MATERNAL TOUCH RELATES TO FACE SENSITIVITY IN CHILDREN

Master'sMASTER OF SOCIAL SCIENCE

Brain activation during face perception: evidence of a developmental change.

Behavioral studies suggest that children under age 10 process faces using a piecemeal strategy based on individual distinctive facial features, whereas older children use a configural strategy based on the spatial relations among the face's features. The purpose of this study was to determine whether activation of the fusiform gyrus, which is involved in face processing in adults, is greater during face processing in older children (12-14 years) than in younger children (8-10 years). Functional MRI scans were obtained while children viewed faces and houses. A developmental change was observed: Older children, but not younger children, showed significantly more activation in bilateral fusiform gyri for faces than for houses. Activation in the fusiform gyrus correlated significantly with age and with a behavioral measure of configural face processing. Regions believed to be involved in processing basic facial features were activated in both younger and older children. Some evidence was also observed for greater activation for houses versus faces for the older children than for the younger children, suggesting that processing of these two stimulus types becomes more differentiated as children age. The current results provide biological insight into changes in visual processing of faces that occur with normal development

Using multi-modal neuroimaging to characterise social brain specialisation in infants

The specialised regional functionality of the mature human cortex partly emerges through experience-dependent specialisation during early development. Our existing understanding of functional specialisation in the infant brain is based on evidence from unitary imaging modalities and has thus focused on isolated estimates of spatial or temporal selectivity of neural or haemodynamic activation, giving an incomplete picture. We speculate that functional specialisation will be underpinned by better coordinated haemodynamic and metabolic changes in a broadly orchestrated physiological response. To enable researchers to track this process through development, we develop new tools that allow the simultaneous measurement of coordinated neural activity (EEG), metabolic rate, and oxygenated blood supply (broadband near-infrared spectroscopy) in the awake infant. In 4- to 7-month-old infants, we use these new tools to show that social processing is accompanied by spatially and temporally specific increases in coupled activation in the temporal-parietal junction, a core hub region of the adult social brain. During non-social processing, coupled activation decreased in the same region, indicating specificity to social processing. Coupling was strongest with high-frequency brain activity (beta and gamma), consistent with the greater energetic requirements and more localised action of high-frequency brain activity. The development of simultaneous multimodal neural measures will enable future researchers to open new vistas in understanding functional specialisation of the brain

Dorsal and ventral stream activation and object recognition performance in school-age children

We explored how developing neural artifact and animal representations in the dorsal and ventral stream play a role in children's increasingly more proficient interactions with objects. In thirty-three 6- to 10-year-old children and 11 adults, we used fMRI to track the development of (1) the cortical category preference for tools compared to animals and (2) the response to complex objects (as compared to scrambled objects) during a passive viewing task. In addition, we related a cognitive skill that improved substantially from age 6 to 10, namely the ability to recognize tools from unusual viewpoints, to the development of cortical object processing. In multiple complementary analyses we showed that those children who were better at recognizing tools from unusual viewpoints outside the scanner showed a reduced cortical response to tools and animals when viewed inside the scanner, bilaterally in intraparietal and inferotemporal cortex. In contrast, the cortical preference for tools in the dorsal and ventral visual stream did not predict object recognition performance, and was organized in an adult-like manner at six. While cortical tool preference did not change with age, the findings suggest that animal-preferring regions in the ventral visual stream may develop later, concordant with previous reports of a protracted development in similar regions for faces. We thus conclude that intraparietal and inferotemporal cortical networks that support aspects of object processing irrespective of tool or animal category, continue to develop during the school-age years and contribute to the development of object recognition skills during this period

Looking and Thinking: The Relationship Between Attention Functioning and Executive Functioning in 2.5- and 3.5-year-olds

Attention is the initial step in a cascade of perception and action. Cognitive processing, and subsequent encoding and retrieval are dependent on the success of attentional engagement and efficiency. Attention can be described as the ability to maintain an alert state, orient to internal and external events, and self-regulate responses to those events. In infancy, attention develops from being primarily exogenously drawn to endogenously controlled. Executive attention develops in late infancy and on in to early childhood and is considered a higher level of attentional functioning that involves not only attending to objects but attending to specific features of objects. Although executive attention is thought to build upon basic attentional processing such as orienting, alerting, and shifting, the relationship between these attention functions is unclear. Further, the relationship between these attentional functions and those involved in common measures of executive functioning (e.g., a collection of cognitive processes that aid in goal directed behavior) is unclear. The current project aims to characterize the relationship between different aspects of attention during the toddler to early childhood years via multiple methods to examine these relationships between brain and behavior during a battery of attention and executive functioning tasks. Specifically, fNIRS is employed to examine connectivity of these three attentional networks at rest (e.g., resting state functional connectivity) and compare how connectivity between and within regions relates to event-related hemodynamics, functional connectivity, and eye-movement data in a battery of tasks. Further, behavioral data and risk survey criteria are used to probe both eye-movement and neural data as well as group children by performance and risk level to further probe the developmental profiles associated with various brain-behavioral relationships

The Developmental Trajectory of Contour Integration in Autism Spectrum Disorders

Sensory input is inherently ambiguous and complex, so perception is believed to be achieved by combining incoming sensory information with prior knowledge. One model envisions the grouping of sensory features (the local dimensions of stimuli) to be the outcome of a predictive process relying on prior experience (the global dimension of stimuli) to disambiguate possible configurations those elements could take. Contour integration, the linking of aligned but separate visual elements, is one example of perceptual grouping. Kanizsa-type illusory contour (IC) stimuli have been widely used to explore contour integration processing. Consisting of two conditions which differ only in the alignment of their inducing elements, one induces the experience of a shape apparently defined by a contour and the second does not. This contour has no counterpart in actual visual space – it is the visual system that fills-in the gap between inducing elements. A well-tested electrophysiological index associated with this process (the IC-effect) provided us with a metric of the visual system’s contribution to contour integration. Using visually evoked potentials (VEP), we began by probing the limits of this metric to three manipulations of contour parameters previously shown to impact subjective experience of illusion strength. Next we detailed the developmental trajectory of contour integration processes over childhood and adolescence. Finally, because persons with autism spectrum disorders (ASDs) have demonstrated an altered balance of global and local processing, we hypothesized that contour integration may be atypical. We compared typical development to development in persons with ASDs to reveal possible mechanisms underlying this processing difference. Our manipulations resulted in no differences in the strength of the IC-effect in adults or children in either group. However, timing of the IC-effect was delayed in two instances: 1) peak latency was delayed by increasing the extent of contour to be filled-in relative to overall IC size and 2) onset latency was delayed in participants with ASDs relative to their neurotypical counterparts

The temporal dynamics of size perception in adults and children

In a series of experiments, the influence of familiar object size on the speed of processing was investigated in adults and children, using a simple reaction time (RT) approach. In chapter 2, we demonstrated that children exhibited size-constancy-like responses starting from the age of five, although this conclusion was limited by task accuracy (experiment 1). The influence of symbolic and familiar size on simple RT was explored in 3 to 6-year-olds and adults (experiment 2). The task was conducted under reduced viewing conditions to enhance the contribution of familiar size as a visual cue. Although, we were unable to observe an effect of familiar or symbolic size on RT, we attributed this result to important methodological issues. In chapter 3, we report six experiments where we tested the influence of familiar size on simple RTs, measured under regular and reduced viewing conditions. The effect of animacy on RTs was also examined. We found that RTs were affected by familiar size in a manner that reflected the level of congruency between the physical size and the stored representation of size, such that congruent stimuli were responded to faster than incongruent stimuli. We also observed an animacy effect on RT: participants reacted faster to animals than non-animals. Finally, in chapter 4 we report an ERP study that investigated the electrophysiological correlates of familiar size. Results showed that the visual system processes familiar size around 100 ms after stimulus onset. Taken together, our findings demonstrate that familiar size is an automatic property of visual processing that can affect speeded motor responses. Future research could investigate the neural mechanisms underlying familiar object size and animacy, and specifically whether these mechanisms develop with age

How the brain grasps tools: fMRI & motion-capture investigations

Humans’ ability to learn about and use tools is considered a defining feature of our species, with most related neuroimaging investigations involving proxy 2D picture viewing tasks. Using a novel tool grasping paradigm across three experiments, participants grasped 3D-printed tools (e.g., a knife) in ways that were considered to be typical (i.e., by the handle) or atypical (i.e., by the blade) for subsequent use. As a control, participants also performed grasps in corresponding directions on a series of 3D-printed non-tool objects, matched for properties including elongation and object size. Project 1 paired a powerful fMRI block-design with visual localiser Region of Interest (ROI) and searchlight Multivoxel Pattern Analysis (MVPA) approaches. Most remarkably, ROI MVPA revealed that hand-selective, but not anatomically overlapping tool-selective, areas of the left Lateral Occipital Temporal Cortex and Intraparietal Sulcus represented the typicality of tool grasping. Searchlight MVPA found similar evidence within left anterior temporal cortex as well as right parietal and temporal areas. Project 2 measured hand kinematics using motion-capture during a highly similar procedure, finding hallmark grip scaling effects despite the unnatural task demands. Further, slower movements were observed when grasping tools, relative to non-tools, with grip scaling also being poorer for atypical tool, compared to non-tool, grasping. Project 3 used a slow-event related fMRI design to investigate whether representations of typicality were detectable during motor planning, but MVPA was largely unsuccessful, presumably due to a lack of statistical power. Taken together, the representations of typicality identified within areas of the ventral and dorsal, but not ventro-dorsal, pathways have implications for specific predictions made by leading theories about the neural regions supporting human tool-use, including dual visual stream theory and the two-action systems model

Brain Function in Early Childhood: Individual Differences in Age and Attentive Traits

Children, like adults, are unique individuals with complex interwoven relationships between brain function, behaviour, and phenotypic traits, which further interact with rapid developmental processes. A nuanced description of variability between children will add to our knowledge of how they think and behave, and potentially advance the development of personalized early interventions. With functional magnetic resonance imaging (fMRI), we have gained insight into brain responses – however, due to practical considerations, we have been unable to render a complete understanding of brain-behaviour relationships in young children. The use of naturalistic stimuli in fMRI studies has increased the ecological validity and the retention of developmental neuroimaging data. In this dissertation, I sought to explore the relationships between age, attentive traits, and inter-individual variability of brain function in young children in naturalistic paradigms. I conducted a scoping review to synthesize the current and historical task- and naturalistic-fMRI literature on the development of visual processing in the brain, through the lens of two influential theories: the interactive specialization and maturational frameworks. I found that while there is generally a consensus of progressive development of visual brain function throughout childhood, there is not enough evidence to fully support other aspects of these theories. I also conducted two experiments, using naturalistic fMRI and an analysis technique called inter-subject correlation (ISC), which quantifies the spatiotemporal similarity of brain activity between individuals, to explore how age and attentive traits affect inter-individual variability of brain function in children aged 4-8 years. I found that children’s brain responses to movies “homogenized” with increasing age in our sample, with greater variability seen in the younger children. Further, both inattention and hyperactivity were associated with ISC in the sample, though the relationships with these traits were different in widespread regions of the brain. Together, my research advances our understanding of functional brain responses in children and underscores the importance of an individual differences approach to developmental neuroimaging