About the Mechanisms of Auditory Verbal Hallucinations: A Positron Emission Tomographic Study

1. 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

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. Example of Statistical Analysis

10. 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)

11. Activity in ROI Across all Subjects Wernenicke’s area Broca’s area Left/Right supplementary motor area (SMA)

12. Results • The comparison of (Read - Look) activated Broca’s area, Wernicke’s area, and the SMA area as intended, with minimal differences. • The only significant difference was that the Read task activated motor planning neural resources. • 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.

13. Activation in of supplementary motor area (SMA) • Note Control subjects and NAVHs show laterality in the left SMA, while AVHs show laterality in right.

14. 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.