Lack of asymmetrical transfer for linguistic stimuli in schizophrenia: An ERP study

School of Psychology, Trinity College Dublin, Dublin, Leinster, Ireland
Clinical Neurophysiology (Impact Factor: 3.1). 06/2005; 116(5):1019-27. DOI: 10.1016/j.clinph.2004.12.008
Source: PubMed


To assess the mechanisms underlying lack of speeded information transfer asymmetry (faster right to left) for verbal information in schizophrenia.
Interhemispheric transfer times (IHTT) between the hemispheres were assessed using a lateralized lexical-decision task in males with schizophrenia (N = 12) and matched controls (N = 12). Words were presented to the left visual field (LVF), right visual field (RVF), or bilaterally (BVF) while 128-channel EEG was recorded continuously. A direct measure of IHTT in each direction was obtained by comparing the latencies of the N160 evoked potential (EP) component in the hemispheres contralateral and ipsilateral to stimulation.
Controls showed faster information transfer from the right to left hemisphere (R-to-L) for linguistic stimuli. The two groups did not differ for IHTTs L-to-R. Lack of IHTT asymmetry in the schizophrenia groups was associated with an overall concomitant decrease in the amplitude of the N160 in the right hemisphere.
Differences in IHTT asymmetry may be attributed to lack of right hemisphere activation and not callosal dysfunction as has been previously suggested.
It is suggested that a relative excess of myelinated axons in the right hemisphere speeds IHTT faster R-to-L, findings are discussed with reference to differences in right hemisphere white matter connectivity in schizophrenia.

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Available from: Ian J Kirk, Dec 09, 2015
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    • "Numerous studies of IHTT have shown that neural information travels more quickly from the right hemisphere of the brain to the left hemisphere, than from left hemisphere of the brain to right hemisphere in neurologically healthy adults (e.g., [29,30,31,32]). Miller [33] has proposed that the right hemisphere of the brain contains a greater number of heavily myelinated axons than the left hemisphere, enhancing its performance in fast parallel processes. Studies combining electrophysiology and anatomical imaging have shown that the speed of hemispheric transfer is inversely correlated with fractional anisotropic values in the posterior corpus callosum [34], suggesting that greater callosal integrity may result in quicker hemispheric transfer. "
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    • "To correct bad channels, spline interpolation was performed from good channels. Consistent with prior ERP IHTT research (Barnett and Kirk 2005; Iwabuchi and Kirk 2009; Patson et al. 2007; Steger et al. 2001), data were average rereferenced. Polar average reference effect correction was also implanted to correct for inadequate surface sampling (Junghöfer et al. 1999). "
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    • "Endrass et al., 2002), and that transfer times would be greatest in the AH group. Word stimuli activate a large cortical network, and there is evidence from previous studies (Barnett and Kirk, 2005; Endrass et al., 2002; Rockstroh et al., 2001) that evoked responses for verbal stimuli show important interhemispheric transfer differences from those evoked in response to tones in patients with psychosis. Following Crow's (1998) hypothesis that cerebral lateralization is altered in schizophrenia, and that language processing is consequently affected in this group of patients, we further hypothesised that differences in interhemispheric transfer time may be specific to word stimuli. "
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