RESUMEN
Reduced auditory evoked response (AER) suppression in a paired-stimulus paradigm (where suppression equals the difference between S1 and S2 amplitudes divided by S1 amplitude) may index genetic liability for schizophrenia. The present report is a multiple-channel electroencephalographic (EEG) study of AER suppression among 20 normal and 20 schizophrenia subjects. The typical paired-stimulus paradigm was used to evoke time-locked AERs. AER responses were scored at P50 and N100 in the time domain using both single (Cz) and multichannel data (after reduction using principal components analysis, PCA), and were scored for information in the gamma (20-50 Hz) and low-frequency (1-20 Hz) ranges using multichannel information (also after PCA). The time domain analyses demonstrated that schizophrenia patients differ from normal in amplitude of response to the first, but not to the second, stimulus for both P50 and N100. The frequency domain data demonstrated that schizophrenia patients differed from normal on amplitude of the low-frequency response (LFR) to the first, but not to the second, stimulus. The groups did not differ significantly on amplitudes of the gamma-band responses. Group separations were largest for the multichannel N100 and LFR data, with the LFR demonstrating a modestly better risk ratio for differentiating schizophrenia from normal subjects. The present results suggest two novel differences from previous AER suppression studies: (1) S1 amplitudes largely determine differences between normal and schizophrenia groups on AER suppression, and (2) frequency domain analyses may provide important complimentary information when studying AERs in schizophrenia.
Asunto(s)
Electroencefalografía , Potenciales Evocados Auditivos/fisiología , Esquizofrenia/fisiopatología , Estimulación Acústica , Adulto , Interpretación Estadística de Datos , Femenino , Análisis de Fourier , Humanos , Masculino , Psicología del Esquizofrénico , Procesamiento de Señales Asistido por ComputadorRESUMEN
OBJECTIVE: Reduced auditory evoked response (AER) suppression in a paired-stimulus paradigm may index genetic liability for schizophrenia. In most published studies of AER suppression, scores are based on data averaged over numerous stimulus presentations and recorded from few channels. It is unclear whether averaged data are equally representative of single trial responses in normal and schizophrenia subjects. In the present report, we used 148 channel magnetoencephalography to investigate grand-average and single trial responses on AER suppression. METHODS: The typical paired-stimulus paradigm was used to evoke time-locked AERs from 20 normal and 20 schizophrenia patients. Gamma band response (GBR) and low frequency response (LFR) characteristics were measured on grand-averaged and single trial data. Generalized eigenvalue decomposition was used to reduce the multiple channel information to a vector that accounted for the most AER variance for the GBR and LFR. RESULTS: Group performances on grand-average and single trials were similar. A remarkable difference, which replicates previous studies, was that schizophrenia subjects had smaller LFR amplitudes in response to the first stimulus than normal. CONCLUSIONS: These findings are inconsistent with the "poor suppression" theory often used to explain schizophrenia-normal group differences when using the paired-stimulus paradigm.
Asunto(s)
Potenciales Evocados Auditivos , Magnetoencefalografía , Esquizofrenia/fisiopatología , Estimulación Acústica , Adulto , Encéfalo/fisiopatología , Mapeo Encefálico , Femenino , Humanos , Masculino , Valores de ReferenciaRESUMEN
Using binaural stimuli, schizophrenia subjects have worse auditory evoked response (AER) suppression than normals in a paired-click paradigm. In this study we investigated hemispheric differences in AER suppression between groups using monaural and binaural stimulus presentation. Auditory evoked responses from 12 schizophrenia and 12 normal subjects were recorded with a 148-channel whole-head biomagnetometer. One hundred and twenty pairs of clicks were presented in three counterbalanced blocks (left, right, binaural). With monaural stimuli, patients had worse M100 suppression than normals in ipsilateral (effect size -2.13) but not in contralateral hemisphere (effect size -0.43). The groups did not differ on gamma band response suppression. Overall, the best group separations were obtained with binaural stimulus presentation on M100 suppression (effect size -4.14).
Asunto(s)
Potenciales Evocados Auditivos/fisiología , Lateralidad Funcional/fisiología , Inhibición Neural , Esquizofrenia/fisiopatología , Estimulación Acústica , Adulto , Estudios de Casos y Controles , Femenino , Humanos , Magnetoencefalografía , Masculino , Tiempo de Reacción/fisiologíaRESUMEN
Schizophrenia is associated with an absence of the lateralizations that typify the human brain. Previous evidence emphasized structural changes, particularly reduced asymmetry in extension and surface of the planum temporale, although gross structural deviations occur only in a minority of patients. The present study describes an absence of lateralization on a robust functional measure that characterized schizophrenia patients: healthy subjects but not schizophrenics displayed a contralateral left-hemispheric dominance of the auditory evoked magnetic field to right-ear auditory stimulation. Absence of contralateral dominance in response to auditory stimuli among schizophrenia patients may indicate a failure to establish unequivocal left-hemispheric dominance of the phonological loop as hypothesized by Crow.
Asunto(s)
Potenciales Evocados Auditivos/fisiología , Lateralidad Funcional/fisiología , Esquizofrenia/fisiopatología , Estimulación Acústica , Estudios de Casos y Controles , Femenino , Humanos , Magnetoencefalografía , MasculinoRESUMEN
The relationship between gamma band response (GBR) and P50 suppression was investigated among 10 DSM-IV schizophrenia patients and 10 normal comparison subjects using neuromagnetic and electrical recordings. In a paired-click paradigm, the neuromagnetic GBR and M100 suppression data improved schizophrenia-normal group separations over the typical electrical, vertex-recorded P50 suppression measure. The neuromagnetic GBR was also superior to the magnetic equivalent of P50 (M50) for discriminating schizophrenia and normal subjects. Our data are consistent with the hypothesis that P50 may be a subcomponent of the GBR, and that P50 suppression may be a proxy for GBR suppression. Measurement of the GBR should be given consideration as another, and perhaps better, means for evaluating auditory-evoked response abnormalities among schizophrenia patients.