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Left auditory cortex gamma synchronization and auditory hallucination symptoms in schizophrenia.

Spencer KM, Niznikiewicz MA, Nestor PG, Shenton ME, McCarley RW - BMC Neurosci (2009)

Bottom Line: Phase locking factor (PLF) and evoked power were reduced in SZ at fronto-central electrodes, replicating prior findings.PLF was reduced in SZ for non-homologous right and left hemisphere sources.Furthermore, the correlations between source evoked power and PLF found in HC was reduced in SZ for the LH sources.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Service, Veterans Affairs Boston Healthcare System and Department of Psychiatry, Harvard Medical School, Research 151C, 150 S, Huntington Ave, Boston, MA 02130, USA. kevin_spencer@hms.harvard.edu

ABSTRACT

Background: Oscillatory electroencephalogram (EEG) abnormalities may reflect neural circuit dysfunction in neuropsychiatric disorders. Previously we have found positive correlations between the phase synchronization of beta and gamma oscillations and hallucination symptoms in schizophrenia patients. These findings suggest that the propensity for hallucinations is associated with an increased tendency for neural circuits in sensory cortex to enter states of oscillatory synchrony. Here we tested this hypothesis by examining whether the 40 Hz auditory steady-state response (ASSR) generated in the left primary auditory cortex is positively correlated with auditory hallucination symptoms in schizophrenia. We also examined whether the 40 Hz ASSR deficit in schizophrenia was associated with cross-frequency interactions. Sixteen healthy control subjects (HC) and 18 chronic schizophrenia patients (SZ) listened to 40 Hz binaural click trains. The EEG was recorded from 60 electrodes and average-referenced offline. A 5-dipole model was fit from the HC grand average ASSR, with 2 pairs of superior temporal dipoles and a deep midline dipole. Time-frequency decomposition was performed on the scalp EEG and source data.

Results: Phase locking factor (PLF) and evoked power were reduced in SZ at fronto-central electrodes, replicating prior findings. PLF was reduced in SZ for non-homologous right and left hemisphere sources. Left hemisphere source PLF in SZ was positively correlated with auditory hallucination symptoms, and was modulated by delta phase. Furthermore, the correlations between source evoked power and PLF found in HC was reduced in SZ for the LH sources.

Conclusion: These findings suggest that differential neural circuit abnormalities may be present in the left and right auditory cortices in schizophrenia. In addition, they provide further support for the hypothesis that hallucinations are related to cortical hyperexcitability, which is manifested by an increased propensity for high-frequency synchronization in modality-specific cortical areas.

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PLF time-frequency maps of source activity for HC and SZ.
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Figure 2: PLF time-frequency maps of source activity for HC and SZ.

Mentions: The PLF source data are shown in Figure 2. PLF was reduced overall in SZ compared to HC (F[1,32] = 5.70, p < 0.05). There was a main effect of Source (F[4,128] = 6.07, p < 0.0001), indicating that the PLF of the sources differed, but the Group × Source interaction was not significant (F[4,128] = 0.938, p = 0.427). Post-hoc t-tests (Bonferroni-corrected) found that PLF of the RH tangential dipole was significantly reduced in SZ (t[32] = 2.80, p < 0.05), while the PLF reduction of the LH radial dipole in SZ was nearly significant (t[32] = 2.73, p = 0.050). (The rationale for the dipole labeling scheme is given below in the Methods.)


Left auditory cortex gamma synchronization and auditory hallucination symptoms in schizophrenia.

Spencer KM, Niznikiewicz MA, Nestor PG, Shenton ME, McCarley RW - BMC Neurosci (2009)

PLF time-frequency maps of source activity for HC and SZ.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2719648&req=5

Figure 2: PLF time-frequency maps of source activity for HC and SZ.
Mentions: The PLF source data are shown in Figure 2. PLF was reduced overall in SZ compared to HC (F[1,32] = 5.70, p < 0.05). There was a main effect of Source (F[4,128] = 6.07, p < 0.0001), indicating that the PLF of the sources differed, but the Group × Source interaction was not significant (F[4,128] = 0.938, p = 0.427). Post-hoc t-tests (Bonferroni-corrected) found that PLF of the RH tangential dipole was significantly reduced in SZ (t[32] = 2.80, p < 0.05), while the PLF reduction of the LH radial dipole in SZ was nearly significant (t[32] = 2.73, p = 0.050). (The rationale for the dipole labeling scheme is given below in the Methods.)

Bottom Line: Phase locking factor (PLF) and evoked power were reduced in SZ at fronto-central electrodes, replicating prior findings.PLF was reduced in SZ for non-homologous right and left hemisphere sources.Furthermore, the correlations between source evoked power and PLF found in HC was reduced in SZ for the LH sources.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Service, Veterans Affairs Boston Healthcare System and Department of Psychiatry, Harvard Medical School, Research 151C, 150 S, Huntington Ave, Boston, MA 02130, USA. kevin_spencer@hms.harvard.edu

ABSTRACT

Background: Oscillatory electroencephalogram (EEG) abnormalities may reflect neural circuit dysfunction in neuropsychiatric disorders. Previously we have found positive correlations between the phase synchronization of beta and gamma oscillations and hallucination symptoms in schizophrenia patients. These findings suggest that the propensity for hallucinations is associated with an increased tendency for neural circuits in sensory cortex to enter states of oscillatory synchrony. Here we tested this hypothesis by examining whether the 40 Hz auditory steady-state response (ASSR) generated in the left primary auditory cortex is positively correlated with auditory hallucination symptoms in schizophrenia. We also examined whether the 40 Hz ASSR deficit in schizophrenia was associated with cross-frequency interactions. Sixteen healthy control subjects (HC) and 18 chronic schizophrenia patients (SZ) listened to 40 Hz binaural click trains. The EEG was recorded from 60 electrodes and average-referenced offline. A 5-dipole model was fit from the HC grand average ASSR, with 2 pairs of superior temporal dipoles and a deep midline dipole. Time-frequency decomposition was performed on the scalp EEG and source data.

Results: Phase locking factor (PLF) and evoked power were reduced in SZ at fronto-central electrodes, replicating prior findings. PLF was reduced in SZ for non-homologous right and left hemisphere sources. Left hemisphere source PLF in SZ was positively correlated with auditory hallucination symptoms, and was modulated by delta phase. Furthermore, the correlations between source evoked power and PLF found in HC was reduced in SZ for the LH sources.

Conclusion: These findings suggest that differential neural circuit abnormalities may be present in the left and right auditory cortices in schizophrenia. In addition, they provide further support for the hypothesis that hallucinations are related to cortical hyperexcitability, which is manifested by an increased propensity for high-frequency synchronization in modality-specific cortical areas.

Show MeSH
Related in: MedlinePlus