Lack of asymmetrical transfer for linguistic stimuli in schizophrenia: an ERP study.
ABSTRACT 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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ABSTRACT: The present study sought to investigate the effects of aging on interhemispheric transfer time (IHTT). Poffenberger (1912) devised a behavioural paradigm thought to be a measure of IHTT. In this paradigm IHTT is estimated by calculating the crossed-uncrossed difference (CUD); the difference in speed of response between responses made in response to stimuli contralateral to responding hand (crossed) and those made by hands ipsilateral to the stimuli (uncrossed). IHTT can also be estimated through event related potentials (ERPs) by calculating latency differences between the waveforms over the ipsilateral and contralateral hemispheres. Results from previous experiments comparing younger and older participants with these two methods are inconsistent. Twenty three younger (18-25 years) and 23 older (65-77 years) participants had their electroencephalogram (EEG) recorded whilst completing the Poffenberger paradigm. IHTT estimates from the two measures were compared between the groups. Older participants were found to have a faster IHTT estimate from the P1 ERP component compared to younger participants. This result is in contrast to the current literature. Replication of this result is recommended before firm conclusions about its implications can be made.Plymouth Student Scientist. 10/2013; 6(2):78-97.
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ABSTRACT: Little is known about the functional impact of putative deficits in white-matter connectivity across the corpus callosum (CC) in individuals with autism spectrum disorders (ASDs). We utilized the temporal sensitivity of event-related potentials to examine the interhemispheric transfer time (IHTT) of basic visual information across the CC in youth with high-functioning ASD relative to healthy controls. We conducted two experiments: a visual letter matching experiment (n = 46) and a visual picture matching experiment, (n = 48) and utilized both electrophysiological (N1 and P1 amplitudes and latencies) and behavioral [response times (RTs), error rates] indices of IHTT. There were no significant group differences on either experiment for RTs, error rates, or N1 and P1 latencies, suggesting that on basic tasks the timing of information flow across the CC may not be altered in high functioning ASD.Journal of Autism and Developmental Disorders 07/2013; · 3.06 Impact Factor
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ABSTRACT: Dysconnectivity hypothesis posits that schizophrenia relates to abnormalities in neuronal connectivity. However, little is known about the alterations of the interhemispheric resting-state functional connectivity (FC) in patients with paranoid schizophrenia. In the present study, we used a newly developed voxel-mirrored homotopic connectivity (VMHC) method to investigate the interhemispheric FC of the whole brain in patients with paranoid schizophrenia at rest. Forty-nine first-episode, drug-naive patients with paranoid schizophrenia and 50 age-, gender-, and education-matched healthy subjects underwent a resting-state functional magnetic resonance imaging (fMRI) scans. An automated VMHC approach was used to analyze the data. Patients exhibited lower VMHC than healthy subjects in the precuneus (PCu), the precentral gyrus, the superior temporal gyrus (STG), the middle occipital gyrus (MOG), and the fusiform gyrus/cerebellum lobule VI. No region showed greater VMHC in the patient group than in the control group. Significantly negative correlation was observed between VMHC in the precentral gyrus and the PANSS positive/total scores, and between VMHC in the STG and the PANSS positive/negative/total scores. Our results suggest that interhemispheric resting-state FC of VMHC is reduced in paranoid schizophrenia with clinical implications for psychiatric symptomatology thus further contribute to the dysconnectivity hypothesis of schizophrenia.Progress in Neuro-Psychopharmacology and Biological Psychiatry 09/2013; · 3.55 Impact Factor