Modality-general and modality-specific processes in hallucinations

Abstract

There is a growing recognition in psychosis research of the importance of hallucinations in modalities other than the auditory. This has focused attention on cognitive and neural processes that might be shared by, and which might contribute distinctly to, hallucinations in different modalities. In this article, I address some issues around the modality-generality of cognitive and neural processes in hallucinations, including the role of perceptual and reality-monitoring systems, top-down and bottom-up processes in relation to the psychological and neural substrates of hallucinations, and the phenomenon of simultaneous multimodal hallucinations of the same entity. I suggest that a functional systems approach, inspired by some neglected aspects of the writings of A. R. Luria, can help us to understand patterns of hallucinatory experience across modalities and across clinical and non-clinical groups. Understanding the interplay between modality-general and modality-specific processes may bear fruit for improved diagnosis and therapeutic approaches to dealing with distressing hallucinations.

A Review of Multimodal Hallucinations: Categorization, Assessment, Theoretical Perspectives, and Clinical Recommendations

“…This concept stems from the inner speech misattribution theory of AHs in schizophrenia, 53 which posited that such experiences are the outcome of misattributing one’s inner speech to an external entity. As Fernyhough 43 suggested, the same mechanism could be translated to other modalities, with evidence for its analog in vision: PD patients with VHs have stronger visual imagery than those without hallucinations. 54 Furthermore, someone’s tendency to be a visualizer or verbalizer relates to their proneness to MMHs.…”

“…An elegant discussion of these theories with regards to MMHs can be found in Fernyhough’s paper. 43 The present review builds on this work and aims to synthesize how these theories stand up to scrutiny given the available evidence on MMHs.…”

“…Finally, it is important to consider how MMHs can be conceptualized through dysconnectivity between elements of a functional system, 43 , 80 a framework that might allow one to understand how modality-general and modality-specific processes interact. Evidence of aberrant connectivity of neural networks has been found in relation to AHs in schizophrenia 81 and to VHs in PD.…”

Comparing Primary Voice-Hearers with and without Hallucinations in Other Sensory Modalities

“…This is important because hallucinatory experiences which are congruent in time and relatedness may harness activation of discrete neurological networks compared to those which are incongruent. In other words, we may glean insights into whether hallucinations are likely mediated by a central reality testing mechanism or discrete brain regions [20]. Such information will have key implications for developing an inclusive etiological model that can be applied to hallucinatory experiences across more than one sensory domain.…”

The neurodevelopment of anomalous perception: Evidence in cortical folding patterns for prenatal predispositions to hallucinations in schizophrenia

“…Parkinson’s disease)? Are sulcal anomalies a modality-specific or general risk factor for hallucinations (63)? A recent study showing general sulcal deviations in schizophrenia patients with visual hallucinations suggests the latter (22).…”