CROSS-MODAL NEUROPLASTICITY : Auditory spatial recalibration following visuo-motor adaptation

“I think I heard a child screaming in this room full of smoke! Or, maybe, could it be a piece of metal that fell on the ground? No, I heard it again. I am sure now. It is a child and it comes from 20 meters ahead, slightly on the left. Call for backup I will enter first!” Mapping the auditory space requires paying attention to several auditory cues as the ones illustrated in the example above: identity, location and direction of sounds. In the absence of visual information, it will be even more important to rely on these cues to be able to navigate properly. The visual input can be reduced following visual loss or decrease of conscious visual perception, a condition called unilateral spatial neglect; or in particular conditions such as in the example above, when firefighters have to rescue a child from a house full of smoke. When the visual input is reduced, the other sensory modalities will have to adjust their responses in order to maintain an adaptative behavior. The neuroplasticity induced by the modulation of a sensory modality on another sensory modality is referred as cross-modal plasticity. This thesis is composed of two major parts and includes five studies. The first part, involving two studies, is dedicated to the investigation of the neural substrates of sound lateralization and auditory neglect in patients with brain lesions. The second part, involving three studies, is dedicated to the investigation of cross-modal plasticity and focuses on prism adaptation. Two studies investigated auditory spatial deficits using an anatomo-clinical imaging approach on patients with a first unilateral stroke. Results showed that contralateral auditory extinction was associated with similar temporo-parieto-frontal regions on either hemisphere; that ipsilateral auditory extinction in patients with left hemispheric damage was associated with lesions involving intrahemispheric white matter connections; and that auditory sound segregation deficits linked to the inability to correctly use implicit spatial cues were predominantly induced by lesions including a large left temporo-parietal network. Three studies investigated the plasticity in sound localization induced by prism adaptation, a visuo-motor training used in the rehabilitation of neglect deficits. Two of them focused on the neural correlates modulated by prism adaptation during visual and auditory detection tasks. The last study investigated the effect of this adaptation on the alleviation of auditory spatial deficits occurring after a brain lesion. The results of these studies showed that the inferior parietal lobule is similarly modulated by the adaptation during a visual or auditory task, suggesting a supramodal role of this region. Moreover, the results of these studies allowed specifying for which patients this adaptation is efficient to alleviate auditory spatial deficits. Overall, these studies contributed to a better understanding of the nature of auditory spatial deficits in patients with brain damages. They showed the intrinsic ability of the healthy and damaged adult brain to adapt and improve. These findings illustrate how we can use the visual modality to help recover auditory spatial deficits. These results could potentially allow the development of new neurorehabilitation strategies. -- “Je crois que j’ai entendu un cri d’enfant provenant de cette pièce pleine de fumée! Ou bien était-ce un objet en métal tombé sur le sol? Non, je l’ai entendu à nouveau. J’en suis sûr maintenant. C’est un enfant et ça vient de 20 mètres devant, légèrement sur la gauche. Appelle du renfort, je rentre en premier. ” Pour se représenter l’espace auditif, il faut tenir compte de nombreux indices tels que ceux illustrés dans l’exemple précédent : l’identité d’un son, sa localisation dans l’espace et son mouvement. En l’absence d’information visuelle, ces indices sont encore plus importants pour pouvoir s’orienter correctement. L’information visuelle peut se retrouver réduite pour plusieurs raisons : suite à une perte de la capacité visuelle, suite à une diminution de la conscience de l’espace visuel liée à un syndrome que l’on nomme héminégligence, ou dans des conditions particulières comme celle de l’exemple cité au début : lorsque des sapeurs-pompiers doivent sauver un enfant pris au piège dans une maison pleine de fumée. Lorsque l’information visuelle est réduite, les autres modalités sensorielles doivent s’ajuster afin que l’individu puisse conserver un comportement adaptatif. Cette neuroplasticité induite par la modulation d’un sens en réponse à un autre sens, s’appelle plasticité cross-modale. Cette thèse s’articule autour de deux axes principaux et inclut cinq études. Le premier axe est dédié à l’étude des corrélats anatomiques des déficits spatiaux auditifs et comporte deux études focalisées sur les déficits spatiaux auditifs de patients cérébrolésés. Le deuxième axe est dédié à l’étude de la plasticité cross-modale et comporte trois études focalisant sur l’adaptation prismatique. Les deux premières recherches ont permis d’étudier les déficits spatiaux auditifs en utilisant une méthode d’analyse permettant les corrélations anatomo-cliniques. Les résultats ont démontré que l’extinction auditive contralatérale est provoquée par des lésions dans des régions temporo-fronto- pariétales similaires de chaque hémisphère ; que l’extinction auditive ipsilatérale à la suite de lésions impliquant l’hémisphère gauche pouvait être liée à des déconnections calleuses intra-hémisphériques ; et que les déficits de ségrégation liés à l’incapacité d’utiliser les indices spatiaux implicites étaient provoqués principalement par des lésions situées au sein d’un large réseau temporo-pariétal dans l’hémisphère gauche. Les trois études suivantes ont permis d’étudier la plasticité induite par l’adaptation prismatique, un protocole de réhabilitation utilisé pour diminuer les déficits spatiaux des patients héminégligents. Ces études ont permis de confirmer le rôle supramodal du lobule pariétal inférieur, qui est modulé de façon similaire par l’adaptation dans chacune des modalités sensorielles (vision, audition); et de préciser pour quels patients cette adaptation est utile pour diminuer les déficits spatiaux auditifs. En résumé, ces études ont contribué à une meilleure compréhension de la nature des déficits spatiaux auditifs que les patients peuvent présenter suite à une lésion cérébrale. Elles ont également permis de dévoiler la capacité du cerveau adulte sain ou cérébrolésé à s’adapter et ont aussi démontré que l’on peut utiliser la vision pour aider la réhabilitation des déficits spatiaux auditifs. Ces résultats pourraient potentiellement permettre le développement de nouvelles stratégies thérapeutiques en neuroréhabilitation

Sustained Attention and Intra-Individual Reaction Time Variability in 8 To 12 Years Old Children

The development of attention in children is a heterogeneous process. Some attentional capacities develop faster than others because they are dependant of the structural changes that occur during childhood. In this study we tested 156 children in order to determine the development of attention between eight and twelve years old. As this study took place in a primary school, we focused principally in sustained attention because it is a capacity that underlies every learning activity. Sustained attention is the ability to stay on task, which means the ability to consciously inhibit internal and external distracters in order to maintain a performance at the same level all along the task..

Media use, attention, mental health and academic performance among 8 to 12 year old children

The rise in digital media consumption, especially among children, raises the societal question of its impact on cognition, mental health and academic achievement. Here, we review the impact of three different ways of measuring technology use—total hours of media consumed, hours of video game play and number of media used concurrently—in a study surveying 156 eight-to-twelve year-old children. At stake is the question of whether different technology uses may have different effects, which could explain some of the past mixed findings. We collected data over three sessions relating to children’s media uses as well as (i) attentional and behavioral control abilities, (ii) psychological distress, psychosocial functioning, and sleep, and (iii) academic achievement and motivation. While attentional control abilities were assessed using both cognitive tests (D2, SART, BLAST) and questionnaires (mind-wandering; Connors), mental health and sleep were all questionnaire-based (K6, Strength and Difficulties Questionnaire-SDQ, Sleep Quality/Quantity). Finally, academic performance was based on self-reported grades, with motivational variables being measured through the grit and the growth-mindset questionnaires. We present partial correlation analyses and construct a psychological network to assess the structural associations between different forms of media consumption and the three categories of measures. Our results are in line with those observed with adults: children consume large amounts of media and media multitask substantially. Partial correlation analyses show that media multitasking specifically was mostly correlated with negative mental health, while playing video games was associated with faster responding and better mental health. No significant partial correlations were observed for total hours on media. Psychological network analysis complement these first results by indicating that all three ways of consuming technology are only indirectly related to self-reported grades. Thus, technology uses appear to only indirectly relate to academic performance, while more directly affecting mental health. This work emphasizes the need to differentiate among technology uses when considering their impact on human behavior, It also highlights the importance of characterizing the variety of technology uses that need to be considered, if one is to understand how every day digital consumption impacts human behavior

Media use, attention, mental health and academic performance among 8 to 12 year old children

The rise in digital media consumption, especially among children, raises the societal question of its impact on cognition, mental health and academic achievement. Here, we investigate three different ways of measuring technology use-—total hours of media consumed, hours of video game play and number of media used concurrently—-in 118 eight-to-twelve year-old children. At stake is the question of whether different technology uses have different effects, which could explain some of the past mixed findings. We collected data about children’s media uses as well as (i) attentional and behavioral control abilities, (ii) psychological distress, psychosocial functioning, and sleep, and (iii) academic achievement and motivation. While attentional control abilities were assessed using both cognitive tests and questionnaires, mental health and sleep were all questionnaire-based. Finally, academic performance was based on self-reported grades, with motivational variables being measured through the grit and the growth-mindset questionnaires. We present partial correlation analyses and construct a psychological network to assess the structural associations between different forms of media consumption and the three categories of measures. We observe that children consume large amounts of media and media multitask substantially. Partial correlation analyses show that media multitasking specifically was mostly correlated with negative mental health, while playing video games was associated with faster responding and better mental health. No significant partial correlations were observed for total hours on media. Psychological network analysis complement these first results by indicating that all three ways of consuming technology are only indirectly related to self-reported grades. Thus, technology uses appear to only indirectly relate to academic performance, while more directly affecting mental health. This work emphasizes the need to differentiate among technology uses if one is to understand how every day digital consumption impacts human behavior