The internal structure of the phenomenology of auditory verbal hallucinations
Background: Auditory verbal hallucinations (AVH) do not have uniform pathological significance. They affect patients with different brain disorders, and vary along multiple phenomenological dimensions. Evidence indicates that some of the phenomenological variables have specific neural substrates. Therefore, a comprehensive characterization of the phenomenological variations of AVH and the interrelationship between these variables was undertaken. Method: Twenty phenomenological variables were identified; on each AVH had a binary value (present or absent). Information about 11 of these variables were obtained from 30 patients. Hierarchical cluster (HC) and multidimensional scaling (MDS) analyses were performed to investigate the hidden structure and dimensions of these variables. Results: HC yielded two main clusters with further sub-clusters in each. The first cluster included hallucinations with low linguistic complexity, repetitive content, attributed to self, located in outer space, and associated with different kinds of control strategies. The second cluster included hallucinations with high linguistic complexity, systematized content, multiple voices, attributed to others, and located in inner space. In MDS, three dimensions were identified: linguistic complexity, self-other attribution, and inner-outer space location. Conclusion: The patterns of clustering and dimensional configuration of AVH characteristics were in accord with intuitive expectation and validated the patients' descriptions of their experiences. These findings could reflect aspects of the neural mechanisms of AVH. For example, the presence of neural specificity for each phenomenological variable, intermediate neural commonality for groups of variables, and a final common pathway for all subtypes of AVH. Another example is a differential level of language dysfunction according to the linguistic complexity of AVH.