Developmental dyslexia is a cognitive disorder characterized by difficulties in linguistic processing. Our purpose is to distinguish subtypes of developmental dyslexia by the level of speech–EEG frequency entrainment (δ: 1–4; β: 12.5–22.5; γ1: 25–35; and γ2: 35–80 Hz) in word/pseudoword auditory discrimination. Depending on the type of disabilities, dyslexics can divide into two subtypes—with less pronounced phonological deficits (NoPhoDys—visual dyslexia) and with more pronounced ones (PhoDys—phonological dyslexia). For correctly recognized stimuli, the δ-entrainment is significantly worse in dyslexic children compared to controls at a level of speech prosody and syllabic analysis. Controls and NoPhoDys show a stronger δ-entrainment in the left-hemispheric auditory cortex (AC), anterior temporal lobe (ATL), frontal, and motor cortices than PhoDys. Dyslexic subgroups concerning normolexics have a deficit of δ-entrainment in the left ATL, inferior frontal gyrus (IFG), and the right AC. PhoDys has higher δ-entrainment in the posterior part of adjacent STS regions than NoPhoDys. Insufficient low-frequency β changes over the IFG, the inferior parietal lobe of PhoDys compared to NoPhoDys correspond to their worse phonological short-term memory. Left-dominant 30 Hz-entrainment for normolexics to phonemic frequencies characterizes the right AC, adjacent regions to superior temporal sulcus of dyslexics. The pronounced 40 Hz-entrainment in PhoDys than the other groups suggest a hearing “reassembly” and a poor phonological working memory. Shifting up to higher-frequency γ-entrainment in the AC of NoPhoDys can lead to verbal memory deficits. Different patterns of cortical reorganization based on the left or right hemisphere lead to differential dyslexic profiles.

Abstract:Trying to prove the validity of Eysenck's theories for the biological basis of personality many data for the differences between extraverts and introverts were collected. It was obtained, that the ERP differences between extraverts and introverts depend on the intensity and frequency of stimulation, but the papers concerning task difficulty dependence are very limited. The purpose of this work was to investigate how the task complexity affects ERP differences between extraverts and introverts. For testing the extraversion we used Eysenck Personality Questionary (EPQ). We recorded EEG under four equal audio series of pseudo-randomized low and high tones. We changed the level of task complexity by different instructions: 1 -passive listening; 2 -answering with the right index finger to the low tone and the left index finger to the high tone; 3 -counting the low tones; 4 -answering with the right index finger to low tones; We averaged stimulus locked ERP across each series and tones for extraverts and introverts separately. It was evident that the ERP differences between extraverts and introverts depend on the task complexity. We found P2, N2 and P3 latency differences and N1, P2, N2 and P3 amplitude differences. As whole extraverts showed larger N2 amplitudes and shorter N2 latencies. The differences were more pronounced in the task supposed less complexity and decreased with the increase of task complexity. Keywords: Event-related potentials, EEG, Extravert, Introvert, Personality type;Introduction: There are data that interindividual differences and introversion-extraversion dimension can modulate cortical arousal and inhibition. The most popular and investigated theory combining the personality characteristics and functions of the central nervous system is the arousal theory [1]. According to this theory there exists an optimal level of cortical arousal and he ascribes lower cortical arousal compared to optimal for extraverts and higher cortical arousal compared to optimal level for the introverts. There are many arguments and evidences that there is a relationship between personality introversion/extraversion and event-related potentials (ERP). Event-related potentials (ERPs) are small changes in the ongoing EEG activity, which reflect the patterns of neuronal activity evoked by external stimuli (in different modalities), cognitive processing or preparation and execution of movement. The components of auditory evoked potentials include negative N1, which peaks at around 100 ms, the consecutive positivity P2, with latency of about 160-200 ms, the negative pick N2 evoked 180 to 325 ms and the P3 positivity which appear around 300 -400 ms after stimulus presentation. While the N1 and P2 have predominant sources in modality-specific areas, the later N2 and P3 may reflect activity of widespread associative cortical networks. The N1 and P2 components are affected by both exogenous (stimulus intensity and frequency) and endogenous (attentional demands) factors [2]. The N1 becomes more prominent and its laten...

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