Neural correlates of statistical learning in developmental dyslexia: An electroencephalography study.

The human brain extracts statistical regularities from the surrounding environment in a process called statistical learning. Behavioural evidence suggests that developmental dyslexia affects statistical learning. However, surprisingly few studies have assessed how developmental dyslexia affects the neural processing underlying this type of learning. We used electroencephalography to explore the neural correlates of an important aspect of statistical learning - sensitivity to transitional probabilities - in individuals with developmental dyslexia. Adults diagnosed with developmental dyslexia (n = 17) and controls (n = 19) were exposed to a continuous stream of sound triplets. Every so often, a triplet ending had a low transitional probability given the triplet's first two sounds ("statistical deviants"). Furthermore, every so often a triplet ending was presented from a deviant location ("acoustic deviants"). We examined mismatch negativity elicited by statistical deviants (sMMN), and MMN elicited by location deviants (i.e., acoustic changes). Acoustic deviants elicited a MMN which was larger in the control group than in the developmental dyslexia group. Statistical deviants elicited a small, yet significant, sMMN in the control group, but not in the developmental dyslexia group. However, the difference between the groups was not significant. Our findings indicate that the neural mechanisms underlying pre-attentive acoustic change detection and implicit statistical auditory learning are both affected in developmental dyslexia.

Unpredictability of the "when" influences prediction error processing of the "what" and "where".

The capability to establish accurate predictions is an integral part of learning. Whether predictions about different dimensions of a stimulus interact with each other, and whether such an interaction affects learning, has remained elusive. We conducted a statistical learning study with EEG (electroencephalography), where a stream of consecutive sound triplets was presented with deviants that were either: (a) statistical, depending on the triplet ending probability, (b) physical, due to a change in sound location or (c) double deviants, i.e. a combination of the two. We manipulated the predictability of stimulus-onset by using random stimulus-onset asynchronies. Temporal unpredictability due to random onsets reduced the neurophysiological responses to statistical and location deviants, as indexed by the statistical mismatch negativity (sMMN) and the location MMN. Our results demonstrate that the predictability of one stimulus attribute influences the processing of prediction error signals of other stimulus attributes, and thus also learning of those attributes.

Neocortical substrates of feelings evoked with music in the ACC, insula, and somatosensory cortex.

Neurobiological models of emotion focus traditionally on limbic/paralimbic regions as neural substrates of emotion generation, and insular cortex (in conjunction with isocortical anterior cingulate cortex, ACC) as the neural substrate of feelings. An emerging view, however, highlights the importance of isocortical regions beyond insula and ACC for the subjective feeling of emotions. We used music to evoke feelings of joy and fear, and multivariate pattern analysis (MVPA) to decode representations of feeling states in functional magnetic resonance (fMRI) data of n = 24 participants. Most of the brain regions providing information about feeling representations were neocortical regions. These included, in addition to granular insula and cingulate cortex, primary and secondary somatosensory cortex, premotor cortex, frontal operculum, and auditory cortex. The multivoxel activity patterns corresponding to feeling representations emerged within a few seconds, gained in strength with increasing stimulus duration, and replicated results of a hypothesis-generating decoding analysis from an independent experiment. Our results indicate that several neocortical regions (including insula, cingulate, somatosensory and premotor cortices) are important for the generation and modulation of feeling states. We propose that secondary somatosensory cortex, which covers the parietal operculum and encroaches on the posterior insula, is of particular importance for the encoding of emotion percepts, i.e., preverbal representations of subjective feeling.

When the statistical MMN meets the physical MMN.

How do listeners respond to prediction errors within patterned sequence of sounds? To answer this question we carried out a statistical learning study using electroencephalography (EEG). In a continuous auditory stream of sound triplets the deviations were either (a) statistical, in terms of transitional probability, (b) physical, due to a change in sound location (left or right speaker) or (c) a double deviants, i.e. a combination of the two. Statistical and physical deviants elicited a statistical mismatch negativity and a physical MMN respectively. Most importantly, we found that effects of statistical and physical deviants interacted (the statistical MMN was smaller when co-occurring with a physical deviant). Results show, for the first time, that processing of prediction errors due to statistical learning is affected by prediction errors due to physical deviance. Our findings thus show that the statistical MMN interacts with the physical MMN, implying that prediction error processing due to physical sound attributes suppresses processing of learned statistical properties of sounds.

Processing of hierarchical syntactic structure in music.

Hierarchical structure with nested nonlocal dependencies is a key feature of human language and can be identified theoretically in most pieces of tonal music. However, previous studies have argued against the perception of such structures in music. Here, we show processing of nonlocal dependencies in music. We presented chorales by J. S. Bach and modified versions in which the hierarchical structure was rendered irregular whereas the local structure was kept intact. Brain electric responses differed between regular and irregular hierarchical structures, in both musicians and nonmusicians. This finding indicates that, when listening to music, humans apply cognitive processes that are capable of dealing with long-distance dependencies resulting from hierarchically organized syntactic structures. Our results reveal that a brain mechanism fundamental for syntactic processing is engaged during the perception of music, indicating that processing of hierarchical structure with nested nonlocal dependencies is not just a key component of human language, but a multidomain capacity of human cognition.

Differences in electric brain responses to melodies and chords.

The music we usually listen to in everyday life consists of either single melodies or harmonized melodies (i.e., of melodies "accompanied" by chords). However, differences in the neural mechanisms underlying melodic and harmonic processing have remained largely unknown. Using EEG, this study compared effects of music-syntactic processing between chords and melodies. In melody blocks, sequences consisted of five tones, the final tone being either regular or irregular (p = .5). Analogously, in chord blocks, sequences consisted of five chords, the final chord function being either regular or irregular. Melodies were derived from the top voice of chord sequences, allowing a proper comparison between melodic and harmonic processing. Music-syntactic incongruities elicited an early anterior negativity with a latency of approximately 125 msec in both the melody and the chord conditions. This effect was followed in the chord condition, but not in the melody condition, by an additional negative effect that was maximal at approximately 180 msec. Both effects were maximal at frontal electrodes, but the later effect was more broadly distributed over the scalp than the earlier effect. These findings indicate that melodic information (which is also contained in the top voice of chords) is processed earlier and with partly different neural mechanisms than harmonic information of chords.

Short-term effects of processing musical syntax: an ERP study.

We investigated influences of short-term experience on music-syntactic processing, using a chord-sequence paradigm in which sequences ended on a harmony that was syntactically either regular or irregular. In contrast to previous studies (in which block durations were rather short), chord sequences were presented to participants for around 2 h while they were watching a silent movie with subtitles. Results showed that the music-syntactically irregular chord functions elicited an early right anterior negativity (ERAN), and that the ERAN amplitude significantly declined over the course of the experiment. The ERAN has previously been suggested to reflect the processing of music-syntactic irregularities, and the present data show that the cognitive representations of musical regularities are influenced by the repeated presentation of unexpected, irregular harmonies. Because harmonies were task-irrelevant, the data suggest that cognitive representations of musical regularities can change implicitly, i.e., even when listeners do not attend to the harmonies, and when they are presumably oblivious of the changes of such representations. Although the ERAN amplitude was significantly reduced, it was still present towards the end of the experiment at the right anterior electrodes, indicating that cognitive representations of basic music-syntactic regularities cannot easily be erased.

Children with specific language impairment also show impairment of music-syntactic processing.

Both language and music consist of sequences that are structured according to syntactic regularities. We used two specific event-related brain potential (ERP) components to investigate music-syntactic processing in children: the ERAN (early right anterior negativity) and the N5. The neural resources underlying these processes have been posited to overlap with those involved in the processing of linguistic syntax. Thus, we expected children with specific language impairment (SLI, which is characterized by deficient processing of linguistic syntax) to demonstrate difficulties with music-syntactic processing. Such difficulties were indeed observed in the neural correlates of music-syntactic processing: neither an ERAN nor an N5 was elicited in children with SLI, whereas both components were evoked in age-matched control children with typical language development. Moreover, the amplitudes of ERAN and N5 were correlated with subtests of a language development test. These data provide evidence for a strong interrelation between the language and the music processing system, thereby setting the ground for possible effects of musical training in SLI therapy.

EEG correlates of moderate intermittent explosive disorder.

OBJECTIVE: We investigated electroencephalographic (EEG) correlates of moderate intermittent explosive disorder (mIED), which is characterized by uncontrollable, impulsive attacks that either manifest in aggressive outbursts of temper, or in implosive, auto-aggressive behaviour. METHODS: In two Experiments, EEG data were recorded during rest conditions, and while subjects were presented with auditory and visual stimuli. Additionally, scores of the I7 impulsivity scale (designed to capture acting on impulse) were obtained. RESULTS: In Experiment 1, individuals with mIED showed a stronger increase in the power of oscillatory activity in the beta band, along with a stronger power decrease in the theta band in response to both visual and auditory stimuli. Based on discriminant function analysis, a model of discriminant functions was derived that clearly separated the mIED group from the control group. In Experiment 2, subjects were categorized into either of two groups (supposedly without mIED, with mIED) based on this model of discriminant functions. Results showed that I7 impulsivity scores clearly differed between groups. CONCLUSIONS: The present data show a relation between oscillatory brain activity and mIED. They indicate that this brain activity is related to the impulsivity facet of impulsive action, and suggest that mIED can be assessed based on the analysis of electrophysiological data. SIGNIFICANCE: To our knowledge, this is the first study on EEG correlates of (m)IED. Results open up new perspectives for future investigations on disorders characterized by substantial impulsivity.

Investigating the relationship of music and language in children: influences of musical training and language impairment.

Language and music are human universals involving perceptually discrete elements organized in hierarchically structured sequences. The set of principles governing the combination of these structural elements into sequences is known as syntax. A violation of expectancies concerning syntactic regularities may be reflected by two ERP components: the ERAN (early right anterior negativity) and the ELAN (early left anterior negativity). The ERAN is evoked by a violation of musical regularities, whereas the ELAN is linked to syntax processing in the language domain. There is evidence from adult data to suggest that both ERAN and ELAN are, at least partly, generated in the same brain regions. Therefore, it seems plausible to expect transfer effects between music and language due to shared processing resources. Moreover, the ERAN is larger in adults with formal musical training (musicians) than in those without, indicating that more specific representations of musical regularities lead to heightened musical expectancies. The aim of this study is to investigate these issues in child development. We conducted two experimental sessions with the same participants and compared children with and without musical training (11 years old) and children with or without language impairment (5 years old). In a music experiment, the reactions to chord sequences ending either with a (regular) tonic or with an (irregular) supertonic were compared. For a language experiment we used syntactically correct and incorrect sentences. Preliminary results show that an ERAN is present in both groups and appears to have a larger amplitude in musically trained children. In addition, there are indications of an enhanced negativity in response to a syntactic violation in the musically trained children. The relationship between the ERP components is, moreover, manifested in the finding that an ERAN is present in linguistically nonimpaired children at the age of 5 years but not in children with language impairment of the same age.