Profile of auditory information-processing deficits in schizophrenia

Abstract

Schizophrenia patients exhibit abnormalities in several different auditory event-related potential (ERP) measures. It is unclear how these abnormalities relate to each other, since multiple measures are rarely acquired from the same sample. This study addressed two related questions: 1) Are specific auditory ERP measures differentially impaired in schizophrenia? 2) Do abnormalities co-aggregate within the same patients? Nine auditory ERP measures were acquired in a single testing session from 23 schizophrenia patients and 22 healthy subjects. Hierarchical oblique factor analysis revealed that these measures aggregated into four factors, with each loading primarily on a single factor. Patient deficits were observed for two independent factors: N100/mismatch negativity (MMN) and P3a/P3b. N100/MMN abnormalities were associated with symptoms of alogia and formal thought disorder. P3a/P3b abnormalities were associated with avolition, attentional disturbances and delusions. We conclude that deficits in different ERP measures of early sensory processing at the level of the auditory cortex co-occur in patients. These likely represent a single differential deficit indexing the physiological abnormality underlying impaired language and verbal processing. This is relatively independent of a higher cortical deficit that mediates cognitive stimulus evaluation and underlies deficits in motivation, attention and reality testing. Such multidimensional profiling of ERP abnormalities may help to clarify the clinical and genetic heterogeneity of schizophrenia.

Figure 1

Standardized z-scores for each of the 9 auditory ERP measures. Data were scaled so that control subjects had mean z=0 and standard deviation=1 for each measure, and patient deficits were scored as negative values. Error bars represent the standard error of the mean.

Figure 2

Standardized z-scores for each of the 4 primary factors identified by the hierarchical oblique factor analysis. Data were scaled so that control subjects had mean z=0 and standard deviation=1 for each measure. Patient deficits were scored as negative values. Error bars represent the standard error of the mean.

Figure 3

Scatterplot of patient z-scores for factors 1 versus factor 4. Solid line represents the regression fit between the two variables. The dotted lines represent the 95% confidence interval of this fit. The lack of association between the two sets of factor scores indicates that the ERP abnormalities indexed by these two factors manifest themselves independently in different patient subgroups.