Attention-deficit / hyperactivity disorder (ADHD) is a neurobehavioral disorder characterized by attention deficit, hyperactivity, and impulsivity. Currently, the diagnosis of ADHD is based on standard questionnaires such as DSM-IV and DSM-V. These are structured interviews, administrated to parents and teachers, to evaluate the presence and the severity level of the symptoms in different social fields. However, this indirect and subjective methodology should be supported by more objective measures based on instrumental clinical analyses. \par In the past, the EEG was used to extract and evaluate the ratio between the powers in the theta and beta bands (theta/beta ratio). This ratio was defined by the FDA (Food and Drug Administration) as a diagnostic measure for ADHD. In the last 5 years, this ratio has been declared not diagnostic, due to the high number of studies that did not confirm its specificity values in ADHD. The fundamental problem in diagnosing ADHD is the lack of any physiological or biological marker of the disease. \par In recent years, ADHD has also been related to various sleep problems and their coexistence intensifies the pre-existing symptomatology. Although the association between sleep disorders and ADHD is well known, the correlation with more specific aspects related to the microstructure of sleep and with possible modifications of brain functioning during sleep has not been completely understood. \par One of the aspects of sleep microstructure that has seen a growing interest in neurological disorders research and other diseases research are sleep spindles. Their variations and disruptions have been associated with cognitive faculties and intelligence, with various disease conditions (eg Schizophrenia, mental retardation, abnormal maturation), with post-stroke recovery processes, and they seem to be involved in sleep-dependent memory consolidation. In addition to the interest in sleep spindles, there is also an increase in studies related to dynamic changes in brain activity during sleep. \par The oscillatory activity of the brain, in terms of EEG power and analysis of connectivity, has been poorly studied in ADHD, as well as the temporal variations before, during and after the spindle event have not yet been investigated. Therefore, this doctoral thesis studies EEG activity, through spectral analysis and parameters related to graph theory, in order to provide more detailed information about brain functioning during sleep in ADHD and to evaluate the possibility of using these features as new biomarkers. \par The novelty described in this thesis consists in the analysis of different time periods, chosen after the power spectra analysis of the EEG signal, in order to evaluate temporal and dynamic changes of spindles activity. Spectral and connectivity analysis showed differences between the spindle and the other two epochs, before and after spindle onset respectively, in both groups in almost all parameters. Furthermore, the comparison between the two groups showed that the differences were concentrated in the left hemisphere. Last but not least, the results raise attention to the gamma band and confirm the increasingly growing literature concerning this band, thus underlining how the activities in this frequency range have a cognitive meaning able to describe and differentiate some neuropsychiatric disorders.
Il disturbo da deficit di attenzione/iperattività (ADHD), è un disturbo neurocomportamentale caratterizzato da deficit di attenzione, iperattività e impulsività. Attualmente, la diagnosi di ADHD si basa su questionari standard come DSM-IV e DSM-V. Si tratta di interviste strutturate, compilate da genitori e insegnanti, per valutare la presenza e il livello di gravità delle sintomatologie in diversi ambiti sociali. Tuttavia, questa metodologia indiretta e soggettiva dovrebbe essere supportata da misure più obiettive basate sull'analisi clinica strumentale. In passato, l'EEG è stato utilizzato per estrarre e valutare il rapporto tra le potenze nelle bande theta e beta (theta/beta ratio). Tale rapporto era stato definito dalla FDA (Food and Drug Administration) come misura diagnostica per l'ADHD. Negli ultimi 5 anni, a causa dell'elevato numero di studi che non hanno confermato i valori di specificità di questo rapporto nell'ADHD, esso è stato dichiarato non utilizzabile ai fini diagnostici. Il problema fondamentale nella diagnosi dell'ADHD è la mancanza di un qualsiasi marker fisiologico o biologico della malattia. \par Negli ultimi anni, l'ADHD è stato anche correlato con vari problemi del sonno e la copresenza di questi ultimi intensifica la sintomatologia preesistente. Sebbene l'associazione tra disturbi del sonno e ADHD sia ben nota, la correlazione con aspetti più specifici legati alla microstruttura del sonno e con eventuali modificazioni del funzionamento cerebrale, durante il sonno, non è stata ancora completamente compresa. \par Uno degli aspetti della microstruttura del sonno che ha visto un crescente interesse nell'ambito della ricerca sui disturbi neurologici e altre patologie sono i fusi del sonno. Le loro variazioni e anomalie sono state associate alle facoltà cognitive e all'intelligenza, a varie condizioni di malattia (ad es. Schizofrenia, ritardo mentale, anormale maturazione), a processi di recupero post-ictus, nonché si credono essere coinvolti nel consolidamento della memoria durante il sonno. In aggiunta all'interesse per i fusi del sonno, vi è anche un aumento degli studi relativi alle modifiche dinamiche delle attività del cervello nel sonno. \par L'attività oscillatoria del cervello, in termini di potenza dell'EEG e dell'analisi della connettività, è stata poco studiata nell'ADHD, così come anche le variazioni temporali prima, durante e dopo l'evento del fuso non sono ancora state indagate. Questa tesi studia l'attività EEG attraverso l'analisi spettrale e attraverso parametri legati alla teoria dei grafi, al fine di fornire informazioni più dettagliate sul funzionamento del cervello durante il sonno nell'ADHD ed eventualmente valutare la possibilità di utilizzare queste caratteristiche come nuovi biomarcatori. \par La novità descritta consiste nell'analisi di diverse epoche temporali, scelte dagli spettri di potenza del segnale EEG. L'analisi spettrale e della connettività hanno evidenziato differenze tra il fuso e le altre due epoche, rispettivamente prima e dopo il fuso, in entrambi i gruppi analizzati (ADHD e soggetti sani) in quasi tutti i parametri. Inoltre, il confronto tra i due gruppi ha mostrato che le differenze erano concentrate nell'emisfero sinistro. Ultimo ma non meno importante, i risultati portano l'attenzione sulla banda gamma e confermano la sempre più crescente letteratura, riguardante questa banda. Ciò, sottolinea come le attività presenti in questa gamma abbiano un significato cognitivo in grado di descrivere e differenziare alcuni disturbi neuropsichiatrici.
Connectivity and frequency analyses of sleep EEG in ADHD and healthy children / DE DEA, Federica. - (2019 Mar 29).
Connectivity and frequency analyses of sleep EEG in ADHD and healthy children
DE DEA, FEDERICA
2019-03-29
Abstract
Attention-deficit / hyperactivity disorder (ADHD) is a neurobehavioral disorder characterized by attention deficit, hyperactivity, and impulsivity. Currently, the diagnosis of ADHD is based on standard questionnaires such as DSM-IV and DSM-V. These are structured interviews, administrated to parents and teachers, to evaluate the presence and the severity level of the symptoms in different social fields. However, this indirect and subjective methodology should be supported by more objective measures based on instrumental clinical analyses. \par In the past, the EEG was used to extract and evaluate the ratio between the powers in the theta and beta bands (theta/beta ratio). This ratio was defined by the FDA (Food and Drug Administration) as a diagnostic measure for ADHD. In the last 5 years, this ratio has been declared not diagnostic, due to the high number of studies that did not confirm its specificity values in ADHD. The fundamental problem in diagnosing ADHD is the lack of any physiological or biological marker of the disease. \par In recent years, ADHD has also been related to various sleep problems and their coexistence intensifies the pre-existing symptomatology. Although the association between sleep disorders and ADHD is well known, the correlation with more specific aspects related to the microstructure of sleep and with possible modifications of brain functioning during sleep has not been completely understood. \par One of the aspects of sleep microstructure that has seen a growing interest in neurological disorders research and other diseases research are sleep spindles. Their variations and disruptions have been associated with cognitive faculties and intelligence, with various disease conditions (eg Schizophrenia, mental retardation, abnormal maturation), with post-stroke recovery processes, and they seem to be involved in sleep-dependent memory consolidation. In addition to the interest in sleep spindles, there is also an increase in studies related to dynamic changes in brain activity during sleep. \par The oscillatory activity of the brain, in terms of EEG power and analysis of connectivity, has been poorly studied in ADHD, as well as the temporal variations before, during and after the spindle event have not yet been investigated. Therefore, this doctoral thesis studies EEG activity, through spectral analysis and parameters related to graph theory, in order to provide more detailed information about brain functioning during sleep in ADHD and to evaluate the possibility of using these features as new biomarkers. \par The novelty described in this thesis consists in the analysis of different time periods, chosen after the power spectra analysis of the EEG signal, in order to evaluate temporal and dynamic changes of spindles activity. Spectral and connectivity analysis showed differences between the spindle and the other two epochs, before and after spindle onset respectively, in both groups in almost all parameters. Furthermore, the comparison between the two groups showed that the differences were concentrated in the left hemisphere. Last but not least, the results raise attention to the gamma band and confirm the increasingly growing literature concerning this band, thus underlining how the activities in this frequency range have a cognitive meaning able to describe and differentiate some neuropsychiatric disorders.File | Dimensione | Formato | |
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