Phd in PSYCHOLOGY AND COGNITIVE SCIENCE

Thesis title: Caratteristiche di sonno misurate con strumenti obiettivi nei bambini e adolescenti con autismo

Sleep problems are frequently reported in children and adolescents with autism spectrum disorder (ASD). The available literature, based mostly on subjective measures, suggests that insomnia symptoms may be common in this clinical population, affecting daytime functioning. In contrast, studies using objective sleep measures, such as actigraphy and polysomnography, are scarce and describe a highly heterogeneous picture. The electrophysiology of sleep received scant attention. In fact, to date, the topographical distributions of electroencephalographic (EEG) activity across the entire sleep period remain completely unexplored. The few available empirical findings focused on EEG oscillations specific to NREM (Non-Rapid Eye Movement) sleep, such as Slow Wave Activity (SWA) and sleep spindles, suggesting an atypical expression in ASD. Considering the fragmentary nature of the existing evidence, this thesis aimed to investigate sleep patterns in ASD using primarily objective measures of sleep. The first study aimed to compare sleep patterns assessed by subjective (i.e., sleep diaries) and objective (i.e., actigraphy) measures between children and adolescents with ASD (N=36) and those with typical development (N=24), and to examine their relationship with demographic, clinical, and cognitive characteristics within the ASD group. Participants wore an actigraph on their wrist for one week, and each morning, within 15 minutes of awakening, caregivers filled in a sleep diary. The main finding pointed to a higher frequency of sleep-related difficulties reported by caregivers in the clinical sample, while no difference was found between the two groups in the actigraphic sleep measures. Within the ASD sample, younger age was related with poorer sleep quality, as assessed by actigraphy and sleep diaries. Comparisons between children with ASD with average and below-average intelligent quotients showed more pronounced sleep problems in the latter, as detected by both sleep diaries and, to a lesser extent, by actigraphy. The results suggest a possible tendency for caregivers to overestimate sleep difficulties in children with ASD. Among the variables examined, only age seemed to influence sleep quality as assessed by objective and subjective measures. In fact, children diagnosed with ASD at an earlier age tend to exhibit more severe clinical profiles that seem to include greater sleep problems. Similarly, in children and adolescents with ASD and lower cognitive functioning, symptoms are generally more severe, and sleep difficulties may also be more pronounced. However, the small effects observed in the actigraphic measures suggest that this aspect requires further investigation. The second study employed polysomnography, the gold standard for objective sleep assessment, with the primary aim of comparing the macrostructural patterns and the EEG topographies of a full night’s sleep between children and adolescents with Asperger’s Syndrome (AS) (N=8) and a control group (N=16), who underwent overnight polysomnographic recording with a 19-channel EEG montage. The secondary aim of the study was to investigate, in a fully exploratory manner, the nature of potential alterations in delta or sigma EEG activity in which the typical oscillations of NREM sleep (i.e., SWA and sleep spindles) are expressed. Topographic analyses showed a more pronounced frontal SWA pattern in the AS group, particularly during stage N3. Considering that SWA, especially during childhood, reflects cortical maturation processes, assuming higher intensities during infancy, it was hypothesized that the enhanced expression of slow-frequency activity in the clinical sample may reflect a delayed maturation of the frontal areas. The results for stage N3 appeared to support this hypothesis, showing that, in individuals with AS, the SWA profile was similar to that observed in younger controls. Furthermore, in the clinical sample, SWA was predominantly expressed at slow frequencies around 1 Hz, and slow waves were more numerous, larger and steeper. Further analyses excluded a contribution from altered homeostatic regulation, suggesting that the observed SWA pattern in AS may represent a stable feature throughout the night. This study represents an initial attempt to achieve an in-depth understanding of the electrophysiology of sleep in ASD. The results suggest that SWA expression in AS may be more comparable to that of younger ages, probably reflecting atypical and potentially delayed maturation of frontal regions. Overall, the two studies did not reveal objective alterations in sleep macrostructure indicative of reduced sleep quality in ASD, in contrast to findings from the literature based on subjective measures. Instead, the results of the second study point to a possible involvement of atypical EEG patterns related to neurodevelopment in ASD.