Auditory Verbal Imagery Research Articles

Monitoring Processes and Their Neuronal Correlates as the Basis of Auditory Verbal Hallucinations in a Non-clinical Sample.

Auditory verbal hallucinations (AVH) are a characteristic symptom of psychosis. An influential cognitive model accounting for the mechanisms in the generation of AVHs describes a defective monitoring of inner speech, leading to the misidentification of internally generated thoughts as externally generated events. In this study, we utilized an inner speech paradigm during a simultaneous measurement with functional near-infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI), in order to replicate the findings of neural correlates of inner speech and auditory verbal imagery (AVI) in healthy subjects, reported in earlier studies, and to provide the first validation of the paradigm for fNIRS measurements. To this end, 20 healthy subjects were required to generate and silently recite first and second person sentences in their own voice (inner speech) and imagine the same sentences in a different, alien voice (AVI). Furthermore, questionnaires were deployed to assess the predisposition to acoustic hallucinations and schizotypal traits to investigate their connection to activation patterns associated with inner speech and monitoring processes. The results showed that both methods, fNIRS and fMRI, exhibited congruent activations in key brain areas, claimed to be associated with monitoring processes, indicating that the paradigm seems to be applicable using fNIRS alone. Furthermore, the results showed similar brain areas activated during inner speech and monitoring processes to those from earlier studies. However, our results indicate that the activations were dependent more on the sentence form and less on the imaging condition, showing more active brain areas associated with second person sentences. Integration of the sentence construction into the model of inner speech and deficient monitoring processes as the basis for the formation of AVHs should be considered in further studies. Furthermore, negative correlations between questionnaires' scores and activations in precentral gyrus and premotor cortex indicate a relationship of schizotypal characteristics and a deficient activation pattern.

Do patients with hallucinations imagine speech right?

A direct relationship between auditory verbal hallucinations (AVHs) and decreased left-hemispheric lateralization in speech perception has been often described, although it has not been conclusively proven. The specific lateralization of AVHs has been poorly explored. However, patients with verbal hallucinations show a weak Right Ear Advantage (REA) in verbal perception compared to non AVHs listeners suggesting that left-hemispheric language area are involved in AVHs. In the present study, 29 schizophrenia patients with AVHs, 31 patients with psychotic bipolar disorder who experienced frequent AVHs, 27 patients with schizophrenia who had never experienced AVHs and 57 healthy controls were required to imagine hearing a voice in one ear alone. In line with previous evidence healthy controls confirmed the expected REA for auditory imagery, and the same REA was also found in non-hallucinator patients. However, in line with our hypothesis, patients with schizophrenia and psychotic bipolar disorder with AVHs showed no lateral bias. Results extend the relationship between abnormal asymmetry for verbal stimuli and AVHs to verbal imagery, suggesting that atypical verbal imagery may reflect a disruption of inter-hemispheric connectivity between areas implicated in the generation and monitoring of verbal imagery and may be predictive of a predisposition for AVHs. Results also indicate that the relationship between AVHs and hemispheric lateralization for auditory verbal imagery is not specific to schizophrenia but may extend to other disorders as well.

Spatiotemporal properties of magnetic fields induced by auditory speech sound imagery and perception.

Brain computer interface (BCI) technologies, which enable direct communication between the brain and external devices, have been developed. BCI technology can be utilized in neural prosthetics to restore impaired movement, including speech production. However, most of the BCI systems that have been developed are the "P300-speller" type, which can only detect objects that users direct his/her attention at. To develop more versatile BCI systems that can detect a user's intention or thoughts, the brain responses associated with verbal imagery need to be clarified. In this study, the brain magnetic fields associated with auditory verbal imagery and speech hearing were recorded using magnetoencephalography (MEG) carried out on 8 healthy adults. Although the magnetic fields lagged slightly and were long-lasting, significant deflections were observed even for verbal imagery, in the temporal regions, as well as for actual speech hearing. Also, sources for the deflections were localized in the association auditory cortices. Cross-correlations were calculated between envelopes of the imagined/presented speech sound and the evoked brain responses in the temporal areas. Measurable correlations were obtained for the presented speech sound; however, no significant correlations were observed for the imagined speech sound. These results indicate that auditory verbal imagery undoubtedly activates the auditory cortex, at least, and generates some observable neural responses.

The effect of auditory verbal imagery on signal detection in hallucination-prone individuals

Cognitive models have suggested that auditory hallucinations occur when internal mental events, such as inner speech or auditory verbal imagery (AVI), are misattributed to an external source. This has been supported by numerous studies indicating that individuals who experience hallucinations tend to perform in a biased manner on tasks that require them to distinguish self-generated from non-self-generated perceptions. However, these tasks have typically been of limited relevance to inner speech models of hallucinations, because they have not manipulated the AVI that participants used during the task. Here, a new paradigm was employed to investigate the interaction between imagery and perception, in which a healthy, non-clinical sample of participants were instructed to use AVI whilst completing an auditory signal detection task. It was hypothesized that AVI-usage would cause participants to perform in a biased manner, therefore falsely detecting more voices in bursts of noise. In Experiment 1, when cued to generate AVI, highly hallucination-prone participants showed a lower response bias than when performing a standard signal detection task, being more willing to report the presence of a voice in the noise. Participants not prone to hallucinations performed no differently between the two conditions. In Experiment 2, participants were not specifically instructed to use AVI, but retrospectively reported how often they engaged in AVI during the task. Highly hallucination-prone participants who retrospectively reported using imagery showed a lower response bias than did participants with lower proneness who also reported using AVI. Results are discussed in relation to prominent inner speech models of hallucinations.

Poor supplementary motor area activation differentiates auditory verbal hallucination from imagining the hallucination

Neuronal underpinnings of auditory verbal hallucination remain poorly understood. One suggested mechanism is brain activation that is similar to verbal imagery but occurs without the proper activation of the neuronal systems that are required to tag the origins of verbal imagery in one's mind. Such neuronal systems involve the supplementary motor area. The supplementary motor area has been associated with awareness of intention to make a hand movement, but whether this region is related to the sense of ownership of one's verbal thought remains poorly known. We hypothesized that the supplementary motor area is related to the distinction between one's own mental processing (auditory verbal imagery) and similar processing that is attributed to non-self author (auditory verbal hallucination). To test this hypothesis, we asked patients to signal the onset and offset of their auditory verbal hallucinations during functional magnetic resonance imaging. During non-hallucination periods, we asked the same patients to imagine the hallucination they had previously experienced. In addition, healthy control subjects signaled the onset and offset of self-paced imagery of similar voices. Both hallucinations and the imagery of hallucinations were associated with similar activation strengths of the fronto-temporal language-related circuitries, but the supplementary motor area was activated more strongly during the imagery than during hallucination. These findings suggest that auditory verbal hallucination resembles verbal imagery in language processing, but without the involvement of the supplementary motor area, which may subserve the sense of ownership of one's own verbal imagery.

The role of amygdala during auditory verbal imagery of derogatory appraisals by others

We tend to simulate or recall others’ appraisals through auditory verbal imagery (AVI) process to react appropriately. In particular, the ability to imagine derogatory appraisals by others may be critically important for social survival. In this study, we investigated the neural correlates implicated in the processing of unpleasant emotion related to derogatory remark and its self-directedness during AVI process. Twenty-three right-handed healthy human subjects participated in our study. We asked each subject to imagine hearing one’s own or another person’s voice saying derogatory or non-derogatory neutral remarks during the scanning of functional magnetic imaging. A test of the interaction between derogatory emotion and its self-directedness revealed significant activation of the amygdala. Additionally, we observed decreased neural activity in the anterior cingulate cortex (ACC) during imagery of derogatory remarks compared to neutral remarks. Our findings indicate an important role of the amygdala in the processing of unpleasant emotion or self-relevance of information in the real world may also be expanded to the processing of self-directedness of unpleasant emotion in the imagined world, and thereby contribute to human higher social cognitive process. This study also suggests that deactivation of ACC may enable us to enact vivid affective responses, and thereby contribute to an effective simulation of social interaction.

Hallucinatory disorder, an original clinical picture? Clinical and imaging data

Objective The aim of this study was to verify the existence of areas of clinical and neurofunctional homogeneity in a group of patients with auditory verbal hallucinations (AVHs) as an isolated symptom, attributable to what we have called “Hallucinatory Disorder” (HD) in an attempt to propose a clinical picture that is distinct from Schizophrenia. Method Nine patients clinically characterised by chronic AVHs were compared with nine schizophrenic patients using the Structured Clinical Interview for DSM-III-R, BPRS, PANSS, SAPS, SANS, HRS-A, HRS-D, CDSS, MMSE, CGI and PSYRATS. Both groups of patients and nine healthy subjects underwent EEG and SPECT examinations. Results Considering the psychopathological dimensions of Schizophrenia, in the HD patients clinical evaluations revealed a mono-dimensional clinical profile, whereas all these dimensions contributed to the clinical picture of the schizophrenic patients. The SPECT data showed that the schizophrenic patients had a reduced rCBF in some areas of the right frontal lobe, while the HD patients did not show any area of hypoperfusion. The SPECT hyperperfusion data showed an activation pattern in the HD patients that was characterised by the involvement of various cortical and subcortical cerebral areas, similar to those found in studies of inner speech and auditory verbal imagery. Conclusions The two groups of patients present significant differences that seem capable of supporting the proposed hypothesis that HD may be an independent nosographical entity.

Audiovisual phonological mismatch produces early negativity in auditory cortex

During silent reading, visual information provided by letters is converted to auditory information in the mind. The purpose of this study was to identify the primary locus for auditory verbal imagery in the brain. Neuromagnetic recording was obtained from 10 right-handed study participants, who were instructed to identify infrequently occurring phonological mismatches between a random-ordered sequence of syllable sounds and a visually presented syllabogram sequence. The activity difference in early latency, calculated by subtracting the averaged responses to matched syllables from the averaged responses to mismatched syllables, showed a spatiotemporal profile strikingly similar to that of mismatch negativity. Auditory imagery of forthcoming verbal sounds may establish a memory trace as a template for imagery-based mismatch negativity generation in the auditory cortex.

Subvocalization in auditory-verbal imagery: just a form of motor imagery?

Previous studies have provided evidence for subvocal rehearsal (“inner voice”) and phonological storage (“inner ear”) in auditory-verbal imagery. The question remains to be answered whether the inner voice mainly involves higher-order language systems, or primarily relies on motor systems associated with articulatory-kinesthetic processing. On the basis of models of auditory imagery and working memory, we predicted that, if auditory-verbal imagery is a form of motor imagery, performance on a novel auditory-verbal imagery task would be affected by concurrent articulatory suppression as well as by concurrent finger tapping. In contrast, we predicted that performance on a visuospatial control task would be significantly affected by concurrent tapping only. The auditory imagery task consisted of indicating, for bisyllabic words, the syllable that carried the stress. A significant interaction was observed between task (verbal vs. visual) and type of interference (articulatory suppression vs. tapping). Tapping affected reaction times on the visual task significantly more than articulatory suppression. However, both interference conditions affected the verbal task to an equal extent. The present findings confirm the role of subvocalization in auditory-verbal imagery and provide evidence for a strong involvement of articulatory-kinesthetic motor processing.

The functional neuroanatomy of metrical stress evaluation of perceived and imagined spoken words.

We hypothesized that areas in the temporal lobe that have been implicated in the phonological processing of spoken words would also be activated during the generation and phonological processing of imagined speech. We tested this hypothesis using functional magnetic resonance imaging during a behaviorally controlled task of metrical stress evaluation. Subjects were presented with bisyllabic words and had to determine the alternation of strong and weak syllables. Thus, they were required to discriminate between weak-initial words and strong-initial words. In one condition, the stimuli were presented auditorily to the subjects (by headphones). In the other condition the stimuli were presented visually on a screen and subjects were asked to imagine hearing the word. Results showed activation of the supplementary motor area, inferior frontal gyrus (Broca's area) and insula in both conditions. In the superior temporal gyrus (STG) and in the superior temporal sulcus (STS) strong activation was observed during the auditory (perceptual) condition. However, a region located in the posterior part of the STS/STG also responded during the imagery condition. No activation of this same region of the STS was observed during a control condition which also involved processing of visually presented words, but which required a semantic decision from the subject. We suggest that processing of metrical stress, with or without auditory input, relies in part on cortical interface systems located in the posterior part of STS/STG. These results corroborate behavioral evidence regarding phonological loop involvement in auditory-verbal imagery.

Temporal organization of "internal speech" as a basis for cerebellar modulation of cognitive functions.

The sequencing of smooth and rhythmically "sculptured" words and phrases at a speaker's habitual speech rate (4 Hz to 6 Hz) critically depends on the cerebellum. Besides overt performance, the cerebellum also seems to organize the syllabic structure of "auditory verbal imagery" or "internal speech"--that is, a prearticulatory but otherwise fully elaborated and temporally organized representation of verbal utterances. As a consequence, cerebellar disorders may compromise cognitive operations that involve a speech code, such as verbal working memory, or disrupt cognitive processes that encompass linguistic mediation. Besides the temporal organization of syllable strings at a prearticulatory level, cerebellar patients are impaired in speech perception tasks requiring the encoding of durational parameters of the acoustic signal. The hemodynamic responses associated with these two aspects of verbal-acoustic communication--internal speech and speech perception--were found to be organized along the rostro-caudal direction within paravermal aspects of the superior right cerebellar hemisphere. Those areas of the right cerebellar hemisphere thus might provide a common platform for the computation of temporal aspects of verbal utterances in the domains of both speech production and perception.

A functional study of auditory verbal imagery.

We used functional MRI to examine the functional anatomy of inner speech and different forms of auditory verbal imagery (imagining speech) in normal volunteers. We hypothesized that generating inner speech and auditory verbal imagery would be associated with left inferior frontal activation, and that generating auditory verbal imagery would involve additional activation in the lateral temporal cortices. Subjects were scanned, while performing inner speech and auditory verbal imagery tasks, using a 1.5 Tesla magnet. The generation of inner speech was associated with activation in the left inferior frontal/insula region, the left temporo-parietal cortex, right cerebellum and the supplementary motor area. Auditory verbal imagery in general, as indexed by the three imagery tasks combined, was associated with activation in the areas engaged during the inner speech task, plus the left precentral and superior temporal gyri (STG), and the right homologues of all these areas. These results are consistent with the use of the 'articulatory loop' during both inner speech and auditory verbal imagery, and the greater engagement of verbal self-monitoring during auditory verbal imagery.

Functional anatomy of auditory verbal imagery in schizophrenic patients with auditory hallucinations.

This study investigated the functional neuroanatomy of inner speech and auditory verbal imagery in schizophrenic patients predisposed to auditory hallucinations. Eight patients with schizophrenia with a history of prominent auditory hallucinations and six comparison subjects underwent functional magnetic resonance imaging while generating inner speech or imagining external speech. Patients showed no differences while generating inner speech but experienced a relatively attenuated response in the posterior cerebellar cortex, hippocampi, and lenticular nuclei bilaterally and the right thalamus, middle and superior temporal cortex, and left nucleus accumbens during auditory verbal imagery. Patients with schizophrenia who were prone to auditory hallucinations show attenuated activation when processing inner speech in areas implicated in verbal self-monitoring.

Auditory verbal imagery in differing form

Auditory verbal imagery in differing form

Functional anatomy of inner speech and auditory verbal imagery.

The neural correlates of inner speech and of auditory verbal imagery were examined in normal volunteers, using positron emission tomography (PET). Subjects were shown single words which they used to generate short, stereotyped sentences without speaking. In an inner speech task, sentences were silently articulated, while in an auditory verbal imagery condition, subjects imagined sentences being spoken to them in an another person's voice. Inner speech was associated with increased activity in the left inferior frontal gyrus. Auditory verbal imagery was associated with increases in the same region, and in the left premotor cortex, the supplementary motor area and the left temporal cortex. The data suggest that the silent articulation of sentences involves activity in an area concerned with speech generation, while imagining speech is associated with additional activity in regions associated with speech perception.

Functional anatomy of inner speech and auditory verbal imagery

The neural correlates of inner speech and of auditory verbal imagery were examined in normal volunteers, using positron emission tomography (PET). Subjects were shown single words which they used to generate short, stereotyped sentences without speaking. In an inner speech task, sentences were silently articulated, while in an auditory verbal imagery condition, subjects imagined sentences being spoken to them in an another person's voice. Inner speech was associated with increased activity in the left inferior frontal gyrus. Auditory verbal imagery was associated with increases in the same region, and in the left premotor cortex, the supplementary motor area and the left temporal cortex. The data suggest that the silent articulation of sentences involves activity in an area concerned with speech generation, while imagining speech is associated with additional activity in regions associated with speech perception.