Effect of deviant probability and interstimulus/interdeviant interval on the auditory N1 and mismatch negativity in the cat auditory cortex

A Dual Role for the Dorsolateral Prefrontal Cortex (DLPFC) in Auditory Deviance Detection

BACKGROUND

In the oddball paradigm, the dorsolateral prefrontal cortex (DLPFC) is often associated with active cognitive responses, such as maintaining information in working memory or adapting response strategies. While some evidence points to the DLPFC's role in passive auditory deviance perception, a detailed understanding of the spatiotemporal neurodynamics involved remains unclear.

METHODS

In this study, event-related optical signals (EROS) and event-related potentials (ERPs) were simultaneously recorded for the first time over the prefrontal cortex using a 64-channel electroencephalography (EEG) system, during passive auditory deviance perception in 12 right-handed young adults (7 women and 5 men). In this oddball paradigm, deviant stimuli (a 1500 Hz pure tone) elicited a negative shift in the N1 ERP component, related to mismatch negativity (MMN), and a significant positive deflection associated with the P300, compared to standard stimuli (a 1000 Hz tone).

RESULTS

We hypothesize that the DLPFC not only participates in active tasks but also plays a critical role in processing deviant stimuli in passive conditions, shifting from pre-attentive to attentive processing. We detected enhanced neural activity in the left middle frontal gyrus (MFG), at the same timing of the MMN component, followed by later activation at the timing of the P3a ERP component in the right MFG.

CONCLUSIONS

Understanding these dynamics will provide deeper insights into the DLPFC's role in evaluating the novelty or unexpectedness of the deviant stimulus, updating its cognitive value, and adjusting future predictions accordingly. However, the small number of subjects could limit the generalizability of the observations, in particular with respect to the effect of handedness, and additional studies with larger and more diverse samples are necessary to validate our conclusions.

Probing Beat Perception with Event-Related Potentials (ERPs) in Human Adults, Newborns, and Nonhuman Primates

The aim of this chapter is to give an overview of how the perception of rhythmic temporal regularity such as a regular beat in music can be studied in human adults, human newborns, and nonhuman primates using event-related brain potentials (ERPs). First, we discuss different aspects of temporal structure in general, and musical rhythm in particular, and we discuss the possible mechanisms underlying the perception of regularity (e.g., a beat) in rhythm. Additionally, we highlight the importance of dissociating beat perception from the perception of other types of structure in rhythm, such as predictable sequences of temporal intervals, ordinal structure, and rhythmic grouping. In the second section of the chapter, we start with a discussion of auditory ERPs elicited by infrequent and frequent sounds: ERP responses to regularity violations, such as mismatch negativity (MMN), N2b, and P3, as well as early sensory responses to sounds, such as P1 and N1, have been shown to be instrumental in probing beat perception. Subsequently, we discuss how beat perception can be probed by comparing ERP responses to sounds in regular and irregular sequences, and by comparing ERP responses to sounds in different metrical positions in a rhythm, such as on and off the beat or on strong and weak beats. Finally, we will discuss previous research that has used the aforementioned ERPs and paradigms to study beat perception in human adults, human newborns, and nonhuman primates. In doing so, we consider the possible pitfalls and prospects of the technique, as well as future perspectives.

Shank3 mutations enhance early neural responses to deviant tones in dogs

Both enhanced discrimination of low-level features of auditory stimuli and mutations of SHANK3 (a gene that encodes a synaptic scaffolding protein) have been identified in autism spectrum disorder patients. However, experimental evidence regarding whether SHANK3 mutations lead to enhanced neural processing of low-level features of auditory stimuli is lacking. The present study investigated this possibility by examining effects of Shank3 mutations on early neural processing of pitch (tone frequency) in dogs. We recorded electrocorticograms from wild-type and Shank3 mutant dogs using an oddball paradigm in which deviant tones of different frequencies or probabilities were presented along with other tones in a repetitive stream (standards). We found that, relative to wild-type dogs, Shank3 mutant dogs exhibited larger amplitudes of early neural responses to deviant tones and greater sensitivity to variations of deviant frequencies within 100 ms after tone onsets. In addition, the enhanced early neural responses to deviant tones in Shank3 mutant dogs were observed independently of the probability of deviant tones. Our findings highlight an essential functional role of Shank3 in modulations of early neural detection of novel sounds and offer new insights into the genetic basis of the atypical auditory information processing in autism patients.

The Role of Action-Effect Contingency on Sensory Attenuation in the Absence of Movement

Stimuli that have been generated by a person's own willed motor actions generally elicit a suppressed electrophysiological, as well as phenomenological, response than identical stimuli that have been externally generated. This well-studied phenomenon, known as sensory attenuation, has mostly been studied by comparing ERPs evoked by self-initiated and externally generated sounds. However, most studies have assumed a uniform action-effect contingency, in which a motor action leads to a resulting sensation 100% of the time. In this study, we investigated the effect of manipulating the probability of action-effect contingencies on the sensory attenuation effect. In Experiment 1, participants watched a moving, marked tickertape while EEG was recorded. In the full-contingency (FC) condition, participants chose whether to press a button by a certain mark on the tickertape. If a button press had not occurred by the mark, a sound would be played a second later 100% of the time. If the button was pressed before the mark, the sound was not played. In the no-contingency (NC) condition, participants observed the same tickertape; in contrast, however, if participants did not press the button by the mark, a sound would occur only 50% of the time (NC-inaction). Furthermore, in the NC condition, if a participant pressed the button before the mark, a sound would also play 50% of the time (NC-action). In Experiment 2, the design was identical, except that a willed action (as opposed to a willed inaction) triggered the sound in the FC condition. The results were consistent across the two experiments: Although there were no differences in N1 amplitude between conditions, the amplitude of the Tb and P2 components were smaller in the FC condition compared with the NC-inaction condition, and the amplitude of the P2 component was also smaller in the FC condition compared with the NC-action condition. The results suggest that the effect of contingency on electrophysiological indices of sensory attenuation may be indexed primarily by the Tb and P2 components, rather than the N1 component which is most commonly studied.

Visual mismatch responses index surprise signalling but not expectation suppression

The ability to distinguish between commonplace and unusual sensory events is critical for efficient learning and adaptive behaviour. This has been investigated using oddball designs in which sequences of often-appearing (i.e., expected) stimuli are interspersed with rare (i.e., surprising) deviants. Resulting differences in electrophysiological responses following surprising compared to expected stimuli are known as visual mismatch responses (VMRs). VMRs are thought to index co-occurring contributions of stimulus repetition effects, expectation suppression (that occurs when one's expectations are fulfilled), and expectation violation (i.e., surprise) responses; however, these different effects have been conflated in existing oddball designs. To better isolate and quantify effects of expectation suppression and surprise, we adapted an oddball design based on Fast Periodic Visual Stimulation (FPVS) that controls for stimulus repetition effects. We recorded electroencephalography (EEG) while participants (N = 48) viewed stimulation sequences in which a single face identity was periodically presented at 6 Hz. Critically, one of two different face identities (termed oddballs) appeared as every 7th image throughout the sequence. The presentation probabilities of each oddball image within a sequence varied between 10 and 90%, such that participants could form expectations about which oddball face identity was more likely to appear within each sequence. We also included 'expectation neutral' 50% probability sequences, whereby consistently biased expectations would not be formed for either oddball face identity. We found that VMRs indexed surprise responses, and effects of expectation suppression were absent. That is, ERPs were more negative-going at occipitoparietal electrodes for surprising compared to neutral oddballs, but did not differ between expected and neutral oddballs. Surprising oddball-evoked ERPs were also highly similar across the 10-40% appearance probability conditions. Our findings indicate that VMRs which are not accounted for by repetition effects are best described as an all-or-none surprise response, rather than a minimisation of prediction error responses associated with expectation suppression.

Single-Trial EEG-fMRI Reveals the Generation Process of the Mismatch Negativity

Although research on the mismatch negativity (MMN) has been ongoing for 40 years, the generation process of the MMN remains largely unknown. In this study, we used a single-trial electro-encephalography (EEG)-functional magnetic resonance imaging (fMRI) coupling method which can analyze neural activity with both high temporal and high spatial resolution and thus assess the generation process of the MMN. We elicited the MMN with an auditory oddball paradigm while recording simultaneous EEG and fMRI. We divided the MMN into five equal-durational phases. Utilizing the single-trial variability of the MMN, we analyzed the neural generators of the five phases, thereby determining the spatiotemporal generation process of the MMN. We found two distinct bottom-up prediction error propagations: first from the auditory cortex to the motor areas and then from the auditory cortex to the inferior frontal gyrus (IFG). Our results support the regularity-violation hypothesis of MMN generation.

Auditory Mismatch Negativity in Response to Changes of Counter-Balanced Interaural Time and Level Differences

Interaural time differences (ITD) and interaural level differences (ILD) both signal horizontal sound source location. To achieve a unified percept of our acoustic environment, these two cues require integration. In the present study, we tested this integration of ITD and ILD with electroencephalography (EEG) by measuring the mismatch negativity (MMN). The MMN can arise in response to spatial changes and is at least partly generated in auditory cortex. In our study, we aimed at testing for an MMN in response to stimuli with counter-balanced ITD/ILD cues. To this end, we employed a roving oddball paradigm with alternating sound sequences in two types of blocks: (a) lateralized stimuli with congruently combined ITD/ILD cues and (b) midline stimuli created by counter-balanced, incongruently combined ITD/ILD cues. We observed a significant MMN peaking at about 112–128 ms after change onset for the congruent ITD/ILD cues, for both lower (0.5 kHz) and higher carrier frequency (4 kHz). More importantly, we also observed significant MMN peaking at about 129 ms for incongruently combined ITD/ILD cues, but this effect was only detectable in the lower frequency range (0.5 kHz). There were no significant differences of the MMN responses for the two types of cue combinations (congruent/incongruent). These results suggest that—at least in the lower frequency ranges (0.5 kHz)—ITD and ILD are processed independently at the level of the MMN in auditory cortex.

Effects of Background Music on Objective and Subjective Performance Measures in an Auditory BCI

Several studies have explored brain computer interface (BCI) systems based on auditory stimuli, which could help patients with visual impairments. Usability and user satisfaction are important considerations in any BCI. Although background music can influence emotion and performance in other task environments, and many users may wish to listen to music while using a BCI, auditory, and other BCIs are typically studied without background music. Some work has explored the possibility of using polyphonic music in auditory BCI systems. However, this approach requires users with good musical skills, and has not been explored in online experiments. Our hypothesis was that an auditory BCI with background music would be preferred by subjects over a similar BCI without background music, without any difference in BCI performance. We introduce a simple paradigm (which does not require musical skill) using percussion instrument sound stimuli and background music, and evaluated it in both offline and online experiments. The result showed that subjects preferred the auditory BCI with background music. Different performance measures did not reveal any significant performance effect when comparing background music vs. no background. Since the addition of background music does not impair BCI performance but is preferred by users, auditory (and perhaps other) BCIs should consider including it. Our study also indicates that auditory BCIs can be effective even if the auditory channel is simultaneously otherwise engaged.

Mismatch negativity in common marmosets: Whole-cortical recordings with multi-channel electrocorticograms

Mismatch negativity (MMN) is a component of event-related potentials (ERPs) evoked by violations of regularity in sensory stimulus-series in humans. Recently, the MMN has received attention as a clinical and translatable biomarker of psychiatric disorders such as schizophrenia, and for the development animal models of these psychiatric disorders. In this study, we investigated the generation of MMN in common marmosets, which are an important non-human primate model with genetic manipulability. We recorded the electrocorticograms (ECoGs) from two common marmosets with epidurally implanted electrodes covering a wide range of cortical regions. ECoG recordings were conducted in a passive listening condition with a roving oddball paradigm. We compared the ERPs evoked by repeatedly presented standard stimuli and those evoked by the deviant stimuli. Significant differences in the ERPs were observed in several cortical areas. In particular, deviant stimuli elicited larger negative activity than standard stimuli in the temporal area. In addition, the latency and polarity of the activity were comparable to human MMNs. This is thus the first report of MMN-like activity in common marmosets. Our findings have the potential to advance future gene-manipulation studies that aim to establish non-human primate models of schizophrenia.

Perceiving temporal regularity in music: the role of auditory event-related potentials (ERPs) in probing beat perception

The aim of this chapter is to give an overview of how the perception of a regular beat in music can be studied in humans adults, human newborns, and nonhuman primates using event-related brain potentials (ERPs). Next to a review of the recent literature on the perception of temporal regularity in music, we will discuss in how far ERPs, and especially the component called mismatch negativity (MMN), can be instrumental in probing beat perception. We conclude with a discussion on the pitfalls and prospects of using ERPs to probe the perception of a regular beat, in which we present possible constraints on stimulus design and discuss future perspectives.

Cortical mapping of mismatch negativity with deviance detection property in rat

Mismatch Negativity (MMN) is an N-methyl-d-aspartic acid (NMDA)-mediated, negative deflection in human auditory evoked potentials in response to a cognitively discriminable change. MMN-like responses have been extensively investigated in animal models, but the existence of MMN equivalent is still controversial. In this study, we aimed to investigate how closely the putative MMN (MMNp) in rats exhibited the comparable properties of human MMN. We used a surface microelectrode array with a grid of 10×7 recording sites within an area of 4.5×3.0 mm to densely map evoked potentials in the auditory cortex of anesthetized rats under the oddball paradigm. Firstly, like human MMN, deviant stimuli elicited negative deflections in auditory evoked potentials following the positive middle-latency response, termed P1. Secondly, MMNp exhibited deviance-detecting property, which could not be explained by simple stimulus specific adaptation (SSA). Thirdly, this MMNp occurred focally in the auditory cortex, including both the core and belt regions, while P1 activation focus was obtained in the core region, indicating that both P1 and MMNp are generated in the auditory cortex, yet the sources of these signals do not completely overlap. Fourthly, MMNp significantly decreased after the application of AP5 (D-(-)-2-amino-5-phosphonopentanoic acid), an antagonist at NMDA receptors. In stark contrast, AP5 affected neither P1 amplitude nor SSA of P1. These results provide compelling evidence that the MMNp we have examined in rats is functionally comparable to human MMN. The present work will stimulate translational research into MMN, which may help bridge the gap between electroencephalography (EEG)/magnetoencephalography (MEG) studies in humans and electrophysiological studies in animals.

Predictions not commands: active inference in the motor system

The descending projections from motor cortex share many features with top-down or backward connections in visual cortex; for example, corticospinal projections originate in infragranular layers, are highly divergent and (along with descending cortico-cortical projections) target cells expressing NMDA receptors. This is somewhat paradoxical because backward modulatory characteristics would not be expected of driving motor command signals. We resolve this apparent paradox using a functional characterisation of the motor system based on Helmholtz's ideas about perception; namely, that perception is inference on the causes of visual sensations. We explain behaviour in terms of inference on the causes of proprioceptive sensations. This explanation appeals to active inference, in which higher cortical levels send descending proprioceptive predictions, rather than motor commands. This process mirrors perceptual inference in sensory cortex, where descending connections convey predictions, while ascending connections convey prediction errors. The anatomical substrate of this recurrent message passing is a hierarchical system consisting of functionally asymmetric driving (ascending) and modulatory (descending) connections: an arrangement that we show is almost exactly recapitulated in the motor system, in terms of its laminar, topographic and physiological characteristics. This perspective casts classical motor reflexes as minimising prediction errors and may provide a principled explanation for why motor cortex is agranular.

Effects of musical training and event probabilities on encoding of complex tone patterns

BACKGROUND

The human auditory cortex automatically encodes acoustic input from the environment and differentiates regular sound patterns from deviant ones in order to identify important, irregular events. The Mismatch Negativity (MMN) response is a neuronal marker for the detection of sounds that are unexpected, based on the encoded regularities. It is also elicited by violations of more complex regularities and musical expertise has been shown to have an effect on the processing of complex regularities. Using magnetoencephalography (MEG), we investigated the MMN response to salient or less salient deviants by varying the standard probability (70%, 50% and 35%) of a pattern oddball paradigm. To study the effects of musical expertise in the encoding of the patterns, we compared the responses of a group of non-musicians to those of musicians.

RESULTS

We observed significant MMN in all conditions, including the least salient condition (35% standards), in response to violations of the predominant tone pattern for both groups. The amplitude of MMN from the right hemisphere was influenced by the standard probability. This effect was modulated by long-term musical training: standard probability changes influenced MMN amplitude in the group of non-musicians only.

CONCLUSION

This study indicates that pattern violations are detected automatically, even if they are of very low salience, both in non-musicians and musicians, with salience having a stronger impact on processing in the right hemisphere of non-musicians. Long-term musical training influences this encoding, in that non-musicians benefit to a greater extent from a good signal-to-noise ratio (i.e. high probability of the standard pattern), while musicians are less dependent on the salience of an acoustic environment.

Searching for the mismatch negativity in primary auditory cortex of the awake monkey: deviance detection or stimulus specific adaptation?

The mismatch negativity (MMN) is a preattentive component of the auditory event-related potential that is elicited by a change in a repetitive acoustic pattern. While MMN has been extensively used in human electrophysiological studies of auditory processing, the neural mechanisms and brain regions underlying its generation remain unclear. We investigate possible homologs of the MMN in macaque primary auditory cortex (A1) using a frequency oddball paradigm in which rare "deviant" tones are randomly interspersed among frequent "standard" tones. Standards and deviants had frequencies equal to the best frequency (BF) of the recorded neural population or to a frequency that evoked a response half the amplitude of the BF response. Early and later field potentials, current source density components, multiunit activity, and induced high-gamma band responses were larger when elicited by deviants than by standards of the same frequency. Laminar analysis indicated that differences between deviant and standard responses were more prominent in later activity, thus suggesting cortical amplification of initial responses driven by thalamocortical inputs. However, unlike the human MMN, larger deviant responses were characterized by the enhancement of "obligatory" responses rather than the introduction of new components. Furthermore, a control condition wherein deviants were interspersed among many tones of variable frequency replicated the larger responses to deviants under the oddball condition. Results suggest that differential responses under the oddball condition in macaque A1 reflect stimulus-specific adaptation rather than deviance detection per se. We conclude that neural mechanisms of deviance detection likely reside in cortical areas outside of A1.

The mismatch negativity (MMN)--a unique window to disturbed central auditory processing in ageing and different clinical conditions

In this article, we review clinical research using the mismatch negativity (MMN), a change-detection response of the brain elicited even in the absence of attention or behavioural task. In these studies, the MMN was usually elicited by employing occasional frequency, duration or speech-sound changes in repetitive background stimulation while the patient was reading or watching videos. It was found that in a large number of different neuropsychiatric, neurological and neurodevelopmental disorders, as well as in normal ageing, the MMN amplitude was attenuated and peak latency prolonged. Besides indexing decreased discrimination accuracy, these effects may also reflect, depending on the specific stimulus paradigm used, decreased sensory-memory duration, abnormal perception or attention control or, most importantly, cognitive decline. In fact, MMN deficiency appears to index cognitive decline irrespective of the specific symptomatologies and aetiologies of the different disorders involved.

Comprehensive model of how reality distortion and symptoms occur in schizophrenia: could impairment in learning-dependent predictive perception account for the manifestations of schizophrenia?

Conventional wisdom has not laid out a clear and uniform profile of schizophrenia as a unitary entity. One of the key first steps in elucidating the neurobiology of this entity would be to characterize the essential and common elements in the group of entities called schizophrenia. Kraepelin in his introduction notes 'the conviction seems to be more and more gaining ground that dementia praecox on the whole represents, a well characterized form of disease, and that we are justified in regarding the majority of the clinical pictures which are brought together here as the expression of a single morbid process, though outwardly they often diverge very far from one another'. But what is that single morbid process? We suggest that just as the uniform defect in all types of cancer is impaired regulation of cell proliferation, the primary defect in the group of entities called schizophrenia is persistent defective hierarchical temporal processing. This manifests in the form of chronic memory-prediction errors or deficits in learning-dependent predictive perception. These deficits account for the symptoms that present as reality distortion (delusions, thought disorder and hallucinations). This constellation of symptoms corresponds with the profile of most patients currently diagnosed as suffering from schizophrenia. In this paper we describe how these deficits can lead to the various symptoms of schizophrenia.

Sequential temporo-fronto-temporal activation during monitoring of the auditory environment for temporal patterns

Subjects detected rarely occurring shifts between two simple tone-patterns, in a paradigm that dissociated the effects of rarity from those of pitch, habituation, and attention. Whole-head magnetoencephalography suggested that rare attended pattern-shifts evoked activity first in the superior temporal plane (sTp, peak ~100 ms), then superior temporal sulcus (sTs, peak ~130 ms), then posteroventral prefrontal (pvpF, peak ~230 ms), and anterior temporal cortices (aT, peak ~370 ms). Activity was more prominent in the right hemisphere. After subtracting the effects of nonshift tones (balanced for pitch and habituation status), weak but consistent differential effects of pattern-shifts began in aT at 90-130 ms, spread to sTs and sTp at ∼130 ms, then pvpF, and finally returned to aT. Cingulate activity resembled prefrontal. Responses to pattern shifts were greatly attenuated when the same stimuli were ignored, suggesting that the initial superior temporal activity reflected an attention-related mismatch negativity. The prefrontal activity at ~230 ms corresponded in latency and task correlates with simultaneously recorded event-related potential components N2b and P3a; the subsequent temporal activity corresponded to the P3b. These results were confirmed in sensors specific for frontal or temporal cortex, and thus are independent of the inverse method used. Overall, these results suggest that auditory working memory for temporal patterns begins with detection of the pattern change by an interaction of anterior and superior temporal structures, followed by identification of the event and its consequences led by posteroventral prefrontal and cingulate cortices, and finally, definitive encoding of the event in anterior temporal areas.

Striatal prediction error modulates cortical coupling

Both perceptual inference and motor responses are shaped by learned probabilities. For example, stimulus-induced responses in sensory cortices and preparatory activity in premotor cortex reflect how (un)expected a stimulus is. This is in accordance with predictive coding accounts of brain function, which posit a fundamental role of prediction errors for learning and adaptive behavior. We used functional magnetic resonance imaging and recent advances in computational modeling to investigate how (failures of) learned predictions about visual stimuli influence subsequent motor responses. Healthy volunteers discriminated visual stimuli that were differentially predicted by auditory cues. Critically, the predictive strengths of cues varied over time, requiring subjects to continuously update estimates of stimulus probabilities. This online inference, modeled using a hierarchical Bayesian learner, was reflected behaviorally: speed and accuracy of motor responses increased significantly with predictability of the stimuli. We used nonlinear dynamic causal modeling to demonstrate that striatal prediction errors are used to tune functional coupling in cortical networks during learning. Specifically, the degree of striatal trial-by-trial prediction error activity controls the efficacy of visuomotor connections and thus the influence of surprising stimuli on premotor activity. This finding substantially advances our understanding of striatal function and provides direct empirical evidence for formal learning theories that posit a central role for prediction error-dependent plasticity.

Memory-prediction errors and their consequences in schizophrenia

Cognitive deficits play a central role in the onset of schizophrenia. Cognitive impairment precedes the onset of psychosis in at least a subgroup of patients, and accounts for considerable dysfunction. Yet cognitive deficits as currently measured are not significantly related to hallucinations and delusions. Part of this counterintuitive absence of a relationship may be caused by the lack of an organizing principle of cognitive impairment in schizophrenia research. We review literature suggesting that a system of memory-based prediction is central to human perception, thought and action , and forward the notion that many of the symptoms of schizophrenia are a result of a failure of this system.

Neurophysiological and neurochemical animal models of schizophrenia: focus on glutamate

Deficits in N-methyl-d-aspartate receptor (NMDAR) function play a critical role in the pathophysiology of schizophrenia. Animal models are needed to investigate possible mechanisms underlying NMDA dysfunction in schizophrenia as well as development of new therapeutic approaches. A major difficulty in developing animal models for schizophrenia is the identification of quantifiable measures that can be tested in a similar fashion in both humans and animals. The majority of animal models utilize analogous measures, wherein species-specific behaviors are used as presumed parallel manifestations of a common underlying construct. In vivo microdialysis and electrophysiology represent two methodologies in which homologous measures can instead be obtained in both animals and humans. In both techniques, well-validated, NMDA-sensitive measures are analyzed in rodents using probes implanted directly into cortex or subcortical structures. We discuss the currently available data from studies that used these methods in non-human primate and rodent glutamate models. In addition, we emphasize the possible relevance of the amphetamine-challenge studies to positive symptoms and of EEG measures to cognitive deficits in schizophrenia.

A dual role for prediction error in associative learning

Confronted with a rich sensory environment, the brain must learn statistical regularities across sensory domains to construct causal models of the world. Here, we used functional magnetic resonance imaging and dynamic causal modeling (DCM) to furnish neurophysiological evidence that statistical associations are learnt, even when task-irrelevant. Subjects performed an audio-visual target-detection task while being exposed to distractor stimuli. Unknown to them, auditory distractors predicted the presence or absence of subsequent visual distractors. We modeled incidental learning of these associations using a Rescorla–Wagner (RW) model. Activity in primary visual cortex and putamen reflected learning-dependent surprise: these areas responded progressively more to unpredicted, and progressively less to predicted visual stimuli. Critically, this prediction-error response was observed even when the absence of a visual stimulus was surprising. We investigated the underlying mechanism by embedding the RW model into a DCM to show that auditory to visual connectivity changed significantly over time as a function of prediction error. Thus, consistent with predictive coding models of perception, associative learning is mediated by prediction-error dependent changes in connectivity. These results posit a dual role for prediction-error in encoding surprise and driving associative plasticity.

Deviance-elicited Changes in Event-related Potentials are Attenuated by Ketamine in Mice

Background: People with schizophrenia exhibit reduced ability to detect change in the auditory environment, which has been linked to abnormalities in N-methyl-D-aspartate (NMDA) receptor-mediated glutamate neurotransmission. This ability to detect changes in stimulus qualities can be measured with electroencephalography using auditory event-related potentials (ERPs). For example, reductions in the N100 and mismatch negativity (MMN), in response to pitch deviance, have been proposed as endophenotypes of schizophrenia. This study examines a novel rodent model of impaired pitch deviance detection in mice using the NMDA receptor antagonist ketamine. Methods: ERPs were recorded from unanesthetized mice during a pitch deviance paradigm prior to and following ketamine administration. First, N40 amplitude was evaluated using stimuli between 4 and 10 kHz to assess the amplitude of responses across the frequency range used. The amplitude and latency of the N40 were analyzed following standard (7 kHz) and deviant (5–9 kHz) stimuli. Additionally, we examined which portions of the ERP are selectively altered by pitch deviance to define possible regions for the mouse MMN. Results: Mice displayed increased N40 amplitude that was followed by a later negative component between 50 and 75 msec in response to deviant stimuli. Both the increased N40 and the late N40 negativity were attenuated by ketamine. Ketamine increased N40 latency for both standard and deviant stimuli alike. Conclusions: The mouse N40 and a subsequent temporal region have deviance response properties similar to the human N100 and, possibly, MMN. Deviance responses were abolished by ketamine, suggesting that ketamine-induced changes in mice mimic deviance detection deficits in schizophrenia.

The mismatch negativity (MMN) in basic research of central auditory processing: a review

In the present article, the basic research using the mismatch negativity (MMN) and analogous results obtained by using the magnetoencephalography (MEG) and other brain-imaging technologies is reviewed. This response is elicited by any discriminable change in auditory stimulation but recent studies extended the notion of the MMN even to higher-order cognitive processes such as those involving grammar and semantic meaning. Moreover, MMN data also show the presence of automatic intelligent processes such as stimulus anticipation at the level of auditory cortex. In addition, the MMN enables one to establish the brain processes underlying the initiation of attention switch to, conscious perception of, sound change in an unattended stimulus stream.

Nonhuman primate event-related potentials indexing covert shifts of attention

A half-century's worth of research has established the existence of numerous event-related potential components measuring different cognitive operations in humans including the selection of stimuli by covert attention mechanisms. Surprisingly, it is unknown whether nonhuman primates exhibit homologous electrophysiological signatures of selective visual processing while viewing complex scenes. We used an electrophysiological technique with macaque monkeys analogous to procedures for recording scalp event-related potentials from humans and found that monkeys exhibit short-latency visual components sensitive to sensory processing demands and lateralizations related to shifting of covert attention similar to the human N2pc component. These findings begin to bridge the gap between the disparate literatures by using electrophysiological measurements to study the deployment of visual attention in the brains of humans and nonhuman primates.

ERP Repetition Effects and Mismatch Negativity Generation

Neuronal adaptation is a ubiquitous property of the cortex. This review presents evidence from MMN studies that show ERP components with similar adaptive properties. Specifically, I consider the empirical evidence from the perspective of a predictive coding model of perceptual learning and inference. Within this framework, ERP and neuronal repetition effects (repetition suppression) are seen as reductions in prediction error, a process that requires synaptic modifications. Repetition positivity is a human auditory ERP component, which shows similar properties to stimulus-specific adaptation of auditory cortex neurons; a candidate mechanism for auditory trace formation.

Mismatch Negativity and Stimulus-Specific Adaptation in Animal Models

Animal models of MMN may serve both to further our understanding of neural processing beyond pure sensory coding and for unraveling the neural and pharmacological processes involved in the generation of MMN. We start this review by discussing the methodological issues that are especially important when pursuing a single-neuron correlate of MMN. Correlates of MMN have been studied in mice, rats, cats, and primates. Whereas essentially all of these studies demonstrated the presence of stimulus-specific adaptation, in the sense that responses to deviant tones are larger than the responses to standard tones, the presence of real MMN has been established only in a few. We argue for the use of more and better controls in order to clarify the situation. Finally, we discuss in detail the relationships between stimulus-specific adaptation of single-neuron responses, as established in the cat auditory cortex, and MMN. We argue that this is currently the only fully established correlate of true change detection, and hypothesize that it precedes and probably induces the neural activity that is eventually measured as MMN.

Synaptic plasticity and dysconnection in schizophrenia

Current pathophysiological theories of schizophrenia highlight the role of altered brain connectivity. This dysconnectivity could manifest 1) anatomically, through structural changes of association fibers at the cellular level, and/or 2) functionally, through aberrant control of synaptic plasticity at the synaptic level. In this article, we review the evidence for these theories, focusing on the modulation of synaptic plasticity. In particular, we discuss how dysconnectivity, observed between brain regions in schizophrenic patients, could result from abnormal modulation of N-methyl-D-aspartate (NMDA)-dependent plasticity by other neurotransmitter systems. We focus on the implication of the dysconnection hypothesis for functional imaging at the systems level. In particular, we review recent advances in measuring plasticity in the human brain using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) that can be used to address dysconnectivity in schizophrenia. Promising experimental paradigms include perceptual and reinforcement learning. We describe how theoretical and causal models of brain responses might contribute to a mechanistic understanding of synaptic plasticity in schizophrenia.

Auditory streaming affects the processing of successive deviant and standard sounds

This study investigated the temporal relation between two early mechanisms of auditory information processing: the segregation of the auditory input into streams and the automatic deviance detection indicated by the mismatch negativity (MMN). To address this question the processing of successive deviant and standard tones within streaming and nonstreaming conditions was analyzed. In the streaming condition the amplitude reduction of MMN elicited by the second of two successive deviants was found to be smaller for successive deviants presented in different than in same streams. No corresponding MMN differences were obtained in a nonstreaming condition. These results demonstrate that stream segregation precedes deviance detection. Moreover, modulations of the N1 amplitudes elicited by successive standard tones in the streaming condition demonstrate that not only deviance-related processing but even initial sound processing is affected by streaming.

Memory-based or afferent processes in mismatch negativity (MMN): a review of the evidence

The mismatch negativity (MMN) is an electromagnetic response to any discriminable change in regular auditory input. This response is usually interpreted as being generated by an automatic cortical change-detection process in which a difference is found between the current input and the representation of the regular aspects of the preceding auditory input. Recently, this interpretation was questioned by Jääskeläinen et al. (2004) who proposed that the MMN is a product of an N1 (N1a) difference wave emerging in the subtraction procedure used to visualize and quantify the MMN. We now evaluate this "adaptation hypothesis" of the MMN in the light of the available data. It is shown that the MMN cannot be accounted for by differential activation of the afferent N1 transient detectors by repetitive ("standard") stimuli and deviant ("novel") stimuli and that the presence of a memory representation of the standard is required for the elicitation of MMN.

Midlatency auditory event-related potentials in mice: comparison to midlatency auditory ERPs in humans

Midlatency event-related potentials (ERPs) reflect early stages in processing of modality specific information. In humans, the auditory midlatency ERPs most investigated are the P1, N1 and P2. Abnormalities of these ERPs in neuropsychiatric disorders such as schizophrenia point to deficits in information processing at early stages. Investigations of corresponding ERPs in mice might thus permit to elucidate the molecular biology of such abnormalities. We conducted studies in mice and humans in order to establish the correspondence of midlatency ERPs in mice to the human P1, N1 and P2. We investigated their so-called recovery function-i.e. their systematic amplitude changes as a function of varying stimulus onset asynchrony (SOA). Furthermore, we explored effects of specific genetic alterations (ERK1 gene deletion Gdi1 gene deletion) on this measure. In mice, P1-like activity showed a significant recovery not present in human data. In contrast, N1-like and P2-like activity in mice demonstrated similar recovery functions as the corresponding ERPs in human subjects and could be best fitted by the same function. In addition, ERK1 gene knockout mice showed a significantly different N1 recovery function compared to wild-type mice, possibly related to enhanced memory functions in these mice. Our results indicate that midlatency ERPs in mice share some, but not all, characteristics with the human P1, N1 and P2. As in humans, N1 recovery may provide an assessment of auditory sensory memory function. Investigations of these ERPs in mice may thus permit to elucidate the abnormalities underlying deficient generation of these ERPs in neuropsychiatric disorders.

Representation of the standard: stimulus context effects on the process generating the mismatch negativity component of event-related brain potentials

In the auditory oddball paradigm, the frequent occurrence of a sound (the "standard") forms the basis of deviance detection. The incoming sounds are compared with the cortical representation of the standard and those sounds that do not match it elicit the mismatch negativity (MMN) event-related brain potential. Here we address the issue of whether the relative probability of the sounds in a sequence was a critical factor influencing which sounds would be represented as standards in the deviant comparison process. One frequent (F1) and two infrequent (D1 and D2) sounds that differed only in duration were presented in a sequence. D1 occurred proportionally as frequently with respect to D2 as F1 occurred with respect to D1. If the proportional relationship of sounds were critical then D1 could serve as a "standard" to D2 and thus D2 should elicit two MMNs. However, D2 elicited MMN only with respect to F1. This result as well as those obtained in two control conditions suggests that "standards" are not established on the basis of relative probability; they emerge as a result of global characteristics, the longer-term context, of the sound sequence.