered a prodromal phase of Alzheimer’s disease, AD) is most recognized by its implications for decline in memory function, research suggests that deficits in attention are present early in aMCI and may be predictive of progression to AD. The present study used functional magnetic resonance imaging to examine differences in the brain during the attention network test between 8 individuals with aMCI and 8 neurologically healthy, demographically matched controls. While there were no significant behavioral differences between groups for the alerting and orienting functions, patients with aMCI showed more activity in neural regions typically associated with the networks subserving these functions (e.g., temporoparietal junction and posterior parietal regions, respectively). More importantly, there were both behavioral (i.e., greater conflict effect) and corresponding neural deficits in executive control (e.g., less activation in the prefrontal and anterior cingulate cortices). Although based on a small number of patients, our findings suggest that deficits of attention, especially the executive control of attention, may significantly contribute to the behavioral and cognitive deficits of aMCI.
The sociocommunicative impairments that define autism spectrum disorder (ASD) are not present at birth but emerge gradually over the first two years of life. In typical development, basic attentional processes may provide a critical foundation for sociocommunicative abilities. Therefore early attentional dysfunction in ASD may result in atypical development of social communication. Prior research has demonstrated that persons with ASD exhibit early and lifelong impairments in attention. The primary aim of this paper is to provide a review of the extant research on attention in ASD using a framework of functionally independent attentional networks as conceptualized by Posner and colleagues: the alerting, orienting and executive control networks (Posner and Petersen, 1990; Petersen & Posner, 2012). The neural substrates and typical development of each attentional network is briefly discussed, a review of the ASD attention literature is presented, and a hypothesis is proposed that links aberrant attentional mechanisms, specifically impaired disengagement of attention, with the emergence of core ASD symptoms.
autism; attention; development; alerting; arousal; orienting; disengagement; executive control
To determine whether behavioral dissociations and interactions occur between the attentional functions—alerting, orienting, and conflict resolution—depending upon stroke location and to determine the approximate proportion of patients who can be classified into 1 of these 3 anatomical networks.
We recruited 110 anatomically unselected acute stroke patients and 62 age-matched controls. Subjects underwent the attention network test (ANT), which provides a measure of each attention type. Their performance was related to lesion anatomy on MRI using a voxel-lesion mapping approach.
Patients as a whole performed poorer than controls, but there were no group differences in the size of attentional effects. Specific deficits in 1 of the 3 ANT-tested functions were found in the following lesion locations: alerting deficiency with bilateral anteromedial thalamus and upper brainstem (17% of patients); orienting impairment with right pulvinar and right temporoparietal cortex (15%); conflict resolution with bilateral prefrontal and premotor areas (23%). Lesions to right frontoparietal regions also modified interactions among the 3 types of attention.
More than half of all stroke patients can be expected to have a lesion location classifiable into 1 of the 3 principal attention networks. Our results have potential implications for therapy personalization in focal brain diseases including stroke.
Although previous research has shown that positive affect (PA) and negative affect (NA) modulate attentional functioning in distinct ways, few studies have considered whether the links between affect and attentional functioning may vary as a function of age. Using the Attention Network Test (Fan et al., 2002), we tested whether participants’ current state of PA and NA influenced distinct attentional functions (i.e., alerting, orienting, and executive attention) and how the relationships between affective states and attentional functioning differ in younger (18–25 years) and older (60–85 years) age groups. While there were age differences in alerting efficiency, these age differences were mediated by PA, indicating that the higher state PA found in older adults may contribute to age differences in alerting. Furthermore, age group moderated the relationship between PA and orienting as well as NA and orienting. That is, higher levels of PA and lower levels of NA were associated with enhanced orienting efficiency in older adults. Neither PA nor NA had any influence on executive attention. The current results suggest that PA and NA may influence attentional functioning in distinct ways, but that these patterns may depend on age groups.
affect; age differences; attentional networks; individual differences; attention
The purpose of the current study was to investigate potential genetic and environmental correlations between working memory and three behavioral aspects of the attention network (i.e., executive, alerting, and orienting) using a twin design. Data were from 90 monozygotic (39% male) and 112 same-sex dizygotic (41% male) twins. Individual differences in working memory performance (digit span) and parent-rated measures of executive, alerting, and orienting attention included modest to moderate genetic variance, modest shared environmental variance, and modest to moderate nonshared environmental variance. As hypothesized, working memory performance was correlated with executive and alerting attention, but not orienting attention. The correlation between working memory, executive attention, and alerting attention was completely accounted for by overlapping genetic covariance, suggesting a common genetic mechanism or mechanisms underlying the links between working memory and certain parent-rated indicators of attentive behavior.
Behavioral genetics; Working memory; Parent-rated attention; Middle childhood; Twins
Hemispatial neglect is a debilitating disorder marked by a constellation of spatial and non-spatial attention deficits. Patients’ alertness deficits have shown to interact with lateralized attention processes and correspondingly, improving tonic/general alertness as well as phasic/moment-to-moment alertness has shown to ameliorate spatial bias. However, improvements are often short-lived and inconsistent across tasks and patients. In an attempt to more effectively activate alertness mechanisms by exercising both tonic and phasic alertness, we employed a novel version of a continuous performance task (tonic and phasic alertness training, TAPAT). Using a between-subjects longitudinal design and employing sensitive outcome measures of spatial and non-spatial attention, we compared the effects of 9 days of TAPAT (36 min/day) in a group of patients with chronic neglect (N = 12) with a control group of chronic neglect patients (N = 12) who simply waited during the same training period. Compared to the control group, the group trained on TAPAT significantly improved on both spatial and non-spatial measures of attention with many patients failing to exhibit a lateralized attention bias at the end of training. TAPAT was effective for patients with a range of behavioral profiles and lesions, suggesting that its effectiveness may rely on distributed or lower-level attention mechanisms that are largely intact in patients with neglect. In a follow-up experiment, to determine if TAPAT is more effective in improving spatial attention than an active treatment that directly trains spatial attention, we trained three chronic neglect patients on both TAPAT and search training. In all three patients, TAPAT training was more effective in improving spatial attention than search training suggesting that, in chronic neglect, training alertness is a more effective treatment approach than directly training spatial attention.
attention; visual; rehabilitation; neurological disorders; hemispatial neglect
Consciousness has many aspects. These include awareness of the world, feelings of control over one's behaviour and mental state (volition), and the notion of continuing self. Focal (executive) attention is used to control details of our awareness and is thus closely related to volition. Experiments suggest an integrated network of neural areas involved in executive attention. This network is associated with our voluntary ability to select among competing items, to correct error and to regulate our emotions. Recent neuroimaging studies suggest that these various functions involve separate areas of the anterior cingulate. We have adopted a strategy of using marker tasks, shown to activate the brain area by imaging studies, as a means of tracing the development of attentional networks. Executive attention appears to develop first to regulate distress during the first year of life. During later childhood the ability to regulate conflict among competing stimuli builds upon the earlier cingulate anatomy to provide a means of cognitive control. During childhood the activation of cingulate structures relates both to the child's success on laboratory tasks involving conflict and to parental reports of self-regulation and emotional control. These studies indicate a start in understanding the anatomy, circuitry and development of executive attention networks that serve to regulate both cognition and emotion.
The loss of one sensory modality can lead to a reorganization of the other intact sensory modalities. In the case of individuals who are born profoundly deaf, there is growing evidence of changes in visual functions. Specifically, deaf individuals demonstrate enhanced visual processing in the periphery, and in particular enhanced peripheral visual attention. To further characterize those aspects of visual attention that may be modified by deafness, deaf and hearing individuals were compared on the Attentional Network Test (ANT). The ANT was selected as it provides a measure of the efficiency of three neurally distinct subsystems of visual attention: alerting, orienting and executive control. The alerting measure refers to the efficiency with which a temporal cue is used to direct attention towards a target event, and the orienting measure is an indicator of the efficiency with which a spatial cue focuses attention upon that target’s spatial location. The executive control measure, on the other hand, is an indicator of the amount of interference from peripheral flankers on processing that central target. In two separate experiments, deaf and hearing individuals displayed similar alerting and orienting abilities indicating comparable attention across populations. As predicted by enhanced peripheral attention, deaf subjects were found to have larger flanker interference effects than hearing subjects. These results indicate that not all aspects of visual attention are modified by early deafness, suggesting rather specific effects of cross-modal plasticity.
Attention; Deafness; Peripheral vision; Flanker; Orienting; Attentional Network Test
Individuals diagnosed with autism spectrum disorder (ASD) exhibit lifelong abnormalities in the adaptive allocation of visual attention. The ubiquitous nature of attentional impairments in ASD has led some authors to hypothesize that atypical attentional modulation may be a factor in the development of higher-level sociocommunicative deficits.
Participants were 20 children with ASD and 20 age- and Nonverbal IQ-matched typically developing (TD) children. We used the Attention Network Test (ANT) to investigate the efficiency and independence of three discrete attentional networks: alerting, orienting, and executive control. Additionally, we sought to investigate the relationship between each attentional network and measures of sociocommunicative symptom severity in children with ASD.
Results indicate that the orienting, but not alerting or executive control, networks may be impaired in children with ASD. In contrast to TD children, correlational analyses suggest that the alerting and executive control networks may not function as independently in children with ASD. Additionally, an association was found between the alerting network and social impairment and between the executive control network and IQ in children with ASD.
The results provide further evidence of an impairment in the visuospatial orienting network in ASD and suggest that there may be greater interdependence of alerting and executive control networks in ASD. Furthermore, decreased ability to efficiently modulate levels of alertness was related to increased sociocommunicative deficits, suggesting that domain-general attentional function may be associated with ASD symptomatology.
Autism; reaction time; visual attention; alerting; orienting; executive control
It is unclear how threat-related attentional biases affect multiple attention systems. This study used a new modification of a reaction time paradigm to examine whether inter-trial task-irrelevant fearful faces influenced the efficiency of alerting, orienting, and executive attention, and whether effects varied with level of state anxiety. Participants, 63 non-disordered adults (17 males and 46 females), reported on their subjective state anxiety and completed a modified version of the Attention Network Test in which fearful or neutral faces or control stimuli were presented briefly (50 ms) between trials of the task, but provided no task-relevant information. Across all participants, state anxiety was positively correlated with alerting, whereas fearful versus neutral faces were linked to decreased alerting efficiency. Contrasting high and low anxiety groups showed that fearful versus neutral faces reduced executive attention in the low state anxiety group only, suggesting decreased distraction by irrelevant stimuli in the high state anxiety group. Results document threat-related attentional biases that varied with attention system but failed to find enhanced bias effects among those with higher state anxiety in a typical range. This modification of the Attention Network Test, which added presentation of emotional distracters, provides a potentially useful new method for assessing the impact of task-irrelevant emotional stimuli on three aspects of attention performance.
threat-related attentional biases; attention systems; state anxiety
It has been widely accepted that attention can be divided into three subnetworks - alerting, orienting and executive control (EC), and the subnetworks of attention are linked to distinct brain regions. However, the association between specific white matter fibers and the subnetworks of attention is not clear enough. Using diffusion tensor imaging (DTI), the white matter connectivity related to the performance of attention was assessed by attention network test (ANT) in 85 healthy adolescents. Tract-based spatial statistics (TBSS) and probabilistic diffusion tractography analysis demonstrated that cerebellothalamic tract was involved in alerting, while orienting depended upon the superior longitudinal fasciculus (SLF). In addition, EC was under the control of anterior corona radiata (ACR). Our findings suggest that different fiber pathways are involved in the three distinct subnetworks of attention. The current study will yield more precise information about the structural substrates of attention function and may aid the efforts to understand the neurophysiology of several attention disorders.
We examined the effect of cognitive fatigue on the Attention Networks Test (ANT). Participants were 228 non-demented older adults. Cognitive fatigue was operationally defined as decline in alerting, orienting, and executive attention performance over the course ANT. Anchored in a theoretical model implicating the frontal basal ganglia circuitry as the core substrate of fatigue, we hypothesized that cognitive fatigue would be observed only in executive attention. Consistent with our prediction, significant cognitive fatigue effect was observed in executive attention but not in alerting or orienting. In contrast, orienting improved over the course of the ANT and alerting showed a trend, though insignificant, that was consistent with learning. Cognitive fatigue is conceptualized as an executive failure to maintain and optimize performance over acute but sustained cognitive effort resulting in performance that is lower and more variable than the individual’s optimal ability.
Cognitive Fatigue; Executive Control; Aging; Attention Networks
Both neuropsychological and functional neuroimaging studies have identified that the posterior parietal lobe (PPL) is critical for the attention function. However, the unique role of distinct parietal cortical subregions and their underlying white matter (WM) remains in question. In this study, we collected both magnetic resonance imaging and diffusion tensor imaging (DTI) data in normal participants, and evaluated their attention performance using attention network test (ANT), which could isolate three different attention components: alerting, orienting and executive control. Cortical thickness, surface area and DTI parameters were extracted from predefined PPL subregions and correlated with behavioural performance. Tract-based spatial statistics (TBSS) was used for the voxel-wise statistical analysis. Results indicated structure-behaviour relationships on multiple levels. First, a link between the cortical thickness and WM integrity of the right inferior parietal regions and orienting performance was observed. Specifically, probabilistic tractography demonstrated that the integrity of WM connectivity between the bilateral inferior parietal lobules mediated the orienting performance. Second, the scores of executive control were significantly associated with the WM diffusion metrics of the right supramarginal gyrus. Finally, TBSS analysis revealed that alerting performance was significant correlated with the fractional anisotropy of local WM connecting the right thalamus and supplementary motor area. We conclude that distinct areas and features within PPL are associated with different components of attention. These findings could yield a more complete understanding of the nature of the PPL contribution to visuospatial attention.
Visual neglect is a multi-component syndrome including prominent attentional disorders. Research on the functional mechanisms of neglect is now moving from the description of dissociations in patients' performance to the identification of the possible component deficits and of their interaction with compensatory strategies. In recent years, the dissection of attentional deficits in neglect has progressed in parallel with increasing comprehension of the anatomy and function of large-scale brain networks implicated in attentional processes. This review focuses on the anatomy and putative functions of attentional circuits in the brain, mainly subserved by fronto-parietal networks, with a peculiar although not yet completely elucidated role for the right hemisphere. Recent results are discussed concerning the influence of a non-spatial attentional function, phasic alertness, on conscious perception in normal participants and on conflict resolution in neglect patients. The rapid rate of expansion of our knowledge of these systems raises hopes for the development of effective strategies to improve the functioning of the attentional networks in brain-damaged patients.
attention; neglect; consciousness; parietal lobe; frontal lobe