ADHD is a heterogenous disorder encompassing neurodevelopmental deficits in cognitive control. Auditory distraction is a common clinically reported symptom in ADHD, yet empirical research investigating the manifestation of auditory distraction in the disorder is remarkably scarce. Findings from cognitive hearing science highlight the crucial role cognitive control plays in an individual’s ability to gate, attenuate and/or compensate for auditory distraction. However the field is yet to extensively test hypotheses in normal hearing populations with neurodevelopmental deficits in cognitive control such as ADHD. This thesis contributes to narrowing the gap within these two fields of research by studying auditory distraction in this clinical population to a greater extent than previous reports in the literature.

Using a combination of both behavioural and neuroimaging methods, the research presented here was able to show that adults and adolescents with ADHD are inherently more susceptible to auditory distraction than their non-ADHD counterparts. At the behavioural level, impaired task performance due to auditory distraction was more likely to manifest in ADHD participants when the working memory system was under high processing load. At the neural level, functional aberrancy in auditory attention was evident at early stages of sensory processing in a variety of tasks, implicating both exogenous and endogenous control systems in ADHD. Furthermore, the distribution of ADHD-symptom severity across participants was shown to correlate with increases in both cortical activity to auditory distractors and intrinsic functional connectivity between auditory and exogenous attention networks.

In line with evidence from cognitive hearing science, the general findings of this thesis demonstrate that cognitive control plays an important role in the ability to perceive sound under suboptimal listening conditions and hamper distraction. In addition, findings challenge theories of ADHD that question the extent in which sensory-related attentional control is impaired. More empirical research on the auditory modality in ADHD is therefore encouraged in order to revise models, improve diagnostic tools, and develop evidence-based interventions targeting study/work environments.

Adhd är en heterogen neuropsykiatrisk funktionsnedsättning som kännetecknas av nedsatt kognitiv kontroll. Ett vanligt förekommande symptom vid adhd är ljudöverkänslighet, vilket innebär en ökad känslighet för distraherande ljud, men empirisk forskning kring ljudkänslighetens roll i adhd är anmärkningsvärt knapphändig. Forskning från kognitiv hörselvetenskap belyser den viktiga roll kognitiv kontroll spelar i en individs förmåga att filtrera, dämpa och/eller kompensera för ljudöverkänslighet hos personer med hörselnedsättningar. Emellertid saknas det forskning kring hur detta fungerar hos normalhörande personer med nedsättningar i kognitiv kontroll till följd av neuropsykiatriska funktionsnedsättningar så som adhd. Målet med denna avhandling är att bidra till att minska kunskapsklyftan inom dessa två forskningsområden genom att studera känsligheten för distraherande ljud i denna kliniska population.

Genom att kombinera beteende- och hjärnavbildningsmetoder framkom att vuxna och ungdomar med adhd-diagnos påverkas mer av distraherande ljud än personer utan adhd. På beteendenivån uppvisade adhd-deltagare svårigheter med distraherande ljud främst när arbetsminnessystemet var under hög belastning. På neural nivå framkom funktionella avvikelser under tidig auditiv bearbetning för en mängd olika uppgifter. Detta tyder på störningar i både exogena och endogena kontrollsystem i adhd. Det fanns också samband mellan adhd-symptomens svårighetsgrad och neurala förändringar, där ökande mängd symptom hängde samman med såväl ökad kortikal aktivitet som svar på distraherande ljud som ökade neurala kopplingar mellan auditiva områden och exogena uppmärksamhetsnätverk.

I linje med teorier från kognitiv hörselvetenskap visar fynden i den här avhandlingen att kognitiv kontroll spelar en viktig roll i förmågan att uppfatta ljud under suboptimala lyssningsförhållanden samt att hantera distraherande ljud. Dessutom utmanar resultaten teorier som ifrågasätter huruvida sensorisk uppmärksamhetskontroll är nedsatt i adhd. Mer empirisk forskning om den auditiva domänens roll i adhd behövs för att revidera modeller, förbättra diagnostiska verktyg och utveckla evidensbaserade interventioner inriktade på studie- och arbetsmiljöer.

Speech perception in noise is dependent on stimulus-driven and knowledge-driven processes. Here we investigate the neural correlates and time course of discrepancies between incoming auditory information (i.e. stimulus-driven processing) and linguistic expectations (knowledge-driven processing) by including 20 normal hearing adults in a MEG study. Participants read 48 rhyming sentence pairs beforehand. In the scanner, they listened to sentences that corresponded exactly to the read sentences except that the last word (presented after 1600 millisecond delay and with 50% intelligibility) was only correct in half of the cases. Otherwise, it was 1) phonologically but not semantically related, 2) semantically but not phonologically related, or 3) neither phonologically nor semantically related to the sentence. Participants indicated by button press whether the last word matched the sentence they had read outside the scanner. Behavioural results showed more errors in condition 1 than in conditions 2 or 3, suggesting that phonological compatibility overrides semantic discrepancy when intelligibility is poor. Event-related field analysis demonstrated larger activity on frontal sites for correct than unrelated words, suggesting that the former were more accurately expected than the latter. An early M170 component was also observed, possibly reflecting expectation violation in the auditory modality. Dipole analysis will reveal whether M170 could be modulated by type of linguistic discrepancy. Distributed-network analysis will further our understanding of the time course and neural correlates of discrepancies between incoming auditory information and linguistic expectations.

The purpose of this study is to examine whether the neural correlates of lexical expectations could be used to predict speech in noise perception. We analyse mag-netoencephalography (MEG) data from 20 normal hearing participants, who read a set of couplets (a pair of phrases with rhyming end words) prior to the experiment. During the experiment, the participants are asked to listen to the couplets, whose intelligibility is set to 80%. However, the last word is pronounced with a delay of 1600 ms (i.e. expectation gap) and is masked at 50% of intelligibility. At the end of each couplet, the participants are asked to indicate if the last word was cor-rect, i.e. corresponding to the expected word. Given the oscillatory characteristics of neural patterns of lexical expectations during the expectation gap, can we predict the participant’s actual perception of the last word? In order to approach this re-search question, we aim to identify the correlation patterns between the instances of neural pre-activation, occurring during the interval of the expectation gap and the type of the given answer. According to the sequential design of the experiment, the expectation gap is placed 4400 ms prior to the time interval dedicated to the participant’s answer. Machine Learning approach has been chosen as the main tool for the pattern recognition.