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The present study examined opposing and following vocal responses to altered auditory feedback (AAF) to determine how damage to left-hemisphere brain networks impairs the internal forward model and feedback mechanisms in post-stroke aphasia. Forty-nine subjects with aphasia and sixty age-matched controls performed speech vowel production tasks while their auditory feedback was altered using randomized ± 100 cents upward and downward pitch-shift stimuli. Data analysis revealed that when vocal responses were averaged across all trials (i.e., opposing and following), the overall magnitude of vocal compensation was significantly reduced in the aphasia group compared with controls. In addition, when vocal responses were analyzed separately for opposing and following trials, subjects in the aphasia group showed a significantly lower percentage of opposing and higher percentage of following vocal response trials compared with controls, particularly for the upward pitch-shift stimuli. However, there was no significant difference in the magnitude of opposing and following vocal responses between the two groups. These findings further support previous evidence on the impairment of vocal sensorimotor control in aphasia and provide new insights into the distinctive impact of left-hemisphere stroke on the internal forward model and feedback mechanisms. In this context, we propose that the lower percentage of opposing responses in aphasia may be accounted for by deficits in feedback-dependent mechanisms of audio-vocal integration and motor control. In addition, the higher percentage of following responses may reflect aberrantly increased reliance of the speech system on the internal forward model for generating sensory predictions during vocal error detection and motor control. [ABSTRACT FROM AUTHOR]

Simple Summary: We propose a more comprehensive scheme underlying cerebellar reserve. Under pathological conditions, the internal forward model continuously updates itself to adjust the predictive control, where two reorganizing steps function cooperatively: updating predictions in the residual or affected cerebellar cortex (predictive step) and adjusting the updated predictions with the current status at the cerebellar nuclei (filtering step). Cerebellar reserve compensates for and restores functions lost through cerebellar damage. This is a fundamental property of cerebellar circuitry. Clinical studies suggest (1) the involvement of synaptic plasticity in the cerebellar cortex for functional compensation and restoration, and (2) that the integrity of the cerebellar reserve requires the survival and functioning of cerebellar nuclei. On the other hand, recent physiological studies have shown that the internal forward model, embedded within the cerebellum, controls motor accuracy in a predictive fashion, and that maintaining predictive control to achieve accurate motion ultimately promotes learning and compensatory processes. Furthermore, within the proposed framework of the Kalman filter, the current status is transformed into a predictive state in the cerebellar cortex (prediction step), whereas the predictive state and sensory feedback from the periphery are integrated into a filtered state at the cerebellar nuclei (filtering step). Based on the abovementioned clinical and physiological studies, we propose that the cerebellar reserve consists of two elementary mechanisms which are critical for cerebellar functions: the first is involved in updating predictions in the residual or affected cerebellar cortex, while the second acts by adjusting its updated forecasts with the current status in the cerebellar nuclei. Cerebellar cortical lesions would impair predictive behavior, whereas cerebellar nuclear lesions would impact on adjustments of neuronal commands. We postulate that the multiple forms of distributed plasticity at the cerebellar cortex and cerebellar nuclei are the neuronal events which allow the cerebellar reserve to operate in vivo. This cortico-deep cerebellar nuclei loop model attributes two complementary functions as the underpinnings behind cerebellar reserve. [ABSTRACT FROM AUTHOR]

Cerebellar reserve compensates for and restores functions lost through cerebellar damage. This is a fundamental property of cerebellar circuitry. Clinical studies suggest (1) the involvement of synaptic plasticity in the cerebellar cortex for functional compensation and restoration, and (2) that the integrity of the cerebellar reserve requires the survival and functioning of cerebellar nuclei. On the other hand, recent physiological studies have shown that the internal forward model, embedded within the cerebellum, controls motor accuracy in a predictive fashion, and that maintaining predictive control to achieve accurate motion ultimately promotes learning and compensatory processes. Furthermore, within the proposed framework of the Kalman filter, the current status is transformed into a predictive state in the cerebellar cortex (prediction step), whereas the predictive state and sensory feedback from the periphery are integrated into a filtered state at the cerebellar nuclei (filtering step). Based on the abovementioned clinical and physiological studies, we propose that the cerebellar reserve consists of two elementary mechanisms which are critical for cerebellar functions: the first is involved in updating predictions in the residual or affected cerebellar cortex, while the second acts by adjusting its updated forecasts with the current status in the cerebellar nuclei. Cerebellar cortical lesions would impair predictive behavior, whereas cerebellar nuclear lesions would impact on adjustments of neuronal commands. We postulate that the multiple forms of distributed plasticity at the cerebellar cortex and cerebellar nuclei are the neuronal events which allow the cerebellar reserve to operate in vivo. This cortico-deep cerebellar nuclei loop model attributes two complementary functions as the underpinnings behind cerebellar reserve.

Abstract Auditory verbal hallucinations (AVH) are a cardinal symptom of psychosis but also occur in 6–13% of the general population. Voice perception is thought to engage an internal forward model that generates predictions, preparing the auditory cortex for upcoming sensory feedback. Impaired processing of sensory feedback in vocalization seems to underlie the experience of AVH in psychosis, but whether this is the case in nonclinical voice hearers remains unclear. The current study used electroencephalography (EEG) to investigate whether and how hallucination predisposition (HP) modulates the internal forward model in response to self-initiated tones and self-voices. Participants varying in HP (based on the Launay-Slade Hallucination Scale) listened to self-generated and externally generated tones or self-voices. HP did not affect responses to self vs. externally generated tones. However, HP altered the processing of the self-generated voice: increased HP was associated with increased pre-stimulus alpha power and increased N1 response to the self-generated voice. HP did not affect the P2 response to voices. These findings confirm that both prediction and comparison of predicted and perceived feedback to a self-generated voice are altered in individuals with AVH predisposition. Specific alterations in the processing of self-generated vocalizations may establish a core feature of the psychosis continuum.

The motor and sensory systems work collaboratively to fulfill cognitive tasks, such as speech. For example, it has been hypothesized that neural signals generated in the motor system can transfer directly to the sensory system along a neural pathway (termed as motor-to-sensory transformation). Previous studies have demonstrated that the motor-to-sensory transformation is crucial for speech production. However, it is still unclear how neural representation dynamically evolves among distinct neural systems and how such representational transformation depends on task demand and the degrees of motor involvement. Using three speech tasks – overt articulation, silent articulation, and imagined articulation, the present fMRI study systematically investigated the representational formats and their dynamics in the motor-to-sensory transformation. Frontal-parietal-temporal neural pathways were observed in all three speech tasks in univariate analyses. The extent of the motor-to-sensory transformation network differed when the degrees of motor engagement varied among tasks. The representational similarity analysis (RSA) revealed that articulatory and acoustic information was represented in motor and auditory regions, respectively, in all three tasks. Moreover, articulatory information was cross-represented in the somatosensory and auditory regions in overt and silent articulation tasks. These results provided evidence for the dynamics and task-dependent transformation between representational formats in the motor-to-sensory transformation. [ABSTRACT FROM AUTHOR]

The cerebellum, which is responsible for motor control and learning, has been suggested to act as a Smith predictor for compensation of time-delays by means of internal forward models. However, insights about how forward model predictions are integrated in the Smith predictor have not yet been unveiled. To fill this gap, a novel bio-inspired modular control architecture that merges a recurrent cerebellar-like loop for adaptive control and a Smith predictor controller is proposed. The goal is to provide accurate anticipatory corrections to the generation of the motor commands in spite of sensory delays and to validate the robustness of the proposed control method to input and physical dynamic changes. The outcome of the proposed architecture with other two control schemes that do not include the Smith control strategy or the cerebellar-like corrections are compared. The results obtained on four sets of experiments confirm that the cerebellum-like circuit provides more effective corrections when only the Smith strategy is adopted and that minor tuning in the parameters, fast adaptation and reproducible configuration are enabled. [ABSTRACT FROM AUTHOR]

Self-generated overt actions are preceded by a slow negativity as measured by electroencephalogram, which has been associated with motor preparation. Recent studies have shown that this neural activity is modulated by the predictability of action outcomes. It is unclear whether inner speech is also preceded by a motor-related negativity and influenced by the same factor. In three experiments, we compared the contingent negative variation elicited in a cue paradigm in an active vs. passive condition. In Experiment 1, participants produced an inner phoneme, at which an audible phoneme whose identity was unpredictable was concurrently presented. We found that while passive listening elicited a late contingent negative variation, inner speech production generated a more negative late contingent negative variation. In Experiment 2, the same pattern of results was found when participants were instead asked to overtly vocalize the phoneme. In Experiment 3, the identity of the audible phoneme was made predictable by establishing probabilistic expectations. We observed a smaller late contingent negative variation in the inner speech condition when the identity of the audible phoneme was predictable, but not in the passive condition. These findings suggest that inner speech is associated with motor preparatory activity that may also represent the predicted action-effects of covert actions., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

When we move our articulator organs to produce overt speech, the brain generates a corollary discharge that acts to suppress the neural and perceptual responses to our speech sounds. Recent research suggests that inner speech – the silent production of words in one's mind – is also accompanied by a corollary discharge. Here, we show that this corollary discharge contains information about the temporal and physical properties of inner speech. In two experiments, participants produced an inner phoneme at a precisely-defined moment in time. An audible phoneme was presented 300 ms before, concurrently with, or 300 ms after participants produced the inner phoneme. We found that producing the inner phoneme attenuated the N1 component of the event-related potential – an index of auditory cortex processing – but only when the inner and audible phonemes occurred concurrently and matched on content. If the audible phoneme was presented before or after the production of the inner phoneme, or if the inner phoneme did not match the content of the audible phoneme, there was no attenuation of the N1. These results suggest that inner speech is accompanied by a temporally-precise and content-specific corollary discharge. We conclude that these results support the notion of a functional equivalence between the neural processes that underlie the production of inner and overt speech, and may provide a platform for identifying inner speech abnormalities in disorders in which they have been putatively associated, such as schizophrenia. [ABSTRACT FROM AUTHOR]

We here provide neural evidence that the cerebellar circuit can predict future inputs from present outputs, a hallmark of an internal forward model. Recent computational studies hypothesize that the cerebellum performs state prediction known as a forward model. To test the forward-model hypothesis, we analyzed activities of 94 mossy fibers (inputs to the cerebellar cortex), 83 Purkinje cells (output from the cerebellar cortex to dentate nucleus), and 73 dentate nucleus cells (cerebellar output) in the cerebro-cerebellum, all recorded from a monkey performing step-tracking movements of the right wrist. We found that the firing rates of one population could be reconstructed as a weighted linear sum of those of preceding populations. We then went on to investigate if the current outputs of the cerebellum (dentate cells) could predict the future inputs of the cerebellum (mossy fibers). The firing rates of mossy fibers at time t + t1 could be well reconstructed from as a weighted sum of firing rates of dentate cells at time t, thereby proving that the dentate activities contained predictive information about the future inputs. The average goodness-of-fit (R2) decreased moderately from 0.89 to 0.86 when t1 was increased from 20 to 100 ms, hence indicating that the prediction is able to compensate the latency of sensory feedback. The linear equations derived from the firing rates resembled those of a predictor known as Kalman filter composed of prediction and filtering steps. In summary, our analysis of cerebellar activities supports the forward-model hypothesis of the cerebellum. [ABSTRACT FROM AUTHOR]

The terminology of cerebellar dysmetria embraces a ubiquitous symptom in motor deficits, oculomotor symptoms, and cognitive/emotional symptoms occurring in cerebellar ataxias. Patients with episodic ataxia exhibit recurrent episodes of ataxia, including motor dysmetria. Despite the consensus that cerebellar dysmetria is a cardinal symptom, there is still no agreement on its pathophysiological mechanisms to date since its first clinical description by Babinski. We argue that impairment in the predictive computation for voluntary movements explains a range of characteristics accompanied by dysmetria. Within this framework, the cerebellum acquires and maintains an internal forward model, which predicts current and future states of the body by integrating an estimate of the previous state and a given efference copy of motor commands. Two of our recent studies experimentally support the internal-forward-model hypothesis of the cerebellar circuitry. First, the cerebellar outputs (firing rates of dentate nucleus cells) contain predictive information for the future cerebellar inputs (firing rates of mossy fibers). Second, a component of movement kinematics is predictive for target motions in control subjects. In cerebellar patients, the predictive component lags behind a target motion and is compensated with a feedback component. Furthermore, a clinical analysis has examined kinematic and electromyography (EMG) features using a task of elbow flexion goal-directed movements, which mimics the finger-to-nose test. Consistent with the hypothesis of the internal forward model, the predictive activations in the triceps muscles are impaired, and the impaired predictive activations result in hypermetria (overshoot). Dysmetria stems from deficits in the predictive computation of the internal forward model in the cerebellum. Errors in this fundamental mechanism result in undershoot (hypometria) and overshoot during voluntary motor actions. The predictive computation of the forward model affords error-based motor learning, coordination of multiple degrees of freedom, and adequate timing of muscle activities. Both the timing and synergy theory fit with the internal forward model, microzones being the elemental computational unit, and the anatomical organization of converging inputs to the Purkinje neurons providing them the unique property of a perceptron in the brain. We propose that motor dysmetria observed in attacks of ataxia occurs as a result of impaired predictive computation of the internal forward model in the cerebellum.

Skilled movement is mediated by motor commands executed with extremely fine temporal precision. The question of how the brain incorporates temporal information to perform motor actions has remained unanswered. This study investigated the effect of stimulus temporal predictability on response timing of speech and hand movement. Subjects performed a randomized vowel vocalization or button press task in two counterbalanced blocks in response to temporally-predictable and unpredictable visual cues. Results indicated that speech and hand reaction time was decreased for predictable compared with unpredictable stimuli. This finding suggests that a temporal predictive code is established to capture temporal dynamics of sensory cues in order to produce faster movements in responses to predictable stimuli. In addition, results revealed a main effect of modality, indicating faster hand movement compared with speech. We suggest that this effect is accounted for by the inherent complexity of speech production compared with hand movement. Lastly, we found that movement inhibition was faster than initiation for both hand and speech, suggesting that movement initiation requires a longer processing time to coordinate activities across multiple regions in the brain. These findings provide new insights into the mechanisms of temporal information processing during initiation and inhibition of speech and hand movement. [ABSTRACT FROM AUTHOR]

The predictive coding model suggests that neural processing of sensory information is facilitated for temporally-predictable stimuli. This study investigated how temporal processing of visually-presented sensory cues modulates movement reaction time and neural activities in speech and hand motor systems. Event-related potentials (ERPs) were recorded in 13 subjects while they were visually-cued to prepare to produce a steady vocalization of a vowel sound or press a button in a randomized order, and to initiate the cued movement following the onset of a go signal on the screen. Experiment was conducted in two counterbalanced blocks in which the time interval between visual cue and go signal was temporally-predictable (fixed delay at 1000 ms) or unpredictable (variable between 1000 and 2000 ms). Results of the behavioral response analysis indicated that movement reaction time was significantly decreased for temporally-predictable stimuli in both speech and hand modalities. We identified premotor ERP activities with a left-lateralized parietal distribution for hand and a frontocentral distribution for speech that were significantly suppressed in response to temporally-predictable compared with unpredictable stimuli. The premotor ERPs were elicited approximately −100 ms before movement and were significantly correlated with speech and hand motor reaction times only in response to temporally-predictable stimuli. These findings suggest that the motor system establishes a predictive code to facilitate movement in response to temporally-predictable sensory stimuli. Our data suggest that the premotor ERP activities are robust neurophysiological biomarkers of such predictive coding mechanisms. These findings provide novel insights into the temporal processing mechanisms of speech and hand motor systems. [ABSTRACT FROM AUTHOR]

• Speech production control requires predicting the sensory consequences of the action. • The motor-based auditory prediction may be mediated by somatosensory estimation. • The inferior parietal lobe (IPL) is a hub linking motor simulation and auditory estimation. • The aIPL and pIPL play distinct roles in the predictive processes during speech production. • Speech tasks modulate the connectivity strength of the cascaded predictive neural network. Internal forward models hypothesize functional links between motor and sensory systems for predicting the consequences of actions. Recently, the cascaded theory proposes that somatosensory estimation in the inferior parietal lobe (IPL) can be a relay computational structure, converting motor signals into predictions of auditory consequences in a serial processing manner during speech production. The study used fMRI with functional connectivity (FC) analyses to investigate the proposed cascaded processes using three speech tasks: overt articulation (OA), silent articulation (SA) and imagined articulation (IA). The FC results showed that connectivity between aIPL and STG was increased in OA compared with SA , suggesting that the relationship between somatosensory and auditory estimations can be modulated by speech tasks. Moreover, stronger connectivity between IFGoper and pIPL, and between pIPL and STG were observed in SA and IA compared with OA. These results are consistent with a cascaded process in the internal forward models. [ABSTRACT FROM AUTHOR]

Despite several pieces of evidence, which suggest that the human brain employs internal models for motor control and learning, the location of these models in the brain is not yet clear. In this study, we used transcranial direct current stimulation (tDCS) to manipulate right cerebellar function, while subjects adapt to a visuomotor task. We investigated the effect of this manipulation on the internal forward and inverse models by measuring two kinds of behavior: generalization of training in one direction to neighboring directions (as a proxy for inverse models) and localization of the hand position after movement without visual feedback (as a proxy for forward model). The experimental results showed no effect of cerebellar tDCS on generalization, but significant effect on localization. These observations support the idea that the cerebellum is a possible brain region for internal forward, but not inverse model formation. We also used a realistic human head model to calculate current density distribution in the brain. The result of this model confirmed the passage of current through the cerebellum. Moreover, to further explain some observed experimental results, we modeled the visuomotor adaptation process with the help of a biologically inspired method known as population coding. The effect of tDCS was also incorporated in the model. The results of this modeling study closely match our experimental data and provide further evidence in line with the idea that tDCS manipulates FM's function in the cerebellum. [ABSTRACT FROM AUTHOR]

The predictive coding model suggests that voice motor control is regulated by a process in which the mismatch (error) between feedforward predictions and sensory feedback is detected and used to correct vocal motor behavior. In this study, we investigated how predictions about timing of pitch perturbations in voice auditory feedback would modulate ERP and behavioral responses during vocal production. We designed six counterbalanced blocks in which a +100 cents pitch-shift stimulus perturbed voice auditory feedback during vowel sound vocalizations. In three blocks, there was a fixed delay (500, 750 or 1000 ms) between voice and pitch-shift stimulus onset (predictable), whereas in the other three blocks, stimulus onset delay was randomized between 500, 750 and 1000 ms (unpredictable). We found that subjects produced compensatory (opposing) vocal responses that started at 80 ms after the onset of the unpredictable stimuli. However, for predictable stimuli, subjects initiated vocal responses at 20 ms before and followed the direction of pitch shifts in voice feedback. Analysis of ERPs showed that the amplitudes of the N1 and P2 components were significantly reduced in response to predictable compared with unpredictable stimuli. These findings indicate that predictions about temporal features of sensory feedback can modulate vocal motor behavior. In the context of the predictive coding model, temporally-predictable stimuli are learned and reinforced by the internal feedforward system, and as indexed by the ERP suppression, the sensory feedback contribution is reduced for their processing. These findings provide new insights into the neural mechanisms of vocal production and motor control. [ABSTRACT FROM AUTHOR]

Our ability to properly move and react in different situations is largely dependent on our perception of our limbs' position. At least three sources - vision, proprioception, and internal forward models (FMs) - seem to contribute to this perception. To the best of our knowledge, the effect of each source has not been studied individually. Specifically, role of FM has been ignored in some previous studies. We hypothesized that FM has a critical role in subjects' perception which needs to be considered in the relevant studies to obtain more reliable results. Therefore, we designed an experiment with the goal of investigating FM and proprioception role in subjects' perception of their hand's position. Three groups of subjects were recruited in the study. Based on the experiment design, it was supposed that subjects in different groups relied on proprioception, FM, and both of them for estimating their unseen hand's position. Comparing the results of three groups revealed significant difference between their estimation' errors. FM provided minimum estimation error, while proprioception had a bias error in the tested region. Integrating proprioception with FM decreased this error. Integration of two Gaussian functions, fitted to the error distribution of FM and proprioception groups, was simulated and created a mean error value almost similar to the experimental observation. These results suggest that FM role needs to be considered when studying the perceived position of the limbs. This can lead to gain better insights into the mechanisms underlying the perception of our limbs' position which might have potential clinical and rehabilitation applications, e.g., in the postural control of elderly which are at high risk of falls and injury because of deterioration of their perception with age. [ABSTRACT FROM AUTHOR]

The author focuses on whether the brain is using the same policy in the interaction with people and manipulation of different objects. Topics discussed include the suggestion of the theory-model based theory that some internal models are existing in the brain, the challenge involving the understanding the brain function, and the definition of stereotype as the fixed generalization about a group of people.

The importance of action-perception loops necessitates efficient computations linking motor and sensory systems. Corollary discharge (CD), a concept in motor-to-sensory transformation, has been proposed to predict the sensory consequences of actions for efficient motor and cognitive control. The predictive computation has been assumed to realize via inhibiting sensory reafference when actions are executed. Continuous control throughout the course of action demands inhibitory function ubiquitously on all potential reafference when sensory consequences are not available before execution. However, the temporal and functional characteristics of CD are unclear. When does CD begin to operate? To what extent does CD inhibit sensory processes? How is the inhibitory function implemented in neural computation? Using a delayed articulation paradigm with three types of auditory probes (speech, nonspeech, and nonhuman sounds) in an electroencephalography experiment with 20 human participants (7 males), we found that preparing to speak without knowing what to say (general preparation) suppressed neural responses to each type of auditory probe, suggesting a generic inhibitory function of CD in motor intention. Moreover, power and phase coherence in low-frequency bands (1-8 Hz) were both suppressed, indicating that inhibition was mediated by dampening response amplitude and adding temporal variance to sensory processes. Furthermore, inhibition was stronger for sounds that humans can produce than nonhuman sounds, hinting that the generic inhibitory function of CD is regulated by the established motor-sensory associations. These results suggest a functional and temporal granularity of corollary discharge that mediates multifaceted computations in motor and cognitive control., Competing Interests: The authors declare no competing financial interests., (Copyright © 2022 Zheng et al.)

Musicians and musically untrained individuals have been shown to differ in a variety of functional brain processes such as auditory analysis and sensorimotor interaction. At the same time, internally operating forward models are assumed to enable the organism to discriminate the sensory outcomes of self-initiated actions from other sensory events by deriving predictions from efference copies of motor commands about forthcoming sensory consequences. As a consequence, sensory responses to stimuli that are triggered by a self-initiated motor act are suppressed relative to the same but externally-initiated stimuli, a phenomenon referred to as motor-induced suppression (MIS) of sensory cortical feedback. Moreover, MIS in the auditory domain has been shown to be modulated by the predictability of certain properties such as frequency or stimulus onset. The present study compares auditory processing of predictable and unpredictable self-initiated zero-delay speech sounds and piano tones between musicians and musical laymen by means of an event-related potential (ERP) and topographic pattern analysis (microstate analysis or EP mapping) approach. Taken together, our findings suggest that besides the known effect of MIS, internally operating forward models also facilitate early acoustic analysis of complex tones by means of faster processing time as indicated by shorter auditory N1-like microstate durations in the first ~ 200 ms after stimulus onset. In addition, musicians seem to profit from this facilitation also during the analysis of speech sounds as indicated by comparable auditory N1-like microstate duration patterns between speech and piano conditions. In contrast, non-musicians did not show such an effect.

Purpose:We sought to compare the effects of physical practice (PP) and mental practice (MP) on the immediate and long-term learning of the finger-to-thumb opposition sequence task (FOS) in children; in addition, we investigated the transfer of this learning to an untrained sequence of movements and to the contralateral untrained hand.Method:This study included thirty-six 9- and 10-year-old children who were randomly allocated into 3 groups: MP, PP, and no practice (NP). The MP and PP groups were subjected to a single session of training with the dominant trained hand. MP participants were trained by mentally rehearsing the movements, PP participants were trained by executing the movements, and the NP group had no training. The performance of the trained sequence (TS) and untrained reverse sequence (URS) by each of the 3 groups was evaluated under identical conditions before training, after 5 min, and at 4 days, 7 days, and 28 days after training.Results:Whereas both trained groups (MP and PP) showed statistically significant improvement in TS using the trained hand at all assessment points after the training, only MP participants were able to transfer the performance gains from the TS to the URS and from the trained hand to the untrained opposite hand.Conclusion:Children were able to learn the FOS through MP or PP with a similar level of performance. Unlike PP, MP allowed for the transfer of performance gain to the URS and to the opposite hand, suggesting that the internal representations developed by MP were effector-independent. [ABSTRACT FROM AUTHOR]

Musicians and musically untrained individuals have been shown to differ in a variety of functional brain processes such as auditory analysis and sensorimotor interaction. At the same time, internally operating forward models are assumed to enable the organism to discriminate the sensory outcomes of self-initiated actions from other sensory events by deriving predictions from efference copies of motor commands about forthcoming sensory consequences. As a consequence, sensory responses to stimuli that are triggered by a self-initiated motor act are suppressed relative to the same but externally initiated stimuli, a phenomenon referred to as motor-induced suppression (MIS) of sensory cortical feedback. Moreover, MIS in the auditory domain has been shown to be modulated by the predictability of certain properties such as frequency or stimulus onset. The present study compares auditory processing of predictable and unpredictable self-initiated 0-delay speech sounds and piano tones between musicians and musical laymen by means of an event-related potential (ERP) and topographic pattern analysis (TPA) [microstate analysis or evoked potential (EP) mapping] approach. As in previous research on the topic of MIS, the amplitudes of the auditory event-related potential (AEP) N1 component were significantly attenuated for predictable and unpredictable speech sounds in both experimental groups to a comparable extent. On the other hand, AEP N1 amplitudes were enhanced for unpredictable self-initiated piano tones in both experimental groups similarly and MIS did not develop for predictable self-initiated piano tones at all. The more refined EP mapping revealed that the microstate exhibiting a typical auditory N1-like topography was significantly shorter in musicians when speech sounds and piano tones were self-initiated and predictable. In contrast, non-musicians only exhibited shorter auditory N1-like microstate durations in response to self-initiated and predictable piano tones. Taken together, our findings suggest that besides the known effect of MIS, internally operating forward models also facilitate early acoustic analysis of complex tones by means of faster processing time as indicated by shorter auditory N1-like microstate durations in the first ∼200 ms after stimulus onset. In addition, musicians seem to profit from this facilitation also during the analysis of speech sounds as indicated by comparable auditory N1-like microstate duration patterns between speech and piano conditions. In contrast, non-musicians did not show such an effect [ABSTRACT FROM AUTHOR]

The present study focused on whether the movement correction capability during interceptive action can be improved by practice and investigated what practice method would enable the improvement. Two possible practice methods were conducted, i.e., practice with direct interception of an accelerating target (within-trial target velocity changes; WT practice), and practice with interception of 2 constant-velocity targets that are presented in uncertain order (inter-trial target velocity changes; IT practice). After practice, the rate of movement correction and movement kinematics of both groups were investigated at post- and transfer tests that included various novel target conditions. In the post-test, only the IT practice group showed improved rate of movement correction and movement velocity patterns with rapid acceleration for the accelerating targets despite having no direct experience with target velocity change during practice. In the transfer test, the WT practice group showed a relatively high rate of movement correction for the novel target velocity changes. These results indicate that movement correction capability during interception can be improved by practice. However, WT and IT practices lead to the development of different movement correction strategies. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The present study investigated the neural mechanisms of voice pitch control for different levels of harmonic complexity in the auditory feedback. Methods: Event-related potentials (ERPs) were recorded in response to+200 cents pitch perturbations in the auditory feedback of self-produced natural human vocalizations, complex and pure tone stimuli during active vocalization and passive listening conditions. Results: During active vocal production, ERP amplitudes were largest in response to pitch shifts in the natural voice, moderately large for non-voice complex stimuli and smallest for the pure tones. However, during passive listening, neural responses were equally large for pitch shifts in voice and non-voice complex stimuli but still larger than that for pure tones. Conclusions: These findings suggest that pitch change detection is facilitated for spectrally rich sounds such as natural human voice and non-voice complex stimuli compared with pure tones. Vocalization-induced increase in neural responses for voice feedback suggests that sensory processing of naturally-produced complex sounds such as human voice is enhanced by means of motor-driven mechanisms (e.g. efference copies) during vocal production. Significance: This enhancement may enable the audio-vocal system to more effectively detect and correct for vocal errors in the feedback of natural human vocalizations to maintain an intended vocal output for speaking. [Copyright &y& Elsevier]

Disturbances of self are a common feature of schizophrenic psychopathology, with patients reporting that their thoughts and actions are controlled by external forces, as shown in first-rank symptoms (FRS). One widely accepted explanatory model of FRS suggests a deficiency in the internal forward model system. Recent studies in the field of cognitive sciences, however, have generated new insights into how complex sensory and motor systems contribute to the sense of self-recognition, and it is becoming clear that the forward model conceptualization does not have unique access to representations about the self. We briefly evaluate the forward model explanation of FRS, reassess the distinction made between the sense of agency and body ownership, and outline recent developments in 4 domains of sensory-motor control that have supplemented our understanding of the processes underlying the sense of self-recognition. The application of these findings to FRS will open up new research directions into the processes underlying these symptoms. [ABSTRACT FROM PUBLISHER]

During goal-directed movements, primates are able to rapidly and accurately control an online trajectory despite substantial delay times incurred in the sensorimotor control loop. To address the problem of large delays, it has been proposed that the brain uses an internal forward model of the arm to estimate current and upcoming states of a movement, which are more useful for rapid online control. To study online control mechanisms in the posterior parietal cortex (PPC), we recorded from single neurons while monkeys performed a joystick task. Neurons encoded the static target direction and the dynamic movement angle of the cursor. The dynamic encoding properties of many movement angle neurons reflected a forward estimate of the state of the cursor that is neither directly available from passive sensory feedback nor compatible with outgoing motor commands and is consistent with PPC serving as a forward model for online sensorimotor control. In addition, we found that the space-time tuning functions of these neurons were largely separable in the angle-time plane, suggesting that they mostly encode straight and approximately instantaneous trajectories. [ABSTRACT FROM AUTHOR]

Predictive control of grasping forces when manipulating objects in the environment is suggested to reflect internal models that capture the causal relationship between actions and their consequences. The anatomical correlate of predictive control of grasping within the central nervous system is not completely understood. One structure which has been related to the neural representation of internal models is the cerebellum. Given its stereotyped cytoarchitecture, the widespread connections with cortical and subcortical sensory-motor structures and the neural activity of cerebellar Purkinje cells during sensory-motor tasks, the cerebellum has long been considered to play a major role in the establishment and maintenance of sensory-motor representations related to voluntary movement. Such representations are necessary to predict the consequences of our own movements. Here we review theoretical concepts, electrophysiological, imaging and behavioural data suggesting the cerebellum to be the anatomical and functional correlate of internal models relevant for predictive control of grasping. [ABSTRACT FROM AUTHOR]

Abstract: Impaired hand function is a frequent finding in movement disorders. The skilled control of prehensile finger forces is an essential feature of tool use in daily life. In healthy subjects, grip force is precisely adjusted to the mechanical object properties, such as weight and surface friction. Grip force is accurately scaled to be only a small amount higher than the minimum necessary to prevent a hand-held object from slipping. When an object is lifted and moved around in space, grip force is modulated in parallel with the movement-induced fluctuations in load. The absence of a temporal delay between grip and load force profiles implies that the central nervous system is able to predict the load variations before the intended manipulation. Sensory information is used to adjust the level of applied finger forces efficiently to the requirements of the mechanical object properties and the task at hand. The characteristics of impaired finger force control include inefficient grip force scaling and imprecision of the temporal coupling between grip and load force profiles. Here, we review the characteristics of deficient grip force behavior in movement disorders, e.g. Parkinson''s disease, task-specific dystonia, Gille de la Tourette''s syndrome and cerebellar disease. Grip force analysis is a highly sensitive method to document even subtle impairments of finger force control and may be used both as a diagnostic tool and for the objective evaluation of treatment in neurological movement disorders. [Copyright &y& Elsevier]

Abstract: Healthy subjects adjust their grip force economically to the weight of a hand-held object. In addition, inertial loads, which arise from arm movements with the grasped object, are anticipated by parallel grip force modulations. Internal forward models have been proposed to predict the consequences of voluntary movements. Anesthesia of the fingers impairs grip force economy but the feedforward character of the grip force/load coupling is preserved. To further analyze the role of sensory input for internal forward models and to characterize the consequences of central nervous system damage for anticipatory grip force control, we measured grip force behavior in neurological patients. We tested a group of stroke patients with varying degrees of impaired fine motor control and sensory loss, a single patient with complete and permanent differentation from all tactile and proprioceptive input, and a group of patients with amyotrophic lateral sclerosis (ALS) that exclusively impairs the motor system without affecting sensory modalities. Increased grip forces were a common finding in all patients. Sensory deficits were a strong but not the only predictor of impaired grip force economy. The feedforward mode of grip force control was typically preserved in the stroke patients despite their central sensory deficits, but was severely disturbed in the patient with peripheral sensory deafferentation and in a minority of stroke patients. Moderate deficits of feedforward control were also obvious in ALS patients. Thus, the function of the internal forward model and the precision of grip force production may depend on a complex anatomical and functional network of sensory and motor structures and their interaction in time and space. [Copyright &y& Elsevier]

The terminology of cerebellar dysmetria embraces a ubiquitous symptom in motor deficits, oculomotor symptoms, and cognitive/emotional symptoms occurring in cerebellar ataxias. Patients with episodic ataxia exhibit recurrent episodes of ataxia, including motor dysmetria. Despite the consensus that cerebellar dysmetria is a cardinal symptom, there is still no agreement on its pathophysiological mechanisms to date since its first clinical description by Babinski. We argue that impairment in the predictive computation for voluntary movements explains a range of characteristics accompanied by dysmetria. Within this framework, the cerebellum acquires and maintains an internal forward model, which predicts current and future states of the body by integrating an estimate of the previous state and a given efference copy of motor commands. Two of our recent studies experimentally support the internal-forward-model hypothesis of the cerebellar circuitry. First, the cerebellar outputs (firing rates of dentate nucleus cells) contain predictive information for the future cerebellar inputs (firing rates of mossy fibers). Second, a component of movement kinematics is predictive for target motions in control subjects. In cerebellar patients, the predictive component lags behind a target motion and is compensated with a feedback component. Furthermore, a clinical analysis has examined kinematic and electromyography (EMG) features using a task of elbow flexion goal-directed movements, which mimics the finger-to-nose test. Consistent with the hypothesis of the internal forward model, the predictive activations in the triceps muscles are impaired, and the impaired predictive activations result in hypermetria (overshoot). Dysmetria stems from deficits in the predictive computation of the internal forward model in the cerebellum. Errors in this fundamental mechanism result in undershoot (hypometria) and overshoot during voluntary motor actions. The predictive computation of the forward model affords error-based motor learning, coordination of multiple degrees of freedom, and adequate timing of muscle activities. Both the timing and synergy theory fit with the internal forward model, microzones being the elemental computational unit, and the anatomical organization of converging inputs to the Purkinje neurons providing them the unique property of a perceptron in the brain. We propose that motor dysmetria observed in attacks of ataxia occurs as a result of impaired predictive computation of the internal forward model in the cerebellum. [ABSTRACT FROM AUTHOR]

Actions influence sensory processing in a complex way to shape behavior. For example, during actions, a copy of motor signals-termed "corollary discharge" (CD) or "efference copy" (EC)-can be transmitted to sensory regions and modulate perception. However, the sole inhibitory function of the motor copies is challenged by mixed empirical observations as well as multifaceted computational demands for behaviors. We hypothesized that the content in the motor signals available at distinct stages of actions determined the nature of signals (CD vs. EC) and constrained their modulatory functions on perceptual processing. We tested this hypothesis using speech in which we could precisely control and quantify the course of action. In three electroencephalography (EEG) experiments using a novel delayed articulation paradigm, we found that preparation without linguistic contents suppressed auditory responses to all speech sounds, whereas preparing to speak a syllable selectively enhanced the auditory responses to the prepared syllable. A computational model demonstrated that a bifurcation of motor signals could be a potential algorithm and neural implementation to achieve the distinct functions in the motor-to-sensory transformation. These results suggest that distinct motor signals are generated in the motor-to-sensory transformation and integrated with sensory input to modulate perception., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Neural representation can be induced without external stimulation, such as in mental imagery. Our previous study found that imagined speaking and imagined hearing modulated perceptual neural responses in opposite directions, suggesting motor-to-sensory transformation and memory retrieval as two separate routes that induce auditory representation (Tian and Poeppel, 2013). We hypothesized that the precision of representation induced from different types of speech imagery led to different modulation effects. Specifically, we predicted that the one-to-one mapping between motor and sensory domains established during speech production would evoke a more precise auditory representation in imagined speaking than retrieving the same sounds from memory in imagined hearing. To test this hypothesis, we built the function of representational precision as the modulation of connection strength in a neural network model. The model fitted the magnetoencephalography (MEG) imagery repetition effects, and the best-fitting parameters showed sharper tuning after imagined speaking than imagined hearing, consistent with the representational precision hypothesis. Moreover, this model predicted that different types of speech imagery would affect perception differently. In an imagery-adaptation experiment, the categorization of /ba/-/da/ continuum from male and female human participants showed more positive shifts towards the preceding imagined syllable after imagined speaking than imagined hearing. These consistent simulation and behavioral results support our hypothesis that distinct mechanisms of speech imagery construct auditory representation with varying degrees of precision and differentially influence auditory perception. This study provides a mechanistic connection between neural-level activity and psychophysics that reveals the neural computation of mental imagery., (Copyright © 2019 Ma and Tian.)

The neural basis of mental imagery has been investigated by localizing the underlying neural networks, mostly in motor and perceptual systems, separately. However, how modality-specific representations are top-down induced and how the action and perception systems interact in the context of mental imagery is not well understood. Imagined speech production ("articulation imagery"), which induces the kinesthetic feeling of articulator movement and its auditory consequences, provides a new angle because of the concurrent involvement of motor and perceptual systems. On the basis of previous findings in mental imagery of speech, we argue for the following regarding the induction mechanisms of mental imagery and the interaction between motor and perceptual systems: (1) Two distinct top-down mechanisms, memory retrieval and motor simulation, exist to induce estimation in perceptual systems. (2) Motor simulation is sufficient to internally induce the representation of perceptual changes that would be caused by actual movement (perceptual associations); however, this simulation process only has modulatory effects on the perception of external stimuli, which critically depends on context and task demands. Considering the proposed simulation-estimation processes as common mechanisms for interaction between motor and perceptual systems, we outline how mental imagery (of speech) relates to perception and production, and how these hypothesized mechanisms might underpin certain neural disorders.