Elsevier

Biological Psychiatry

Volume 64, Issue 5, 1 September 2008, Pages 369-375
Biological Psychiatry

Archival Report
γ-Band Auditory Steady-State Responses Are Impaired in First Episode Psychosis

https://doi.org/10.1016/j.biopsych.2008.02.021Get rights and content

Background

In chronic schizophrenia and chronic bipolar disorder, γ band (30–100 Hz) auditory steady-state electroencephalogram responses (ASSRs) are reduced in power and phase locking, likely reflecting neural circuit dysfunction. Here we examined whether γ ASSR deficits are also present at first hospitalization for psychosis.

Methods

Subjects were 16 first episode schizophrenia patients (SZ), 16 first episode affective disorder patients (AFF) (13 with bipolar disorder), and 33 healthy control subjects (HC). Stimuli were 20-, 30-, and 40-Hz binaural click trains. The ASSR phase locking and evoked power were analyzed with the Morlet wavelet transform.

Results

At 40-Hz stimulation, SZ and AFF had significantly reduced phase locking compared with HC. This deficit was more pronounced over the left hemisphere in SZ. Evoked power at 40 Hz was also reduced in the patients compared with HC. At 30-Hz stimulation phase locking and evoked power were reduced in both patient groups. The 20-Hz ASSR did not differ between groups, but phase locking and evoked power of the 40-Hz harmonic of the 20-Hz ASSR were reduced in both SZ and AFF. Phase locking of this 40-Hz harmonic was correlated with total positive symptoms in SZ.

Conclusions

The γ ASSR deficit is present at first hospitalization for both schizophrenia and affective disorder but shows a left hemisphere bias in first hospitalized SZ. Some of the neural circuitry abnormalities underlying the γ ASSR deficit might be common to psychoses in general, whereas others might be specific to particular disorders.

Section snippets

Subjects

This study was approved by the McLean Hospital Institutional Review Board. After complete description of the study to the subjects, written informed consent was obtained.

Subjects were 32 first-episode psychosis patients and 34 healthy control subjects (HC; 14 female) paid for their participation. The HC were recruited from the local community through newspaper advertisements and were free of Axis I or II disorders (Structured Clinical Interview for DSM-III-R Non-Patient Edition [SCID-NP], 15;

Results

The ASSR was maximal—as is typical—for 40-Hz stimulation in both the phase locking and evoked power data (Figure 1). Also, during 20-Hz stimulation a robust harmonic was apparent at 40 Hz.

Discussion

This study demonstrates that the γ ASSR deficit is present at first hospitalization for both schizophrenia and affective disorder, particularly bipolar disorder (we note that the effects reported for the AFF group did not change appreciably when the non-bipolar patients were removed from the analyses). Thus, the γ ASSR deficit that has been observed in chronic psychosis patients does not seem to be due to brain abnormalities that only arise because of the chronic state, although progressive

References (40)

  • E.F. Torrey et al.

    Neurochemical markers for schizophrenia, bipolar disorder, and major depression in postmortem brains

    Biol Psychiatry

    (2005)
  • J. Gallinat et al.

    Reduced oscillatory gamma-band responses in unmedicated schizophrenic patients indicate impaired frontal network processing

    Clin Neurophysiol

    (2004)
  • D.A. Lewis et al.

    Cortical inhibitory neurons and schizophrenia

    Nat Rev Neurosci

    (2005)
  • K.M. Spencer et al.

    Neural synchrony indexes disordered perception and cognition in schizophrenia

    Proc Natl Acad Sci U S A

    (2004)
  • R. Galambos et al.

    A 40 Hz auditory potential recorded from the human scalp

    Proc Natl Acad Sci U S A

    (1981)
  • M.A. Pastor et al.

    Activation of human cerebral and cerebellar cortex by auditory stimulation at 40 Hz

    J Neurosci

    (2002)
  • C.A. Brenner et al.

    EEG synchronization to modulated auditory tones in schizophrenia, schizoaffective disorder, and schizotypal personality disorder

    Am J Psychiatry

    (2003)
  • J.S. Kwon et al.

    Gamma frequency-range abnormalities to auditory stimulation in schizophrenia

    Arch Gen Psychiatry

    (1999)
  • B.F. O'Donnell et al.

    Event-related potential abnormalities in bipolar disorder: Relationship to symptoms, medication, and substance disorders

  • B.F. O'Donnell et al.

    Neural synchronization deficits to auditory stimulation in bipolar disorder

    NeuroReport

    (2004)
  • Cited by (266)

    View all citing articles on Scopus
    View full text