About the Mechanisms of Auditory Verbal Hallucinations: A Positron Emission Tomographic Study
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Example of Statistical Analysis
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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)
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Activity in ROI Across all Subjects
Wernenicke’s area
Left/Right supplementary motor area (SMA)
Broca’s area
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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.
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Activation in of supplementary motor area (SMA)
• Note Control subjects and NAVHs show laterality in the left SMA, while AVHs show laterality in right.
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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.