Visual illusions: An interesting tool to investigate developmental dyslexia and autism spectrum disorder

A visual illusion refers to a percept that is different in some aspect from the physical stimulus. Illusions are a powerful non-invasive tool for understanding the neurobiology of vision, telling us, indirectly, how the brain processes visual stimuli. There are some neurodevelopmental disorders characterized by visual deficits. Surprisingly, just a few studies investigated illusory perception in clinical populations. Our aim is to review the literature supporting a possible role for visual illusions in helping us understand the visual deficits in developmental dyslexia and autism spectrum disorder. Future studies could develop new tools – based on visual illusions – to identify an early risk for neurodevelopmental disorders

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Disruption to control network function correlates with altered dynamic connectivity in the wider autism spectrum.

Autism is a common developmental condition with a wide, variable range of co-occurring neuropsychiatric symptoms. Contrasting with most extant studies, we explored whole-brain functional organization at multiple levels simultaneously in a large subject group reflecting autism's clinical diversity, and present the first network-based analysis of transient brain states, or dynamic connectivity, in autism. Disruption to inter-network and inter-system connectivity, rather than within individual networks, predominated. We identified coupling disruption in the anterior-posterior default mode axis, and among specific control networks specialized for task start cues and the maintenance of domain-independent task positive status, specifically between the right fronto-parietal and cingulo-opercular networks and default mode network subsystems. These appear to propagate downstream in autism, with significantly dampened subject oscillations between brain states, and dynamic connectivity configuration differences. Our account proposes specific motifs that may provide candidates for neuroimaging biomarkers within heterogeneous clinical populations in this diverse condition

Age-related changes in global motion coherence: conflicting haemodynamic and perceptual responses

Our aim was to use both behavioural and neuroimaging data to identify indicators of perceptual decline in motion processing. We employed a global motion coherence task and functional Near Infrared Spectroscopy (fNIRS). Healthy adults (n = 72, 18-85) were recruited into the following groups: young (n = 28, mean age = 28), middle-aged (n = 22, mean age = 50), and older adults (n = 23, mean age = 70). Participants were assessed on their motion coherence thresholds at 3 different speeds using a psychophysical design. As expected, we report age group differences in motion processing as demonstrated by higher motion coherence thresholds in older adults. Crucially, we add correlational data showing that global motion perception declines linearly as a function of age. The associated fNIRS recordings provide a clear physiological correlate of global motion perception. The crux of this study lies in the robust linear correlation between age and haemodynamic response for both measures of oxygenation. We hypothesise that there is an increase in neural recruitment, necessitating an increase in metabolic need and blood flow, which presents as a higher oxygenated haemoglobin response. We report age-related changes in motion perception with poorer behavioural performance (high motion coherence thresholds) associated with an increased haemodynamic response

Reduced 2D form coherence and 3D structure from motion sensitivity in developmental dyscalculia

Developmental dyscalculia (DD) is a specific learning disability affecting the development of numerical and arithmetical skills. The origin of DD is typically attributed to the suboptimal functioning of key regions within the dorsal visual stream (parietal cortex) which support numerical cognition. While DD individuals are often impaired in visual numerosity perception, the extent to which they also show a wider range of visual dysfunctions is poorly documented. In the current study we measured sensitivity to global motion (translational and flow), 2D static form (Glass patterns) and 3D structure from motion in adults with DD and control subjects. While sensitivity to global motion was comparable across groups, thresholds for static form and structure from motion were higher in the DD compared to the control group, irrespective of associated reading impairments. Glass pattern sensitivity predicted numerical abilities, and this relation could not be explained by recently reported differences in visual crowding. Since global form sensitivity has often been considered an index of ventral stream function, our findings could indicate a cortical dysfunction extending beyond the dorsal visual stream. Alternatively, they would fit with a role of parietal cortex in form perception under challenging conditions requiring multiple element integration

A percepção da configuração do movimento biológico em bebés

Tese de doutoramento em Psicologia BásicaPara compreender os outros, interpretar as suas ações, emoções ou intenções, é necessário aprender a descodificar o movimento dos nossos parceiros sociais. Para isso, primeiro, precisamos de ser capazes de orientar a nossa atenção para o movimento das outras pessoas; em seguida, necessitámos de integrar o movimento das diferentes partes do corpo (por exemplo, dos membros) na configuração coerente e global de um corpo humano em movimento—a isto designamos de processamento configural; só então é que finalmente somos capazes de interpretar o objetivo e o significado de uma ação. O processamento configural do movimento biológico é um processo básico, mas altamente relevante na interpretação do significado de uma ação e, consequentemente, crucial para a interação social e para a cognição social humana. A investigação acerca do desenvolvimento da percepção do movimento biológico indica que o processamento configural surge durante o primeiro ano de vida (Bertenthal, 1993), associado à maturação cortical dos bebés e ao seu desenvolvimento sociocognitivo (Pavlova, 2012). A presente dissertação pretende investigar o desenvolvimento do processamento configural na percepção do movimento biológico durante a primeira metade do primeiro ano de vida dos bebés. Para isso, combinamos duas técnicas de investigação da Psicologia do Desenvolvimento, distintas mas complementares: o functional near-infrared spectroscopy (fNIRS) e o procedimento de atenção preferencial (preferential looking). Nesta dissertação são então apresentados os resultados de quatro estudos experimentais, dois de fNIRS e dois comportamentais, realizados em bebés com idades compreendidas entre os três e os sete meses de idade. No Capítulo 1 é apresentada uma extensa revisão da literatura sobre o papel do processamento configural na percepção do movimento biológico, ou seja, sobre como esta competência perceptual é relevante para a cognição-social humana e, em particular, para o desenvolvimento sociocognitivo dos bebés. No Capítulo 2 e 3 são apresentados e discutidos dois estudos de fNIRS realizados com bebés de sete meses. Estes foram os primeiros estudos realizados na infância, que mediram a resposta hemodinâmica do cérebro ao movimento humano utilizando displays de pontos de luz (point-light walkers) como estímulos. Estes estudos visaram investigar se a percepção do movimento biológico é sustentada, na infância tal como nos adultos, pelo funcionamento do sulco temporal superior direito (STS direito). O STS é uma área central do córtex humano para o processamento de estímulos sociais, e o processamento da configuração do movimento biológico parece também ocorrer neste local em adultos (Deen, Koldewyn, Kanwisher, & Saxe, 2015). No Capítulo 4, são apresentados dois estudos de atenção preferencial, um longitudinal e outro transversal. Os dois estudos pretendem perceber quando é que os bebés preferem uma configuração coerente do movimento humano. Especificamente, procuram descobrir quando, na infância, surge uma preferência pela configuração coerente e global humana de uma pessoa a andar em relação a um estímulo cujas posições dos pontos de luz foram randomizadas. Bebés de três e cinco meses foram testados num estudo transversal, e bebés de três, cinco e sete meses de idade, longitudinalmente. Finalmente, no Capítulo 5, discutimos e concluímos acerca as implicações das nossas descobertas. Encontramos importantes mudanças de desenvolvimento na percepção da configuração do movimento biológico durante os primeiros meses de vida—os nossos resultados contribuem para uma compreensão mais completa da percepção do movimento biológico em bebés e das origens e desenvolvimento da cognição social humana.To understand others, interpret their actions, emotions or intentions, we have to learn how to decode human motion. For that, first, we need to start by paying attention to the motion of others; afterward, we have to be able to integrate the individual and local motion of moving body parts (such as limbs) into the coherent and motion configuration of a whole human body acting—this is called configural processing; only then we are finally able to predict, interpret, and understand the goal and meaning of an action. Configural processing is a basic but highly relevant process in biological motion perception with implications on action understanding, social interaction and in human social cognition. Developmental research on biological motion perception indicates that configural processing emerges during our first year of life (Bertenthal, 1993), associated to important cortical specializations, and to infants’ social-cognitive development (Pavlova, 2012). The present dissertation investigated the development of configural processing in biological motion during the first half of infants’ first year of life. For that, two distinct but complementary techniques from developmental research were combined: functional near-infrared spectroscopy (fNIRS) and the preferential looking procedure. This dissertation presents and discusses the outcomes of two neuroimaging and two behavioral experiments conducted with infants, aged from three to seven months of age, on the perception of biological motion configuration. Chapter 1 begins with an extensive literature revision on the role of configural processing in biological motion perception, namely, on how this basic perceptual skill is relevant for human social abilities and, in particular, for infants’ social-cognitive development. In Chapter 2 and 3, two fNIRS experiments conducted with seven months old infants are presented and discussed. These were the first fNIRS studies conducted in infancy, using point-light walkers as stimuli. They intended to investigate whether the perception of biological motion is underpinned, in infants as in adults, by the right superior temporal sulcus (right STS) functioning. The right STS is a cornerstone for human social-cognition, and biological motion configural processing occurs in this site in the adults brain (Deen, Koldewyn, Kanwisher, & Saxe, 2015). In Chapter 4, two preferential looking experiments, one longitudinal and another cross sectional, are presented. These two studies intended to find when, in infancy, emerges a preference for biological motion configuration. Specifically, when, in infants aged three to seven months, emerges a preference for the coherent motion configuration of a person walking in relation to scrambled display. Finally, in Chapter 5, we discuss and conclude about the implications of our findings. We found important developmental changes in the perception of biological motion configuration during the first few months of life—our results contribute to a broader understanding of biological motion perception in infancy thus to the origins of human social-cognition.The Portuguese Science Foundation through an individual doctoral grant attributed to Isabel C. Lisboa (PD/BD/105966/2014) supported this research. This grant was supported by Fundo Social Europeu and by national founds from MEC