Abstract
We studied differences in imaginary coherence (IC) of the gamma band between brain regions of female schizophrenia patients during the auditory oddball task using magnetoencephalography (MEG). Subjects were 12 right-handed female schizophrenia patients, who were evaluated by the Positive and Negative Syndrome Scales (PANSS). Functional connectivity during an auditory oddball task was reconstructed in low gamma (30 - 50 Hz) and high gamma (50 - 100 Hz and 100 - 150 Hz) bands, and represented by IC using seeds determined by the significant oscillatory power changes obtained by event-related synchronization (ERS) and event-related desynchronization (ERD) power measurements. Gamma ERS (30 - 50 Hz) power was decreased in the left precuneus at 500 - 750 ms and in the right precuneus at 750 - 1000 ms. IC in the gamma band (50 - 100 Hz) was decreased between the right precuneus (seed) and right paracentral lobule (target) and between the right precuneus and right hypothalamus at 0 - 250 ms. IC in the gamma band (100 - 150 Hz) was increased between the left precuneus and right cuneus (Brodmann area 7) at 250 - 500 ms, between the left precuneus and right culmen at 500 - 750 ms, and between the left precuneus and right cuneus (Brodmann area 17), between the left precuneus and right posterior cingulate cortex, and between the left precuneus and right caudate nucleus at 750 - 1000 ms. In the high gamma band (50 - 100 Hz) at 0 - 250 ms, significant positive correlations were shown between IC and conceptual disorganization in PANSS scores, between IC and unusual thought content score, and between IC and positive scale score. IC within the high gamma band in female schizophrenia patients showed two types of functional disconnection, intrahemispheric and interhemispheric. IC between the right or left precuneus and other specific cortical areas showed dysfunction, suggesting that the parietal lobe plays an important role in dysfunction in connectivity in the gamma band during the oddball task.
Highlights
Advances in magnetoencephalography (MEG) and electroencephalography (EEG) technology have made it possible to obtain noninvasive mapping of changes in large-scale networks during perceptual and higher cognitive processes
Functional connectivity during an auditory oddball task was reconstructed in low gamma (30 - 50 Hz) and high gamma (50 - 100 Hz and 100 - 150 Hz) bands, and represented by imaginary coherence (IC) using seeds determined by the significant oscillatory power changes obtained by event-related synchronization (ERS) and event-related desynchronization (ERD) power measurements
IC between the right precuneus and right hypothalamus was decreased in the gamma band (50 - 100 Hz) at 0 - 250 ms, and showed a significant positive correlation with conceptual disorganization, unusual thought content, and the positive symptoms scale in Positive and Negative Syndrome Scales (PANSS)
Summary
Advances in magnetoencephalography (MEG) and electroencephalography (EEG) technology have made it possible to obtain noninvasive mapping of changes in large-scale networks during perceptual and higher cognitive processes. Study of event-related potentials (ERP) has revealed that gamma-band synchronization plays an important role in information processing in the networks of neurons in the brain [1,2]. Schizophrenic patients who had specific frequency deficits in the generation and maintenance of coherent gamma-range oscillations underwent auditory steady state event-related potential testing, where the stimulus-driven activity may reflect the capacity for integrated, bottom-up activity of auditory sensory network processing [21]. High gamma band activity (60 - 200 Hz) is thought to have an important role for cortical computation through establishing correlation between the modulation of high gamma oscillations and specific cognitive functions, and impairment of high gamma activity has been reported in neuropsychiatric disorders such as schizophrenia [27]. Impairments in long-range synchronization in schizophrenia are probably related to changes in white matter volume and organization, because long distance synchronization of oscillatory responses is thought to be mediated by reciprocal cortico-cortical connections [2]
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