Mechanisms of sustained perceptual entrainment after stimulus offset

Temporal alignment of neural activity to rhythmic stimulation has been suggested to result from a resonating internal neural oscillator mechanism, but can also be explained by interval-based temporal prediction. Here, we investigate behavioural and brain responses in the post-stimulation period to compare an oscillatory versus an interval-based account. Hickok et al.'s (2015) behavioural paradigm yielded results that relate to a neural oscillatory entrainment mechanism. We adapted the paradigm to an event-related potential (ERP) suitable design: a periodic sequence was followed, in half of the trials, by near-threshold targets embedded in noise. The targets were played in various phases in relation to the preceding sequences' period. Participants had to detect whether targets were played or not, and their EEG was recorded. Both behavioural results and the P300 component of the ERP were not only partially consistent with an oscillatory mechanism but also partially consistent with an interval-based attentional gain mechanism. Instead, data obtained in the post-entrainment period can best be explained with a combination of both mechanisms.

Conditional deviant repetition in the oddball paradigm modulates processing at the level of P3a but not MMN

The auditory system has an amazing ability to rapidly encode auditory regularities. Evidence comes from the popular oddball paradigm, in which frequent (standard) sounds are occasionally exchanged for rare deviant sounds, which then elicit signs of prediction error based on their unexpectedness (e.g., MMN and P3a). Here, we examine the widely neglected characteristics of deviants being bearers of predictive information themselves; naive participants listened to sound sequences constructed according to a new, modified version of the oddball paradigm including two types of deviants that followed diametrically opposed rules: one deviant sound occurred mostly in pairs (repetition rule), the other deviant sound occurred mostly in isolation (non-repetition rule). Due to this manipulation, the sound following a first deviant (either the same deviant or a standard) was either predictable or unpredictable based on its conditional probability associated with the preceding deviant sound. Our behavioral results from an active deviant detection task replicate previous findings that deviant repetition rules (based on conditional probability) can be extracted when behaviorally relevant. Our electrophysiological findings obtained in a passive listening setting indicate that conditional probability also translates into differential processing at the P3a level. However, MMN was confined to global deviants and was not sensitive to conditional probability. This suggests that higher-level processing concerned with stimulus selection and/or evaluation (reflected in P3a) but not lower-level sensory processing (reflected in MMN) considers rarely encountered rules.

Neural signatures of automatic repetition detection in temporally regular and jittered acoustic sequences

Detection of repeating patterns within continuous sound streams is crucial for efficient auditory perception. Previous studies demonstrated a remarkable sensitivity of the human auditory system to periodic repetitions in unfamiliar, meaningless sounds. Automatic repetition detection was reflected in different EEG markers, including sustained activity, neural synchronisation, and event-related responses to pattern occurrences. The current study investigated how listeners' attention and the temporal regularity of a sound modulate repetition perception, and how this influence is reflected in different EEG markers that were previously suggested to subserve dissociable functions. We reanalysed data of a previous study in which listeners were presented with sequences of unfamiliar artificial sounds that either contained repetitions of a certain sound segment or not. Repeating patterns occurred either regularly or with a temporal jitter within the sequences, and participants' attention was directed either towards the pattern repetitions or away from the auditory stimulation. Across both regular and jittered sequences during both attention and in-attention, pattern repetitions led to increased sustained activity throughout the sequence, evoked a characteristic positivity-negativity complex in the event-related potential, and enhanced inter-trial phase coherence of low-frequency oscillatory activity time-locked to repeating pattern onsets. While regularity only had a minor (if any) influence, attention significantly strengthened pattern repetition perception, which was consistently reflected in all three EEG markers. These findings suggest that the detection of pattern repetitions within continuous sounds relies on a flexible mechanism that is robust against in-attention and temporal irregularity, both of which typically occur in naturalistic listening situations. Yet, attention to the auditory input can enhance processing of repeating patterns and improve repetition detection.

Deviants violating higher-order auditory regularities can become predictive and facilitate behaviour

The human auditory system is believed to represent regularities inherent in auditory information in internal models. Sounds not matching the standard regularity (deviants) elicit prediction error, alerting the system to information not explainable within currently active models. Here, we examine the widely neglected characteristic of deviants bearing predictive information themselves. In a modified version of the oddball paradigm, using higher-order regularities, we set up different expectations regarding the sound following a deviant. Higher-order regularities were defined by the relation of pitch within tone pairs (rather than absolute pitch of individual tones). In a deviant detection task participants listened to oddball sequences including two deviant types following diametrically opposed rules: one occurred mostly in succession (high repetition probability) and the other mostly in isolation (low repetition probability). Participants in Experiment 1 were not informed (naïve), whereas in Experiment 2 they were made aware of the repetition rules. Response times significantly decreased from first to second deviant when repetition probability was high-albeit more in the presence of explicit rule knowledge. There was no evidence of a facilitation effect when repetition probability was low. Significantly more false alarms occurred in response to standards following high compared with low repetition probability deviants, but only in participants aware of the repetition rules. These findings provide evidence that not only deviants violating lower- but also higher-order regularities can inform predictions about auditory events. More generally, they confirm the utility of this new paradigm to gather further insights into the predictive properties of the human brain.

Markov chains as a proxy for the predictive memory representations underlying mismatch negativity

Events not conforming to a regularity inherent to a sequence of events elicit prediction error signals of the brain such as the Mismatch Negativity (MMN) and impair behavioral task performance. Events conforming to a regularity lead to attenuation of brain activity such as stimulus-specific adaptation (SSA) and behavioral benefits. Such findings are usually explained by theories stating that the information processing system predicts the forthcoming event of the sequence via detected sequential regularities. A mathematical model that is widely used to describe, to analyze and to generate event sequences are Markov chains: They contain a set of possible events and a set of probabilities for transitions between these events (transition matrix) that allow to predict the next event on the basis of the current event and the transition probabilities. The accuracy of such a prediction depends on the distribution of the transition probabilities. We argue that Markov chains also have useful applications when studying cognitive brain functions. The transition matrix can be regarded as a proxy for generative memory representations that the brain uses to predict the next event. We assume that detected regularities in a sequence of events correspond to (a subset of) the entries in the transition matrix. We apply this idea to the Mismatch Negativity (MMN) research and examine three types of MMN paradigms: classical oddball paradigms emphasizing sound probabilities, between-sound regularity paradigms manipulating transition probabilities between adjacent sounds, and action-sound coupling paradigms in which sounds are associated with actions and their intended effects. We show that the Markovian view on MMN yields theoretically relevant insights into the brain processes underlying MMN and stimulates experimental designs to study the brain's processing of event sequences.

Perceptual learning of random acoustic patterns: Impact of temporal regularity and attention

Perceptual learning is a powerful mechanism to enhance perceptual abilities and to form robust memory representations of previously unfamiliar sounds. Memory formation through repeated exposure takes place even for random and complex acoustic patterns devoid of semantic content. The current study sought to scrutinise how perceptual learning of random acoustic patterns is shaped by two potential modulators: temporal regularity of pattern repetition and listeners' attention. To this end, we adapted an established implicit learning paradigm and presented short acoustic sequences that could contain embedded repetitions of a certain sound segment (i.e., pattern) or not. During each experimental block, one repeating pattern recurred across multiple trials, while the other patterns were presented in only one trial. During the presentation of sound sequences that contained either temporally regular or jittered within-trial pattern repetitions, participants' attention was directed either towards or away from the auditory stimulation. Overall, we found a memory-related modulation of the event-related potential (ERP) and an increase in inter-trial phase coherence for patterns that recurred across multiple trials (compared to non-recurring patterns), accompanied by a performance increase in a (within-trial) repetition detection task when listeners attended the sounds. Remarkably, we show a memory-related ERP effect even for the first pattern occurrence per sequence when participants attended the sounds, but not when they were engaged in a visual distractor task. These findings suggest that learning of unfamiliar sound patterns is robust against temporal irregularity and inattention, but attention facilitates access to established memory representations upon first occurrence within a sequence.

Within- and between-subject consistency of perceptual segmentation in periodic noise: A combined behavioral tapping and EEG study

It is remarkable that human listeners can perceive periodicity in noise, as the isochronous repetition of a particular noise segment is not accompanied by salient physical cues in the acoustic signal. Previous research suggested that listeners rely on short temporally local and idiosyncratic features to perceptually segment periodic noise sequences. The present study sought to test this assumption by disentangling consistency of perceptual segmentation within and between listeners. Presented periodic noise sequences either consisted of seamless repetitions of a 500-ms segment or of repetitions of a 200-ms segment that were interleaved with 300-ms portions of random noise. Both within- and between-subject consistency was stronger for interleaved (compared with seamless) periodic sequences. The increased consistency likely resulted from reduced temporal jitter of potential features used for perceptual segmentation when the recurring segment was shorter and occurred interleaved with random noise. These results support the notion that perceptual segmentation of periodic noise relies on subtle temporally local features. However, the finding that some specific noise sequences were segmented more consistently across listeners than others challenges the assumption that the features are necessarily idiosyncratic. Instead, in some specific noise samples, a preference for certain spectral features is shared between individuals.

Auditory representations for long lasting sounds: Insights from event-related brain potentials and neural oscillations

The basic features of short sounds, such as frequency and intensity including their temporal dynamics, are integrated in a unitary representation. Knowledge on how our brain processes long lasting sounds is scarce. We review research utilizing the Mismatch Negativity event-related potential and neural oscillatory activity for studying representations for long lasting simple versus complex sounds such as sinusoidal tones versus speech. There is evidence for a temporal constraint in the formation of auditory representations: Auditory edges like sound onsets within long lasting sounds open a temporal window of about 350 ms in which the sounds' dynamics are integrated into a representation, while information beyond that window contributes less to that representation. This integration window segments the auditory input into short chunks. We argue that the representations established in adjacent integration windows can be concatenated into an auditory representation of a long sound, thus, overcoming the temporal constraint.

Intention-based predictive information modulates auditory deviance processing

The human brain is highly responsive to (deviant) sounds violating an auditory regularity. Respective brain responses are usually investigated in situations when the sounds were produced by the experimenter. Acknowledging that humans also actively produce sounds, the present event-related potential study tested for differences in the brain responses to deviants that were produced by the listeners by pressing one of two buttons. In one condition, deviants were unpredictable with respect to the button-sound association. In another condition, deviants were predictable with high validity yielding correctly predicted deviants and incorrectly predicted (mispredicted) deviants. Temporal principal component analysis revealed deviant-specific N1 enhancement, mismatch negativity (MMN) and P3a. N1 enhancements were highly similar for each deviant type, indicating that the underlying neural mechanism is not affected by intention-based expectation about the self-produced forthcoming sound. The MMN was abolished for predictable deviants, suggesting that the intention-based prediction for a deviant can overwrite the prediction derived from the auditory regularity (predicting a standard). The P3a was present for each deviant type but was largest for mispredicted deviants. It is argued that the processes underlying P3a not only evaluate the deviant with respect to the fact that it violates an auditory regularity but also with respect to the intended sensorial effect of an action. Overall, our results specify current theories of auditory predictive processing, as they reveal that intention-based predictions exert different effects on different deviance-specific brain responses.

A link between age, affect, and predictions?

The prevalence of depressive symptoms decreases from late adolescence to middle age adulthood. Furthermore, despite significant losses in motor and cognitive functioning, overall emotional well-being tends to increase with age, and a bias to positive information has been observed multiple times. Several causes have been discussed for this age-related development, such as improvement in emotion regulation, less regret, and higher socioeconomic status. Here, we explore a further explanation. Our minds host mental models that generate predictions about forthcoming events to successfully interact with our physical and social environment. To keep these models faithful, the difference between the predicted and the actual event, that is, the prediction error, is computed. We argue that prediction errors are attenuated in the middle age and older mind, which, in turn, may translate to less negative affect, lower susceptibility to affective disorders, and possibly, to a bias to positive information. Our proposal is primarily linked to perceptual inferences, but may hold as well for higher-level, cognitive, and emotional forms of error processing.

Action effect predictions in 'what', 'when', and 'whether' intentional actions

It has been proposed that intentional action can be separated into three major types depending on the nature of the action choice - what (selecting what to do), when (selecting when to act) and whether (to perform the action or not). While many theories on action control assume that intentional action involves the prediction of action effects, there has not been any attempt to compare the three types of intentional actions (what, when, whether) with respect to action-effect prediction. Here, we employ an action-effect prediction paradigm where participants select the action on every trial based on either the what (choosing between alternative actions), when (choosing to respond at different time points) or whether (choosing to perform an action or not) action components, and each action choice is followed by either a predicted (standard) or a mispredicted (deviant) tone. We found a significant P2 difference between standard/deviant tones reflecting the formation of action-effect predictions regardless of whether the action choice was based on the 'what', 'when' or 'whether' decision. Furthermore, our analysis revealed that this P2 difference for the prediction effect was not observable in non-action trials within the 'whether' condition, which suggests an action-specific prediction process.

Hearing "Birch" Hampers Saying "Duck"-An Event-Related Potential Study on Phonological Interference in Immediate and Delayed Word Production

When speakers name a picture (e.g., "duck"), a distractor word phonologically related to an alternative name (e.g., "birch" related to "bird") slows down naming responses compared with an unrelated distractor word. This interference effect obtained with the picture-word interference task is assumed to reflect the phonological coactivation of close semantic competitors and is critical for evaluating contemporary models of word production. In this study, we determined the event-related brain potential (ERP) signature of this effect in immediate and delayed versions of the picture-word interference task. ERPs revealed a differential processing of related and unrelated distractors: an early (305-436 msec) and a late (537-713 msec) negativity for related as compared with unrelated distractors. In the behavioral data, the interference effect was only found in immediate naming, whereas its ERP signature was also present in delayed naming. The time window of the earlier ERP effect suggests that the behavioral interference effect indeed emerges at a phonological processing level, whereas the functional significance of the later ERP effect is as yet not clear. The finding of a robust ERP correlate of phonological coactivation might facilitate future research on lexical processing in word production.

Neural entrainment via perceptual inferences

Entrainment depends on sequential neural phase reset by regular stimulus onset, a temporal parameter. Entraining to sequences of identical stimuli also entails stimulus feature predictability, but this component is not readily separable from temporal regularity. To test if spectral regularities concur with temporal regularities in determining the strength of auditory entrainment, we devised sound sequences that varied in conditional perceptual inferences based on deviant sound repetition probability: Strong inference (100% repetition probability: If a deviant appears, then it will repeat), weak inference (75% repetition probability), no inference (50%: A deviant may or may not repeat with equal probability). We recorded EEG data from 15 young human participants pre-attentively listening to the experimental sound sequences delivered either isochronously or anisochronously ( ± 20 % jitter), at both delta (1.67 Hz) and theta (6.67 Hz) stimulation rates. Strong perceptual inferences significantly enhanced entrainment at either stimulation rate, and determined positive correlations between precision in phase distribution at the onset of deviant trials, and entrained power. We conclude that both spectral predictability and temporal regularity govern entrainment via neural phase control.

The Predictive Brain Must Have a Limitation in Short-Term Memory Capacity

Traditionally, short-term memory (STM) has been assessed by asking participants to remember words, visual objects, or numbers for a short amount of time before their recall or recognition of those items is tested. However, this focus on memory for past sensory input might have obscured potential theoretical insights into the function of this cognitive faculty. Here, we suggest that STM may have an important role in predicting future sensory input. This reconceptualization of STM may provide a functional explanation for its capacity limitation.

Auditory Pattern Representations Under Conditions of Uncertainty-An ERP Study

The auditory system is able to recognize auditory objects and is thought to form predictive models of them even though the acoustic information arriving at our ears is often imperfect, intermixed, or distorted. We investigated implicit regularity extraction for acoustically intact versus disrupted six-tone sound patterns via event-related potentials (ERPs). In an exact-repetition condition, identical patterns were repeated; in two distorted-repetition conditions, one randomly chosen segment in each sound pattern was replaced either by white noise or by a wrong pitch. In a roving-standard paradigm, sound patterns were repeated 1-12 times (standards) in a row before a new pattern (deviant) occurred. The participants were not informed about the roving rule and had to detect rarely occurring loudness changes. Behavioral detectability of pattern changes was assessed in a subsequent behavioral task. Pattern changes (standard vs. deviant) elicited mismatch negativity (MMN) and P3a, and were behaviorally detected above the chance level in all conditions, suggesting that the auditory system extracts regularities despite distortions in the acoustic input. However, MMN and P3a amplitude were decreased by distortions. At the level of MMN, both types of distortions caused similar impairments, suggesting that auditory regularity extraction is largely determined by the stimulus statistics of matching information. At the level of P3a, wrong-pitch distortions caused larger decreases than white-noise distortions. Wrong-pitch distortions likely prevented the engagement of restoration mechanisms and the segregation of disrupted from true pattern segments, causing stronger informational interference with the relevant pattern information.

Word class and word frequency in the MMN looking glass

The effects of lexical meaning and lexical familiarity on auditory deviance detection were investigated by presenting oddball sequences of words, while participants ignored the stimuli. Stimulus sequences were composed of words that were varied in word class (nouns vs. functions words) and frequency of language use (high vs. low frequency) in a factorial design with the roles of frequently presented stimuli (Standards) and infrequently presented ones (Deviants) were fully crossed. Deviants elicited the Mismatch Negativity component of the event-related brain potential. Modulating effects of lexical meaning were obtained, revealing processing advantages for denotationally meaningful items. However, no effect of word frequency was observed. These results demonstrate that an apparently low-level function, such as auditory deviance detection utilizes information from the mental lexicon even for task-irrelevant stimuli.

The encoding of stochastic regularities is facilitated by action-effect predictions

Our brains continuously build and update predictive models of the world, sources of prediction being drawn for example from sensory regularities and/or our own actions. Yet, recent results in the auditory system indicate that stochastic regularities may not be easily encoded when a rare medium pitch deviant is presented between frequent high and low pitch standard sounds in random order, as reflected in the lack of sensory prediction error event-related potentials [i.e., mismatch negativity (MMN)]. We wanted to test the implication of the predictive coding theory that predictions based on higher-order generative models-here, based on action intention, are fed top-down in the hierarchy to sensory levels. Participants produced random sequences of high and low pitch sounds by button presses in two conditions: In a "specific" condition, one button produced high and the other low pitch sounds; in an "unspecific" condition, both buttons randomly produced high or low-pitch sounds. Rare medium pitch deviants elicited larger MMN and N2 responses in the "specific" compared to the "unspecific" condition, despite equal sound probabilities. These results thus demonstrate that action-effect predictions can boost stochastic regularity-based predictions and engage higher-order deviance detection processes, extending previous notions on the role of action predictions at sensory levels.

Cross-modal predictive processing depends on context rather than local contingencies

Visual symbols or events may provide predictive information on to-be-expected sound events. When the perceived sound does not confirm the visual prediction, the incongruency response (IR), a prediction error signal of the event-related brain potentials, is elicited. It is unclear whether predictions are derived from lower-level local contingencies (e.g., recent events or repetitions) or from higher-level global rules applied top-down. In a recent study, sound pitch was predicted by a preceding note symbol. IR elicitation was confined to the condition where one of two sounds was presented more frequently and was not present with equal probability of both sounds. These findings suggest that local repetitions support predictive cross-modal processing. On the other hand, IR has also been observed with equal stimulus probabilities, where visual patterns predicted the upcoming sound sequence. This suggests the application of global rules. Here, we investigated the influence of stimulus repetition on the elicitation of the IR by presenting identical trial trains of a particular visual note symbol cueing a particular sound resulting either in a congruent or an incongruent pair. Trains of four different lengths: 1, 2, 4, or 7 were presented. The IR was observed already after a single presentation of a congruent visual-cue-sound combination and did not change in amplitude as trial train length increased. We conclude that higher-level associations applied in a top-down manner are involved in elicitation of the prediction error signal reflected by the IR, independent from local contingencies.

Change detection of auditory tonal patterns defined by absolute versus relative pitch information. A combined behavioural and EEG study

The human auditory system often relies on relative pitch information to extract and identify auditory objects; such as when the same melody is played in different keys. The current study investigated the mental chronometry underlying the active discrimination of unfamiliar melodic six-tone patterns by measuring behavioural performance and event-related potentials (ERPs). In a roving standard paradigm, such patterns were either repeated identically within a stimulus train, carrying absolute frequency information about the pattern, or shifted in pitch (transposed) between repetitions, so only relative pitch information was available to extract the pattern identity. Results showed that participants were able to use relative pitch to detect when a new melodic pattern occurred. Though in the absence of absolute pitch sensitivity significantly decreased and behavioural reaction time to pattern changes increased. Mismatch-Negativity (MMN), an ERP indicator of auditory deviance detection, was elicited at approximately 206 ms after stimulus onset at frontocentral electrodes, even when only relative pitch was available to inform pattern discrimination. A P3a was elicited in both conditions, comparable in amplitude and latency. Increased latencies but no differences in amplitudes of N2b, and P3b suggest that processing at higher levels is affected when, in the absence of absolute pitch cues, relative pitch has to be extracted to inform pattern discrimination. Interestingly, the response delay of approximately 70 ms on the behavioural level, already fully manifests at the level of N2b. This is in accordance with recent findings on implicit auditory learning processes and suggests that in the absence of absolute pitch cues a slowing of target selection rather than a slowing of the auditory pattern change detection process causes the deterioration in behavioural performance.

Attentional Processing of Disgust and Fear and Its Relationship With Contamination-Based Obsessive-Compulsive Symptoms: Stronger Response Urgency to Disgusting Stimuli in Disgust-Prone Individuals

Disgust has recently been characterized as a low-urgency emotion, particularly compared to fear. The aim of the present study is to clarify whether behavioral inhibition during disgust engagement is characteristic of a low-urgency emotion and thus indicates self-imposed attentional avoidance in comparison to fear. Therefore, 54 healthy participants performed an emotional go/no-go task with disgust- and fear-relevant as well as neutral pictures. Furthermore, heart rate activity and facial muscle activity on the fear-specific m. corrugator supercilli and the disgust-specific m. levator labii were assessed. The results partially support the temporal urgency hypothesis of disgust. The emotion conditions significantly differed in emotional engagement and in the facial muscle activity of the m. levator labii as expected. However, contrary to our expectations, no differences between the emotion conditions regarding behavioral inhibition as well as heart rate change could be found. Furthermore, individuals with a higher-trait disgust proneness showed faster reactions and higher activity of the m. levator labii in response to disgust stimuli. The results show that different trait levels influence attentional engagement and physiological parameters but have only a small effect on behavioral inhibition.

Omission related brain responses reflect specific and unspecific action-effect couplings

When an auditory stimulus is predicted but unexpectedly omitted, an omission response can be observed in the EEG. This endogenous response to the absence of a stimulus demonstrates the important role of prediction in perception. SanMiguel et al. (2013a) showed that in order to observe an omission response, a specific prediction concerning the identity of an upcoming stimulus is necessary. They used button presses coupled to either a single sound (predictable identity), or a random sound (unpredictable identity). In the event-related potentials, a sequence of omission responses consisting of oN1, oN2, and oP3 was observed in the single condition but not in the random condition. Given the importance of omission studies to understand the role of prediction in perception, we replicated this study. We enhanced statistical power by doubling the sample size and adjusting data pre-processing, and applied temporal principal component analysis and replication Bayes statistics. Results in the single sound condition were successfully replicated. Principal component analysis additionally revealed attenuated oN1 and oP3 omission responses in the random sound condition. These results suggest the existence of both specific and unspecific predictions along the sound processing hierarchy, where precision weighting possibly influences the strength of prediction error. Results are discussed in the framework of predictive coding and are congruent with everyday life, where uncertainty often requires broader or more general predictions.

What exactly is missing here? The sensory processing of unpredictable omissions is modulated by the specificity of expected action-effects

We select our actions according to the desired outcomes; for instance, piano players press certain keys to generate specific musical notes. It is well-described that the omission of a predicted action-effect may elicit prediction error signals in the brain, but what happens in the case of simultaneous effector-specific (by contrast to effector-unspecific) predictions? To answer this question, we asked participants to press left and right keys to generate tones A and B; based on the action-effect association, the tones' identity was either predictable or unpredictable, while rarely, the expected input was omitted. Crucially, the data show that omissions following hand-specific associations reliably elicited a late omission N1 (oN1) component, by contrast to the hand-unspecific associations, where the late oN1 was rather weak. An additional condition where both key-presses generated a unique tone was implemented. Here, rare omissions of the expected tone generated both early and late oN1 responses, by contrast to the condition in which two simultaneous action-effect representations had to be maintained, where only late oN1 responses were elicited. Finally, omission P3 (oP3) responses were strongly elicited for all omission types without differences, indicating that a general expectation based on a tone presentation (rather than which tone), is likely indexed at this stage. The present results emphasize the top-down effects of action intention on the sensory processing of omissions, where unspecific (vs. specific) and multiple (vs. single) action-effect representations are associated with processing costs at the early sensory levels.

Encoding of deterministic and stochastic auditory rules in the human brain: The mismatch negativity mechanism does not reflect basic probability

Regularities in a sequence of sounds can be automatically encoded in a predictive model by the auditory system. When a sound deviates from the one predicted by the model, a mismatch negativity (MMN) is elicited, which is taken to reflect a prediction error at a particular level of the model hierarchy. Although there are many studies on deterministic regularities, only a few have investigated the brain's ability to encode non-deterministic regularities. We studied a simple stochastic regularity: two tone pitches (standards, each occurring on 45% of trials); this regularity was occasionally violated by another tone pitch (deviant, occurring on 10% of trials). We found MMN when the deviant's pitch was outside those of the standards, but not when it was between them. Importantly, when we alternated the occurrence of the same two standards, making them deterministic, the deviant elicited MMN, even when its pitch was between those of the standards. Thus, although the MMN system is extremely powerful in establishing even quite complex deterministic regularities, it fails with a simple stochastic regularity. We argue that the MMN system does not know basic probability.

Action Intention-based and Stimulus Regularity-based Predictions: Same or Different?

We act on the environment to produce desired effects, but we also adapt to the environmental demands by learning what to expect next, based on experience: How do action-based predictions and sensory predictions relate to each other? We explore this by implementing a self-generation oddball paradigm, where participants performed random sequences of left and right button presses to produce frequent standard and rare deviant tones. By manipulating the action–tone association as well as the likelihood of a button press over the other one, we compare ERP effects evoked by the intention to produce a specific tone, tone regularity, and both intention and regularity. We show that the N1b and Tb components of the N1 response are modulated by violations of tone regularity only. However, violations of action intention as well as of regularity elicit MMN responses, which occur similarly in all three conditions. Regardless of whether the predictions at sensory levels were based on either intention, regularity, or both, the tone deviance was further and equally well detected at hierarchically higher processing level, as reflected in similar P3a effects between conditions. We did not observe additive prediction errors when intention and regularity were violated concurrently, suggesting the two integrate despite presumably having independent generators. Even though they are often discussed as individual prediction sources in the literature, this study represents to our knowledge the first to directly compare them. Finally, these results show how, in the context of action, our brain can easily switch between top–down intention-based expectations and bottom–up regularity cues to efficiently predict future events.

Auditory Predictions and Prediction Errors in Response to Self-Initiated Vowels

It has been suggested that speech production is accomplished by an internal forward model, reducing processing activity directed to self-produced speech in the auditory cortex. The current study uses an established N1-suppression paradigm comparing self- and externally initiated natural speech sounds to answer two questions: (1) Are forward predictions generated to process complex speech sounds, such as vowels, initiated via a button press? (2) Are prediction errors regarding self-initiated deviant vowels reflected in the corresponding ERP components? Results confirm an N1-suppression in response to self-initiated speech sounds. Furthermore, our results suggest that predictions leading to the N1-suppression effect are specific, as self-initiated deviant vowels do not elicit an N1-suppression effect. Rather, self-initiated deviant vowels elicit an enhanced N2b and P3a compared to externally generated deviants, externally generated standard, or self-initiated standards, again confirming prediction specificity. Results show that prediction errors are salient in self-initiated auditory speech sounds, which may lead to more efficient error correction in speech production.

Beta power encodes contextual estimates of temporal event probability in the human brain

To prepare for an impending event of unknown temporal distribution, humans internally increase the perceived probability of event onset as time elapses. This effect is termed the hazard rate of events. We tested how the neural encoding of hazard rate changes by providing human participants with prior information on temporal event probability. We recorded behavioral and electroencephalographic (EEG) data while participants listened to continuously repeating five-tone sequences, composed of four standard tones followed by a non-target deviant tone, delivered at slow (1.6 Hz) or fast (4 Hz) rates. The task was to detect a rare target tone, which equiprobably appeared at either position two, three or four of the repeating sequence. In this design, potential target position acts as a proxy for elapsed time. For participants uninformed about the target's distribution, elapsed time to uncertain target onset increased response speed, displaying a significant hazard rate effect at both slow and fast stimulus rates. However, only in fast sequences did prior information about the target's temporal distribution interact with elapsed time, suppressing the hazard rate. Importantly, in the fast, uninformed condition pre-stimulus power synchronization in the beta band (Beta 1, 15-19 Hz) predicted the hazard rate of response times. Prior information suppressed pre-stimulus power synchronization in the same band, while still significantly predicting response times. We conclude that Beta 1 power does not simply encode the hazard rate, but-more generally-internal estimates of temporal event probability based upon contextual information.

Presentation Probability of Visual–Auditory Pairs Modulates Visually Induced Auditory Predictions

Predictions about forthcoming auditory events can be established on the basis of preceding visual information. Sounds being incongruent to predictive visual information have been found to elicit an enhanced negative ERP in the latency range of the auditory N1 compared with physically identical sounds being preceded by congruent visual information. This so-called incongruency response (IR) is interpreted as reduced prediction error for predicted sounds at a sensory level. The main purpose of this study was to examine the impact of probability manipulations on the IR. We manipulated the probability with which particular congruent visual–auditory pairs were presented (83/17 vs. 50/50 condition). This manipulation led to two conditions with different strengths of the association of visual with auditory information. A visual cue was presented either above or below a fixation cross and was followed by either a high- or low-pitched sound. In 90% of trials, the visual cue correctly predicted the subsequent sound. In one condition, one of the sounds was presented more frequently (83% of trials), whereas in the other condition both sounds were presented with equal probability (50% of trials). Therefore, in the 83/17 condition, one congruent combination of visual cue and corresponding sound was presented more frequently than the other combinations presumably leading to a stronger visual–auditory association. A significant IR for unpredicted compared with predicted but otherwise identical sounds was observed only in the 83/17 condition, but not in the 50/50 condition, where both congruent visual cue–sound combinations were presented with equal probability. We also tested whether the processing of the prediction violation is dependent on the task relevance of the visual information. Therefore, we contrasted a visual–auditory matching task with a pitch discrimination task. It turned out that the task only had an impact on the behavioral performance but not on the prediction error signals. Results suggest that the generation of visual-to-auditory sensory predictions is facilitated by a strong association between the visual cue and the predicted sound (83/17 condition) but is not influenced by the task relevance of the visual information.

Modulation of Cognitive and Emotional Control in Age-Related Mild-to-Moderate Hearing Loss

Progressive hearing loss is a common phenomenon in healthy aging and may affect the perception of emotions expressed in speech. Elderly with mild to moderate hearing loss often rate emotional expressions as less emotional and display reduced activity in emotion-sensitive brain areas (e.g., amygdala). However, it is not clear how hearing loss affects cognitive and emotional control mechanisms engaged in multimodal speech processing. In previous work we showed that negative, task-relevant and -irrelevant emotion modulates the two types of control in younger and older adults without hearing loss. To further explore how reduced hearing capacity affects emotional and cognitive control, we tested whether moderate hearing loss (>30 dB) at frequencies relevant for speech impacts cognitive and emotional control. We tested two groups of older adults with hearing loss (HL; N = 21; mean age = 70.5) and without hearing loss (NH; N = 21; mean age = 68.4). In two EEG experiments participants observed multimodal video clips and either categorized pronounced vowels (cognitive conflict) or their emotions (emotional conflict). Importantly, the facial expressions were either matched or mismatched with the corresponding vocalizations. In both conflict tasks, we found that negative stimuli modulated behavioral conflict processing in the NH but not the HL group, while the HL group performed at chance level in the emotional conflict task. Further, we found that the amplitude difference between congruent and incongruent stimuli was larger in negative relative to neutral N100 responses across tasks and groups. Lastly, in the emotional conflict task, neutral stimuli elicited a smaller N200 response than emotional stimuli primarily in the HL group. Consequently, age-related hearing loss not only affects the processing of emotional acoustic cues but also alters the behavioral benefits of emotional stimuli on cognitive and emotional control, despite preserved early neural responses. The resulting difficulties in the multimodal integration of incongruent emotional stimuli may lead to problems in processing complex social information (irony, sarcasm) and impact emotion processing in the limbic network. This could be related to social isolation and depression observed in the elderly with age-related hearing loss.

Endogenous Covert Spatial Orienting in Audition Cost-Benefit Analyses of Reaction Times and Event related Potentials

The present study examines mechanisms of endogenous covert spatial orienting in audition as revealed by event-related brain potentials (ERPs) and reaction times (RTs). In one experimental condition, subjects were instructed to respond to any target tone irrespective of whether it was presented in a valid (spatially predictive cue), neutral (uninformative cue), or invalid (misleading cue) trial. In another experimental condition, only target tones presented at a cued position required a response—that is, subjects could completely ignore tones presented at the uncued ear. Cue validity had an effect on RT, which consisted in benefits for valid trials and in costs for invalid trials relative to the RTs in neutral trials. There were also distinct ERP effects of cue validity in the 100–300 msec time range. These ERP effects were enlarged in the condition in which uncued tones could be ignored. The effects of cue validity on RTs and ERPs demonstrated covert orienting in audition both for stimuli requiring an overt response and also for stimuli that did not require a behavioural response. It is argued that this attentional selection is located at intermediate stages of information processing, rather than at peripheral stages such as basic sensory-specific processing or response selection.

The Influence of Negative Emotion on Cognitive and Emotional Control Remains Intact in Aging

Healthy aging is characterized by a gradual decline in cognitive control and inhibition of interferences, while emotional control is either preserved or facilitated. Emotional control regulates the processing of emotional conflicts such as in irony in speech, and cognitive control resolves conflict between non-affective tendencies. While negative emotion can trigger control processes and speed up resolution of both cognitive and emotional conflicts, we know little about how aging affects the interaction of emotion and control. In two EEG experiments, we compared the influence of negative emotion on cognitive and emotional conflict processing in groups of younger adults (mean age = 25.2 years) and older adults (69.4 years). Participants viewed short video clips and either categorized spoken vowels (cognitive conflict) or their emotional valence (emotional conflict), while the visual facial information was congruent or incongruent. Results show that negative emotion modulates both cognitive and emotional conflict processing in younger and older adults as indicated in reduced response times and/or enhanced event-related potentials (ERPs). In emotional conflict processing, we observed a valence-specific N100 ERP component in both age groups. In cognitive conflict processing, we observed an interaction of emotion by congruence in the N100 responses in both age groups, and a main effect of congruence in the P200 and N200. Thus, the influence of emotion on conflict processing remains intact in aging, despite a marked decline in cognitive control. Older adults may prioritize emotional wellbeing and preserve the role of emotion in cognitive and emotional control.

Audio-visual synchrony and spatial attention enhance processing of dynamic visual stimulation independently and in parallel: A frequency-tagging study

The neural processing of a visual stimulus can be facilitated by attending to its position or by a co-occurring auditory tone. Using frequency-tagging, we investigated whether facilitation by spatial attention and audio-visual synchrony rely on similar neural processes. Participants attended to one of two flickering Gabor patches (14.17 and 17 Hz) located in opposite lower visual fields. Gabor patches further "pulsed" (i.e. showed smooth spatial frequency variations) at distinct rates (3.14 and 3.63 Hz). Frequency-modulating an auditory stimulus at the pulse-rate of one of the visual stimuli established audio-visual synchrony. Flicker and pulsed stimulation elicited stimulus-locked rhythmic electrophysiological brain responses that allowed tracking the neural processing of simultaneously presented Gabor patches. These steady-state responses (SSRs) were quantified in the spectral domain to examine visual stimulus processing under conditions of synchronous vs. asynchronous tone presentation and when respective stimulus positions were attended vs. unattended. Strikingly, unique patterns of effects on pulse- and flicker driven SSRs indicated that spatial attention and audiovisual synchrony facilitated early visual processing in parallel and via different cortical processes. We found attention effects to resemble the classical top-down gain effect facilitating both, flicker and pulse-driven SSRs. Audio-visual synchrony, in turn, only amplified synchrony-producing stimulus aspects (i.e. pulse-driven SSRs) possibly highlighting the role of temporally co-occurring sights and sounds in bottom-up multisensory integration.

The digitization of the Wundt estate at Leipzig University

Wilhelm M. Wundt (1832-1920) was one of the most important German scholars of the 19th and early 20th centuries and famously founded the first institute for experimental psychology in Leipzig in 1879. Wundt's institute established a teaching and research facility that attracted a large number of students from all over the world and contributed greatly to the development of modern psychology. Until now, the relatively poor indexing and documentation as well as the difficulty in accessing the Wundt estate has prevented a widespread and comprehensive investigation and consideration of these documents. The digitization project described in this article has rectified these problems and will hopefully provide a valuable source for students and researchers interested in Wundt's work. (PsycINFO Database Record

Positive emotion impedes emotional but not cognitive conflict processing

Cognitive control enables successful goal-directed behavior by resolving a conflict between opposing action tendencies, while emotional control arises as a consequence of emotional conflict processing such as in irony. While negative emotion facilitates both cognitive and emotional conflict processing, it is unclear how emotional conflict processing is affected by positive emotion (e.g., humor). In 2 EEG experiments, we investigated the role of positive audiovisual target stimuli in cognitive and emotional conflict processing. Participants categorized either spoken vowels (cognitive task) or their emotional valence (emotional task) and ignored the visual stimulus dimension. Behaviorally, a positive target showed no influence on cognitive conflict processing, but impeded emotional conflict processing. In the emotional task, response time conflict costs were higher for positive than for neutral targets. In the EEG, we observed an interaction of emotion by congruence in the P200 and N200 ERP components in emotional but not in cognitive conflict processing. In the emotional conflict task, the P200 and N200 conflict effect was larger for emotional than neutral targets. Thus, our results show that emotion affects conflict processing differently as a function of conflict type and emotional valence. This suggests that there are conflict- and valence-specific mechanisms modulating executive control.

How regularity representations of short sound patterns that are based on relative or absolute pitch information establish over time: An EEG study

The recognition of sound patterns in speech or music (e.g., a melody that is played in different keys) requires knowledge about pitch relations between successive sounds. We investigated the formation of regularity representations for sound patterns in an event-related potential (ERP) study. A pattern, which consisted of six concatenated 50 ms tone segments differing in fundamental frequency, was presented 1, 2, 3, 6, or 12 times and then replaced by another pattern by randomly changing the pitch of the tonal segments (roving standard paradigm). In an absolute repetition condition, patterns were repeated identically, whereas in a transposed condition, only the pitch relations of the tonal segments of the patterns were repeated, while the entire patterns were shifted up or down in pitch. During ERP measurement participants were not informed about the pattern repetition rule, but were instructed to discriminate rarely occurring targets of lower or higher sound intensity. EPRs for pattern changes (mismatch negativity, MMN; and P3a) and for pattern repetitions (repetition positivity, RP) revealed that the auditory system is able to rapidly extract regularities from unfamiliar complex sound patterns even when absolute pitch varies. Yet, enhanced RP and P3a amplitudes, and improved behavioral performance measured in a post-hoc test, in the absolute as compared with the transposed condition suggest that it is more difficult to encode patterns without absolute pitch information. This is explained by dissociable processing of standards and deviants as well as a back propagation mechanism to early sensory processing stages, which is effective after less repetitions of a standard stimulus for absolute pitch.

Implicit expectations influence target detection in children and adults

When a sound occurs at a predictable time, it gets processed more efficiently. Predictability of the temporal structure of acoustic inflow has been found to influence the P3b of event-related potentials in young adults, such that highly predictable compared to less predictable input leads to earlier P3b peak latencies. In our study, we wanted to investigate the influence of predictability on target processing indexed by the P3b in children (10-12 years old) and young adults. To do that, we used an oddball paradigm with two conditions of predictability (high and low). In the High-predictability condition, a high-pitched target tone occurred most of the time in the fifth position of a five-tone pattern (after four low-pitched non-target sounds), whereas in the Low-predictability condition, no such rule was implemented. The target tone occurred randomly following 2, 3, 4, 5, or 6 non-target tones. In both age groups, reaction time to predictable targets was faster than to non-predictable targets. Remarkably, this effect was largest in children. Consistent with the behavioral responses, the onset latency of the P3b response elicited by targets in both groups was earlier in the predictable than the unpredictable conditions. However, only the children had significantly earlier peak latency responses for predictable targets. Our results demonstrate that target stimulus predictability increases processing speed in children and adults even when predictability was only implicitly derived by the stimulus statistics. Children did have larger effects of predictability, seeming to benefit more from predictability for target detection.

Interrelation of attention and prediction in visual processing: Effects of task-relevance and stimulus probability

The potentially interactive influence of attention and prediction was investigated by measuring event-related potentials (ERPs) in a spatial cueing task with attention (task-relevant) and prediction (probabilistic) cues. We identified distinct processing stages of this interactive influence. Firstly, in line with the attentional gain hypothesis, a larger amplitude response of the contralateral N1, and Nd1 for attended gratings was observed. Secondly, conforming to the attenuation-by-prediction hypothesis, a smaller negativity in the time window directly following the peak of the N1 component for predicted compared to unpredicted gratings was observed. In line with the hypothesis that attention and prediction interface, unpredicted/unattended stimuli elicited a larger negativity at central-parietal sites, presumably reflecting an increased prediction error signal. Thirdly, larger P3 responses to unpredicted stimuli pointed to the updating of an internal model. Attention and prediction can be considered as differentiated mechanisms that may interact at different processing stages to optimise perception.

Distraction by Novel and Pitch-Deviant Sounds in Children

The control of attention is an important part of our executive functions and enables us to focus on relevant information and to ignore irrelevant information. The ability to shield against distraction by task-irrelevant sounds is suggested to mature during school age. The present study investigated the developmental time course of distraction in three groups of children aged 7–10 years. Two different types of distractor sounds that have been frequently used in auditory attention research—novel environmental and pitch-deviant sounds—were presented within an oddball paradigm while children performed a visual categorization task. Reaction time measurements revealed decreasing distractor-related impairment with age. Novel environmental sounds impaired performance in the categorization task more than pitch-deviant sounds. The youngest children showed a pronounced decline of novel-related distraction effects throughout the experimental session. Such a significant decline as a result of practice was not observed in the pitch-deviant condition and not in older children. We observed no correlation between cross-modal distraction effects and performance in standardized tests of concentration and visual distraction. Results of the cross-modal distraction paradigm indicate that separate mechanisms underlying the processing of novel environmental and pitch-deviant sounds develop with different time courses and that these mechanisms develop considerably within a few years in middle childhood.

The Feedback-related Negativity Codes Components of Abstract Inference during Reward-based Decision-making

Behavioral control is influenced not only by learning from the choices made and the rewards obtained but also by “what might have happened,” that is, inference about unchosen options and their fictive outcomes. Substantial progress has been made in understanding the neural signatures of direct learning from choices that are actually made and their associated rewards via reward prediction errors (RPEs). However, electrophysiological correlates of abstract inference in decision-making are less clear. One seminal theory suggests that the so-called feedback-related negativity (FRN), an ERP peaking 200–300 msec after a feedback stimulus at frontocentral sites of the scalp, codes RPEs. Hitherto, the FRN has been predominantly related to a so-called “model-free” RPE: The difference between the observed outcome and what had been expected. Here, by means of computational modeling of choice behavior, we show that individuals employ abstract, “double-update” inference on the task structure by concurrently tracking values of chosen stimuli (associated with observed outcomes) and unchosen stimuli (linked to fictive outcomes). In a parametric analysis, model-free RPEs as well as their modification because of abstract inference were regressed against single-trial FRN amplitudes. We demonstrate that components related to abstract inference uniquely explain variance in the FRN beyond model-free RPEs. These findings advance our understanding of the FRN and its role in behavioral adaptation. This might further the investigation of disturbed abstract inference, as proposed, for example, for psychiatric disorders, and its underlying neural correlates.