Cerebral correlates of alerting, orienting and reorienting of visuospatial attention: an event-related fMRI study

Altered Intrinsic Brain Activity in Ischemic Stroke Patients Assessed Using the Percent Amplitude of a Fluctuation Method

Ischemic stroke is a vascular disease that may cause cognitive and behavioral abnormalities. This study aims to assess abnormal brain function in ischemic stroke patients using the percent amplitude of fluctuation (PerAF) method and further explore the feasibility of PerAF as an imaging biomarker for investigating ischemic stroke pathophysiology mechanisms. Sixteen ischemic stroke patients and 22 healthy controls (HCs) underwent resting state functional magnetic resonance imaging (rs-fMRI) scanning, and the resulting data were analyzed using PerAF. Then a correlation analysis was conducted between PerAF values and Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores. Finally, the abnormal PerAF values were extracted and defined as features for support vector machine (SVM) analysis. Compared with HCs, ischemic stroke patients showed decreased PerAF in the bilateral cuneus, left middle frontal gyrus, precuneus and right inferior temporal gyrus, and increased PerAF in the bilateral orbital part of middle frontal gyrus and right orbital part of superior frontal gyrus. Correlation analyses revealed that PerAF values in the left orbital part of middle frontal gyrus was negatively correlated with the MoCA scores. The SVM classification of the PerAF values achieved an area under the curve (AUC) of 0.98 and an accuracy of 94.74%. Abnormal brain function has been found among ischemic stroke patients, which may be correlated with visual impairment, attention deficits, and dysregulation of negative emotions following a stroke. Our findings may support the potential of PerAF as a sensitive biomarker for investigating the underlying mechanisms of ischemic stroke.

Integrating brain function and structure in the study of the human attentional networks: a functionnectome study

Attention is a heterogeneous function theoretically divided into different systems. While functional magnetic resonance imaging (fMRI) has extensively characterized their functioning, the role of white matter in cognitive function has gained recent interest due to diffusion-weighted imaging advancements. However, most evidence relies on correlations between white matter properties and behavioral or cognitive measures. This study used a new method that combines the signal from distant voxels of fMRI images using the probability of structural connection given by high-resolution normative tractography. We analyzed three fMRI datasets with a visual perceptual task and three attentional manipulations: phasic alerting, spatial orienting, and executive attention. The phasic alerting network engaged temporal areas and their communication with frontal and parietal regions, with left hemisphere dominance. The orienting network involved bilateral fronto-parietal and midline regions communicating by association tracts and interhemispheric fibers. The executive attention network engaged a broad set of brain regions and white matter tracts connecting them, with a particular involvement of frontal areas and their connections with the rest of the brain. These results partially confirm and extend previous knowledge on the neural substrates of the attentional system, offering a more comprehensive understanding through the integration of structure and function.

Cortical Correlates of Visuospatial Switching Processes Between Egocentric and Allocentric Frames of Reference: A fNIRS Study

Human beings represent spatial information according to egocentric (body-to-object) and allocentric (object-to-object) frames of reference. In everyday life, we constantly switch from one frame of reference to another in order to react effectively to the specific needs of the environment and task demands. However, to the best of our knowledge, no study to date has investigated the cortical activity of switching and non-switching processes between egocentric and allocentric spatial encodings. To this aim, a custom-designed visuo-spatial memory task was administered and the cortical activities underlying switching vs non-switching spatial processes were investigated. Changes in concentrations of oxygenated and deoxygenated haemoglobin were measured using functional near-infrared spectroscopy (fNIRS). Participants were asked to memorize triads of geometric objects and then make two consecutive judgments about the same triad. In the non-switching condition, both spatial judgments considered the same frame of reference: only egocentric or only allocentric. In the switching condition, if the first judgment was egocentric, the second one was allocentric (or vice versa). The results showed a generalized activation of the frontal regions during the switching compared to the non-switching condition. Additionally, increased cortical activity was found in the temporo-parietal junction during the switching condition compared to the non-switching condition. Overall, these results illustrate the cortical activity underlying the processing of switching between body position and environmental stimuli, showing an important role of the temporo-parietal junction and frontal regions in the preparation and switching between egocentric and allocentric reference frames.

A low-activity cortical network selectively encodes syntax

Syntax, the abstract structure of language, is a hallmark of human cognition. Despite its importance, its neural underpinnings remain obscured by inherent limitations of non-invasive brain measures and a near total focus on comprehension paradigms. Here, we address these limitations with high-resolution neurosurgical recordings (electrocorticography) and a controlled sentence production experiment. We uncover three syntactic networks that are broadly distributed across traditional language regions, but with focal concentrations in middle and inferior frontal gyri. In contrast to previous findings from comprehension studies, these networks process syntax mostly to the exclusion of words and meaning, supporting a cognitive architecture with a distinct syntactic system. Most strikingly, our data reveal an unexpected property of syntax: it is encoded independent of neural activity levels. We propose that this "low-activity coding" scheme represents a novel mechanism for encoding information, reserved for higher-order cognition more broadly.

Segregation of Neural Circuits Involved in Social Gaze and Non-Social Arrow Cues: Evidence from an Activation Likelihood Estimation Meta-Analysis

Orienting attention by social gaze cues shares some characteristics with orienting attention by non-social arrow cues, but it is unclear whether they rely on similar neural mechanisms. The present ALE-meta-analysis assessed the pattern of brain activation reported in 40 single experiments (18 with arrows, 22 with gaze), with a total number of 806 participants. Our findings show that the network for orienting attention by social gaze and by non-social arrow cues is in part functionally segregated. Orienting by both types of cues relies on the activity of brain regions involved in endogenous attention (the superior frontal gyrus). Importantly, only orienting by gaze cues was also associated with the activity of brain regions involved in exogenous attention (medial frontal gyrus), processing gaze, and mental state attribution (superior temporal sulcus, temporoparietal junction).

Systemic neurophysiological signals of auditory predictive coding

Predictive coding framework posits that our brain continuously monitors changes in the environment and updates its predictive models, minimizing prediction errors to efficiently adapt to environmental demands. However, the underlying neurophysiological mechanisms of these predictive phenomena remain unclear. The present study aimed to explore the systemic neurophysiological correlates of predictive coding processes during passive and active auditory processing. Electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and autonomic nervous system (ANS) measures were analyzed using an auditory pattern-based novelty oddball paradigm. A sample of 32 healthy subjects was recruited. The results showed shared slow evoked potentials between passive and active conditions that could be interpreted as automatic predictive processes of anticipation and updating, independent of conscious attentional effort. A dissociated topography of the cortical hemodynamic activity and distinctive evoked potentials upon auditory pattern violation were also found between both conditions, whereas only conscious perception leading to imperative responses was accompanied by phasic ANS responses. These results suggest a systemic-level hierarchical reallocation of predictive coding neural resources as a function of contextual demands in the face of sensory stimulation. Principal component analysis permitted to associate the variability of some of the recorded signals.

Resting-state functional connectivity and structural differences between smokers and healthy non-smokers

Previous studies have shown an association between cigarette use and altered resting-state functional connectivity (rsFC) in many large-scale networks, sometimes complemented by measures of cortical atrophy. In this study, we aimed to further explore the neural differences between smokers and healthy non-smokers through the integration of functional and structural analyses. Imaging data of fifty-two smokers and forty-five non-smokers were analyzed through an independent component analysis for group differences in rsFC. Smokers showed lower rsFC within the dorsal attention network (DAN) in the left superior and middle frontal gyrus and left superior division of the lateral occipital cortex compared to non-smokers; moreover, cigarette use was found to be associated with reduced grey matter volume in the left superior and middle frontal gyrus and right orbitofrontal cortex, partly overlapping with functional findings. Within smokers, daily cigarette consumption was positively associated with increased rsFC within the cerebellar network and the default mode network and decreased rsFC within the visual network and the salience network, while carbon monoxide level showed a positive association with increased rsFC within the sensorimotor network. Our results suggest that smoking negatively impacts rsFC within the DAN and that changes within this network might serve as a circuit-based biomarker for structural deficits.

Neural correlates of prediction error in patients with schizophrenia: evidence from an fMRI meta-analysis

Abnormal processes of learning from prediction errors, i.e. the discrepancies between expectations and outcomes, are thought to underlie motivational impairments in schizophrenia. Although dopaminergic abnormalities in the mesocorticolimbic reward circuit have been found in patients with schizophrenia, the pathway through which prediction error signals are processed in schizophrenia has yet to be elucidated. To determine the neural correlates of prediction error processing in schizophrenia, we conducted a meta-analysis of whole-brain neuroimaging studies that investigated prediction error signal processing in schizophrenia patients and healthy controls. A total of 14 studies (324 schizophrenia patients and 348 healthy controls) using the reinforcement learning paradigm were included. Our meta-analysis showed that, relative to healthy controls, schizophrenia patients showed increased activity in the precentral gyrus and middle frontal gyrus and reduced activity in the mesolimbic circuit, including the striatum, thalamus, amygdala, hippocampus, anterior cingulate cortex, insula, superior temporal gyrus, and cerebellum, when processing prediction errors. We also found hyperactivity in frontal areas and hypoactivity in mesolimbic areas when encoding prediction error signals in schizophrenia patients, potentially indicating abnormal dopamine signaling of reward prediction error and suggesting failure to represent the value of alternative responses during prediction error learning and decision making.

The impact of brain lesions on tDCS-induced electric fields

Transcranial direct current stimulation (tDCS) can enhance motor and language rehabilitation after stroke. Though brain lesions distort tDCS-induced electric field (E-field), systematic accounts remain limited. Using electric field modelling, we investigated the effect of 630 synthetic lesions on E-field magnitude in the region of interest (ROI). Models were conducted for two tDCS montages targeting either primary motor cortex (M1) or Broca's area (BA44). Absolute E-field magnitude in the ROI differed by up to 42% compared to the non-lesioned brain depending on lesion size, lesion-ROI distance, and lesion conductivity value. Lesion location determined the sign of this difference: lesions in-line with the predominant direction of current increased E-field magnitude in the ROI, whereas lesions located in the opposite direction decreased E-field magnitude. We further explored how individualised tDCS can control lesion-induced effects on E-field. Lesions affected the individualised electrode configuration needed to maximise E-field magnitude in the ROI, but this effect was negligible when prioritising the maximisation of radial inward current. Lesions distorting tDCS-induced E-field, is likely to exacerbate inter-individual variability in E-field magnitude. Individualising electrode configuration and stimulator output can minimise lesion-induced variability but requires improved estimates of lesion conductivity. Individualised tDCS is critical to overcome E-field variability in lesioned brains.

Object-based inhibition of return in three-dimensional space: From simple drawings to real objects

Cued to an object in space, inhibition of the attended location can spread to the entire object. Although object-based inhibition of return (IOR) studies in a two-dimensional plane have been documented, the IOR has not been explored when objects cross depth in three-dimensional (3D) space. In the present study, we used a virtual reality technique to adapt the double-rectangle paradigm to a 3D space, and manipulated the cue validity and target location to examine the difference in object-based IOR between far and near spaces under different object representations. The study showed that the object-based IOR of simple drawings existed only in near space, whereas object-based IOR of real objects existed only in far space at first, and as the object similarity decreases, it appeared in both far and near spaces.

Modeling the effects of transcranial magnetic stimulation on spatial attention

Objectives. Transcranial magnetic stimulation (TMS) has been widely used to modulate brain activity in healthy and diseased brains, but the underlying mechanisms are not fully understood. Previous research leveraged biophysical modeling of the induced electric field (E-field) to map causal structure-function relationships in the primary motor cortex. This study aims at transferring this localization approach to spatial attention, which helps to understand the TMS effects on cognitive functions, and may ultimately optimize stimulation schemes.Approach. Thirty right-handed healthy participants underwent a functional magnetic imaging (fMRI) experiment, and seventeen of them participated in a TMS experiment. The individual fMRI activation peak within the right inferior parietal lobule (rIPL) during a Posner-like attention task defined the center target for TMS. Thereafter, participants underwent 500 Posner task trials. During each trial, a 5-pulse burst of 10 Hz repetitive TMS (rTMS) was given over the rIPL to modulate attentional processing. The TMS-induced E-fields for every cortical target were correlated with the behavioral modulation to identify relevant cortical regions for attentional orientation and reorientation.Main results. We did not observe a robust correlation between E-field strength and behavioral outcomes, highlighting the challenges of transferring the localization method to cognitive functions with high neural response variability and complex network interactions. Nevertheless, TMS selectively inhibited attentional reorienting in five out of seventeen subjects, resulting in task-specific behavioral impairments. The BOLD-measured neuronal activity and TMS-evoked neuronal effects showed different patterns, which emphasizes the principal distinction between the neural activity being correlated with (or maybe even caused by) particular paradigms, and the activity of neural populations exerting a causal influence on the behavioral outcome.Significance. This study is the first to explore the mechanisms of TMS-induced attentional modulation through electrical field modeling. Our findings highlight the complexity of cognitive functions and provide a basis for optimizing attentional stimulation protocols.

A voxel-based morphometry study on gray matter correlates of need for cognition and exploratory information seeking

BACKGROUND

Need for cognition (NFC) represents interindividual differences in tendencies to engage and enjoy cognitive endeavors. Exploratory information seeking (EIS) refers to individual tendencies to attain cognitive stimulation through acquiring information related to consumer products or services out of curiosity.

METHODS

The current study aims to provide an in-depth investigation of the relationship between NFC and EIS and extend this relation to determine neuroanatomical correlates of NFC and EIS. This study proposed two central hypotheses: (1) NFC and EIS scores are positively correlated and (2) the gray matter volume (GMV) of brain regions implicated in motivation, valuation, and reward systems are positively associated with both NFC and EIS. Self-report and structural MRI data of 91 Singaporean Chinese participants were utilized for the study.

RESULTS

No statistically significant correlation was revealed between NFC and EIS scores. Neuroanatomical associations of the GMV of brain regions implicated in visuospatial, attentional, and reward processing with individual constructs of interest were explored. When examining NFC and EIS scores, larger GMV in the right pallidum and left fusiform gyrus was found in participants that reported higher levels of NFC (vs. lower NFC levels), larger GMV in the left precuneus in those with greater tendencies to engage in EIS (vs. lower EIS levels), and larger GMV of the left fusiform gyrus associated with greater endorsement of both NFC and EIS. When investigating the exploratory factor analysis-generated factors of NFC and EIS, similar patterns of associations were found between self-reported levels of agreement against factors and GMV of brain regions implicated.

CONCLUSIONS

Correlational analysis and exploratory factor analysis indicated the absence of a relationship between NFC and EIS. Additionally, voxel-based morphometry whole-brain analysis revealed neuroanatomical correlates of the GMV of brain regions implicated in visuospatial, attentional, and reward processing with NFC and EIS.

State-dependent effectiveness of cathodal transcranial direct current stimulation on cortical excitability

The extensive use of transcranial direct current stimulation (tDCS) in experimental and clinical settings does not correspond to an in-depth understanding of its underlying neurophysiological mechanisms. In previous studies, we employed an integrated system of Transcranial Magnetic Stimulation and Electroencephalography (TMS-EEG) to track the effect of tDCS on cortical excitability. At rest, anodal tDCS (a-tDCS) over the right Posterior Parietal Cortex (rPPC) elicits a widespread increase in cortical excitability. In contrast, cathodal tDCS (c-tDCS) fails to modulate cortical excitability, being indistinguishable from sham stimulation. Here we investigated whether an endogenous task-induced activation during stimulation might change this pattern, improving c-tDCS effectiveness in modulating cortical excitability. In Experiment 1, we tested whether performance in a Visuospatial Working Memory Task (VWMT) and a modified Posner Cueing Task (mPCT), involving rPPC, could be modulated by c-tDCS. Thirty-eight participants were involved in a two-session experiment receiving either c-tDCS or sham during tasks execution. In Experiment 2, we recruited sixteen novel participants who performed the same paradigm but underwent TMS-EEG recordings pre- and 10 min post- sham stimulation and c-tDCS. Behavioral results showed that c-tDCS significantly modulated mPCT performance compared to sham. At a neurophysiological level, c-tDCS significantly reduced cortical excitability in a frontoparietal network likely involved in task execution. Taken together, our results provide evidence of the state dependence of c-tDCS in modulating cortical excitability effectively. The conceptual and applicative implications are discussed.

Rewards weaken cross-modal inhibition of return with visual targets

Previous studies have shown that rewards weaken visual inhibition of return (IOR). However, the specific mechanisms underlying the influence of rewards on cross-modal IOR remain unclear. Based on the Posner exogenous cue-target paradigm, the present study was conducted to investigate the effect of rewards on exogenous spatial cross-modal IOR in both visual cue with auditory target (VA) and auditory cue with visual target (AV) conditions. The results showed the following: in the AV condition, the IOR effect size in the high-reward condition was significantly lower than that in the low-reward condition. However, in the VA condition, there was no significant IOR in either the high- or low-reward condition and there was no significant difference between the two conditions. In other words, the use of rewards modulated exogenous spatial cross-modal IOR with visual targets; specifically, high rewards may have weakened IOR in the AV condition. Taken together, our study extended the effect of rewards on IOR to cross-modal attention conditions and demonstrated for the first time that higher motivation among individuals under high-reward conditions weakened the cross-modal IOR with visual targets. Moreover, the present study provided evidence for future research on the relationship between reward and attention.

Specific but not general declines in attention and executive function with aging: Converging cross-sectional and longitudinal evidence across the adult lifespan

Objective

Attention and executive function (EF) are vulnerable to aging. However, whether all these functions generally decline with aging is not known. Furthermore, most evidence is based on cross-sectional data and fewer follow-up data are available in the literature. Longitudinal follow-up studies are necessary to characterize individualized and precise changes in cognitive function. Additionally, relatively few aging studies have included middle-aged adults to examine age-related differences in attention and EF. Therefore, this study aims to examine whether general or specific attention and EF decline with aging from adulthood to old age by combining cross-sectional and longitudinal follow-up approaches.

Methods

This study recruited 253 participants aged 20 to 78  years. passing a prescreening procedure (see main text for detail) for the baseline session, and 123 of them were invited to return 1 ~ 2  years after their first visit to participate in the follow-up session. The participants completed a series of attention and EF tasks at both the baseline and follow-up sessions, which measured alerting, orienting, conflict control, stopping, memory updating, and switching abilities. We applied linear and nonlinear regression models to evaluate the cross-sectional age effect on attention and EF and employed a modified Brinley plot to inspect follow-up performance against baseline in attention and EF.

Results

The results of cross-sectional data showed that older adults exhibited decreased efficiency in alerting, stopping, and memory updating but paradoxically increased efficiency in conflict control and switching abilities and no changes in orienting efficiency with age. However, the results of longitudinal data showed that only alerting and memory updating continued to show decreased efficiency. Furthermore, conflict control and switching showed increased efficiency with aging, whereas the orienting network, and stopping no longer showed decreased efficiency.

Conclusion

Thus, converging the cross-sectional and longitudinal data showed that the alerting and memory updating function exhibited the most robust deficit with age (cross-sectional) and aging (longitudinal). Alerting and memory updating abilities are crucial survival skills for human beings. Therefore, developing methods to prevent and improve an individual’s alertness and working memory ability is an important practical issue in aging research.

Regular recreational Cannabis users exhibit altered neural oscillatory dynamics during attention reorientation

BACKGROUND

Cannabis is the most widely used illicit drug in the United States and is often associated with changes in attention function, which may ultimately impact numerous other cognitive faculties (e.g. memory, executive function). Importantly, despite the increasing rates of cannabis use and widespread legalization in the United States, the neural mechanisms underlying attentional dysfunction in chronic users are poorly understood.

METHODS

We used magnetoencephalography (MEG) and a modified Posner cueing task in 21 regular cannabis users and 32 demographically matched non-user controls. MEG data were imaged in the time-frequency domain using a beamformer and peak voxel time series were extracted to quantify the oscillatory dynamics underlying use-related aberrations in attentional reorienting, as well as the impact on spontaneous neural activity immediately preceding stimulus onset.

RESULTS

Behavioral performance on the task (e.g. reaction time) was similar between regular cannabis users and non-user controls. However, the neural data indicated robust theta-band synchronizations across a distributed network during attentional reorienting, with activity in the bilateral inferior frontal gyri being markedly stronger in users relative to controls (p's < 0.036). Additionally, we observed significantly reduced spontaneous theta activity across this distributed network during the pre-stimulus baseline in cannabis users relative to controls (p's < 0.020).

CONCLUSIONS

Despite similar performance on the task, we observed specific alterations in the neural dynamics serving attentional reorienting in regular cannabis users compared to controls. These data suggest that regular cannabis users may employ compensatory processing in the prefrontal cortices to efficiently reorient their attention relative to non-user controls.

Phasic Alertness is Unaffected by the Attentional Set for Orienting

Warning stimuli preceding target stimuli for behaviour improve behavioural performance, which is referred to as phasic alerting. Similar benefits occur due to preceding orienting cues that draw spatial attention to the targets. It has long been assumed that alerting and orienting effects arise from separate attention systems, but recent views call this into question. As it stands, it remains unclear if the two systems are interdependent, or if they function independently. Here, we investigated whether the current attentional set for orienting modulates the effectiveness of alerting. In three experiments, participants classified visual stimuli in a speeded fashion. These target stimuli were preceded by orienting cues that could predict the target's location, by alerting cues that were neutral regarding the target's location, or by no cues. Alerting cues and orienting cues consisted of the same visual stimuli, linking alerting cues with the attentional set for orienting. The attentional set for orienting was manipulated in blocks, in which orienting cues were either informative or uninformative about the target's location. Results showed that while alerting generally enhanced performance, alerting was unaffected by the informativeness of the orienting cues. These findings show that alerting does not depend on the attentional set that controls orienting based on the informational value of orienting cues. As such, the findings provide a simple dissociation of mechanisms underlying phasic alertness and spatial attentional orienting.

Choosing Sides: Impact of Prismatic Adaptation on the Lateralization of the Attentional System

Seminal studies revealed differences between the effect of adaptation to left- vs. right-deviating prisms (L-PA, R-PA) in normal subjects. Whereas L-PA leads to neglect-like shift in attention, demonstrated in numerous visuo-spatial and cognitive tasks, R-PA has only minor effects in specific aspects of a few tasks. The paucity of R-PA effects in normal subjects contrasts with the striking alleviation of neglect symptoms in patients with right hemispheric lesions. Current evidence from activation studies in normal subjects highlights the contribution of regions involved in visuo-motor control during prism exposure and a reorganization of spatial representations within the ventral attentional network (VAN) after the adaptation. The latter depends on the orientation of prisms used. R-PA leads to enhancement of the ipsilateral visual and auditory space within the left inferior parietal lobule (IPL), switching thus the dominance of VAN from the right to the left hemisphere. L-PA leads to enhancement of the ipsilateral space in right IPL, emphasizing thus the right hemispheric dominance of VAN. Similar reshaping has been demonstrated in patients. We propose here a model, which offers a parsimonious explanation of the effect of L-PA and R-PA both in normal subjects and in patients with hemispheric lesions. The model posits that prismatic adaptation induces instability in the synaptic organization of the visuo-motor system, which spreads to the VAN. The effect is lateralized, depending on the side of prism deviation. Successful pointing with prisms implies reaching into the space contralateral, and not ipsilateral, to the direction of prism deviation. Thus, in the hemisphere contralateral to prism deviation, reach-related neural activity decreases, leading to instability of the synaptic organization, which induces a reshuffling of spatial representations in IPL. Although reshuffled spatial representations in IPL may be functionally relevant, they are most likely less efficient than regular representations and may thus cause partial dysfunction. The former explains, e.g., the alleviation of neglect symptoms after R-PA in patients with right hemispheric lesions, the latter the occurrence of neglect-like symptoms in normal subjects after L-PA. Thus, opting for R- vs. L-PA means choosing the side of major IPL reshuffling, which leads to its partial dysfunction in normal subjects and to recruitment of alternative or enhanced spatial representations in patients with hemispheric lesions.

Gaze-cued shifts of attention and microsaccades are sustained for whole bodies but are transient for body parts

Gaze direction is an evolutionarily important mechanism in daily social interactions. It reflects a person’s internal cognitive state, spatial locus of interest, and predicts future actions. Studies have used static head images presented foveally and simple synthetic tasks to find that gaze orients attention and facilitates target detection at the cued location in a sustained manner. Little is known about how people’s natural gaze behavior, including eyes, head, and body movements, jointly orient covert attention, microsaccades, and facilitate performance in more ecological dynamic scenes. Participants completed a target person detection task with videos of real scenes. The videos showed people looking toward (valid cue) or away from a target (invalid cue) location. We digitally manipulated the individuals in the videos directing gaze to create three conditions: whole-intact (head and body movements), floating heads (only head movements), and headless bodies (only body movements). We assessed their impact on participants’ behavioral performance and microsaccades during the task. We show that, in isolation, an individual’s head or body orienting toward the target-person direction led to facilitation in detection that is transient in time (200 ms). In contrast, only the whole-intact condition led to sustained facilitation (500 ms). Furthermore, observers executed microsaccades more frequently towards the cued direction for valid trials, but this bias was sustained in time only with the joint presence of head and body parts. Together, the results differ from previous findings with foveally presented static heads. In more real-world scenarios and tasks, sustained attention requires the presence of the whole-intact body of the individuals dynamically directing their gaze.

Resting-State Functional Connectivity in the Dorsal Attention Network Relates to Behavioral Performance in Spatial Attention Tasks and May Show Task-Related Adaptation

Between-subject variability in cognitive performance has been related to inter-individual differences in functional brain networks. Targeting the dorsal attention network (DAN) we questioned (i) whether resting-state functional connectivity (FC) within the DAN can predict individual performance in spatial attention tasks and (ii) whether there is short-term adaptation of DAN-FC in response to task engagement. Twenty-seven participants first underwent resting-state fMRI (PRE run), they subsequently performed different tasks of spatial attention [including visual search (VS)] and immediately afterwards received another rs-fMRI (POST run). Intra- and inter-hemispheric FC between core hubs of the DAN, bilateral intraparietal sulcus (IPS) and frontal eye field (FEF), was analyzed and compared between PRE and POST. Furthermore, we investigated rs-fMRI-behavior correlations between the DAN-FC in PRE/POST and task performance parameters. The absolute DAN-FC did not change from PRE to POST. However, different significant rs-fMRI-behavior correlations were revealed for intra-/inter-hemispheric connections in the PRE and POST run. The stronger the FC between left FEF and IPS before task engagement, the better was the learning effect (improvement of reaction times) in VS (r = 0.521, p = 0.024). And the faster the VS (mean RT), the stronger was the FC between right FEF and IPS after task engagement (r = −0.502, p = 0.032). To conclude, DAN-FC relates to the individual performance in spatial attention tasks supporting the view of functional brain networks as priors for cognitive ability. Despite a high inter- and intra-individual stability of DAN-FC, the change of FC-behavior correlations after task performance possibly indicates task-related adaptation of the DAN, underlining that behavioral experiences may shape intrinsic brain activity. However, spontaneous state fluctuations of the DAN-FC over time cannot be fully ruled out as an alternative explanation.

High-definition transcranial direct current stimulation of the occipital cortices induces polarity dependent effects within the brain regions serving attentional reorientation

Numerous brain stimulation studies have targeted the posterior parietal cortex, a key hub of the attention network, to manipulate attentional reorientation. However, the impact of stimulating brain regions earlier in the pathway, including early visual regions, is poorly understood. In this study, 28 healthy adults underwent three high‐definition transcranial direct current stimulation (HD‐tDCS) visits (i.e., anodal, cathodal, and sham). During each visit, they completed 20 min of occipital HD‐tDCS and then a modified Posner task during magnetoencephalography (MEG). MEG data were transformed into the time‐frequency domain and significant oscillatory events were imaged using a beamformer. Oscillatory response amplitude values were extracted from peak voxels in the whole‐brain maps and were statistically compared. Behaviorally, we found that the participants responded slowly when attention reallocation was needed (i.e., the validity effect), irrespective of the stimulation condition. Our neural findings indicated that cathodal HD‐tDCS was associated with significantly reduced theta validity effects in the occipital cortices, as well as reduced alpha validity effects in the left occipital and parietal cortices relative to anodal HD‐tDCS. Additionally, anodal occipital stimulation significantly increased gamma amplitude in right occipital regions relative to cathodal and sham stimulation. Finally, we also found a negative correlation between the alpha validity effect and reaction time following anodal stimulation. Our findings suggest that HD‐tDCS of the occipital cortices has a polarity dependent impact on the multispectral neural oscillations serving attentional reorientation in healthy adults, and that such effects may reflect altered local GABA concentrations in the neural circuitry serving attentional reorientation.

Microscopic Fractional Anisotropy Detects Cognitive Training-Induced Microstructural Brain Changes

Cognitive training-induced neuroplastic brain changes have been reported. This prospective study evaluated whether microscopic fractional anisotropy (μFA) derived from double diffusion encoding (DDE) MRI could detect brain changes following a 4 week cognitive training. Twenty-nine healthy volunteers were recruited and randomly assigned into the training (n = 21) and control (n = 8) groups. Both groups underwent brain MRI including DDE MRI and 3D-T1-weighted imaging twice at an interval of 4–6 weeks, during which the former underwent the training. The training consisted of hour-long dual N-back and attention network tasks conducted five days per week. Training and time-related changes of DDE MRI indices (μFA, fractional anisotropy (FA), and mean diffusivity (MD)) and the gray and white matter volume were evaluated using mixed-design analysis of variance. In addition, any significant imaging indices were tested for correlation with cognitive training-induced task performance changes, using partial correlation analyses. μFA in the left middle frontal gyrus decreased upon the training (53 voxels, uncorrected p < 0.001), which correlated moderately with response time changes in the orienting component of attention (r = −0.521, uncorrected p = 0.032). No significant training and time-related changes were observed for other imaging indices. Thus, μFA can become a sensitive index to detect cognitive training-induced neuroplastic changes.

Altered Functional Connectivity Density and Couplings in Postpartum Depression with and Without Anxiety

Postpartum depression (PPD) is the most common psychological health issue among women, which often comorbids with anxiety (PPD-A). PPD and PPD-A showed highly overlapping clinical symptoms. Identifying disorder-specific neurophysiological markers of PDD and PPD-A is important for better clinical diagnosis and treatments. Here, we performed functional connectivity density (FCD) and resting-state functional connectivity (rsFC) analyses in 138 participants (45 unmedicated patients with first-episode PPD, 31 PDD-A patients and 62 healthy postnatal women, respectively). FCD mapping revealed specifically weaker long-range FCD in right lingual gyrus (LG.R) for PPD patients and significantly stronger long-range FCD in left ventral striatum (VS.L) for PPD-A patients. The follow-up rsFC analyses further revealed reduced functional connectivity between dorsomedial prefrontal cortex (dmPFC) and VS.L in both PPD and PPD-A. PPD showed specific changes of rsFC between LG.R and dmPFC, right angular gyrus and left precentral gyrus, while PPD-A represented specifically abnormal rsFC between VS.L and left ventrolateral prefrontal cortex. Moreover, the altered FCD and rsFC were closely associated with depression and anxiety symptoms load. Taken together, our study is the first to identify common and disorder-specific neural circuit disruptions in PPD and PPD-A, which may facilitate more effective diagnosis and treatments.

Altered social cognition in a community sample of women with disordered eating behaviours: a multi-method approach

Prior work suggests that individuals with an eating disorder demonstrate task-based and overall differences in sociocognitive functioning. However, the majority of studies assessed specifically anorexia nervosa and often employed a single experimental paradigm, providing a piecemeal understanding of the applicability of various lab tasks in denoting meaningful differences across diverse individuals. The current study was designed to address these outstanding issues. Participants were undergraduate females who self-identified as having an official (n = 18) eating disorder diagnosis or disordered eating behaviours with no diagnosis (n = 18), along with a control group (n = 32). Participants completed three social tasks of increasing complexity with different outcome measures, namely a gaze cueing task, passive video-watching using eyetracking, and a task to measure preferred social distance. Results diverged as a function of group across tasks; only the control group produced typical social attention effects, the disordered eating group looked significantly more at faces, and the eating disorder group demonstrated a significantly larger preferred social distance. These results suggest variations in task efficacy and demonstrate that altered sociocognitive functioning extends beyond official eating disorder diagnosis.

Frontal circuit specialisations for decision making

There is widespread consensus that distributed circuits across prefrontal and anterior cingulate cortex (PFC/ACC) are critical for reward-based decision making. The circuit specialisations of these areas in primates were likely shaped by their foraging niche, in which decision making is typically sequential, attention-guided and temporally extended. Here, I argue that in humans and other primates, PFC/ACC circuits are functionally specialised in two ways. First, microcircuits found across PFC/ACC are highly recurrent in nature and have synaptic properties that support persistent activity across temporally extended cognitive tasks. These properties provide the basis of a computational account of time-varying neural activity within PFC/ACC as a decision is being made. Second, the macrocircuit connections (to other brain areas) differ between distinct PFC/ACC cytoarchitectonic subregions. This variation in macrocircuit connections explains why PFC/ACC subregions make unique contributions to reward-based decision tasks and how these contributions are shaped by attention. They predict dissociable neural representations to emerge in orbitofrontal, anterior cingulate and dorsolateral prefrontal cortex during sequential attention-guided choice, as recently confirmed in neurophysiological recordings.

From Gaze Perception to Social Cognition: The Shared-Attention System

When two people look at the same object in the environment and are aware of each other's attentional state, they find themselves in a shared-attention episode. This can occur through intentional or incidental signaling and, in either case, causes an exchange of information between the two parties about the environment and each other's mental states. In this article, we give an overview of what is known about the building blocks of shared attention (gaze perception and joint attention) and focus on bringing to bear new findings on the initiation of shared attention that complement knowledge about gaze following and incorporate new insights from research into the sense of agency. We also present a neurocognitive model, incorporating first-, second-, and third-order social cognitive processes (the shared-attention system, or SAS), building on previous models and approaches. The SAS model aims to encompass perceptual, cognitive, and affective processes that contribute to and follow on from the establishment of shared attention. These processes include fundamental components of social cognition such as reward, affective evaluation, agency, empathy, and theory of mind.

Effect of Cognitive Control on Attentional Processing of Emotional Information Among Older Adults: Evidence From an Eye-Tracking Study

Background: Although numerous studies have suggested that the gradually increasing selective preference for positive information over negative information in older adults depends on cognitive control processes, few have reported the characteristics of different attention stages in the emotional processing of older individuals. The present study used a real-time eye-tracking technique to disentangle the attentional engagement and disengagement processes involved in age-related positivity effect (PE). Methods: Eye movement data from a spatial-cueing task were obtained for 32 older and 32 younger healthy participants. The spatial-cueing task with varied cognitive loads appeared to be an effective way to explore the role of cognitive control during the attention engagement and disengagement stages of emotion processing. Results: Compared with younger adults, older participants showed more positive gaze preferences when cognitive resources were sufficient for face processing at the attention engagement stage. However, the age-related PE was not observed at the attention disengagement stage because older adults had more difficulty disengaging from fearful faces than did the younger adults due to the consumption of attention by the explicit target judgment. Conclusion: The present study highlights how cognitive control moderates positive gaze preferences at different attention processing stages. These findings may have far-reaching implications for understanding, preventing, and intervening in unsuccessful aging and, thus, in promoting active and healthy aging.

Attention recruits frontal cortex in human infants

Young infants learn about the world by overtly shifting their attention to perceptually salient events. In adults, attention recruits several brain regions spanning the frontal and parietal lobes. However, it is unclear whether these regions are sufficiently mature in infancy to support attention and, more generally, how infant attention is supported by the brain. We used event-related functional magnetic resonance imaging (fMRI) in 24 sessions from 20 awake behaving infants 3 mo to 12 mo old while they performed a child-friendly attentional cuing task. A target was presented to either the left or right of the infant's fixation, and offline gaze coding was used to measure the latency with which they saccaded to the target. To manipulate attention, a brief cue was presented before the target in three conditions: on the same side as the upcoming target (valid), on the other side (invalid), or on both sides (neutral). All infants were faster to look at the target on valid versus invalid trials, with valid faster than neutral and invalid slower than neutral, indicating that the cues effectively captured attention. We then compared the fMRI activity evoked by these trial types. Regions of adult attention networks activated more strongly for invalid than valid trials, particularly frontal regions. Neither behavioral nor neural effects varied by infant age within the first year, suggesting that these regions may function early in development to support the orienting of attention. Together, this furthers our mechanistic understanding of how the infant brain controls the allocation of attention.

Anatomy and White Matter Connections of the Middle Frontal Gyrus

BACKGROUND

The middle frontal gyrus (MFG) is involved in attention, working memory, and language-related processing. A detailed understanding of the subcortical white matter tracts connected within the MFG can facilitate improved navigation of white matter lesions in and around this gyrus and explain the postoperative morbidity after surgery. We aimed to characterize the fiber tracts within the MFG according to their connection to neuroanatomic structures through the use of diffusion spectrum imaging-based fiber tractography and validate the findings by gross anatomic dissection for qualitative visual agreement.

METHODS

Tractography analysis was completed using diffusion imaging data from 10 healthy, adult subjects enrolled in the Human Connectome Project. We assessed the MFG as a whole component according to its fiber connectivity with other neural regions. Mapping was completed on all tracts within both hemispheres, with the resultant tract volumes used to calculate a lateralization index. A modified Klingler technique was used on 10 postmortem dissections to demonstrate the location and orientation of the major tracts.

RESULTS

Two major connections of the MFG were identified: the superior longitudinal fasciculus, which connects the MFG to parts of the inferior parietal lobule, posterior temporal lobe, and lateral occipital cortex; and the inferior fronto-occipital fasciculus, which connected the MFG to the lingual gyrus and cuneus. Intra- and intergyral short association, U-shaped fibers were also identified.

CONCLUSIONS

Subcortical white matter pathways integrated within the MFG include the superior longitudinal fasciculus and inferior fronto-occipital fasciculus. The MFG is implicated in a variety of tasks involving attention and memory, making it an important cortical region. The postoperative neurologic outcomes related to surgery in and around the MFG could be clarified in the context of the anatomy of the fiber bundles highlighted in the present study.

Phasic alerting increases visual processing speed in amnestic mild cognitive impairment

External warning cues temporarily increase the brain's sensitivity for upcoming events, helping individuals to flexibly adapt their reactions to the requirements of complex visual environments. Previous studies reported that younger and cognitively normal older adults profit from phasic alerting cues. Such an intact phasic alerting mechanism could be even more relevant in individuals with Alzheimer's disease who are characterized by reduced processing capacities. The present study employed a theory of visual attention based verbal whole report paradigm with auditory cues in order to investigate phasic alerting effects in amnestic mild cognitive impairment (aMCI). Patients with aMCI were also compared to a previously reported sample of cognitively normal older adults. In patients with aMCI, visual processing speed was higher in the cue compared to the no-cue condition. Further, visual processing speed was reduced in patients with aMCI compared to cognitively normal older adults. Taken together, the results suggest that the processing system of patients with aMCI exhibits general declines but can still integrate auditory warning signals on a perceptual level.

Microstructural white matter connectivity underlying the attentional networks system

Nowadays, there is considerable controversy regarding the structural connectivity underlying the attentional networks system (i.e., alerting and vigilance, orienting, and executive control). The present study aimed at further examining and dissociating the white matter connectivity underlying attentional and vigilance functioning by overcoming some critical limitations in previous research. To this end, we performed virtual in vivo dissections of attention-related white matter tracts from thirty healthy adults. Participants completed two sessions of the Attentional Networks Test for Interactions and Vigilance, a suitable task to assess simultaneously phasic alertness, orienting, executive control, and the executive component of vigilance (i.e., the ability to detect infrequent critical signals). Whereas we found a consistent correlation between phasic alertness and both the right dorsolateral prefrontal caudate tract and the splenium of the corpus callosum, evidence obtained for white matter connectivity underlying orienting, executive control, and executive vigilance, was either weak at the best, inconsistent, or null. White matter connectivity seemed to support nevertheless the most reliable performance: overall reaction time for attentional functioning was significantly associated with the left cingulate fasciculus and overall reaction time for executive vigilance was significantly linked to the bilateral superior longitudinal fasciculus I. The present outcomes provide interesting, consistent, and reliable evidence concerning the structural connectivity underlying the alerting network. We still consider that further evidence is necessary to better understand the controversial relationship between attentional/vigilance processes and microstructural white matter connectivity though.

Functional dissociation of multiple-object tracking mechanisms based on hemispheric asymmetries

BACKGROUND

A number of theoretical accounts have been put forward to explain the ability to simultaneously track multiple visually indistinguishable objects over a period of time. Serial processing models of visual tracking focus on the maintenance of the spatial locations of every single item over time. A more recent mechanism describes multiple object tracking as the ability to maintain a higher order representation of an abstract spatial configuration built by the illusory connection of the tracked items through their transition.

OBJECTIVE

The current study investigates the correspondence between these serial and parallel tracking accounts and the right hemispheric specialization for the space-based vs. left hemispheric for object-based attentional processing.

METHODS

Electrophysiological brain responses were recorded in two groups of patients with right- and left hemispheric lesions while performing in a multiple object tracking task.

RESULTS

The results suggest a failure to distinguish single item information for the right hemispheric patients accompanied by the absence of a known electrophysiological marker associated with single item tracking. Importantly, left hemispheric patients showed a graded behavioral and electrophysiological response to probe stimuli as a function of the congruence of the probe with the relevant target stimuli.

CONCLUSIONS

The current data suggest that the differential contribution of serial and parallel tracking mechanisms during object tracking can partly be explained by the different functional contributions of the right and left brain hemispheres.

Diabetic patients are deficient in intentional visuospatial learning and show different learning-related patterns of theta and gamma EEG activity

Introduction: We hypothesized that diabetic patients without mild cognitive impairment would present deficiencies in visuospatial incidental/intentional memory processing and alterations in the underlying EEG alpha, theta and gamma patterns.Methods: Non-diabetic, diabetic-controlled, and diabetic-uncontrolled patients underwent a visuospatial incidental-intentional memory test under simultaneous recording of temporal, parietal, and frontal EEG. The test required patients to solve a maze, with eight objects irrelevant to the task, embedded in it, after an interference instruction, participants were asked to recall the positions of the objects (incidental test). Finally, the participants were explicitly told to study the object positions, and then were asked to recall the objects again (intentional test). Power from baseline, incidental learning, incidental memory, and intentional learning conditions was obtained in alpha, theta, and low-gamma bands. Comparisons were made across groups and conditions for each band, with age, sex, and years from the diagnosis as covariates (ANCOVA with blocking).Results: Diabetic patients showed spared incidental but deficient intentional visuospatial learning. Uncontrolled patients showed a more profound intentional learning deficit as they scored similar numbers of correct positions under incidental and intentional conditions; whereas, non-diabetic and diabetic-controlled patients increased their number after the intentional study. Non-diabetic participants showed increased power during intentional learning compared with the baseline condition in frontal theta, frontoparietal gamma (Fp2 and P4) and frontal alpha (F4) bands; whereas in diabetic patients the power increased in the theta band, in T5 (uncontrolled) and T5 and F7 (controlled).Conclusions: Diabetic patients without mild cognitive impairment show deficient intentional visuospatial learning which was worse in uncontrolled patients. Theta and gamma power increased in healthy participants during intentional learning principally in frontal areas. These EEG power changes were absent in diabetic patients. The reduced accuracy of diabetic patients in intentional visuospatial learning was associated with different EEG learning-related patterns.

The age-related trajectory of visual attention neural function is altered in adults living with HIV: A cross-sectional MEG study

Background

Despite living a normal lifespan, at least 35% of persons with HIV (PWH) in resource-rich countries develop HIV-associated neurocognitive disorder (HAND). This high prevalence of cognitive decline may reflect accelerated ageing in PWH, but the evidence supporting an altered ageing phenotype in PWH has been mixed.

Methods

We examined the impact of ageing on the orienting of visual attention in PWH using dynamic functional mapping with magnetoencephalography (MEG) in 173 participants age 22–72 years-old (94 uninfected controls, 51 cognitively-unimpaired PWH, and 28 with HAND). All MEG data were imaged using a state-of-the-art beamforming approach and neural oscillatory responses during attentional orienting were examined for ageing, HIV, and cognitive status effects.

Findings

All participants responded slower during trials that required attentional reorienting. Our functional mapping results revealed HIV-by-age interactions in left prefrontal theta activity, alpha oscillations in the left parietal, right cuneus, and right frontal eye-fields, and left dorsolateral prefrontal beta activity (p<.005). Critically, within PWH, we observed a cognitive status-by-age interaction, which revealed that ageing impacted the oscillatory gamma activity serving attentional reorienting differently in cognitively-normal PWH relative to those with HAND in the left temporoparietal, inferior frontal gyrus, and right prefrontal cortices (p<.005).

Interpretation

This study provides key evidence supporting altered ageing trajectories across vital attention circuitry in PWH, and further suggests that those with HAND exhibit unique age-related changes in the oscillatory dynamics serving attention function. Additionally, our neural findings suggest that age-related changes in PWH may serve a compensatory function.

Funding

National Institutes of Health, USA.

Arousal and Executive Alterations in Attention Deficit Hyperactivity Disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) is the most common neurobehavioral disorder in childhood and can significantly affect a child's personal and social development and academic achievement. Taking into account the model of attentional networks proposed by Posner et al., the aim of the present study was to review the literature regarding two main explicative models of ADHD, i.e., the inhibition model and the cognitive-energetic model, by discussing behavioral and neurological evidence of both models and the limitations of each model. The review highlights evidence that favors the energetic model and points to an unstable arousal as a potential pathogenetic factor in ADHD.

Development and sex modulate visuospatial oscillatory dynamics in typically-developing children and adolescents

Visuospatial processing is a cognitive function that is critical to navigating one's surroundings and begins to develop during infancy. Extensive research has examined visuospatial processing in adults, but far less work has investigated how visuospatial processing and the underlying neurophysiology changes from childhood to early adolescence, which is a critical period of human development that is marked by the onset of puberty. In the current study, we examined behavioral performance and the oscillatory dynamics serving visuospatial processing using magnetoencephalography (MEG) in a cohort of 70 children and young adolescents aged 8-15 years. All participants performed a visuospatial processing task during MEG, and the resulting oscillatory responses were imaged using a beamformer and probed for developmental and sex-related differences. Our findings indicated that reaction time on the task was negatively correlated with age, and that the amplitude of theta oscillations in the medial occipital cortices increased with age. Significant sex-by-age interactions were also detected, with female participants exhibiting increased theta oscillatory activity in the right prefrontal cortex with increasing age, while male participants exhibited theta increases in the left parietal lobe/left precuneus and left supplementary motor area with increasing age. These data indicate that different nodes of the visuospatial processing network develop earlier in males compared to females (and vice versa) in this age range, which may have major implications for the developmental trajectory of behavioral performance and executive function more generally during the transition through puberty.

Modulation of attention networks serving reorientation in healthy aging

Orienting attention to behaviorally relevant stimuli is essential for everyday functioning and mainly involves activity in the dorsal and ventral frontoparietal networks. Many studies have shown declines in the speed and accuracy of attentional reallocation with advancing age, but the underlying neural dynamics remain less understood. We investigated this age-related decline using magnetoencephalography (MEG) and a Posner task in 94 healthy adults (22-72 years old). MEG data were examined in the time-frequency domain, and significant oscillatory responses were imaged using a beamformer. We found that participants responded slower when attention reallocation was needed (i.e., the validity effect) and that this effect was positively correlated with age. We also found age-related validity effects on alpha activity in the left parietal and beta in the left frontal-eye fields from 350-950 ms. Overall, stronger alpha and beta responses were observed in younger participants during attention reallocation trials, but this pattern was reversed in the older participants. Interestingly, this alpha validity effect fully mediated the relationship between age and behavioral performance. In conclusion, older adults were slower in reorienting attention and exhibited age-related alterations in alpha and beta responses within parietal and frontal regions, which may reflect increased task demands depleting their compensatory resources.

Identification of Visual Attentional Regions of the Temporoparietal Junction in Individual Subjects using a Vivid, Novel Oddball Paradigm

The Temporoparietal Junction (TPJ) of the cerebral cortex is a functionally heterogeneous region that also exhibits substantial anatomical variability across individuals. As a result, the precise functional organization of TPJ remains controversial. One or more regions within TPJ support visual attention processes, but the "attention TPJ" is difficult to functionally observe in individual subjects, and thus is typically identified by averaging across a large group of subjects. However, group-averaging also blurs localization and can obscure functional organization. Here, we develop and test an individual-subject approach to identifying attentional TPJ. This paradigm employs novel oddball images with a strong visual drive to produce robust TPJ responses in individuals. Vivid, novel oddballs drive responses in two TPJ regions bilaterally, a posterior region centered in posterior Superior Temporal Sulcus (TPJ_STS) and an anterior region in ventral Supramarginal Gyrus (TPJ_SMG). Although an attentional reorienting task fails to drive TPJ activation in individuals, group analysis of the attentional reorienting contrast reveals recruitment of right TPJ_STS, but not right TPJ_SMG. Similarly, right TPJ_STS, as identified in individual subjects by the vivid, novel oddball contrast, is activated by attentional reorienting, but right TPJ_SMG is not. These findings advance an individual-subject based approach to understanding the functional organization of TPJ.

Effects of Rest-Break on Mental Fatigue Recovery Determined by a Novel Temporal Brain Network Analysis of Dynamic Functional Connectivity

Mental fatigue is growingly considered to be associated with functional brain dysconnectivity. Although conventional wisdom suggests that rest break is an effective countermeasure, the underlying neural mechanisms and how they modulate fatigue-related brain dysconnectivity is largely unknown. Here, we introduce an empirical method to examine the reorganization of dynamic functional connectivity (FC) in a two-session experiment where one session including a mid-task break (Rest) compared to a successive task design in the other session (No-rest). Temporal brain networks were estimated from 20 participants and the spatiotemporal architecture was examined using our newly developed temporal efficiency analysis framework. We showed that taking a mid-task break leads to a restorative effect towards the end of experiment instead of immediate post-rest behaviour benefits. More importantly, we revealed a potential neural basis of our behaviour observation: the reduced spatiotemporal global integrity of temporal brain network in No-rest session was significantly improved with the break opportunity in the last task block of Rest session. Overall, we provided novel evidence to support beneficial effect of rest breaks in both behaviour performance and brain function. Moreover, these findings extended prior static FC studies of mental fatigue and highlight that altered dynamic FC may underlie cognitive fatigue.

Prefrontal theta modulates sensorimotor gamma networks during the reorienting of attention

The ability to execute a motor plan involves spatiotemporally precise oscillatory activity in primary motor (M1) regions, in concert with recruitment of “higher order” attentional mechanisms for orienting toward current task goals. While current evidence implicates gamma oscillatory activity in M1 as central to the execution of a movement, far less is known about top‐down attentional modulation of this response. Herein, we utilized magnetoencephalography (MEG) during a Posner attention‐reorienting task to investigate top‐down modulation of M1 gamma responses by frontal attention networks in 63 healthy adult participants. MEG data were evaluated in the time–frequency domain and significant oscillatory responses were imaged using a beamformer. Robust increases in theta activity were found in bilateral inferior frontal gyri (IFG), with significantly stronger responses evident in trials that required attentional reorienting relative to those that did not. Additionally, strong gamma oscillations (60–80 Hz) were detected in M1 during movement execution, with similar responses elicited irrespective of attentional reorienting. Whole‐brain voxel‐wise correlations between validity difference scores (i.e., attention reorienting trials—nonreorienting trials) in frontal theta activity and movement‐locked gamma oscillations revealed a robust relationship in the contralateral sensorimotor cortex, supplementary motor area, and right cerebellum, suggesting modulation of these sensorimotor network gamma responses by attentional reorienting. Importantly, the validity difference effect in this distributed motor network was predictive of overall motor function measured outside the scanner and further, based on a mediation analysis this relationship was fully mediated by the reallocation response in the right IFG. These data are the first to characterize the top‐down modulation of movement‐related gamma responses during attentional reorienting and movement execution.

Specific Visual Subregions of TPJ Mediate Reorienting of Spatial Attention

The temporo-parietal junction (TPJ) has been associated with various cognitive and social functions, and is critical for attentional reorienting. Attention affects early visual processing. Neuroimaging studies dealing with such processes have thus far concentrated on striate and extrastriate areas. Here, we investigated whether attention orienting or reorienting modulate activity in visually driven TPJ subregions. For each observer we identified 3 visually responsive subregions within TPJ: 2 bilateral (vTPJant and vTPJpost) and 1 right lateralized (vTPJcent). Cortical activity in these subregions was measured using fMRI while observers performed a 2-alternative forced-choice orientation discrimination task. Covert spatial endogenous (voluntary) or exogenous (involuntary) attention was manipulated using either a central or a peripheral cue with task, stimuli and observers constant. Both endogenous and exogenous attention increased activity for invalidly cued trials in right vTPJpost; only endogenous attention increased activity for invalidly cued trials in left vTPJpost and in right vTPJcent; and neither type of attention modulated either right or left vTPJant. These results demonstrate that vTPJpost and vTPJcent mediate the reorientation of covert attention to task relevant stimuli, thus playing a critical role in visual attention. These findings reveal a differential reorienting cortical response after observers' attention has been oriented to a given location voluntarily or involuntarily.

Brain Activity Associated With Expected Task Difficulty

Previous research shows that people can use a cue to mentally prepare for a cognitive challenge. The response to a cue has been defined as phasic alertness which is reflected in faster responses and increased activity in frontal, parietal, thalamic, and visual brain regions. We examine if and how phasic alertness can be tuned to the expected difficulty of an upcoming challenge. If people in general are able to tune their level of alertness, then an inability to tune may be linked to disease. Twenty-two healthy volunteers performed a cued visual perception task with two levels of task difficulty. Performance and brain activity were compared between these two levels. Performance was lower for difficult stimuli than for easy stimuli. For both cue types, participants showed activation in a network associated with central executive function and deactivation in regions of the default mode network (DMN) and visual cortex. Deactivation was significantly stronger for cues signaling difficult stimuli than for cues signaling easy stimuli. This effect was most prominent in medial prefrontal gyrus, visual, and temporal cortices. Activation did not differ between the cues. Our study shows that phasic alertness is represented by activated as well as deactivated brain regions. However only deactivated brain regions tuned their level of activity to the expected task difficulty. These results suggest that people, in general, are able to tune their level of alertness to an upcoming task. Cognition may be facilitated by a brain-state coupled to expectations about an upcoming cognitive challenge. Unique identifier = 842003004¹.

Phasic alerting effects on visual processing speed are associated with intrinsic functional connectivity in the cingulo-opercular network

Phasic alertness refers to short-lived increases in the brain's "state of readiness", and thus to optimized performance following warning cues. Parametric modelling of whole report task performance based on the computational theory of visual attention (TVA) has demonstrated that visual processing speed is increased in such cue compared to no-cue conditions. Furthermore, with respect to the underlying neural mechanisms, individual visual processing speed has been related to intrinsic functional connectivity (iFC) within the cingulo-opercular network, suggesting that this network's iFC is relevant for the tonic maintenance of an appropriate readiness or alertness state. In the present study, we asked whether iFC in the cingulo-opercular network is also related to the individual ability to actively profit from warning cues, i.e. to the degree of phasic alerting. We obtained resting-state functional magnetic resonance imaging (rs-fMRI) data from 32 healthy young participants and combined an independent component analysis of rs-fMRI time courses and dual regression approach to determine iFC in the cingulo-opercular network. In a separate behavioural testing session, we parametrically assessed the effects of auditory phasic alerting cues on visual processing speed in a TVA-based whole report paradigm. A voxel-wise multiple regression revealed that higher individual phasic alerting effects on visual processing speed were significantly associated with lower iFC in the cingulo-opercular network, with a peak in the left superior orbital gyrus. As phasic alertness was neither related to iFC in other attention-relevant, auditory, or visual networks nor associated with any inter-network connectivity pattern, the results suggest that the individual profit in visual processing speed gained from phasic alerting is primarily associated with iFC in the cingulo-opercular network.

Brain activity sensitive to visual congruency effects relates to divergent thinking

The present study used functional magnetic resonance imagining (fMRI) to examine the role of focused attention in divergent thinking and real-life creativity. Participants completed a Navon task, on which the stimuli consisted of a large letter made up of the smaller version of the same (congruent), or a different (incongruent) letter. Participants were cued to identify a letter at either the local or at the global level. A smaller congruency effect - how much faster people responded on the congruent than on the incongruent trials - was an index of focused attention. Overall, larger behavioral congruency effect was accompanied with increased activation in the anterior superior temporal gyrus (aSTG), and with increased activation in the left precuneus. Individual differences in divergent thinking, however, were associated with smaller behavioral congruency effect, as well as with smaller right aSTG increase on the incongruent versus congruent targets, suggesting that people with better performance on the divergent thinking tests have more focused attention. Real-world creativity was not associated with the congruency effect, or with any of the regions implicated in the congruency effect. Implications and directions for future research are discussed.