Biomedical subjects

Alan T Bates

Publications and source records attributed to Alan T Bates.

4 recordsLinked to original sources

PubMed2003

Abnormal processing of speech during oddball target detection in schizophrenia.

Healthy subjects show increased activation in left temporal lobe regions in response to speech sounds compared to complex nonspeech sounds. Abnormal lateralization of speech-processing regions in the temporal lobes has been posited to be a cardinal feature of schizophrenia. Event-related fMRI was used to test the hypothesis that schizophrenic patients would show an abnormal pattern of hemispheric lateralization when detecting speech compared with complex nonspeech sounds in an auditory oddball target-detection task. We predicted that differential activation for speech in the vicinity of the superior temporal sulcus would be greater in schizophrenic patients than in healthy subjects in the right hemisphere, but less in patients than in healthy subjects in the left hemisphere. Fourteen patients with schizophrenia (selected from an outpatient population, 2 females, 12 males, mean age 35.1 years) and 29 healthy subjects (8 females, 21 males, mean age 29.3 years) were scanned while they performed an auditory oddball task in which the oddball stimuli were either speech sounds or complex nonspeech sounds. Compared to controls, individuals with schizophrenia showed greater differential activation between speech and nonspeech in right temporal cortex, left superior frontal cortex, and the left temporal-parietal junction. The magnitude of the difference in the left temporal parietal junction was significantly correlated with severity of disorganized thinking. This study supports the hypothesis that aberrant functional lateralization of speech processing is an underlying feature of schizophrenia and suggests the magnitude of the disturbance in speech-processing circuits may be associated with severity of disorganized thinking.

Adult↗

PubMed2003

Rostral anterior cingulate cortex dysfunction during error processing in schizophrenia.

Previous research has demonstrated that patients with schizophrenia have an impaired ability to monitor erroneous responses to stimuli internally. Event-related potential (ERP) studies of error-eliciting tasks indicate that, in healthy adults, the commission of an erroneous response is associated with a fronto-centrally distributed negative voltage component termed the error negativity (Ne) or error-related negativity (ERN). In patients with schizophrenia, the Ne/ERN elicited by errors of commission (EoC) is reduced in amplitude compared with that elicited in healthy participants. Functional MRI (fMRI) studies and source localization analyses of ERP data in healthy participants suggest that EoC are associated with activity in the rostral anterior cingulate cortex (ACC). Using event-related fMRI, we examined the brain activity associated with EoC in a group of 10 patients with schizophrenia and 16 matched healthy participants. Patients were stable, partially remitted, medicated out-patients recruited from the community. Participants performed a Go/NoGo task variant that was shown previously to elicit a reduced Ne/ERN during EoC in patients with schizophrenia relative to healthy participants, as well as robust rostral ACC activation during EoC in healthy participants. Patients with schizophrenia were characterized by relative underactivity in the rostral ACC compared with healthy participants. There was also evidence for more widespread underactivity in the limbic system. In contrast to these regions of relative hypoactivity, patients with schizophrenia demonstrated hyperactivity relative to healthy participants in bilateral parietal cortex during both EoC and correctly rejected NoGo trials. Our results are consistent with previous ERP research demonstrating functional abnormalities during error processing in schizophrenia. In light of the role of the rostral ACC and other limbic structures in mediating affective and motivational behaviour, our results suggest there may be a disturbed affective or motivational response to the commission of errors in schizophrenia.

Adult↗

PubMed2002

Error-related negativity and correct response negativity in schizophrenia.

OBJECTIVES: To examine error-related negativity (ERN) and correct response negativity (CRN) in schizophrenia in light of two previous conflicting reports, and to determine their relation to disorganization, psychomotor poverty and reality distortion. METHODS: Event-related potentials were recorded from 21 schizophrenic and 21 control participants who performed a simple go/no-go task. Response-locked potentials were computed for errors of commission and for correct-hits. Scores for reality distortion syndrome, psychomotor poverty syndrome and disorganization syndrome were determined for each schizophrenic participant using the Signs and Symptoms of Psychotic Illness (SSPI) scale. RESULTS: ERN produced during error trials and CRN produced during correct trials were significantly larger in the control participant group than in the schizophrenic participant group. In the schizophrenic patients, ERN amplitude was negatively correlated with psychomotor poverty syndrome score and CRN amplitude was negatively correlated with disorganization syndrome score. CONCLUSIONS: Decreased ERN and CRN in the schizophrenic participant group suggests abnormal internal behavior monitoring in schizophrenic patients. Patients with high disorganization symptoms may employ an abnormal strategy for comparing actual response outcome with desired response outcome, while patients with psychomotor poverty may be less emotionally responsive to errors.

Adolescent↗

PubMed2002

Thought and Language Index: an instrument for assessing thought and language in schizophrenia.

BACKGROUND: Subtle formal thought disorders are difficult to quantify. Their relationship to florid thought disorder is unknown. AIMS: To assess the interrater reliability, sensitivity and factor structure of a new assessment instrument, the Thought and Language Index (TLI), and to determine if minor aberrations detectable in the speech of healthy individuals are related to the more severe formal thought disorders characteristic of schizophrenia. METHOD: Interrater reliability was evaluated by determining the intraclass correlation for the ratings by five assessors. Factor analysis of the TLI scores of 87 patients was performed, and TLI scores in matched patients and controls were compared. RESULTS: The intraclass correlation was good for individual TLI items, and excellent for sub-scale scores. Factor analysis identified three groups of approximately orthogonal disorders. Mild speech aberrations were observed in healthy participants and in patients with schizophrenia. The prevalence of mild aberrations was correlated with the prevalence of definite formal thought disorders. CONCLUSIONS: The TLI is reliable and capable of detecting subtle disorders. Some mild aberrations occurring in the speech of healthy individuals appear to be attenuated forms of the florid disorders characteristic of schizophrenia.

Adult↗