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Schizophrenic patients display abnormal neural responses in auditory cortex to increasing rates of stimulation

Jordan P. Hamm1*, Casey S. Gilmore2, Brett A. Clementz1, Scott R. Sponheim3 and Natalie Picchetti1
  • 1 University of Georgia, Department of Psychology and Neuroscience, United States
  • 2 University of Minnesota, Department of Psychology, United States
  • 3 VA Medical Center, United States

Auditory information processing is abnormal in schizophrenia patients [1]. Two well studied deficits involve amplitude reductions in 1) the n100m auditory-evoked field and 2) the auditory steady-state response (aSSR). While the n100m indexes early stimulus registration in secondary auditory cortices [2], the aSSR indexes a sustained ability of the auditory system to coherently entrain to and oscillate with a repetitive stimulus [3]. Insufficient glutamatergic and GABAergic transmission are theorized to underlie schizophrenia related abnormalities in these indices [4, 5, 6], and predict an abnormal functional relationship between neural responses and increasing stimulus frequency. These predictions have not been thoroughly investigated. Whole head magnetoencephalograms (MEG) were recorded while schizophrenia and healthy subjects heard broadband noise bursts amplitude modulated at 5, 20, 40, and 80 Hz. MEG data were co-registered with magnetic resonance images (MRI), and minimum norm source estimates of evoked fields were analysed in reconstructed individual brain space focusing exclusively on the neural responses in left and right auditory cortices.
Comparisons of transient responses reveal that, relative to healthy subjects, patients display: 1) reduced n100m amplitudes to 40Hz stimuli in both right and left auditory cortices, and 2) a left hemisphere specific deficit in n100m amplitude across all stimulus densities which exacerbates as frequency increases. Comparisons of steady-state responses (Figure 2) reveal that schizophrenia subjects display: 1) normal entrainment to 20Hz stimulation in both hemispheres, 2) reduced entrainment to 40Hz stimulation in right hemisphere only, and 3) reduced entrainment to 80Hz stimulation in both hemispheres. Overall, these results indicate that auditory processing deficits in schizophrenia are most pronounced as stimulus density increases and show distinct patterns in left vs right auditory cortices. Further, given ample time to develop the steady-state neural response (>500ms), some auditory deficits can be compensated for (such as the entrained response to 80Hz stimulation in right hemisphere), while other deficits appear to be resilient over time.

References

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2. Barth DS & Di S. 1991. Brain Res. 565. 109-15.

3. Huchteon B & Yarom Y. 2000. Trends Neurosci. 23. 216-22.

4. Kwon JS et al. 1999. Arch Gen Psychiatry. 56. 1001-5.

5. Javitt DC et al. 1996. Int Rev Neurobiol. 78.69-108.

6. Benes FM & Beretta S. 2001. Neuropsychopharmacology. 25. 1-27.

Keywords: Schizophrenia

Conference: 2010 South East Nerve Net (SENN) and Georgia/South Carolina Neuroscience Consortium (GASCNC) conferences, Atlanta , United States, 5 Mar - 7 Mar, 2010.

Presentation Type: Oral Presentation

Topic: Talks

Citation: Hamm JP, Gilmore CS, Clementz BA, Sponheim SR and Picchetti N (2010). Schizophrenic patients display abnormal neural responses in auditory cortex to increasing rates of stimulation. Front. Neurosci. Conference Abstract: 2010 South East Nerve Net (SENN) and Georgia/South Carolina Neuroscience Consortium (GASCNC) conferences. doi: 10.3389/conf.fnins.2010.04.00008

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Received: 15 Mar 2010; Published Online: 15 Mar 2010.

* Correspondence: Jordan P Hamm, University of Georgia, Department of Psychology and Neuroscience, Athens, United States, jhamm1@gsu.edu