The neural signature of an erroneous thought.

The human brain detects errors in overt behavior fast and efficiently. However, little is known about how errors are monitored that emerge on a mental level. We investigate whether neural correlates of error monitoring can be found during inner speech and whether the involved neural processes differ between these non-motor responses and behavioral motor responses. Therefore, electroencephalographic data were collected while participants performed two versions of a decision task that only differed between these response modalities. Erroneous responses were identified based on participants' metacognitive judgments. Correlates of error monitoring in event-related potentials were analyzed by applying residue iteration decomposition on stimulus-locked activity. Non-motor responses elicited the same cascade of early error-related negativity and late error positivity as motor responses. An analysis of oscillatory brain activity showed a similar theta response for both error types. A multivariate pattern classifier trained on theta from the motor condition could decode theta from the non-motor condition, demonstrating the similarity of both neural responses. These results show that errors in inner speech are monitored and detected utilizing the same neural processes as behavioral errors, suggesting that goal-directed cognition and behavior are supported by a generic error-monitoring system.

Evidence from aphasia suggests a bidirectional relationship between inner speech and executive function.

Research over the past several decades has revealed that non-linguistic cognitive impairments can appear alongside language deficits in individuals with aphasia. One vulnerable cognitive domain is executive function, an umbrella term for the higher-level cognitive processes that allow us to direct our behavior towards a goal. Studies in healthy adults reveal that executive function abilities are supported by inner speech, the ability to use language silently in one's head. Therefore, inner speech may mediate the connection between language and executive function deficits in individuals with aphasia. Here, we investigated whether inner speech ability may link language and cognitive impairments in 59 adults with chronic, post-stroke aphasia. We used two approaches to measure inner speech: one based on internal retrieval of words and one based on internal retrieval plus silent manipulation of the retrieved phonological forms. Then, we examined relationships between these two approaches to measuring inner speech and five aspects of executive function ability: response inhibition, conflict monitoring/resolution, general task-switching ability, phonological control, and semantic control. We also looked for dissociations between inner speech ability and executive function ability. Our results show tentative relationships between inner speech (across multiple measurement approaches) and all aspects of executive function except for response inhibition. We also found evidence for a double dissociation: many participants show intact executive function despite poor inner speech, and vice versa, so neither process is strictly reliant on the other. We suggest that this work provides preliminary evidence of a bidirectional relationship between inner speech and executive function: inner speech supports some aspects of executive function via internal self-cueing and certain aspects of executive function support performance on complex inner speech tasks.

Interdisciplinary approaches to understanding the inner speech, with emphasis on the role of incorporating clinical data.

Neuroscience has largely conceptualized inner speech, sometimes called covert speech, as being a part of the language system, namely, a precursor to overt speech and/or speech without the motor component (impoverished motor speech). Yet interdisciplinary work has strongly suggested that inner speech is multidimensional and situated within the language system as well as in more domain general systems. By leveraging evidence from philosophy, linguistics, neuroscience and cognitive science, we argue that neuroscience can gain a more comprehensive understanding of inner speech processes. We will summarize the existing knowledge on the traditional approach to understanding the neuroscience of inner speech, which is squarely through the language system, before discussing interdisciplinary approaches to understanding the cognitive, linguistic and neural substrates/mechanisms that may be involved in inner speech. Given our own interests in inner speech after brain injury, we finish by discussing the theoretical and clinical benefits of researching inner speech in aphasia through an interdisciplinary lens.

Not Everybody Has an Inner Voice: Behavioral Consequences of Anendophasia.

It is commonly assumed that inner speech-the experience of thought as occurring in a natural language-is a human universal. Recent evidence, however, suggests that the experience of inner speech in adults varies from near constant to nonexistent. We propose a name for a lack of the experience of inner speech-anendophasia-and report four studies examining some of its behavioral consequences. We found that adults who reported low levels of inner speech (N = 46) had lower performance on a verbal working memory task and more difficulty performing rhyme judgments compared with adults who reported high levels of inner speech (N = 47). Task-switching performance-previously linked to endogenous verbal cueing-and categorical effects on perceptual judgments were unrelated to differences in inner speech.

A general theory of consciousness III the human catastrophe.

It is generally assumed that verbal communication can articulate concepts like 'fact' and 'truth' accurately. However, language is fundamentally inaccurate and ambiguous and it is not possible to express exact propositions accurately in an ambiguous medium. Whether truth exists or not, language cannot express it in any exact way. A major problem for verbal communication is that words are fundamentally differently interpreted by the sender and the receiver. In addition, intrapersonal verbal communication - the voice in our head - is a useless extension to the thought process and results in misunderstanding our own thoughts. The evolvement of language has had a profound impact on human life. Most consequential has been that it allowed people to question the old human rules of behavior - the pre-language way of living. As language could not accurately express the old rules, they lost their authority and disappeared. A long period without any rules of how to live together must have followed, probably accompanied by complete chaos. Later, new rules were devised in language, but the new rules were also questioned and had to be enforced by punishment. Language changed the peaceful human way of living under the old rules into violent and aggressive forms of living under punitive control. Religion then tried to incorporate the old rules into the harsh verbal world. The rules were expressed in language through parables: imaginary beings - the gods - who possessed the power of the old rules, but who could be related to through their human appearance and behavior.

Exploring inter-trial coherence for inner speech classification in EEG-based brain-computer interface.

Objective. In recent years, electroencephalogram (EEG)-based brain-computer interfaces (BCIs) applied to inner speech classification have gathered attention for their potential to provide a communication channel for individuals with speech disabilities. However, existing methodologies for this task fall short in achieving acceptable accuracy for real-life implementation. This paper concentrated on exploring the possibility of using inter-trial coherence (ITC) as a feature extraction technique to enhance inner speech classification accuracy in EEG-based BCIs.Approach. To address the objective, this work presents a novel methodology that employs ITC for feature extraction within a complex Morlet time-frequency representation. The study involves a dataset comprising EEG recordings of four different words for ten subjects, with three recording sessions per subject. The extracted features are then classified using k-nearest-neighbors (kNNs) and support vector machine (SVM).Main results. The average classification accuracy achieved using the proposed methodology is 56.08% for kNN and 59.55% for SVM. These results demonstrate comparable or superior performance in comparison to previous works. The exploration of inter-trial phase coherence as a feature extraction technique proves promising for enhancing accuracy in inner speech classification within EEG-based BCIs.Significance. This study contributes to the advancement of EEG-based BCIs for inner speech classification by introducing a feature extraction methodology using ITC. The obtained results, on par or superior to previous works, highlight the potential significance of this approach in improving the accuracy of BCI systems. The exploration of this technique lays the groundwork for further research toward inner speech decoding.

Inner speech and the body error theory.

Inner speech is commonly understood as the conscious experience of a voice within the mind. One recurrent theme in the scientific literature is that the phenomenon involves a representation of overt speech, for example, a representation of phonetic properties that result from a copy of speech instructions that were ultimately suppressed. I propose a larger picture that involves some embodied objects and their misperception. I call it "the Body Error Theory," or BET for short. BET is a form of illusionism, but the particular version I favor is a cross-modal illusion. Newly described here, my hypothesis is that the experience of inner speech arises from a mix of interoception and audition. Specifically, there is the detection of slight but well-confirmed activities in the speech musculature that occur during inner speech, which helps to transform representations of normal but quiet nonverbal sounds that inevitably occur during inner speech, from breathing to background noise, into a mistaken perception of inner speech. Simply put, activities in the speech musculature mix with sounds to create the appearance of speech sounds, which thus explains the "voice within the mind." I also show how BET's cross-modal system fits with standard information processing accounts for speech monitoring and how it accommodates the central insights of leading theories of inner speech. In addition, I show how BET is supported by data from experience-sampling surveys and how it can be empirically tested against its rivals.

Inner speech in the daily lives of people with aphasia.

Introduction: This exploratory, preliminary, feasibility study evaluated the extent to which adults with chronic aphasia (N = 23) report experiencing inner speech in their daily lives by leveraging experience sampling and survey methodology. Methods: The presence of inner speech was assessed at 30 time-points and themes of inner speech at three time-points, over the course of three weeks. The relationship of inner speech to aphasia severity, demographic information (age, sex, years post-stroke), and insight into language impairment was evaluated. Results: There was low attrition (<8%) and high compliance (>94%) for the study procedures, and inner speech was experienced in most sampled instances (>78%). The most common themes of inner speech experience across the weeks were 'when remembering', 'to plan', and 'to motivate oneself'. There was no significant relationship identified between inner speech and aphasia severity, insight into language impairment, or demographic information. In conclusion, adults with aphasia tend to report experiencing inner speech often, with some shared themes (e.g., remembering, planning), and use inner speech to explore themes that are uncommon in young adults in other studies (e.g., to talk to themselves about health). Discussion: High compliance and low attrition suggest design feasibility, and results emphasize the importance of collecting data in age-similar, non-brain-damaged peers as well as in adults with other neurogenic communication disorders to fully understand the experience and use of inner speech in daily life. Clinical implications and future directions are discussed.

Neuropsychological dimensions related to alterations of verbal self-monitoring neural networks in schizophrenic language: systematic review.

Although schizophrenia has traditionally been interpreted as a disorder of thought, contemporary perspectives suggest that it may be more appropriate to conceptualize it as a disorder of language connectivity. The linguistic anomalies present in schizophrenia possess distinctive characteristics that, despite certain connections, are not comparable to aphasic disorders. It is proposed that these anomalies are the result of dysfunctions in verbal self-monitoring mechanisms, which may influence other neuropsychological dimensions. This study set out to examine the neuropsychological dimensions associated with alterations in the neural networks of verbal self-monitoring in schizophrenic language, based on the scientific evidence published to date. Exhaustive searches were conducted in PubMed, Web of Science, and Scopus to identify magnetic resonance studies that evaluated verbal self-monitoring mechanisms in schizophrenia. Of a total of 133 articles identified, 22 were selected for qualitative analysis. The general findings indicated alterations in frontotemporoparietal networks and in systems such as the insula, amygdala, anterior cingulate cortex, putamen, and hippocampus. Despite the heterogeneity of the data, it is concluded that language plays a fundamental role in schizophrenia and that its alterations are linked with other neuropsychological dimensions, particularly emotional and perceptual ones.

Relationships between Self-Talk, Inner Speech, Mind Wandering, Mindfulness, Self-Concept Clarity, and Self-Regulation in University Students.

In this study, the researchers explored novel relationships between the self-related processes of self-talk, inner speech, self-concept clarity, mindfulness, mind wandering, and self-regulation. Using self-report questionnaires (n = 227), we found a small positive association between inner speech use and mind wandering, as well as a medium positive association of mindfulness with self-regulation, in accordance with claims made in the literature. We found a medium positive relationship between mindfulness awareness and inner speech responses, potentially because mindfulness awareness represents an active state of self-focus, requiring verbal self-directed probes. Conversely, the correlations between reports of inner speech use and mindfulness acceptance were medium and negatively associated, perhaps because self-acceptance is a less active process that does not require as much self-directed speech as acquiring self-awareness, or perhaps self-acceptance consists of silencing the mind. Furthermore, the mindfulness-acceptance responses were negatively associated with mind wandering but positively correlated with self-concept clarity and self-regulation (all significant and of medium strength). Another noteworthy result was that mind wandering was negatively correlated with self-concept clarity and self-regulation, in accordance with the view that mind wandering represents a self-escape mechanism and thus impedes the transparency of one's self-view and efforts at controlling oneself. This study pieces together what has been presented in the literature, examining variables that are typically studied in isolation. Further, these results have implications for the future study of self-regulation in that self-focused attention, self-acceptance, and self-concept clarity may be mediators on the paths between self-talk or inner speech use and self-regulation.

Subject-independent meta-learning framework towards optimal training of EEG-based classifiers.

Advances in deep learning have shown great promise towards the application of performing high-accuracy Electroencephalography (EEG) signal classification in a variety of tasks. However, many EEG-based datasets are often plagued by the issue of high inter-subject signal variability. Robust deep learning models are notoriously difficult to train under such scenarios, often leading to subpar or widely varying performance across subjects under the leave-one-subject-out paradigm. Recently, the model agnostic meta-learning framework was introduced as a way to increase the model's ability to generalize towards new tasks. While the original framework focused on task-based meta-learning, this research aims to show that the meta-learning methodology can be modified towards subject-based signal classification while maintaining the same task objectives and achieve state-of-the-art performance. Namely, we propose the novel implementation of a few/zero-shot subject-independent meta-learning framework towards multi-class inner speech and binary class motor imagery classification. Compared to current subject-adaptive methods which utilize large number of labels from the target, the proposed framework shows its effectiveness in training zero-calibration and few-shot models for subject-independent EEG classification. The proposed few/zero-shot subject-independent meta-learning mechanism performs well on both small and large datasets and achieves robust, generalized performance across subjects. The results obtained shows a significant improvement over the current state-of-the-art, with the binary class motor imagery achieving 88.70% and the accuracy of multi-class inner speech achieving an average of 31.15%. Codes will be made available to public upon publication.

Properties of imagined experience across visual, auditory, and other sensory modalities.

Little is known about the perceptual characteristics of mental images nor how they vary across sensory modalities. We conducted an exhaustive survey into how mental images are experienced across modalities, mainly targeting visual and auditory imagery of a single stimulus, the letter "O", to facilitate direct comparisons. We investigated temporal properties of mental images (e.g. onset latency, duration), spatial properties (e.g. apparent location), effort (e.g. ease, spontaneity, control), movement requirements (e.g. eye movements), real-imagined interactions (e.g. inner speech while reading), beliefs about imagery norms and terminologies, as well as respondent confidence. Participants also reported on the five traditional senses and their prominence during thinking, imagining, and dreaming. Overall, visual and auditory experiences dominated mental events, although auditory mental images were superior to visual mental images on almost every metric tested except regarding spatial properties. Our findings suggest that modality-specific differences in mental imagery may parallel those of other sensory neural processes.

Distinct neural mechanisms support inner speaking and inner hearing.

Humans have the ability to mentally examine speech. This covert form of speech production is often accompanied by sensory (e.g., auditory) percepts. However, the cognitive and neural mechanisms that generate these percepts are still debated. According to a prominent proposal, inner speech has at least two distinct phenomenological components: inner speaking and inner hearing. We used transcranial magnetic stimulation to test whether these two phenomenologically distinct processes are supported by distinct neural mechanisms. We hypothesised that inner speaking relies more strongly on an online motor-to-sensory simulation that constructs a multisensory experience, whereas inner hearing relies more strongly on a memory-retrieval process, where the multisensory experience is reconstructed from stored motor-to-sensory associations. Accordingly, we predicted that the speech motor system will be involved more strongly during inner speaking than inner hearing. This would be revealed by modulations of TMS evoked responses at muscle level following stimulation of the lip primary motor cortex. Overall, data collected from 31 participants corroborated this prediction, showing that inner speaking increases the excitability of the primary motor cortex more than inner hearing. Moreover, this effect was more pronounced during the inner production of a syllable that strongly recruits the lips (vs. a syllable that recruits the lips to a lesser extent). These results are compatible with models assuming that the primary motor cortex is involved during inner speech and contribute to clarify the neural implementation of the fundamental ability of silently speaking in one's mind.

Neurophysiological evidence of motor preparation in inner speech and the effect of content predictability.

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.

Looking for the Edge of the World: How 3D Immersive Audio Produces a Shift from an Internalised Inner Voice to Unsymbolised Affect-Driven Ways of Thinking and Heightened Sensory Awareness.

In this practice-based case study, we investigate the subjective aesthetic and affective responses to a shift from 2D stereo-based modelling to 3D object-based Dolby Atmos in an audio installation artwork. Dolby Atmos is an infinite object-based audio format released in 2012 but only recently incorporated into more public-facing formats. Our analysis focuses on the artist Sadia Sadia's 30-channel audio installation 'Notes to an Unknown Lover', based on her book of free verse poetry of the same title, which was rebuilt and reformatted in a Dolby Atmos specified studio. We examine what effect altered spatiality with an infinite number of 'placements' has on the psychoacoustic and neuroaesthetic response to the text. The effectiveness of three-dimensional (3D) object-based audio is interrogated against more traditional stereo and two-dimensional (2D) formats regarding the expression and communication of emotion and what effect altered spatiality with an infinite number of placements has on the psychoacoustic and neuroaesthetic response to the text. We provide a unique examination of the consequences of a shift from 2D to wholly encompassing object-based audio in a text-based artist's audio installation work. These findings may also have promising applications for health and well-being issues.

Bridging phenomenology and neural mechanisms of inner speech: ALE meta-analysis on egocentricity and spontaneity in a dual-mechanistic framework.

The neural mechanisms of inner speech remain unclear despite its importance in a variety of cognitive processes and its implication in aberrant perceptions such as auditory verbal hallucinations. Previous research has proposed a corollary discharge model in which inner speech is a truncated form of overt speech, relying on speech production-related regions (e.g. left inferior frontal gyrus). This model does not fully capture the diverse phenomenology of inner speech and recent research suggesting alternative perception-related mechanisms of generation. Therefore, we present and test a framework in which inner speech can be generated by two separate mechanisms, depending on its phenomenological qualities: a corollary discharge mechanism relying on speech production regions and a perceptual simulation mechanism within speech perceptual regions. The results of the activation likelihood estimation meta-analysis examining inner speech studies support the idea that varieties of inner speech recruit different neural mechanisms.

Self-talk: research challenges and opportunities.

In this review, we discuss major measurement and methodological challenges to studying self-talk. We review the assessment of self-talk frequency, studying self-talk in its natural context, personal pronoun usage within self-talk, experiential sampling methods, and the experimental manipulation of self-talk. We highlight new possible research opportunities and discuss recent advances such as brain imaging studies of self-talk, the use of self-talk by robots, and measurement of self-talk in aphasic patients.

The Self Course: Lessons Learned from Students' Weekly Questions.

In this paper, I tentatively answer 50 questions sampled from a pool of over 10,000 weekly questions formulated by students in a course entitled "The Self". The questions pertain to various key topics related to self-processes, such as self-awareness, self-knowledge, self-regulation, self-talk, self-esteem, and self-regulation. The students' weekly questions and their answers highlight what is currently known about the self. Answers to the student questions also allow for the identification of some recurrent lessons about the self. Some of these lessons include: all self-processes are interconnected (e.g., prospection depends on autobiography), self-terms must be properly defined (e.g., self-rumination and worry are not the same), inner speech plays an important role in self-processes, controversies are numerous (are animals self-aware?), measurement issues abound (e.g., self-recognition as an operationalization of self-awareness), deficits in some self-processes can have devastating effects (e.g., self-regulatory deficits may lead to financial problems), and there are lots of unknowns about the self (e.g., gender differences in Theory-of-Mind).

Robot's Inner Speech Effects on Human Trust and Anthropomorphism.

Inner Speech is an essential but also elusive human psychological process that refers to an everyday covert internal conversation with oneself. We argued that programming a robot with an overt self-talk system that simulates human inner speech could enhance both human trust and users' perception of robot's anthropomorphism, animacy, likeability, intelligence and safety. For this reason, we planned a pre-test/post-test control group design. Participants were divided in two different groups, one experimental group and one control group. Participants in the experimental group interacted with the robot Pepper equipped with an over inner speech system whereas participants in the control group interacted with the robot that produces only outer speech. Before and after the interaction, both groups of participants were requested to complete some questionnaires about inner speech and trust. Results showed differences between participants' pretest and post-test assessment responses, suggesting that the robot's inner speech influences in participants of experimental group the perceptions of animacy and intelligence in robot. Implications for these results are discussed.