The auditory system is tuned to detect rhythmic regularities or irregularities in the environment which can occur on different timescales, i.e. regularities in short (local) and long (global) timescale which could conflict or converge. While MMN and P3b are thought to index local and global deviance, respectively, it is not clear how these hierarchical levels interact and to what extent attention modulates this interaction. We used a hierarchical oddball paradigm with local (sequence-level) and global (block-level) violations of regularities in 5-tone sequences, in attended and unattended conditions. Amplitude of negativity in the N2 timeframe and positivity in the P3b timeframe elicited by the final tone in the sequence were analyzed in a 2*2*2 factorial model (local status, global status, attention condition). We found a significant interaction between the local and global status of the final tone on the N2 amplitude (p<.001, η p 2 = .55), while there was no significant three-way interaction with attention (p > .05), together demonstrating that lower-level prediction error is modulated by detection of higher-order regularity but expressed independently of attention.Regarding P3b amplitude, we found significant main effect of global status (p<.001, η p 2 = .42), and an interaction between global status and attention (p < .001, η p 2 = .70). Thus, higherlevel prediction error, indexed by P3b, is sensitive to global regularity violations if the auditory stream is attended. The results demonstrate the capacity of our auditory perception to rapidly resolve conflicts between different levels of predictive hierarchy as indexed by MMN modulation, while P3b represents a different, attention-dependent system..

In a stable environment the brain can minimize processing required for sensory input by forming a predictive model of the surrounding world and suppressing neural response to predicted stimuli.Unpredicted stimuli lead to a prediction error signal propagation through the perceptual network, and resulting adjustment to the predictive model. The inter-regional plasticity which enables the model-building and model-adjustment is hypothesized to be mediated via glutamatergic receptors.While pharmacological challenge studies with glutamate receptor ligands have demonstrated impact on prediction-error indices, it is not clear how inter-individual differences in the glutamate system affect the prediction-error processing in non-medicated state. In the present study we examined 20 healthy young subjects with resting-state proton MRS spectroscopy to characterize glutamate+glutamine (rs-Glx) levels in their Heschl's gyrus (HG), and related this to HG functional connectivity during a roving auditory oddball protocol. No rs-Glx effects were found within the frontotemporal prediction-error network. Larger rs-Glx signal was related to stronger connectivity between HG and bilateral inferior parietal lobule during unpredictable auditory stimulation. We also found effects of rs-Glx on the coherence of default mode network (DMN) and frontoparietal network (FPN) during unpredictable auditory stimulation. Our results demonstrate the importance of Glx in modulating long-range connections and wider networks in the brain during perceptual inference.

In a stable environment the brain can minimize processing required for sensory input by forming a predictive model of the surrounding world and suppressing neural response to predicted stimuli. Unpredicted stimuli lead to a prediction error signal propagation through the perceptual network, and resulting adjustment to the predictive model. The inter-regional plasticity which enables the model-building and model-adjustment is hypothesized to be mediated via glutamatergic receptors. While pharmacological challenge studies with glutamate receptor ligands have demonstrated impact on prediction-error indices, it is not clear how inter-individual differences in the glutamate system affect the prediction-error processing in non-medicated state. In the present study we examined 20 healthy young subjects with resting-state proton MRS spectroscopy to characterize glutamate + glutamine (rs-Glx) levels in their Heschl’s gyrus (HG), and related this to HG functional connectivity during a roving auditory oddball protocol. No rs-Glx effects were found within the frontotemporal prediction-error network. Larger rs-Glx signal was related to stronger connectivity between HG and bilateral inferior parietal lobule during unpredictable auditory stimulation. We also found effects of rs-Glx on the coherence of default mode network and frontoparietal network during unpredictable auditory stimulation. Our results demonstrate the importance of Glx in modulating long-range connections and wider networks in the brain during perceptual inference.

The brain exploits acoustic temporal regularities in the environment to enable prediction of the timing of future events and to optimize sensory processing and behavior. Periodic sensory inputs have been shown to entrain oscillatory brain activity. But to what extent is this entrainment mechanism instrumental to temporal prediction and under top-down control? The current study addresses these questions by investigating whether the brain can use a cue to predict the precision of a beat, thereby exerting flexible endogenous control via neural entrainment according to the precision needed in the given sensory context. Using sound cues, we informed participants about the acoustic shape (sharp or smooth) of the upcoming target sound, thus inducing two alternative levels of predicted temporal precision: high or low. Participants were asked to detect the delay of a target sound relative to a series of preceding isochronous sounds that were physically constant across all conditions. The results show that the information of the cue modulated the prediction of beat precision. Pre-target beta (15-25 Hz) power, as well as beta and alpha (8-12 Hz) phase locking, was enhanced if the listener predicted a target sound with a high compared to a low temporal precision. Interestingly, pre-target beta power correlated positively with behavioral performance in the delay-detection task but negatively with the variability of the perceptual center (P-center) of the sounds, demonstrating the tight relation between beta oscillations and perceptual temporal precision. This study provides new insight into the predictive processes underlying entrainment to different levels of temporal precision during beat perception and shows for the first time that these processes are in fact under top-down control.

The auditory system is tuned to detect rhythmic regularities or irregularities in the environment which can occur on different timescales, i.e. regularities in short (local) and long (global) timescale which could conflict or converge. While MMN and P3b are thought to index local and global deviance, respectively, it is not clear how these hierarchical levels interact and to what extent attention modulates this interaction. We used a hierarchical oddball paradigm with local (sequence-level) and global (block-level) violations of regularities in 5-tone sequences, in attended and unattended conditions. Amplitude of negativity in the N2 timeframe and positivity in the P3b timeframe elicited by the final tone in the sequence were analyzed in a 2*2*2 factorial model (local status, global status, attention condition). We found a significant interaction between the local and global status of the final tone on the N2 amplitude (p<.001, η p 2 = .55), while there was no significant three-way interaction with attention (p > .05), together demonstrating that lower-level prediction error is modulated by detection of higher-order regularity but expressed independently of attention.Regarding P3b amplitude, we found significant main effect of global status (p<.001, η p 2 = .42), and an interaction between global status and attention (p < .001, η p 2 = .70). Thus, higherlevel prediction error, indexed by P3b, is sensitive to global regularity violations if the auditory stream is attended. The results demonstrate the capacity of our auditory perception to rapidly resolve conflicts between different levels of predictive hierarchy as indexed by MMN modulation, while P3b represents a different, attention-dependent system. 3 1 Introduction 2Our perception relies on prediction to facilitate the decoding of the sensory information. The 3 predictive coding theories of perception suggest that the brain tries to minimize the surprise or 4 prediction error, and continuously uses the unpredicted portion of the sensory input to adjust 5 the predictive models (1). A crucial component of the predictive coding is the hierarchical 6 organization of perceptual systems, with higher levels which represent slower-changing 7 regularities modulating the processing of lower-level predictive units which integrate over 8 shorter time (2). Such nested hierarchical system are crucial in human speech processing, 9where the probability of a sound depends on its immediate local environment such as the 10 syllable structure, whereas word and sentence rules in the given language give wider context 11 which would need to be taken into account when predicting the subsequent sound (3). How 12 such hierarchically nested rules are extracted from the auditory stream, how they interact with 13 each other and other systems such as attention and long-term memory are central to our 14 understanding of auditory perception. 15 Unpredictable deviations from predicted pattern in auditory input are detected and given 16 special processing in the auditory analysis of the incomi...