About the Mechanisms of Auditory Verbal Hallucinations: A Positron

Emission Tomographic Study

Massoud Stephane, Matthew Hagen, Joel Lee, Johnathan Uecker, Patrecia Pardo,

Micheal Kuskowski, Jose Pardo

J Psychiatry Neurosci 2006;31(6):396-405

Introduction

• Auditory Verbal Hallucinations likely result from a disorder of language neural mechanisms.

• Neuropsychological theories suggest that patients who suffer from AVH experience their own inner speech as someone else speaking.

Possible Theories

• Nonself attribution results from a deficit in a system of corollary discharge networks associated with “willed actions” that allows these actions to be labeled as ones own.

• AVHs result from an altered preconscious planning of discourse that produces involuntary inner speech. These verbal hallucinations are essentially unintended, so they are experienced as hallucinations.

In Summary

• It is widely accepted that AVHs result from a disorder of language.

• The Nature of this disorder and the mechanisms attributing one’s own inner speech to another are subject to debate.

Hypothesis

• This study will be focused on the neural correlates of single word reading in patients with and without hallucinations.

• We hypothesize that the neural correlates of reading aloud should differentiate the patients who have hallucinations from those who do not.

Participants• 3 Groups: a. 8 Schizophrenic with a history of AVH

b. 10 Schizophrenic Patients with no history of AVH (NAVH group)

c. 12 healthy male control subject volunteers with no history of Schizophrenia

• Schizophrenic groups were compared to eliminate possible error caused by different medications.

• Therefore allowing only the propensity for verbal hallucinations to distinguish AVH from NAVH.

Methods: Task Paradigm

• Stimuli were common concrete nouns presented in lower case letters above there fixation mark.

• Stimuli appeared on a video monitor for 2.75 seconds with a 250-milisecond interstimulas interval.

• 2 Tasks: a. Reading Condition (Read), subjects read loudly and clearly presented nouns.

b. Look Condition (Look), subjects maintained fixation but were not aloud to read out loud or silently.

Scanning and Image Processing

• Scans were preformed with a Siemens ECAT 953B PET camera in 2D mode.

• Linear wrapping was modeled to Talairach space.

• Read and Look conditions were preformed with a paired t test on mean condition images for each subject.

Example of Statistical Analysis

Region of Interest

• Due to the multiple comparison problem a restriction was placed to ROI on areas classically implicated in language processing.

- Wernickes Area

- Broca’s Area

- Supplementary Motor Area (SMA/pre-SMA)

Activity in ROI Across all Subjects

Wernenicke’s area

Left/Right supplementary motor area (SMA)

Broca’s area

Results

• The comparison of (Read - Look) activated Broca’s area, Wernicke’s area, and the SMA area as intended, with minimal differences.

• What clearly differentiated the AVHs from the NAVHs was a right sided laterality of supplementary motor area (SMA) activation in AVHs and left sided laterality in the NAVHs and Control Subjects.

• The only significant difference was that the Read task activated motor planning neural resources.

Activation in of supplementary motor area (SMA)

• Note Control subjects and NAVHs show laterality in the left SMA, while AVHs show laterality in right.

Conclusion• Lesions to supplementary motor area (SMA) have been shown to give rise to alien limb syndrome which is described as:

- Normal sensation in a limb, but believes that the limb, while still being a part of their body, behaves in a manner that is totally distinct from him or herself.

• Thus the SMA is considered necessary for self-attribution of self-initiated actions which is why a malfunctioning SMA could cause inner speech.