Spatiotemporally dissociable neural signatures for generating and updating expectation over time in children: A High Density-ERP study

Temporal orienting (TO) is the allocation of attentional resources in time based on the a priori generation of temporal expectancy of relevant stimuli as well as the a posteriori updating of this expectancy as a function of both sensory-based evidence and elapsing time. These processes rely on dissociable cognitive mechanisms and neural networks. Yet, although there is evidence that TO may be a core mechanism for cognitive functioning in childhood, the developmental spatiotemporal neural dynamics of this mechanism are little understood. In this study we employed a combined approach based on the application of distributed source reconstruction on a high spatial resolution ERP data array obtained from eighteen 8- to 12-year-old children completing a TO paradigm in which both the cue (Temporal vs. Neutral) and the SOA (Short vs. Long) were manipulated. Results show both cue (N1) and SOA (CNV, Omission Detection Potential and Anterior Anticipatory Index) ERP effects, which were associated with expectancy generation and updating, respectively. Only cue-related effects were correlated with age, as revealed by a reduction of the N1 delta effect with increasing age. Our data suggest that the neural correlates underlying TO are already established at least from 8 to 12 years of age

Neural signatures of task-related fluctuations in auditory attention change with age

Listening in everyday life requires attention to be deployed dynamically – when listening is expected to be difficult and when relevant information is expected to occur – to conserve mental resources. Conserving mental resources may be particularly important for older adults who often experience difficulties understanding speech. We use electro- and magnetoencephalography to investigate the neural and behavioral mechanics of dynamic attention regulation during listening and the effects that aging may have on these. We show that neural alpha oscillatory activity indicates when in time attention is deployed (Experiment 1) and that deployment depends on listening difficulty (Experiment 2). Older adults also show successful attention regulation, although younger adults appear to utilize timing information a bit differently compared to older adults. We further show that the recruited brain regions differ between age groups. Superior parietal cortex is involved in attention regulation in younger adults, whereas posterior temporal cortex is more involved in older adults (Experiment 3). This difference in the sources of alpha activity across age groups was only observed when a task was performed, and not for alpha activity during resting-state recordings (Experiment S1). In sum, our study suggests that older adults employ different neural control strategies compared to younger adults to regulate attention in time under listening challenges

Neuro behavioural precursors of executive function in early development

Executive Function (EF) refers to an interrelated set of neurocognitive systems that underlie behavioral control and cognitive flexibility. EF has pervasive influences on cognition and later development. Previous studies have highlighted that there is a great deal of EF development that goes on from the preschool period through adolescence. In recent years, there has been a growing interest in exploring how executive functions develop in the first three years of life. The present thesis aims to contribute to this literature by exploring how early attentional control, in the form of attentional orienting and executive attention, and working memory interact and co-develop to support forms of complex functioning with an eye toward understanding how EF develops at two levels: brain and behavior. Importantly, we used tasks that rely on looking measures so this line of research can be scaled down to see if/how these skills are related to the emergence of EF from infancy to early childhood. In study 1, we found evidence that attentional control is related to executive control in children aged 24-72 months. In study 2, we replicated these findings, showing that attentional control is related to executive control in toddlers and young children. Critically, our results provide evidence that measures of basic visual dynamics relate to longitudinal changes in cognitive development and executive control. Consistent with previous research, we found task-relevant brain activity among WM and attention tasks in canonical WM and attentional networks. Importantly, there was overlap in the spatial localization of these activation patterns which is consistent with the idea that WM and attention share neural correlates early in development. Moreover, these activation patterns were predictive of later executive control and may serve as biomarkers of emerging cognitive control. Our results set the stage for future work to measure looking dynamics in infancy to predict longer-term executive control outcomes. This work furthers our understanding of how changes in brain function lead to specific developmental cascades from 30- to 42-month

Infant and toddler precursors of attentional processes in Fragile X syndrome: A neurodevelopmental perspective

With the recent sequencing of the human genome, the following question has attracted much interest: can the function of single genes be linked to specific neural and cognitive processes? Within this context, developmental disorders of known genetic origins have been used as naturally-occurring models to link the function (and dysfunction) of genes with cognition. Fragile X syndrome (FXS) is a genetically inherited disorder associated with the silencing of a single gene involved in experience-dependent changes at glutamatergic synapses. In adulthood, it is associated with core attentional difficulties accompanied by seemingly proficient visuo-perception, but the profile of infants and toddlers has not been investigated. In this thesis, fragile X syndrome is used as a tool to investigate how initial changes in a generalised property of all cortical neurones can nonetheless result, in the adult, in core difficulties in the control of attention. I argue that, even in disorders associated with the silencing of a single gene like FXS, the answer requires a developmental approach. Chapter 1 delineates a theoretical distinction between endogenous and exogenous influences on attentional control, whereas Chapter 2 defines methodological issues in assessing atypical attention, such as tools for the assessment of general developmental level and choices of control groups. Part II focuses on tasks tapping endogenous attention control. In particular, Chapters 3 and 4 examine the control of eye-movements and manual response conflict in infants and toddlers with FXS and in typically developing controls. In contrast, Part III concentrates on the exogenous effects of sudden peripheral onsets on visual orienting (Chapter 5) and of the perceptual salience of targets during visual search (Chapter 6). Finally, Part IV traces longitudinal changes in visual search performance. The findings suggest that, like adults with the syndrome, infant and toddlers with FXS display striking deficits in endogenous attention. However, unlike adults, infants are also characterised by atypical exogenous influences on attention and longitudinal changes in performance point to complex developmental relationships between early and later measures of attention. The findings are discussed in terms of their theoretical implications for fragile X syndrome and other developmental disorders affecting attention. They challenge the notion of direct genotype-phenotype mappings that fail to take development into account

Transient and sustained incentive effects on electrophysiological indices of cognitive control in younger and older adults

Preparing for upcoming events, separating task-relevant from task-irrelevant information and efficiently responding to stimuli all require cognitive control. The adaptive recruitment of cognitive control depends on activity in the dopaminergic reward system as well as the frontoparietal control network. In healthy aging, dopaminergic neuromodulation is reduced, resulting in altered incentive-based recruitment of control mechanisms. In the present study, younger adults (18–28 years) and healthy older adults (66–89 years) completed an incentivized flanker task that included gain, loss, and neutral trials. Event-related potentials (ERPs) were recorded at the time of incentive cue and target presentation. We examined the contingent negative variation (CNV), implicated in stimulus anticipation and response preparation, as well as the P3, which is involved in the evaluation of visual stimuli. Both younger and older adults showed transient incentive-based modulation of CNV. Critically, cue-locked and target-locked P3s were influenced by transient and sustained effects of incentives in younger adults, while such modulation was limited to a sustained effect of gain incentives on cue-P3 in older adults. Overall, these findings are in line with an age-related reduction in the flexible recruitment of preparatory and target-related cognitive control processes in the presence of motivational incentives

Spatial Attention-Modulated Surround Suppression Across Development: A Psychophysical Study

Several studies have demonstrated that surrounding a given spatial location of attentional focus is a suppressive field (e.g., Hopf et al., 2006). Though several studies have provided psychophysical (e.g., Cutzu & Tsotsos, 2003) and neural evidence of this effect in young adults (e.g., Boehler et al., 2009), whether this phenomenon is also observed in development was not fully known. Experiment 1 of the current study was therefore conducted to examine whether attention-modulated surround suppression was observed in younger age groups. Participants between the ages of 8 and 22 years were tested on a two-alternative forced choice task, in which their accuracy in discriminating between two red target letters among black distractor letters was measured. A spatial cue guided the participants attention to the upcoming location of one of the target letters. As would be predicted for the young adults, their accuracy increased as the inter-target separation increased, suggesting that visual processing is suppressed in the immediate vicinity of an attended location. Pre-adolescents (12 to 13 years) and adolescents (14 to 17 years) also exhibited attentional surround suppression, but intriguingly their inhibitory surround appeared to be larger than that of young adults. The 8- to 11-year-olds did not exhibit attentional suppression. In Experiment 2, when a central cue instead of a spatial cue was presented, surround suppression was no longer observed in an independent set of 8- to 27-year-olds, suggesting that the findings of Experiment 1 were indeed related to spatial attention. In Experiment 3, yet another independent group of 8- to 9-year-olds were tested on a modified version of the Experiment 1 task, where the cue presentation time was doubled to provide them with more support and more time to complete their top-down feedback processes. With this manipulation, attention-modulated surround suppression was still not observed in the 8- to 11-year-olds. Overall the current study findings suggest that top-down attentional feedback processes are still immature until approximately 12 years of age, and that they continue to be refined throughout adolescence. Protracted white matter maturation and diffuse functional connectivity in younger age groups are some of the potential underlying mechanisms driving the current findings

Attentional refocusing between time and space in older adults:investigation of neural mechanisms and relation to driving

Older adults have a disproportionately high risk of causing collisions at intersections and causing collisions by failing to notice surrounding road signs or signals. Collisions caused by older drivers seem to result from attentional failures. There is limited research exploring the ability to refocus from orienting attention to events changing in time (i.e. temporal attention) to distributing attention spatially (i.e. spatial attention), a process that is particularly important while driving and, if impaired,could cause collisions. The aims of the project were firstly to assess whether the ability to refocus attention from time to space changes throughout the adult lifespan when assessed with a computer based task and in an ecologically valid scenario during simulated driving, secondly, to use magnetoencephalography (MEG) to identify changes to neural mechanism that might explain difficulties in attentional refocusing, and finally, use mobile electroencephalography to explore the neural mechanisms involved in attentional refocusing while driving. Results demonstrated age related declines in the ability to refocus attention from time to space both in a computer-based task and during simulated driving. MEG recorded in a computer-based attention refocusing task revealed that, compared to younger adults, older and middle-aged adults displayed task-related theta deficits in lower level visual processing areas, and instead, displayed compensatory increases in theta power and phase-related connectivity across frontal regions. Increased frontal lobe recruitment likely reflects enhanced top-down attention to cope with impaired lower level attention mechanisms,supporting compensatory recruitment models of ageing. During simulated driving, older participants displayed slower driving speeds and weaker beta desynchronization in preparation to read a road sign, instead displaying a stronger theta power increase in response to the road sign, further demonstrating neural and behavioural compensatory strategies that are only partially successful.Findings warrant the development of a training programme to improve attentional refocusing between time and space while driving

The neurophysiology of intersensory selective attention and task switching

Our ability to selectively attend to certain aspects of the world and ignore others is fundamental to our day-to-day lives. The need for selective attention stems from capacity limitations inherent in our perceptual and cognitive processing architecture. Because not every elemental piece of our environment can be fully processed in parallel, the nervous system must prioritize processing. This prioritization is generally referred to as selective attention. Meanwhile, we are faced with a world that is constantly in flux, such that we have to frequently shift our attention from one piece of the environment to another and from one task to another. This process is generally referred to as task-switching. Neural oscillations in the alpha band (~8-14 Hz) have been shown to index the distribution of selective attention, and there is increasing evidence that oscillations in this band are in fact utilized by the nervous system to suppress distracting, task-irrelevant information. In order to elaborate on what is known of the function of alpha oscillations as well as current models of both intersensory selective attention and task switching, I investigated the dynamics of alpha amplitude modulations within the context of intersenory selective attention and task switching in neurologically typical young adults. Participants were alternately cued to attend to either the visual or auditory aspect of a compound audio-visual stimulus while high-density electroencephalography was recorded. It is typically found that alpha power increases over parieto-occipital cortices when attention is directed away from the visual modality and to the auditory modality. I report evidence that alpha oscillations play a role in task-switching (e.g., when switching from attending the visual task versus repeating this task), specifically as biasing signals, that may operate to re-weight competition among two tasks-sets. I further investigated the development of these same processes in school-aged children and adolescents. While exhibiting typical patterns of alpha modulations relevant to selective attention, Young school-aged children (8-12 years), compared to older participants, did not demonstrate specific task switching modulation of alpha oscillations, suggesting that this process does not fully develop until late adolescence. Finally, children and adolescents on the autism spectrum failed altogether to exhibit differentiation of alpha power between attend-visual and attend-auditory conditions--an effect present in age and IQ matched controls--suggesting that ASD individuals may have a deficit in the overall top-down deployment of alpha oscillatory biasing signals. This could result in an inability to ignore distracting information in the environment, leading to an overwhelming, disordered experience of the world, resulting in profound effects on the both social interaction and cognitive development. Altogether, these findings add to growing evidence that alpha oscillations serve as domain general biasing signals and are integral to our flexible goal-oriented behavior. Furthermore, the flexible use of these biasing signals in selective attention and task switching develops over a protracted period, and appears to be aberrant in autism spectrum disorder

The Development of Attention Systems and Working Memory in Infancy

In this article, we review research and theory on the development of attention and working memory in infancy using a developmental cognitive neuroscience framework. We begin with a review of studies examining the influence of attention on neural and behavioral correlates of an earlier developing and closely related form of memory (i.e., recognition memory). Findings from studies measuring attention utilizing looking measures, heart rate, and event-related potentials (ERPs) indicate significant developmental change in sustained and selective attention across the infancy period. For example, infants show gains in the magnitude of the attention related response and spend a greater proportion of time engaged in attention with increasing age (Richards and Turner, 2001). Throughout infancy, attention has a significant impact on infant performance on a variety of tasks tapping into recognition memory; however, this approach to examining the influence of infant attention on memory performance has yet to be utilized in research on working memory. In the second half of the article, we review research on working memory in infancy focusing on studies that provide insight into the developmental timing of significant gains in working memory as well as research and theory related to neural systems potentially involved in working memory in early development. We also examine issues related to measuring and distinguishing between working memory and recognition memory in infancy. To conclude, we discuss relations between the development of attention systems and working memory