Altered hemispheric asymmetry and positive symptoms in schizophrenia: equivalent current dipole of auditory mismatch negativity
Introduction
Mismatch negativity (MMN) is an event-related potential (ERP) elicited when a sequence of unattended repetitive sounds is interrupted by a deviant stimulus (Näätänen et al., 1978). MMN is elicited by any change in frequency, intensity or duration of tone stimuli, as well as by changes in complex stimuli such as phonetic stimuli (Näätänen, 1992). Since MMN occurs irrespective of whether or not stimuli are being attended, MMN is thought to be an automatic cerebral process for detecting change and an index for automatic process involved in sensory or echoic memory. MMN abnormalities have been found consistently in schizophrenics and interpreted as reflecting the impairment of early preattentive auditory processing in schizophrenia Shelley et al., 1991, Hirayasu et al., 1998, Javitt, 2000. Studies have further suggested that the main cortical source of MMN is localized within the superior temporal plane Scherg et al., 1989, Alho, 1995, Wible et al., 2001. Meanwhile, morphometric studies have also proposed abnormalities of the superior temporal gyrus in schizophrenia Barta et al., 1990, Shenton et al., 1992, Kwon et al., 1999, Gur et al., 2000. However, limits remain in attempts to localize the MMN generator, because most previous electrophysiological studies used a small number of electrodes to record ERP and few studies have used a realistic head model for localization Buchner et al., 1995, Waberski et al., 1998. Therefore, studies using high-density electroencephalography (EEG) recording and a realistic head model are needed for the precise localization of the MMN generator.
In the human brain, many structures are normally lateralized which is consistently larger in one of the hemispheres, occasionally in conjunction with lateralized functions such as language (reviewed in Pearlson and Marsh, 1999). In schizophrenia, many studies have demonstrated a reduced or reversed hemispheric asymmetry, particularly of temporal lobe structures (i.e., planum temporale (PT)) Barta et al., 1997, Kwon et al., 1999. Because it has been suggested that the source of the MMN generator is located in the superior temporal gyrus (STG), an investigation of the hemispheric asymmetry of MMN ECD power in both schizophrenics and controls will be helpful for understanding the pathophysiology of schizophrenia.
With this background, we investigated the location and power of the MMN generator in schizophrenia compared with those in normal volunteers using the equivalent current dipole (ECD) model with high-density EEG acquisition and the subjects' own high-resolution 3-D magnetic resonance images (MRI) for a realistic head model. We also explored the functional hemispheric asymmetry in schizophrenia and its correlation with clinical symptoms to understand the pathophysiology of schizophrenia.
Section snippets
Subjects
Fifteen right-handed schizophrenic patients (male: nine, female: six; mean age 27.8±5.6 years) were recruited from Seoul National University Hospital, Seoul, Korea. All patients met the DSM-IV criteria based on both SCID-IV and information from psychiatric records. Exclusion criteria included a history of auditory dysfunction, electroconvulsive therapy, neurologic illness, major head trauma, or alcohol and drug abuse or dependence. All patients were receiving neuroleptic medication, with a mean
Results
There was no significant difference in MMN generator location between groups (Table 1). The MMN sources of most subjects of both groups (12 subjects in schizophrenia, 13 subjects in comparison group) were clearly localized in the superior temporal gyri (STG), mainly in the HG according to each individual's structural MRI (Fig. 1). The MMN sources of the rest of subjects were located in insula and subgyral space by using individual MRI.
The left MMN ECD power of the schizophrenic patients was
Discussion
Our results suggest that normal functional hemispheric asymmetry is altered in schizophrenia. In the control group, MMN ECD power of the left STG was greater than the right one, but in the schizophrenic patients, a reversal of MMN ECD powers was observed, as was that of normal functional asymmetry. With respect to AC, 86.7% of control subjects (13/15) showed normal functional left hemispherical dominance in contrast with only 13.3% of schizophrenics (2/15). Therefore, it is suggested that
Acknowledgements
This work was supported by the grant No. 04-2001-036 from Seoul National University Hospital.
References (39)
Defining the course of brain structural change and plasticity in schizophrenia
Psychiatry Res.
(1999)- et al.
Activation of Heschl's gyrus during auditory hallucinations
Neuron
(1999) - et al.
Symptom dimensions and brain morphology in schizophrenia and related psychotic disorders
J. Psychiatr. Res.
(1995) - et al.
Abnormalities of auditory evoked magnetic fields and structural changes in the left hemisphere of male schizophrenics: a magnetoencephalographic–magnetic resonance imaging study
Biol. Psychiatry
(1997) - et al.
Impairment of early cortical processing in schizophrenia: an event-related potential confirmation study
Biol. Psychiatry
(1993) - et al.
Associated deficits in mismatch negativity generation and tone matching in schizophrenia
Clin. Neurophysiol.
(2000) - et al.
Impaired sensory processing in male patients with schizophrenia: a magnetoencephalographic study of auditory mismatch detection
Schizophr. Res.
(1999) - et al.
The functional anatomy of auditory hallucinations in schizophrenia
Psychiatry Res.
(2000) - et al.
Superior temporal gyral volumes and laterality correlates of auditory hallucinations in schizophrenia
Biol. Psychiatry
(1999) - et al.
Functional neuroanatomy of auditory working memory in schizophrenia: relation to positive and negative symptoms
Neuroimage
(2001)
Early selective-attention effect on evoked potential reinterpreted
Acta Psychol.
Structural brain imaging in schizophrenia: a selective review
Biol. Psychiatry
Superior temporal gyrus in schizophrenia: a volumetric magnetic resonance imaging study
Schizophr. Res.
Altered hemispheric asymmetry of auditory magnetic fields to tones and syllables in schizophrenia
Biol. Psychiatry
Are auditory hallucinations the consequence of abnormal cerebral lateralization? A morphometric MRI study of the sylvian fissure and planum temporale
Biol. Psychiatry
Mismatch negativity: an index of a preattentive processing deficit in schizophrenia
Biol. Psychiatry
Language and thought disorder in schizophrenia: brain morphological correlates
Schizophr. Res.
Neuroimaging of hallucinations: a review of the literature
Psychiatry Res.
Cerebral generators of mismatch negativity (MMN) and its magnetic counterpart (MMNm) elicited by sound changes
Ear Hear.
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