This constellation of symptoms has been attributed to a failure of a self-monitoring system. Patients hear voices they attribute to others, they have delusions that their thoughts and behaviors are controlled by external forces, and they misinterpret the actions of others as being relevant to themselves. In schizophrenia, this distinction seems to be blurred. Many theoretical models 1 - 3 have been developed to explain how the healthy human brain distinguishes between sensory experiences resulting from self-generated actions and those from external sources. This imprecision correlated with the severity of hallucinations and with the percentage of misattribution errors.Ĭonclusion These data support a connection between auditory verbal hallucinations and the imprecision of the corollary discharge heralding the sensory consequences of thoughts and actions. This pattern was not seen in hallucinating patients. Results In controls, N100 to unaltered self-voice feedback was dampened relative to N100 to altered self-voice or alien auditory feedback. On each trial, subjects judged whether feedback was “self,” “other,” or “unsure.” Clinical ratings were used to assess severity of auditory hallucinations in patients. Main Outcome Measures N100 responses to auditory feedback, which was altered by pitch-shifting the self-voice, substituting an alien voice, or pitch-shifting the alien voice. Participants Twenty patients with schizophrenia and 17 sex- and age-matched healthy control subjects. Setting Community mental health centers and Palo Alto Veterans Affairs Health Care System, Palo Alto, Calif. To assess the relationship between auditory hallucinations and the imprecision of the corollary discharge. Objectives To assess the precision of the forward model in schizophrenia using the N100 component of the auditory event-related potential to speech that is altered or unaltered, in real time, as it is being spoken. Imprecision of the corollary discharge in schizophrenia may contribute to the misperception of inner experiences and thoughts as “voices” or auditory hallucinations. Shared Decision Making and CommunicationĬontext A forward model of intended thoughts and actions prepares sensory cortex for sensations that are a consequence of those actions.Scientific Discovery and the Future of Medicine.Health Care Economics, Insurance, Payment.Clinical Implications of Basic Neuroscience.
Challenges in Clinical Electrocardiography.Such a system would allow the individual to cancel out the effects of self-produced speech and thereby distinguish sounds due to self-produced speech from auditory feedback caused by the environment.
As a result, the cortical suppression decreases and the N100 amplitude increases. When the actual feedback does not match the predicted feedback (by altering the feedback), the discrepancy increases and so does the likelihood that the sound is externally produced. This results in suppression of auditory cortex to the self-produced sound, as can be seen by a reduced N100 amplitude. Self-produced speech sounds can be correctly predicted on the basis of the efference copy and are associated with little or no sensory discrepancy resulting from the comparison between predicted and actual feedback. These predictions are then compared with the actual auditory feedback (reafference).
An internal forward model makes predictions of the auditory feedback (corollary discharge) based on a copy of the motor command (efference copy). A model for determining the auditory consequences of speaking.
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