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Peripersonal space representation in the first year of life: a behavioural and electroencephalographic investigation of the perception of unimodal and multimodal events taking place in the space surrounding the body
Full text linkIn my PhD research project, I wanted to investigate infants’ representation of the peripersonal space, which is the portion of environment between the self and the others. In the last three decades research provided evidence on newborns’ and infants’ perception of their own bodies and of other individuals, whereas not many studies investigated infants’ perception of the portion of space where they can interact with both others and objects, namely the peripersonal space. Considering the importance of the peripersonal space, especially in light of its defensive and interactive functions, I decided to investigate the development of its representation focusing on two aspects. On one side, I wanted to study how newborns and infants processed the space around them, if they differentiated between near and far space, possibly perceiving and integrating depth cues across sensory modalities and when and how they started to respond to different movements occurring in the space surrounding their bodies. On the other side, I was interested in understanding whether already at birth the peripersonal space could be considered as a delimited portion of space with special characteristics and, relatedly, if its boundaries could be determined. In order to respond to my first question, I investigated newborns’ and infants’ looking behaviour in response to visual and audio-visual stimuli depicting different trajectories taking place in the space immediately surrounding their body. Taken together, the results of these studies demonstrated that humans show, since the earliest stages of their development, a rudimentary processing of the space surrounding them. Newborns seemed, in fact, to already differentiate the space around them, through an efficient discrimination of different moving trajectories and a visual preference for those directed towards their own body, possibly due to their higher adaptive relevance. They also seemed to integrate multimodal, audio-visual information about stimuli moving in the near space, showing a facilitated processing of congruent audio-visual approaching stimuli. Furthermore, the results of these studies could help understand the development of the integration of multimodal stimuli with an adaptive valence during infancy. When newborns’ and infants were presented with unimodal, visual stimuli, they all directed their visual preferences to the stimuli moving towards their bodies. Conversely, their pattern of looking times was more complex when they were presented with congruent and incongruent audiovisual stimuli. Right after birth infants showed a spontaneous visual preference for congruent audio-visual stimuli, which was challenged by a similarly strong visual preference for adaptively important visual stimuli moving towards their bodies. The looking behaviours of 5-month-old infants, instead, seemed to be driven only by a spontaneous preference for multimodal congruent stimuli, i.e. depicting motion along the same trajectory, irrespective of the adaptive value of the information conveyed by either of the two sensory components of the stimulus. Nine-month-old infants, finally, seemed to flexibly integrate multisensory integration principles with the necessity of directing their attention to ethologically salient stimuli, as shown by the fact that their visual preference for unexpected, incongruent audio-visual stimuli was challenged by the simultaneous presence of adaptively relevant stimuli. Similarly to what happened with newborns, presenting 9-month-old infants with the two categories of preferred stimuli simultaneously led to the absence of a visual preference. Within my project I also investigated the electroencephalographic correlates of the processing of unimodal, visual and auditory, stimuli depicting different trajectories in a sample of 5-month-old infants. The results seemed to provide evidence in support of the role of the primary sensory cortices in the processing of crossmodal stimuli. Furthermore, they seemed to support the possibility that infants’ brain could allocate, already during the earliest stages of processing, different amounts of attention to stimuli with different adaptive valence. Two further studies addressed my second question, namely whether already at birth the peripersonal space could be considered as a delimited portion of space with special characteristics and if its boundaries could be determined. In these studies I measured newborns’ saccadic reaction times (RTs) to tactile stimuli presented simultaneously to a sound perceived at different distances from their body. The results showed that newborns’ RTs were modulated by the perceived position of the sound and that their modulation was very similar to that shown by adults, suggesting that the boundary of newborns’ peripersonal space could be identified in the perceived sound position in whose correspondence the drop of RTs happened. This suggested that at birth the space immediately surrounding the body seems to be already invested of a special salience and characterised by a more efficient integration of multimodal stimuli. As a consequence, it might be considered as a rudimentary representation of the peripersonal space, possibly serving, as a working space representation, early interactions between newly born humans and their environment. Overall, these findings provide a first understanding of how humans start to process the space surrounding them, which, importantly, is the space linking them with others and the space where their first interactions will take place
Multisensory perception of looming and receding objects in human newborns
Full text linkWhen newborns leave the enclosed spatial environment of the uterus and arrive in the outside world, they are faced with a new audiovisual environment of dynamic objects, actions and events both close to themselves and further away. One particular challenge concerns matching and making sense of the visual and auditory cues specifying object motion [1-5]. Previous research shows that adults prioritise the integration of auditory and visual information indicating looming (for example [2]) and that rhesus monkeys can integrate multisensory looming, but not receding, audiovisual stimuli [4]. Despite the clear adaptive value of correctly perceiving motion towards or away from the self - for defence against and physical interaction with moving objects - such a perceptual ability would clearly be undermined if newborns were unable to correctly match the auditory and visual cues to such motion. This multisensory perceptual skill has scarcely been studied in human ontogeny. Here we report that newborns only a few hours old are sensitive to matches between changes in visual size and in auditory intensity. This early multisensory competence demonstrates that, rather than being entirely naïve to their new audiovisual environment, newborns can make sense of the multisensory cue combinations specifying motion with respect to themselves
Identifying peripersonal space boundaries in newborns
Full text linkPeripersonal space immediately surrounds the body and can be represented in the brain as a multisensory and sensorimotor interface mediating physical and social interactions between body and environment. Very little consideration has been given to the ontogeny of peripersonal spatial representations in early postnatal life, despite the crucial roles of peripersonal space and its adaptive relevance as the space where infants’ earliest interactions take place. Here, we investigated whether peripersonal space could be considered a delimited portion of space with defined boundaries soon after birth. Our findings showed for the first time that newborns’ saccadic reaction times to a tactile stimulus simultaneous to sounds with different intensities changed based on the sound intensity. In particular, they were significantly faster when the sound was lounder than a critical intensity, in a pattern that closely resembled that showed by adults. Therefore, provided that sound intensity on its own can cue newborns’ sound distance perception, we speculate that this critical distance could be considered the boundary of newborns’ rudimentary peripersonal space. Altogether, our findings suggest that soon after birth peripersonal space may be already considered as a bounded portion of space, perhaps instrumental to drive newborns’ attention towards events and people within it
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Newborns Are Sensitive to Impending Collision Within Their Peripersonal Space.
Full text linkImmediately after birth, newborns are introduced within a highly stimulating environment, where many objects move close to them. It would therefore be adaptive for infants to pay more attention to objects that move towards them - on a colliding pathway - and could therefore come into contact and interact with them. The present study aimed at understanding if newborns are able to discriminate between colliding vs. noncolliding trajectories. To address this issue, we measured the looking behaviour of newborns who were presented with videos of different pairings of three events: approaching objects along a colliding course, approaching objects along a non-colliding trajectory, and receding objects. Results outlined that newborns preferred looking at the approaching and colliding movement than at both the receding and the approaching but non-colliding movements. Data also suggest the possible occurrence of a configural effect when two colliding events are displayed simultaneously. Furthermore newborns appeared to look longer at movements directed towards the Peripersonal Space than at those directed away from it
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