Predictive Processing in Poetic Language: Event-Related Potentials Data on Rhythmic Omissions in Metered Speech

Predictions during language comprehension are currently discussed from many points of view. One area where predictive processing may play a particular role concerns poetic language that is regularized by meter and rhyme, thus allowing strong predictions regarding the timing and stress of individual syllables. While there is growing evidence that these prosodic regularities influence language processing, less is known about the potential influence of prosodic preferences (binary, strong-weak patterns) on neurophysiological processes. To this end, the present electroencephalogram (EEG) study examined whether the predictability of strong and weak syllables within metered speech would differ as a function of meter (trochee vs. iamb). Strong, i.e., accented positions within a foot should be more predictable than weak, i.e., unaccented positions. Our focus was on disyllabic pseudowords that solely differed between trochaic and iambic structure, with trochees providing the preferred foot in German. Methodologically, we focused on the omission Mismatch Negativity (oMMN) that is elicited when an anticipated auditory stimulus is omitted. The resulting electrophysiological brain response is particularly interesting because its elicitation does not depend on a physical stimulus. Omissions in deviant position of a passive oddball paradigm occurred at either first- or second-syllable position of the aforementioned pseudowords, resulting in a 2-by-2 design with the factors foot type and omission position. Analyses focused on the mean oMMN amplitude and latency differences across the four conditions. The result pattern was characterized by an interaction of the effects of foot type and omission position for both amplitudes and latencies. In first position, omissions resulted in larger and earlier oMMNs for trochees than for iambs. In second position, omissions resulted in larger oMMNs for iambs than for trochees, but the oMMN latency did not differ. The results suggest that omissions, particularly in initial position, are modulated by a trochaic preference in German. The preferred strong-weak pattern may have strengthened the prosodic prediction, especially for matching, trochaic stimuli, such that the violation of this prediction led to an earlier and stronger prediction error. Altogether, predictive processing seems to play a particular role in metered speech, especially if the meter is based on the preferred foot type.

Language Learning Under Varied Conditions: Neural Indices of Speech Perception in Bilingual Turkish-German Children and in Monolingual Children With Developmental Language Disorder (DLD)

Lateral temporal measures of the auditory evoked potential (AEP) including the T-complex (positive Ta and negative Tb), as well as an earlier negative peak (Na) index maturation of auditory/speech processing. Previous studies have shown that these measures distinguish neural processing in children with typical language development (TD) from those with disorders and monolingual from bilingual children. In this study, bilingual children with Turkish as L1 and German as L2 were compared with monolingual German-speaking children with developmental language disorder (DLD) and monolingual German-speaking children with TD in order to disentangle effects of limited language input vs. reduced perceptual abilities in the processing of speech and non-speech stimuli. Sensory processing reflected by the T-complex (or from lateral temporal electrode sites) was compared in response to a German vowel and a sine-wave tone in the three groups of children, ages 5 through 6 years. Stimuli were presented while children watched a muted video. Auditory evoked potentials (AEPs) were time-locked to the vowels and tones. AEPs to the frequent (standard) stimuli within an oddball paradigm were analyzed at the left (T7) and right (T8) temporal electrode sites.The results revealed language status (monolingual, bilingual, and DLD), stimulus (vowel and tone), and language test measures (receptive and expressive) all influenced the T-complex amplitudes. Particularly, the peak amplitude of Ta was modulated by language status and stimulus type. Bilingual children had significantly more negative Ta responses than the monolingual children with TD for both vowels and tones while DLD children differed from TD children only for the vowel stimulus. The amplitude of the T-complex was overall more negative at the left than at the right site. The Na peak latency was longer for the bilingual group than that observed for the two monolingual groups. The Tb latency was shorter for DLD and bilingual groups than that for TD children in the vowel condition, but no such latency difference between DLD and bilingual children was found. We suggest that the attenuated T-complex for bilingual children indicates continued plasticity of the auditory cortex to allow for learning of novel, second-language speech sounds.

Increased cognitive load during pseudoword processing

Pseudowords (words without semantic meaning) are often used as a control condition in linguistic cognitive experiments, with the expectation that such words, unlike real words, do not activate higher cognitive processes in the brain. However, other theories assume that pseudowords are perceived as new words, leading to an even higher cognitive response. The aim of this study was to investigate the cognitive load of processing a pseudoword by observing event-related potentials in a 3-stimulus oddball paradigm using real target words, real non-target words, and pseudowords as oddball stimuli. The results show a clear task-related P3b triggered by target words, but also a prominent P600 component triggered by pseudowords, indicating difficulty in the classification task due to unknown words. Surprisingly, N400 was decreased for pseudowords compared to target and non-target words at the locations where P3b and P600 were observed, suggesting that task-related effects might inhibit other aspects of cognitive processing. These results could lead to better understanding of the components that may overlap temporally and topographically, and to the more precise control of different cognitive generators involved in event-related potential experiments in pseudowords.

Comparison of Pupil Dilation Responses to Unexpected Sounds in Monkeys and Humans

Pupil dilation in response to unexpected stimuli has been well documented in human as well as in non-human primates; however, this phenomenon has not been systematically compared between the species. This analogy is also crucial for the role of non-human primates as an animal model to investigate neural mechanisms underlying the processing of unexpected stimuli and their evoked pupil dilation response. To assess this qualitatively, we used an auditory oddball paradigm in which we presented subjects a sequence of the same sounds followed by occasional deviants while we measured their evoked pupil dilation response (PDR). We used deviants (a frequency deviant, a pink noise burst, a monkey vocalization and a whistle sound) which differed in the spectral composition and in their ability to induce arousal from the standard. Most deviants elicited a significant pupil dilation in both species with decreased peak latency and increased peak amplitude in monkeys compared to humans. A temporal Principal Component Analysis (PCA) revealed two components underlying the PDRs in both species. The early component is likely associated to the parasympathetic nervous system and the late component to the sympathetic nervous system, respectively. Taken together, the present study demonstrates a qualitative similarity between PDRs to unexpected auditory stimuli in macaque and human subjects suggesting that macaques can be a suitable model for investigating the neuronal bases of pupil dilation. However, the quantitative differences in PDRs between species need to be investigated in further comparative studies.

Electrophysiological Measures of Tactile and Auditory Processing in Children With Autism Spectrum Disorder

Behavioral differences in responding to tactile and auditory stimuli are widely reported in individuals with autism spectrum disorder (ASD). However, the neural mechanisms underlying distinct tactile and auditory reactivity patterns in ASD remain unclear with theories implicating differences in both perceptual and attentional processes. The current study sought to investigate (1) the neural indices of early perceptual and later attentional factors underlying tactile and auditory processing in children with and without ASD, and (2) the relationship between neural indices of tactile and auditory processing and ASD symptomatology. Participants included 14, 6–12-year-olds with ASD and 14 age- and non-verbal IQ matched typically developing (TD) children. Children participated in an event-related potential (ERP) oddball paradigm during which they watched a silent video while being presented with tactile and auditory stimuli (i.e., 80% standard speech sound/a/; 10% oddball speech sound/i/; 10% novel vibrotactile stimuli on the fingertip with standard speech sound/a/). Children’s early and later ERP responses to tactile (P1 and N2) and auditory stimuli (P1, P3a, and P3b) were examined. Non-parametric analyses showed that children with ASD displayed differences in early perceptual processing of auditory (i.e., lower amplitudes at central region of interest), but not tactile, stimuli. Analysis of later attentional components did not show differences in response to tactile and auditory stimuli in the ASD and TD groups. Together, these results suggest that differences in auditory responsivity patterns could be related to perceptual factors in children with ASD. However, despite differences in caregiver-reported sensory measures, children with ASD did not differ in their neural reactivity to infrequent touch-speech stimuli compared to TD children. Nevertheless, correlational analyses confirmed that inter-individual differences in neural responsivity to tactile and auditory stimuli were related to social skills in all children. Finally, we discuss how the paradigm and stimulus type used in the current study may have impacted our results. These findings have implications for everyday life, where individual differences in responding to tactile and auditory stimuli may impact social functioning.

Perception of Prosodic Modulations of Linguistic and Paralinguistic Origin: Evidence From Early Auditory Event-Related Potentials

How listeners handle prosodic cues of linguistic and paralinguistic origin is a central question for spoken communication. In the present EEG study, we addressed this question by examining neural responses to variations in pitch accent (linguistic) and affective (paralinguistic) prosody in Swedish words, using a passive auditory oddball paradigm. The results indicated that changes in pitch accent and affective prosody elicited mismatch negativity (MMN) responses at around 200 ms, confirming the brain’s pre-attentive response to any prosodic modulation. The MMN amplitude was, however, statistically larger to the deviation in affective prosody in comparison to the deviation in pitch accent and affective prosody combined, which is in line with previous research indicating not only a larger MMN response to affective prosody in comparison to neutral prosody but also a smaller MMN response to multidimensional deviants than unidimensional ones. The results, further, showed a significant P3a response to the affective prosody change in comparison to the pitch accent change at around 300 ms, in accordance with previous findings showing an enhanced positive response to emotional stimuli. The present findings provide evidence for distinct neural processing of different prosodic cues, and statistically confirm the intrinsic perceptual and motivational salience of paralinguistic information in spoken communication.

Alteration of Behavioral Inhibitory Control in High-Altitude Immigrants

Behavioral inhibitory control (BIC) acts as a key cognitive ability, which is essential for humans to withhold inappropriate behaviors. Meanwhile, many studies reported that long-term exposure to high altitude (HA) may affect cognitive ability. However, it is not clear whether long-term exposure to HAs may affect the BIC of an individual. To clarify the role of altitude in the behavioral control of adults and the underlying neural mechanism, we explored the BIC neural activity profiles of healthy immigrants from low-altitude (LA) regions to HA regions. Combining a two-choice oddball paradigm and electrophysiological techniques, this study monitored the N2 and P3 event-related components and neural oscillations across LA and HA groups. Results showed longer reaction times (RTs) for the HA group than the LA group. Relative to the LA group, lower N2 and P3 amplitudes were observed for the HA group. Significant positive correlations were also found between P3 amplitude and theta/delta band power across both groups. Importantly, lower theta/delta band powers were only observed for the HA group under the deviant condition. Collectively, these findings suggest that long-term exposure to HAs may attenuate BIC during the response inhibition stage and provide valuable insights into the neurocognitive implications of environmental altitude on BIC.

Increased context adjustment is associated with auditory sensitivities but not with autistic traits

Bayesian models of autism suggest that disruptions in context-sensitive prediction error weighting may underpin sensory perceptual alterations, such as hypersensitivities. We used an auditory oddball paradigm with pure tones arising from high or low uncertainity contexts to determine whether autistic individuals display differences in context adjustment relative to neurotypicals. We did not find group differences in early prediction error responses indexed by mismatch negativity. However, the autism group had larger evoked responses to outliers, at 300ms latency suggesting a greater reorienting of attention to surprising sounds. A dimensional approach revealed a positive correlation between context-dependent prediction errors and auditory sensitivities, but not with autistic traits. These findings suggest that autism studies may benefit from accounting for sensory sensitivities in group comparisons.

Different Patterns of Attention Modulation in Early N140 and Late P300 sERPs Following Ipsilateral vs. Contralateral Stimulation at the Fingers and Cheeks

Intra-hemispheric interference has been often observed when body parts with neighboring representations within the same hemisphere are stimulated. However, patterns of interference in early and late somatosensory processing stages due to the stimulation of different body parts have not been explored. Here, we explore functional similarities and differences between attention modulation of the somatosensory N140 and P300 elicited at the fingers vs. cheeks. In an active oddball paradigm, 22 participants received vibrotactile intensity deviant stimulation either ipsilateral (within-hemisphere) or contralateral (between-hemisphere) at the fingers or cheeks. The ipsilateral deviant always covered a larger area of skin than the contralateral deviant. Overall, both N140 and P300 amplitudes were higher following stimulation at the cheek and N140 topographies differed between fingers and cheek stimulation. For the N140, results showed higher deviant ERP amplitudes following contralateral than ipsilateral stimulation, regardless of the stimulated body part. N140 peak latency differed between stimulated body parts with shorter latencies for the stimulation at the fingers. Regarding P300 amplitudes, contralateral deviant stimulation at the fingers replicated the N140 pattern, showing higher responses and shorter latencies than ipsilateral stimulation at the fingers. For the stimulation at the cheeks, ipsilateral deviants elicited higher P300 amplitudes and longer latencies than contralateral ones. These findings indicate that at the fingers ipsilateral deviant stimulation leads to intra-hemispheric interference, with significantly smaller ERP amplitudes than in contralateral stimulation, both at early and late processing stages. By contrast, at the cheeks, intra-hemispheric interference is selective for early processing stages. Therefore, the mechanisms of intra-hemispheric processing differ from inter-hemispheric ones and the pattern of intra-hemispheric interference in early and late processing stages is body-part specific.

DelIrium VULnerability in GEriatrics (DIVULGE) study: a protocol for a prospective observational study of electroencephalogram associations with incident postoperative delirium

IntroductionDelirium is a neurocognitive disorder common in older adults in acute care settings. Those who develop delirium are at an increased risk of dementia, cognitive decline and death. Electroencephalography (EEG) during delirium in older adults is characterised by slowing and reduced functional connectivity, but markers of vulnerability are poorly described. We aim to identify EEG spectral power and event-related potential (ERP) markers of incident delirium in older adults to understand neural mechanisms of delirium vulnerability. Characterising delirium vulnerability will provide substantial theoretical advances and outcomes have the potential to be translated into delirium risk assessment tools.Methods and analysisWe will record EEG in 90 participants over 65 years of age prior to elective coronary artery bypass grafting (CABG) or transcatheter aortic valve implantation (TAVI). We will record 4-minutes of resting state (eyes open and eyes closed) and a 5-minute frequency auditory oddball paradigm. Outcome measures will include frequency band power, 1/f offset and slope, and ERP amplitude measures. Participants will undergo cognitive and EEG testing before their elective procedures and daily postoperative delirium assessments. Group allocation will be done retrospectively by linking preoperative EEG data according to postoperative delirium status (presence, severity, duration and subtype).Ethics and disseminationThis study is approved by the Human Research Ethics Committee of the Royal Adelaide Hospital, Central Adelaide Local Health Network and the University of South Australia Human Ethics Committee. Findings will be disseminated through peer-reviewed journal articles and presentations at national and international conferences.Trial registration numberACTRN12618001114235 and ACTRN12618000799257.