Abstract

Mother child relationship is the first and the most important social relationship as it has implications on psychological and neural development of the individual. Here we investigated mother child relationship focusing on different aspects and using a combination of behavioural and neuroimaging techniques. In the first study we addressed the association between brain connectivity and interpersonal competences which are at the basis of every social interaction including the ones involved in mother-child relationship. Several studies suggests that higher White Matter (WM) integrity - an index of increased brain connectivity - , is associated with better cognition and behavioural performance. To test the hypothesis that higher WM integrity is associated with higher interpersonal competence we used Diffusion Tensor Imaging (DTI), a neuroimaging technique which allows to study in vivo the anatomy of boundless of axons conveying information in the brain. Then we correlated this information with a self-reported measure of interpersonal competences: the Adolescent Interpersonal Competence Questionnaire (AICQ). Results indicate that Interpersonal competence is associate with higher WM integrity in several major tracts of the right hemisphere, in specific the uncinate fasciculus, the cingulum, the forceps minor, the infero-fronto occipital fasciculus, the inferior longitudinal fasciculus, and the superior longitudinal fasciculus. These results provide the first direct analysis of the neuroanatomical basis of interpersonal competencies and young adult self-reported skills in social contexts. In the second work we used the same paradigm to test one of the main assumption of the attachment theory which states that social skills highly depends on the quality of attachment relationship. Results show higher integrity in four white matter association fibers in the left hemisphere: Uncinate Fasciculus, Cingulum, Superior Longitudinal Fasciculus and Inferior Fronto Occipital Fasciculus. This result supports the idea that the quality of the attachment relationship influences the emotional and social life of the individual from childhood to adulthood. Furthermore, the research represents an explorative approach to the study of mother-child relationship in healthy population, demonstrating the feasibility of using neuroimaging tools coupled with clinical investigations. Together those studies show that efficient structural connectivity is linked with secure attachment, improved social cognition and cognitive ability. Similarities and differences emerged in these studies will be discussed at the end of Chapter 3 in particular regarding left and right hemisphere specialization. In the second part of the thesis we switched the focus on parenting behaviour. Evidence from the literature suggest an association between Axonal Integrity measured with FA and functional connectivity measured with TMS in two region involved in preparing ad executing actions: premotor and motor cortex. Moreover neuroimaging reveals that infant cries activate parts of the premotor cortical system. In line with this evidence we linked parenting and brain functional connectivity conducting a study on motor cortex excitability in response of infant cries. We used event-related transcranial magnetic stimulation (TMS) to investigated the presence and the time course of modulation of motor cortex excitability in young adults who listened to infant cries. TMS was delivered from 0 to 250 ms from sound onset in six steps of 50 ms in 10 females and 10 males. Motor Evoked Potentials (MEPs) were recorded from the biceps brachii (BB) and interosseus dorsalis primus (ID1) muscles. Results indicate an excitatory modulation of MEPs at 100 ms from the onset of the infant cry specific to females and to the ID1 muscle. This modulation is considered as automatic response to natural cry as it was not present in response of control sounds and the effect is found at 100-ms latency which make this modulation not compatible with a voluntary reaction to the stimulus but suggests an automatic, bottom-up audiomotor association. These results indicate that the brains of adult females appear to be tuned to respond to infant cries with automatic motor excitation. This effect may reflect the greater and longstanding burden on females in caregiving infants. The second part of the thesis continue with a study addressing the natural condition in which baby cries arise when the parent is not attending for infant stimulation. In this study we investigated how infant crying, compared to control sounds, captures adults’ attentive resources. Participants were all nulliparous women and men, we investigated the effects of different sounds on cerebral activation of the default mode network (DMN) while listeners engaged in two different kind of tasks: one designed to activate the DMN ( self-referential decision task) and one designed to deactivate the DMN (syllabic counting tasks). We found a strong deactivation of DMN in woman during baby cry which suggest a shift of attention from self-referential thinking toward the baby cry stimuli. In men we found instead a weaker deactivation of DMN during woman cry while their attention was directed toward an external task and simultaneously a sudden woman crying arise. Gender differences found in our studies and in the literature will be discussed. In the third part of the thesis we investigated the ability to discriminate synchrony and asynchrony during interaction between mother and child with typical or atypical development. We tested two kind of population: in the first study we compared parents of children with Autism Spectrum Disorder (ASD) to parents of children with Typical Development (TD). In the second study we used the Autistic Quotient questionnaire to divide the sample in two groups according with their autistic traits. The relevance of this task is due to the extreme importance to promptly individuate cues of abnormal social behavior in those cases in which the child might shows deficit in the social development. We hypothesized that individual related with a child with ASD or an individual with high autistic traits, might show similar social difficulties as the individual with ASD finding more challenging to detect cue of appropriate or unappropriated social behavior. To test this hypothesis we asked parents of children with ASD and parents of children with TD to judge video of interactions between mothers and child with ASD and mothers and child with TD. Each video were 20s long and depicted either a synchrony or asynchrony interaction, as categorized by an expert clinician. Contrary to our initial hypothesis results indicate that parents of children with ASD are as accurate as parents of children with TD in discriminating synchrony and asynchrony interaction with ASD, however they are less accurate than parents of children with TD in judging interaction with TD. In the second study by testing individual with higher autistic traits (HAQ group) versus lower autistic traits (LAQ group) we confirmed this trend. Using the same paradigm we found that both groups were less accurate during asynchrony interaction. However HAQ was more accurate in judging synchrony interaction with ASD while LAQ was more accurate in judging synchrony interaction with TD. This result indicate a facilitation effects in understanding interaction which include people that share similar characteristic with the observer disconfirming the hypothesis that people with higher autistic traits would have more difficulties in understanding social interactions and pointing the attention on other factors which might contribute during this process. A discussion on the need of further investigation using neuroimaging techniques to understand similarities and differences on neural processing of social interactions is provided at the end of Chapter 4.