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dc.contributor.authorGilmore, Casey Steven
dc.description.abstractSchizophrenia patients exhibit characteristic problems in early stages of auditory information processing, which may be related to cognitive dysfunction present in the illness. These problems are related to schizophrenia patients’ inherent inability to generate and/or maintain evoked oscillatory rhythms in response to both transient and repetitive (steady-state) stimuli. These oscillatory rhythms underlie cortical middle- and late-latency auditory evoked responses (MLAERs), P1 and N1, and evoked oscillatory responses at the driving frequency of steady-state stimuli (SSRs). These evoked responses are indices of abnormal sensory encoding and temporal integration ability in schizophrenia. These abnormalities may be attributed to some fundamental characteristics of schizophrenia patients' auditory systems - characteristics whose sum effect is to reduce the signal-to-noise ratio during auditory information processing. The present study examined the hypothesis that increasing the rate of stimulation, i.e. increasing the number of stimuli presented per unit time, would increase signal power sufficiently to normalize evoked oscillatory responses in schizophrenia patients. Steady-state stimuli at various rates (5, 20, 40, 80, and 160 Hz) were presented to 12 normal and 12 schizophrenia subjects while 248 sensor whole-cortex magnetoencephalography was recorded. The FFT power and inter-trial phase coherence in the delta and theta bands underlying MLAERs and in the SSRs at the driving frequencies of the respective rates of stimulation were examined for differences between groups, hemispheres, and rates of stimulation. Results indicated that schizophrenia patients were able to generate essentially normal steady-state responses in response to stimuli with durations sufficiently long enough to allow build-up of the SSR. Steady-state stimuli may also enhance patients’ auditory integration and encoding abilities, perhaps through increased signal strength, as indicated by a lack of schizophrenia-normal differences on low-frequency evoked oscillations subserving the P1 and N1 MLAERs. Finally, the observation that evoked power and inter-trial phase coherence play divergent but complementary roles with regard to MLAER-associated low-frequency evoked oscillatory activity in both normal and schizophrenia subjects was illustrated. Understanding the mechanisms responsible for deficits in the ability to evoke oscillatory responses could help in understanding the relationship between the neuropathology and symptoms of schizophrenia.
dc.subjectAuditory-evoked response
dc.titleIs faster always better?
dc.title.alternativerate of stimulation affects auditory-evoked responses in schizophrenia
dc.description.advisorBrett Clementz
dc.description.committeeBrett Clementz
dc.description.committeeAndrew Sornborger
dc.description.committeeJennifer McDowell

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