May was another busy month on the voice-hearing research front. This month we have papers on:
- Cortical thickness and hearing voices
- How text messages can help people who hear voices
- The co-occurence of hallucinations and delusions
- Interhemispheric transfer times and hearing voices
- Hallucination-proneness and aggressive behaviour
- Emotional prosody deficits and hearing voices
- How voice-hearer’s beliefs about their voices relate to distress
In response to a request I received, I have now included lay summaries of the papers to the blog. Happy reading!
Bern, Switzerland. Claudia van Swam and colleagues, including some familiar names to those working in the hallucinations field, Daniela Hubl and Thomas Dierks, examined differences in cortical thickness in voice-hearers.
- Lay summary: Areas of the brain involved in speech production and speech perception are different in people who hear voices. The authors suggest this supports a model of voices where our own inner speech (talking to ourselves silently in our heads) comes to be experienced as non-self produced voices due to these neural changes.
- Detailed summary: The study found significant differences in cortical thickness between people diagnosed with schizophrenia who heard voices (SZ:AVH+) and people with schizophreia who did not (SZ:AVH-). SZ:AVH+ had reduced thickness in left Broca’s area, the left primary auditory cortex (Heschl’s gyrus), left Wernicke’s area of the left hemisphere, and bilaterally in the postcentral gyrus (bilaterally) compared to SZ:AVH-. SZ:AVH+ also had a significantly increased cortical thickness in the left insular cortex, and bilaterally in the anterior and posterior cingular gyrus/sulcus as well as in the dorsal middle frontal gyrus and parietal lobe compared to SZ:AVH-. However, when reporting the results comparing SZ:AVH+ to healthy controls, the authors found that SZ:AVH+ had alterations in regions responsible for sensory processing (parietal operculum, Heschl’s gyrus and postcentral gyrus) but not in areas related to motor and speech production (premotor cortex and dorsolateral inferior frontal gyrus) in the speech dominant (left) hemisphere. The authors conclude their findings support the proposal of AVHs as due to self-monitoring problems with inner speech.
- Link to paper:
San Diego, USA. Eric Granholm leads a paper looking at how an interactive text-messaging intervention can help people who hear voices.
- Lay summary: This study found that receiving specially designed text messages based around principles of cognitive behavioural therapy, which get voice-hearers to test out their beliefs about their voices, such as how uncontrollable they are, and remind them of ways to cope with their voices, can be helpful and reduce how often voices are heard.
- Detailed summary: People diagnosed with schizophrenia who heard voices were sent a series of text messages each day, the content of which was based around CBT techniques. Participant’s thoughts about their voices were elicited in this manner (e.g., “Do you think your voices are powerful?”), and subsequent messages encouraged participants to question unhelpful beliefs about their voices (e.g., “Maybe your voices can’t really do what they say”) and to try a behavioural experiment (e.g., “Try ignoring them and see what happens”). Participants were also sent personalised messages suggesting coping strategies (based on their previous reports of what they found to be useful coping strategies). Thus, if a participant indicated on their phone that they thought their voices were uncontrollable, they may be sent a message such as “But you said before that listening to music helps” or “Try humming a song when they talk”. The study found that participants experienced a reduction in their beliefs that their voices were uncontrollable, and a reduction (at p=.06) in their belief that their voices were all knowing. It was also found that participants had a reduction in severity of voices, with the probability of reporting a moderate severity of voices decreasing, and the rate of reporting no hallucinations increasing over the time of the study.
- Link to paper:
- Lay summary: Hallucinations and delusions tend to occur together. Hallucinations tend to occur first, with delusions then following.
- Detailed summary: Hallucinations and delusions were assessed in 2,524 adolescents and young adults. It was found that hallucinations and delusions co-occurred at a rate more than chance. The authors term this a “hallucinatory–delusional syndrome”. The authors also report that the content of delusions was contingent on the presence of hallucinations, whereas the type of hallucination experienced was not contingent on presence of delusions, which they take to suggest that delusions may represent a cognitive response to hallucinations and a deepening of the psychotic state. The authors conclude that “the early stages of psychosis may involve perceptual anomalies perceived as hallucinations that, if complicated by delusional ideation under the influence of environmental risks and (liability for) affective dysregulation, give rise to a hallucinatory–delusional syndrome”.
- Link to paper:
Melbourne, Australia. Katherine Henshall and colleagues, including well-known hallucinations researcher David Copolov,examined the relation between auditory hallucinations and interhemispheric transfer times.
- Lay summary: Our brains have two hemispheres, left and right, which are joined by a form of ‘transfer wire’ called the corpus callosum. As the brain gets specific parts of each hemisphere do different jobs, in order to function normally we need our left and right hemispheres to exchange information with each other quickly. If people who hear voices listen to words played to them by an experimenter, they take longer to transfer this information from one hemisphere to another. This timing delay may play a role in causing one’s own thoughts/memories of words to be experienced as hallucinations.
- Detailed summary: Two groups of people with schizophrenia, one who had experienced AVHs in the last week (SZ:AVH+), and one who had not experienced AVHs in the last year (SZ:AVH-), were compared with healthy controls in an auditory ERP task using tones and words as stimuli. Whereas patients and controls did not differ on interhemispheric transfer times for pure tones, differences were found for words. SZ:AVH+ had longer interhemispheric transfer times than both SZ:AVH- and healthy controls. This finding is consistent with the hypothesis that interhemispheric transfer is disrupted in SZ:AVH+, with increased transcallosal conduction times for words specifically (and not tones).
- Link to paper:
- Lay summary: The study found that students who were more prone to hallucinations were more likely to behave aggressively. However, the studies design meant it couldn’t show whether hallucinations caused aggression or vice versa. It is also possible that there is no causal relation, with other factors associated with hallucinations explaining this association. For example, the previously documented association between childhood trauma and hallucinations could be taken to suggest that those with hallucinaitons are more likely to have experienced childhood trauma, making them more likely to have emotional problems resulting in aggressive behaviour. If this were the case it would be experiencing trauma that would be associated with aggressive behaviour, and the relation between hallucinations and aggression would be a red herring.
- Detailed summary: In 759 students, Launay Slade Hallucination Scale (LSHS) scores correlated positively with scores on Buss and Perry’s Aggression Questionnaire (AQ), a self-report scale for measuring external aggressive behaviour. In a hierarchical linear regression, LSHS scores predicted AQ scores, even when a range of other measures were included in the regression, including social desirability, neuroticism, trait anger and anxiety, drug use, the cognitive perceptual subscale of the SPQ.
- Brief thoughts: If we pass over the fact that the authors examine 78 different correlations and only correct their significance value to p<.01 (!), the regression analyses do offer evidence of a relation between LSHS scores and aggressive behaviour. The obvious problem, as I note above, is that of correlation not implying causation, and the problem of confounding variables (e.g., trauma, powerlessness, SES etc).
- Link to paper:
- Lay summary: By comparing the levels of hallucinations experienced by sets of twins we can see what role genes may play in causing hallucinations. This study found a role for genes, but a bigger role for life-events in the genesis of hallucinations.
- Detailed summary: The study recruited participants from the South Korean Twin Registry, and assessed hallucinations using the LSHS (with yes/no answers rather than its traditional Likert Scales). The correlations between LSHS scores were 0.37 for monozygotic male twins (N=170), 0.05 for dizygotic male twins (N=51), 0.30 for monozygotic female twins (N=231) and 0.11 for dizygotic female twins (N=51). After further analyses the study reported that “33% of the variance of hallucinatory experiences was due to genetic differences among people, with the remaining variance being attributable to unique environmental influences.”
- Brief thoughts: I don’t have a background in genetics, so any comments on the methodology of this paper and the validity of its conclusions from someone with expertise in this area would be much appreciated.
- Link to paper:
Durham, England. Lucy Alba-Ferrara and colleagues published a paper arguing that emotional prosody comprehension deficits contribute to the formation of voice-hearing.
- Lay summary: Detecting the prosody of words (i.e., acoustic features such as pitch, amplitude, rhythm and stress) allows us to understand the feelings expressed in speech. If people have a deficit in the ability to recognise emotional prosody, they may mistake their own internally generated thoughts as being other people’s voices, and hence ‘hear voices’
- Detailed summary: The authors propose a model of hearing voices in which such experiences are due to auditory stimuli, either internally or externally generated, not being recognised as self-produced due to emotional prosody comprehension deficits. These deficits are argued to occur due to prefrontal circuitry failing to regulate amygdala activity, biasing attention towards threatening stimuli, which ultimately causes abnormal emotion processing. Additionally, abnormal connectivity between the anterior cingulate cortex and the superior temporal gyrus causes difficulty judging whether a stimulus was internally or externally generated, leading to misattribution of inner auditory objects such as inner speech, resulting in ‘hearing voices’
- Link to paper:
London, England. Emmanuelle Peters and colleagues examine the role of appraisals of voices in relation to affect and behaviour.
- Lay summary: This study found that voice-hearers’ beliefs about the omnipotence of their voices (the extent to which the voices are experienced as powerful and controlling) was strongly related to the amount of distress they experienced as a result of their voices, and related to their general levels of distress (including depression, anxiety, self-esteem and suicidal ideation). Beliefs about the power of voices hence appears essential for therapists to address with their voice-hearing clients.
- Detailed summary: 46 voice-hearers involved in a randomised controlled trial of CBT for psychosis completed the BAVQ-R, and correlations between this measure and levels of distress were examined. The authors found that “The appraisal of voices as omnipotent was significantly associated with both voice-specific and general distress, including depression, anxiety, self-esteem and suicidal ideation”. The malevolence of voices did not explain variance in distress above and beyond that predicted by omnipotence, although believing that voices were malevolent was related to resistance, whereas believing that voices were benevolent was related to engagement. The authors conclude that “beliefs about voice power are key determinants of distress in voice hearers, and should be targeted specifically in psychological interventions.”
- Link to paper:
That’s all for this month. Please leave any comments you have, and God willing I’ll see you again at the end of June.