Human attentional networks: a connectionist model

Recent evidence in cognitive neuroscience has suggested that attention is a complex organ system subserved by at least three attentional networks in the brain, for alerting, orienting, and executive control functions. However, how these different networks work together to give rise to the seemingly unitary mental faculty of attention remains unclear. We describe a connectionist model of human attentional networks to explore the possible interplays among the networks from a computational perspective. This model is developed in the framework of leabra (local, error-driven, and associative, biologically realistic algorithm) and simultaneously involves these attentional networks connected in a biologically inspired way. We evaluate the model by simulating the empirical data collected on normal human subjects using the Attentional Network Test (ANT). The simulation results fit the experimental data well. In addition, we show that the same model, with a single parameter change that affects executive control, is able to simulate the empirical data collected from patients with schizophrenia. This model represents a plausible connectionist explanation for the functional structure and interaction of human attentional networks.     

Development of attentional networks in childhood

Recent research in attention has involved three networks of anatomical areas that carry out the functions of orienting, alerting and executive control (including conflict monitoring). There have been extensive cognitive and neuroimaging studies of these networks in adults. We developed an integrated Attention Network Test (ANT) to measure the efficiency of the three networks with adults. We have now adapted this test to study the development of these networks during childhood. The test is a child-friendly version of the flanker task with alerting and orienting cues. We studied the development of the attentional networks in a cross-sectional experiment with four age groups ranging from 6 through 9 (Experiment 1). In a second experiment, we compared children (age 10 years) and adult performance in both child and adults versions of the ANT. Reaction time and accuracy improved at each age interval and positive values were found for the average efficiency of each of the networks. Alertness showed evidence of change up to and beyond age 10, while conflict scores appear stable after age seven and orienting scores do not change in the age range studied. A final experiment with forty 7-year-old children suggested that children like adults showed independence between the three networks under some conditions.     

The Prediction Analysis of Autistic and Schizotypal Traits in Attentional Networks

ObjectiveEmpirical findings confirmed that autistic and schizotypal traits are associated with attentional function as well as include various dimensions. So far, no study has reported which dimension of these traits relates to attentional networks. This study aimed to find out whether there are associations between attentional networks and autistic traits; and between attentional networks and schizotypal traits. MethodsA total of 449 volunteers was included in this study, and autism-spectrum quotient (AQ), schizotypal personality questionnaire (SPQ), and attention network test (ANT) were used to measure autistic traits and schizotypal traits. The three independent attentional networks, including alerting network, orienting network, and executive control network, were also measured. ResultsAutistic traits were associated with the orienting network, whereas schizotypal traits were associated with the orienting network and executive control network. Furthermore, attentional networks could be predicted by specific dimensions of autistic and schizotypal traits. AQ-attention switching [0.104 (-1.175– -0.025), p=0.041] and AQ-attention to detail [-0.097 (-0.798– -0.001), p=0.049] were significant predictors of orienting network and gender were significant predictor of executive network (Beta=0.107; 95% CI=-0.476–10.139; p=0.031). Whereas, schizotypal dimension “interpersonal” was a significant predictor of all three attentional networks [Alerting: 0.147 (-0.010–0.861), p=0.045; Orienting: 0.147 (0.018–0.733), p=0.040; Executive: 0.198 (0.215–1.309), p=0.006]. ConclusionThis study demonstrated that autistic and schizotypal traits were associated with attentional networks. The specific dimensions of autistic and schizotypal traits could predict attentional networks. Nevertheless, the attentional networks predicted with these two traits were different.     

Neural correlates of attentional deficits in Parkinson's disease patients with mild cognitive impairment

IntroductionDeficits in attentional processing observed in Parkinson's disease (PD) patients with mild cognitive impairment (MCI) increase risk of PD dementia. However, the neural basis of these attentional deficits are presently unknown. The present study aimed to explore the neural correlates of attention dysfunction in PD-MCI using the Attention Network Test (ANT) and functional Magnetic Resonance Imaging (fMRI).MethodFifteen (15) PD-MCI patients, 26 PD patients without MCI (PD-NC) and 22 healthy controls (HC) were scanned (3T Siemens PRISMA) whilst performing the ANT. Reaction time, accuracy and fMRI BOLD activation were compared between groups for the three attentional task components of 1) alerting, 2) orienting, and 3) executive control.ResultsPD-MCI patients showed an overall slower reaction time compared to PD-NC and HC, and showed less interference of reaction time in the orienting effect than HC. fMRI data demonstrated greater activation in the bilateral cerebellum crus 1 during the alerting attention condition in both PD-MCI and PD-NC compared to HC. However, activation was supressed in the left postcentral gyrus in PD-MCI compared to PD-NC and HC.DiscussionAlterations in the alerting attention functional network despite intact task performance in PD-MCI suggests that functional brain changes may precede cognitive changes in the attention domain. Furthermore, increased activation in the cerebellum may reflect an attentional compensatory mechanism unique to the PD pathology. Taken together, the findings suggest that PD has a complex effect on attentional ability that can, at least in part, be elucidated using functional neuroimaging.     

Effects of transcranial direct current stimulation over right posterior parietal cortex on attention function in healthy young adults

Attention involves three distinct networks for alerting, orienting, and executive control. Interventions targeting the specific attentional networks remain lacking. Transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability, which potentially serves as an interventional tool to treat individuals with attention impairment. The purpose of this study was to examine the effects of applying tDCS over the right posterior parietal cortex (PPC) on the performance of the three attentional networks. Twenty‐six healthy young adults performed the Attention Network Test before and after anodal or sham tDCS stimulation over the right PPC. The alerting, orienting, and executive effects were assessed before and after the stimulation. The results demonstrated that the orienting effect was significantly improved after real tDCS relative to sham, whereas the alerting and executive control effects remained unaffected. Consistent with previous clinical and functional imaging studies, this suggests that the right PPC is actively engaged with the spatial orienting of attention.     

Alterations of the attentional networks in patients with anxiety disorders

Cognitive theories of emotion try to explain how anxious people attend to the world. Despite the increase in empirical research in this field, the specific or general attentional impairments of patients with anxiety disorder is not well defined. We decided to investigate the relationship between pathological anxiety and attentional mechanisms from the broader perspective of the attentional networks. In our study, patients with anxiety disorders and control participants carried out a task to assess efficiency of three attentional networks: orienting, alerting, and executive control. The main result was that anxiety disorders are related to both reduced effectiveness of the executive control network and difficulties in disengaging attention from invalid cues, even when using emotionally neutral information. This relationship between these attentional networks and anxiety may in part explain the problems in the day-to-day functioning of these patients.     

The effect of fear on attentional processing in a sample of healthy females

The present experiment examines the effect of fear on efficiency of three attention networks: executive attention, orienting and alerting, in a healthy female sample. International Affective Picture System (IAPS) images were used to elicit both a fear response and a non-emotional response in 100 participants. During the emotion manipulation, participants performed a modified version of the Attention Network Test (ANT). Results showed enhanced executive attention in the fear condition compared to the control condition. Specifically, during a fear experience participants were better able to inhibit irrelevant information resulting in faster response times to a target. There was no effect of fear on orienting while the effect of fear on alerting was inconclusive. It is suggested that enhanced executive attention in fear-eliciting situations may function to focus attention on a potentially threat-related target, thus facilitating subsequent rapid responding.     

Selective impairments of alerting and executive control in HIV-infected patients: evidence from attention network test

Background

Attention ability can be subdivided into three functionally independent networks, i.e., alerting network, orienting network, and executive network. Previous literature has documented that deficits in attention are a common consequence of HIV infection. However, the precise nature of deficits of attention in HIV-infected patients is poorly understood. Accordingly, the aim of the study was to identify whether the HIV-infected patients showed a specific attention network deficit or a general attentional impairment.

Methods

We investigated 27 HIV-infected patients and 31 normal controls with the Attention Network Test (ANT).

Results

The patients exhibited less efficient alerting network and executive network than controls. No significant difference was found in orienting network effect between groups. Our results also indicate a tendency for poorer efficiency on alerting attention and executive attention in patients with CD4 ≤ 200.

Conclusions

Our findings suggest that HIV-infected patients exhibited selective impairments of attention network of alerting and executive control. The link between lower CD4 T cell count and poorer attention network function imply the importance of starting antiretroviral therapy earlier to avoid irreversible neurocognitive impairment.

     

Attentional network task performance in patients with schizophrenia-spectrum disorders: evidence of a specific deficit

Although attentional deficits are frequently displayed by schizophrenia and spectrum patients, the precise nature of the impairment is unclear. The present study investigates attentional performance in 26 schizophrenia-spectrum outpatients and 24 healthy controls using the Attentional Network Task (ANT). We assessed the efficiency of the segregated alerting, orienting, and executive control networks by measuring how response latencies were influenced by alerting cues, spatial cues, and flanking stimuli. In overall ANOVAs we found main effects of cue condition and flanker congruency. The data also revealed a significant interaction of group and flanker type, with schizophrenia-spectrum patients taking longer on average to resolve conflict. These results suggest that compared to the healthy nonpatients, schizophrenia-spectrum patients show a deficit in their executive control network. Considered together, these findings support the notion that schizophrenia-spectrum patients have a specific attentional deficit, rather than a global one. The significance of these findings is considered from both experimental and clinical perspectives.     

Human attentional networks

In recent years it has been possible to treat attention as an organ system with its own anatomy, circuitry and set of functions. We view attention in terms of three interrelated neural networks in the human brain. These networks carry out the specific functions of developing and maintaining the alert state, orienting to sensory input, and executive control. Damage to these networks or their chemical neuromodulators can produce specific neurological and psychiatric deficits. We have conducted behavioral, developmental, and patient studies using functional magnetic resonance imaging (fMRI), event related potentials (ERP), genetics, and computational modeling to investigate the anatomy, circuitry, pathology, and development of attentional networks. The Attentional Network Test (ANT) is developed to measure the efficiency of each of the attention networks. The ANT can also serve as an endophenotype for genetic studies on attentional networks. This paper reviews our work with the ANT in studies of normal performance and various forms of psychopathology.     

Neural correlates of the attention network test in schizophrenia

Attentional deficits are prominent in schizophrenia, affecting nearly all cognitive functions. Human attention comprises three essential components: alerting, orienting and executive control. For the assessment of these functions, the attention network test (ANT) has been proposed and used in healthy controls and patients. In schizophrenia, the ANT has revealed behavioral deficits; however, the corresponding neural correlates have not been examined. In the present study, neural correlates of attention were investigated in 17 schizophrenia patients and 17 healthy controls using the ANT with fMRI. Behavioral deficits emerged in the alertness system with a reduced efficiency for temporal cues. In fMRI, changes were observed for all three domains-alerting, orienting and conflict-and revealed hyper- as well as hypoactivation in patients. Affected regions during alerting comprised a broad fronto-temporo-parieto-occipito-cerebellar network, while differences during orienting mainly tapped fronto-parietal regions and during conflict processing a thalamo-frontal-temporal occipital network including the postcentral regions. In general, hyperactivations were positively correlated with more severe psychopathologial symptoms.     

Deficits in attention performance are associated with insufficiency of slow-wave sleep in insomnia

ObjectiveCognitive impairment is associated with insomnia. However, there is a lack of evidence suggesting a link between insomnia and cognitive dysfunction in objective testing. The objectives of our current study were to assess the differences in components of attentional performance between primary insomnia patients and normal-sleeping controls and to examine potential predictors of attention impairment in patients with insomnia.MethodsWe studied 36 patients (age 40.39 ± 12.36 years; 57.1% male) with insomnia and 25 normal-sleeping controls (age 39.88 ± 12.50 years; 52.9% male) who underwent one-night polysomnography followed by Multiple Sleep Latency Test (MSLT) and Attention Network Task (ANT). ANT reflected three attentional networks termed the alerting, orienting, and executive control networks.ResultsAfter controlling for age, gender, body mass index, depression, anxiety, and education levels, patients with insomnia scored higher on the executive control variable of the ANT compared with normal-sleeping controls (96.75 ± 7.60 vs. 57.00 ± 10.49, p = 0.01). This higher score was independently associated with insufficiency of slow-wave sleep during nighttime sleep (β = −0.38, p = 0.04).ConclusionOur findings suggest that insomnia is associated with deficits in executive control of attention and that the underlying mechanism may be insufficiency of slow-wave sleep in chronic insomnia.     

Which aspects of visual attention are changed by deafness? The case of the Attentional Network Test

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.     

Principal component analysis of behavioural individual differences suggests that particular aspects of visual working memory may relate to specific aspects of attention

The previously separate literatures on visual attention and on visual working memory are converging, with growing interest in how visual attention may relate to visual short-term memory, as exemplified by this special issue. We report exploratory analysis of how individual behavioural differences in separable aspects of attention may relate to particular aspects of visual working memory. Previous work with the Attention Network Test (ANT; Fan, McCandliss, Sommer, Raz, & Posner, 2002) proposed that it can measure three distinct aspects of attention: alerting, spatial orienting, plus executive control of response competition. We implemented the ANT in 50 healthy young adults, who also underwent a behavioural battery of visual working memory (WM) tests. These visual WM tests were all variations on recent paradigms, used here with the aim of measuring potential individual differences in visual WM capacity; WM precision; or WM distractor-filtering. Principal component analysis of the behavioural dataset revealed three main components. Interestingly, each component paired one aspect of ANT scores together with one aspect of WM scores, in terms of the strongest loadings. WM capacity loaded with ANT alerting; WM precision with ANT orienting; and WM filtering with ANT executive control. These results suggest that visual WM may involve separate component processes, and that different aspects of attention relate to different aspects of visual WM, in terms of behavioural individual differences. We discuss the observed pattern in relation to current issues and with respect to possible future work on the potential neural bases of individual differences in the distinct components.     

Presentation modality influences behavioral measures of alerting, orienting, and executive control.

The Attention Network Test (ANT) uses visual stimuli to separately assess the attentional skills of alerting (improved performance following a warning cue), spatial orienting (an additional benefit when the warning cue also cues target location), and executive control (impaired performance when a target stimulus contains conflicting information). This study contrasted performance on auditory and visual versions of the ANT to determine whether the measures it obtains are influenced by presentation modality. Forty healthy volunteers completed both auditory and visual tests. Reaction-time measures of executive control were of a similar magnitude and significantly correlated, suggesting that executive control might be a supramodal resource. Measures of alerting were also comparable across tasks. In contrast, spatial-orienting benefits were obtained only in the visual task. Auditory spatial cues did not improve response times to auditory targets presented at the cued location. The different spatial-orienting measures could reflect either separate orienting resources for each perceptual modality, or an interaction between a supramodal orienting resource and modality-specific perceptual processing.     

Intolerance of uncertainty and attentional networks: Unique associations with alerting

The present study sought to extend our understanding as to how intolerance of uncertainty (IU) relates to information-processing by investigating associations between IU and attentional networks, including alerting, orienting, and executive attention. Based upon prior research, IU was expected to cluster with alerting. An unselected sample of college students (N = 86; 79% women) completed self-report measures of IU and state anxiety, as well as the attention network test. Among the attentional networks, IU only shared a positive association with alerting and the association remained intact after statistically controlling for state anxiety. State anxiety did not moderate the association between IU and alerting. Although two IU dimensions (prospective and inhibitory) both shared a positive association with alerting, only prospective IU was associated with alerting after statistically controlling for state anxiety. The results provide evidence that IU relates to an overfunctioning of the alerting attentional network, which may suggest a role of hypervigilance and a greater influence of bottom-up processing in relation to IU. Implications for how these results advance our understanding of possible links between IU and anxiety disorders are discussed.     

Plasma neuropeptide Y: a biomarker for symptom severity in chronic fatigue syndrome

Background

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.

Methods

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.

Results

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.

Conclusions

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.     

Measuring vigilance while assessing the functioning of the three attentional networks: the ANTI-Vigilance task

Vigilance could be a crucial aspect of attention that may modulate the functioning of the attentional system. Some behavioural tests, such as the Attention Network Test (ANT), have been developed to obtain an individual index of the three attentional networks (alertness, orientation, and executive control). However, alerting network measures are usually inferred using a phasic alertness task, and some indirect indexes of tonic alertness or vigilance have been proposed but not properly evaluated. The general aim for the present study is to provide the ANT with a direct measure of vigilance and then to analyse the relationship between this measure and other alternative indirect indexes. The obtained results suggest that the proposed new test (ANTI-Vigilance or ANTI-V) is useful to achieve a direct measure of vigilance and could be considered as a new tool available in cognitive, clinical or behavioural neurosciences for analysing vigilance in addition to the usual ANT scores. Other alternative indexes (such as global reaction time and global accuracy averaged across conditions) are only moderately correlated to a direct vigilance measure. As a consequence, although they may be to some extent related to the participants' vigilance level, they could not be used isolatedly as appropriate indexes of vigilance. Also, the role played by these global measures in the ANT task, which have been previously associated with some performance measures in applied areas (such as driving performance), is discussed.     

Dysfunctional attentional networks in children with attention deficit/hyperactivity disorder: evidence from an event-related functional magnetic resonance imaging study.

BACKGROUND: Although there is evidence for attentional dysfunction in children with attention deficit/hyperactivity disorder (ADHD), the neural basis of these deficits remains poorly understood. METHODS: We used event-related functional magnetic resonance imaging (fMRI) to investigate brain activations related to three particular aspects of attention: alerting, reorienting, and executive control. Sixteen medication-naive boys with ADHD and 16 healthy boys, aged 8 to 12 years, were studied. RESULTS: Behaviorally, children with ADHD showed a significant impairment only in their executive control system compared to healthy subjects. Neurally, children with ADHD (relative to controls) recruited deviant brain regions for all three attentional networks: less right-sided activation in the anterior cingulate gyrus during alerting, more fronto-striatal-insular activation during reorienting, and less fronto-striatal activation for executive control. ADHD symptom severity was associated with dysregulation of the blood oxygen level dependent (BOLD) signal within the putamen during reorienting and executive control. CONCLUSIONS: Our results demonstrated altered brain mechanism in ADHD associated with all three attentional networks investigated. For alerting and executive attention, our data indicate a deviant mechanism of cortical control, while ADHD children may have adopted altered strategies for reorienting of attention. Our results also stress the etiological role of functional abnormalities in the putamen in medication-naive ADHD.     

Functioning of the three attentional networks and vigilance in primary insomnia

BackgroundResults from cognitive measures in primary insomnia (PI) patients are not consistent with the difficulties in performing daily living tasks of which these patients complain about. Lack of sensitivity of the tests and the data concerning some cognitive functions may explain this discordance. The aim of the present investigation was to better characterize cognitive deficits of PI patients in order to further understand their cognitive complaints. We looked at attentional and executive function because of their high involvement in daily living tasks.MethodsA total of 21 PI patients and 16 good sleepers completed the Attentional Network Test (ANT). We only included untreated PI patients since sleep medication could be a confounding factor when assessing cognition.ResultsWhile PI patients, compared to good sleepers, were found to have a longer overall reaction time (RT) and perform more slowly in the incongruent flanker condition (ie, conflict situation) than in the congruent condition, no group effects were observed for the variables representing the three attentional networks (ie, alerting, orienting, and executive functions).ConclusionsThe present study revealed a conflict resolution deficit in untreated PI patients. This impairment may be linked to the prefrontal alterations reported in neuroimaging studies in these patients. Patients had also an impaired vigilance compared to good sleepers, likely due to the high cognitive load of the ANT. These results would serve to explain the complaints of PI patients about difficulties performing daily living tasks that are demanding and of long duration.