Language Processing In Schizophrenia Research Articles

Combining automatic speech recognition with semantic natural language processing in schizophrenia

Natural language processing (NLP) tools are increasingly used to quantify semantic anomalies in schizophrenia. Automatic speech recognition (ASR) technology, if robust enough, could significantly speed up the NLP research process. In this study, we assessed the performance of a state-of-the-art ASR tool and its impact on diagnostic classification accuracy based on a NLP model. We compared ASR to human transcripts quantitatively (Word Error Rate (WER)) and qualitatively by analyzing error type and position. Subsequently, we evaluated the impact of ASR on classification accuracy using semantic similarity measures. Two random forest classifiers were trained with similarity measures derived from automatic and manual transcriptions, and their performance was compared. The ASR tool had a mean WER of 30.4%. Pronouns and words in sentence-final position had the highest WERs. The classification accuracy was 76.7% (sensitivity 70%; specificity 86%) using automated transcriptions and 79.8% (sensitivity 75%; specificity 86%) for manual transcriptions. The difference in performance between the models was not significant. These findings demonstrate that using ASR for semantic analysis is associated with only a small decrease in accuracy in classifying schizophrenia, compared to manual transcripts. Thus, combining ASR technology with semantic NLP models qualifies as a robust and efficient method for diagnosing schizophrenia.

Language-Related Neurophysiological Deficits in Schizophrenia.

Schizophrenia is a severe psychiatric disorder that affects all aspects of one's life with several cognitive and social dysfunctions. However, there is still no objective and universal index for diagnosis and treatment of this disease. Many researchers have studied language processing in schizophrenia since most of the patients show symptoms related to language processing, such as thought disorder, auditory verbal hallucinations, or delusions. Electroencephalography (EEG) and magnetoencephalography (MEG) with millisecond order high temporal resolution, have been applied to reveal the abnormalities in language processing in schizophrenia. The aims of this review are (a) to provide an overview of recent findings in language processing in schizophrenia with EEG and MEG using neurophysiological indices, providing insights into underlying language related pathophysiological deficits in this disease and (b) to emphasize the advantage of EEG and MEG in research on language processing in schizophrenia.

Spared bottom-up but impaired top-down interactive effects during naturalistic language processing in schizophrenia: evidence from the visual-world paradigm.

People with schizophrenia process language in unusual ways, but the causes of these abnormalities are unclear. In particular, it has proven difficult to empirically disentangle explanations based on impairments in the top-down processing of higher level information from those based on the bottom-up processing of lower level information. To distinguish these accounts, we used visual-world eye tracking, a paradigm that measures spoken language processing during real-world interactions. Participants listened to and then acted out syntactically ambiguous spoken instructions (e.g. 'tickle the frog with the feather', which could either specify how to tickle a frog, or which frog to tickle). We contrasted how 24 people with schizophrenia and 24 demographically matched controls used two types of lower level information (prosody and lexical representations) and two types of higher level information (pragmatic and discourse-level representations) to resolve the ambiguous meanings of these instructions. Eye tracking allowed us to assess how participants arrived at their interpretation in real time, while recordings of participants' actions measured how they ultimately interpreted the instructions. We found a striking dissociation in participants' eye movements: the two groups were similarly adept at using lower level information to immediately constrain their interpretations of the instructions, but only controls showed evidence of fast top-down use of higher level information. People with schizophrenia, nonetheless, did eventually reach the same interpretations as controls. These data suggest that language abnormalities in schizophrenia partially result from a failure to use higher level information in a top-down fashion, to constrain the interpretation of language as it unfolds in real time.

Characterising receptive language processing in schizophrenia using word and sentence tasks

ABSTRACTIntroduction. Language dysfunction is proposed to relate to the speech disturbances in schizophrenia, which are more commonly referred to as formal thought disorder (FTD). Presently, language production deficits in schizophrenia are better characterised than language comprehension difficulties. This study thus aimed to examine three aspects of language comprehension in schizophrenia: (1) the role of lexical processing, (2) meaning attribution for words and sentences, and (3) the relationship between comprehension and production.Methods. Fifty-seven schizophrenia/schizoaffective disorder patients and 48 healthy controls completed a clinical assessment and three language tasks assessing word recognition, synonym identification, and sentence comprehension. Poorer patient performance was expected on the latter two tasks.Results. Recognition of word form was not impaired in schizophrenia, indicating intact lexical processing. Whereas single-word synonym identification was not significantly impaired, there was a tendency to attribute word meanings based on phonological similarity with increasing FTD severity. Importantly, there was a significant sentence comprehension deficit for processing deep structure, which correlated with FTD severity.Conclusions. These findings established a receptive language deficit in schizophrenia at the syntactic level. There was also evidence for a relationship between some aspects of language comprehension and speech production/FTD. Apart from indicating language as another mechanism in FTD aetiology, the data also suggest that remediating language comprehension problems may be an avenue to pursue in alleviating FTD symptomatology.

Corrigendum to “Compensatory effect of general cognitive skills on non-literal language processing in schizophrenia: A preliminary study” [J Neurolinguist 29 (2014) 1–16

E. Varga a, *, , Zs. Schnell b, , T. T enyi , N. N emeth , M. Simon , A. Hajnal , R.A. Horv ath c, , E. Hamvas , R. J arai , S. Fekete , R. Herold a a Department of Psychiatry and Psychotherapy, Medical Faculty, Medical School, University of P ecs, R et utca 2., P ecs, 7623, Hungary b Department of Linguistics and Institute of Psychology, University of P ecs, Hungary c Neuro CT Diagnostic Center, P ecs, Hungary d Department of Neurology, Medical Faculty, University of P ecs, Hungary

A study of the relationship between receptive and expressive language processing in schizophrenia

Event Abstract Back to Event A study of the relationship between receptive and expressive language processing in schizophrenia Eric Tan1*, Gregory Yelland2 and Susan Rossell3, 4 1 Monash University, Monash-Alfred Psychiatry Research Centre, Australia 2 Monash University, Australia 3 Swinburne University of Technology, Brain and Psychological Sciences research centre, Australia 4 Monash-Alfred Psychiatry Research Centre, Australia Background: Traditional language models propose a relationship between the two components of language processing: receptive/comprehension and expressive/production. Dysfunction of language production has been recognised in schizophrenia, notably in the aberrant speech patterns termed formal thought disorder (TD). Presently, language production in schizophrenia is better characterised than language comprehension. This study thus aimed to expand on current understanding of language comprehension in schizophrenia, and examine its relationship to individual TD symptoms. Two aspects were studied: word/lexical recognition, and meaning attribution for words and sentences. Method: Fifty-seven schizophrenia/schizoaffective disorder patients and 48 healthy controls completed a clinical assessment and three language tasks assessing word recognition, synonym identification and sentence comprehension. Poorer patient performance was expected on the latter two tasks. Results: Results indicated that recognition of word form was not impaired in schizophrenia, indicating intact lexical processing. While single word synonym identification was not significantly impaired, there was a tendency to attribute word meanings based on phonological similarity, which increased with severity of some TD symptoms. Importantly, there was a significant sentence comprehension deficit for processing deep structure, which correlated with severity of selective TD symptoms. Conclusions: Sentence comprehension appears to be impaired here, which supports the case for some receptive language processing deficits in schizophrenia. There is also evidence for a relationship between aspects of language comprehension and speech production, which suggests a role for the former in TD aetiology, which differs between individual symptom types (i.e. derailment and circumstantiality). The remediation of language comprehension problems may thus be an avenue to pursue in alleviating TD symptomatology. Keywords: Language, Schizophrenia, syntax, Language comprehension, Language production, formal thought disorder, lexical-semantics Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Language Citation: Tan E, Yelland G and Rossell S (2015). A study of the relationship between receptive and expressive language processing in schizophrenia. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00404 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mr. Eric Tan, Monash University, Monash-Alfred Psychiatry Research Centre, Melbourne, Australia, Eric.Tan@monash.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Eric Tan Gregory Yelland Susan Rossell Google Eric Tan Gregory Yelland Susan Rossell Google Scholar Eric Tan Gregory Yelland Susan Rossell PubMed Eric Tan Gregory Yelland Susan Rossell Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Compensatory effect of general cognitive skills on non-literal language processing in schizophrenia: A preliminary study

Abstract Studies show that patients with schizophrenia have problems with understanding non-literal language, presumably due to theory of mind (ToM) dysfunction, while literal language processing remains intact in these patients. Furthermore, studies about the influence of general intelligence on non-literal language processing show incongruent results in schizophrenia. In the present study, our aim was to identify the influence of good intellectual skills (that is, good neurocognitive skills in general) on non-literal language comprehension on a preliminary sample of schizophrenic patients. 19 patients with schizophrenia and 19 healthy controls (carefully matched for all subtests of WAIS) completed different language tasks in the form of an interview, including conventional and unconventional metaphors, irony, Gricean implicatures, control implicatures and semantics. In the case of the Gricean implicatures, the comprehension of the linguistic incongruity of the utterance and also the comprehension of the intended meaning of the speaker were examined separately. To explore the effect of IQ on non-literal language comprehension, we divided the schizophrenia group into a lower-IQ (IQ ≤ 106) and a higher-IQ (IQ > 106) subgroup by making a median split (median IQ = 106). Our results showed that schizophrenics with lower-IQ were able to understand conventional metaphors presumably relying on their good semantic processing, while they were impaired in the comprehension of unconventional metaphors and irony. However, the higher-IQ schizophrenia subgroup was able to comprehend not only conventional metaphors, but also unconventional metaphors and irony, supposedly using IQ-dependent compensatory mechanisms. Interestingly, both the lower- and the higher-IQ schizophrenia subgroups showed significant impairment in the comprehension of the ToM question of the Gricean implicatures and the patients' IQ had no significant impact on the comprehension of such ToM questions. In conclusion, our findings assume a possible compensatory effect of general cognitive skills on non-literal language processing in schizophrenia. We also argue for the importance of using more complex ToM tasks in order to detect the existing ToM deficit in schizophrenic patients with good cognitive skills.

Cognitive Control and Discourse Comprehension in Schizophrenia

Cognitive deficits across a wide range of domains have been consistently observed in schizophrenia and are linked to poor functional outcome (Green, 1996; Carter, 2006). Language abnormalities are among the most salient and include disorganized speech as well as deficits in comprehension. In this review, we aim to evaluate impairments of language processing in schizophrenia in relation to a domain-general control deficit. We first provide an overview of language comprehension in the healthy human brain, stressing the role of cognitive control processes, especially during discourse comprehension. We then discuss cognitive control deficits in schizophrenia, before turning to evidence suggesting that schizophrenia patients are particularly impaired at processing meaningful discourse as a result of deficits in control functions. We conclude that domain-general control mechanisms are impaired in schizophrenia and that during language comprehension this is most likely to result in difficulties during the processing of discourse-level context, which involves integrating and maintaining multiple levels of meaning. Finally, we predict that language comprehension in schizophrenia patients will be most impaired during discourse processing. We further suggest that discourse comprehension problems in schizophrenia might be mitigated when conflicting information is absent and strong relations amongst individual words are present in the discourse context. “There is no “centre of Speech” in the brain any more than there is a faculty of Speech in the mind. The entire brain, more or less, is at work in a man who uses language” William JamesFrom The Principles of Psychology, 1890 “The mind in dementia praecox is like an orchestra without a conductor” Kraepelin, 1919

Alexithymia and regional gray matter alterations in schizophrenia

Alexithymia is characterized by deficits in emotional self-awareness. Although alexithymia refers to a deficit in recognizing one's own emotions, some studies have focused on the relation between alexithymia and impaired social cognition. An association between alexithymia and schizophrenia has been previously reported, but the brain structures involved remain unclear. The present study investigated associations between alexithymia and specific brain structures to determine whether these regions overlapped with key structures underlying social cognition. Twenty-one patients with schizophrenia and 24 age-, gender- and education level-matched healthy controls underwent structural magnetic resonance imaging. Alexithymia was assessed using the 20-item Toronto Alexithymia Scale (TAS-20). We applied voxel-based morphometry to investigate the correlation between TAS-20 scores and regional brain alterations. TAS-20 scores were significantly higher in patients than controls. Bilateral ventral striatum and left ventral premotor cortex volumes were negatively correlated with TAS-20 total scores in controls, while left supramarginal gyrus (SMG) volume was negatively correlated with TAS-20 total scores in patients. These results suggest that schizophrenia is associated with alexithymia, and that gray matter alterations of the left SMG constitute a key pathology underlying alexithymia in schizophrenia. This association may be related to deficits in self–other distinction, self-disturbance, and language processing in schizophrenia.

Metaphor processing in high and low schizotypal individuals

Two hypotheses were considered regarding the relationship between positive schizotypy and metaphor processing. On the basis of continuity between schizophrenia and schizotypy, high schizotypal individuals would be expected to be impaired at metaphor processing. However, given the right hemisphere processing bias that has been associated with positive schizotypy, they would be expected to be superior at metaphor processing. A story completion task in which participants judged the appropriateness of literal and metaphoric statements was administered to 30 high and 29 low schizotypal individuals. Contrary to both hypotheses, groups did not differ in their ability to discriminate between appropriate and inappropriate statements, whether literal or metaphoric. However, the high schizotypal group demonstrated a less conservative response bias; they were more likely than the low schizotypal group to identify a statement as appropriate, whether it was or was not. Implications of these results for our understanding of language processing in schizophrenia and schizotypy are discussed.

Evidence for reduced somatosensory lateralisation and focalisation in schizophrenia

Neuroimaging studies indicate diminished lateralisation of cerebral activity during motor tasks and language processing in schizophrenia. Some evidence also indicates that decreased lateralisation is accompanied by more diffuse intra-hemispheric activation, suggesting that diminished lateralisation might be part of a more general diminution of regional functional specialisation. In the case of passive processing of elementary somatosensory stimuli, evidence for decreased lateralisation derived from event-related potential studies, is conflicting. The greater spatial resolution of functional magnetic resonance imaging (fMRI) offers the potential to resolve this conflict. We report an fMRI study of 22 right-handed individuals with schizophrenia, 21 right-handed healthy individuals and 10 non-right-handed healthy individuals, designed to test the hypothesis that in schizophrenia there is a diminution of both lateralisation and intra-hemispheric focalisation during the passive processing of vibrotactile stimuli delivered to the right index finger. Significantly reduced lateralisation of activity in primary somatosensory cortex (SI) was observed in the schizophrenia group as compared to the healthy right-handed group. There was a trend for a reduction in SI lateralisation in the schizophrenia group compared to the healthy non-right-handed group. Contralateral SI focalisation was also significantly reduced in the schizophrenia group compared to both healthy groups. SI focalisation was negatively correlated with severity of disorganisation symptoms in the schizophrenia group. These results support the hypothesis that a generalised loss of functional specialisation is fundamental to schizophrenia.

Discriminative Analysis of Brain Function in Language Circuit in Schizophrenia

Introduction: Schizophrenia is a common psychiatric disorder that occurs at a lifetime prevalence rate of approximately 1.4 to 4.6 per 1000 worldwide population (Williamson, 2006). The accumulating evidences from clinical and neuroimaging studies, reviewed in (Li et al., 2008), suggest that structural and functional anomalies in brain language circuit underlie the characteristic symptoms of schizophrenia. We previously reported findings pointing to altered brain activations in language related regions during semantic processing in schizophrenia using voxel-based whole brain and region-of-interests (ROIs) fMRI approaches (Li et al., 2007a; 2007b). In this study, we construct the functional networks of language processing in schizophrenia and healthy controls, and seek the critical biomarkers of the onset of illness by using machine learning methods.

Schizophrenic patients exhibit hyper-reflexivity in a semantic categorical priming task

Semantic priming is a phenomenon that occurs when a semantically related “prime” word produces a faster response time to a sequentially presented “target” word than if they were semantically unrelated. This process of priming is thought to involve two distinct processes, one that is reflexive and unconscious, and the other, which is voluntary and intention-driven. It is believed that a dysfunction in one or both of these processes may result in the pattern of thought disorder in schizophrenia. In an attempt to better understand disorganized speech and thought disorder, we examine language processing in schizophrenia by separately studying reflexive and voluntary priming processes using a lexical decision semantic priming task, that is similar to the landmark study with controls by Neely [(1977). Semantic priming and retrieval from lexical memory: Roles of inhibitionless spreading activation and limited-capacity attention. Journal of Experimental Psychology, 106, 226–254]. In two experiments, we tested a total of 40 schizophrenic and 40 control subjects. In both Experiments 1 and 2, schizophrenic subjects showed greater semantic priming than control subjects in the reflexive task condition, demonstrating that they seem to exhibit excessive priming of the semantic network. On the other hand, in our study, there were no differences in priming between schizophrenic and control subjects in the voluntary task condition. These results support the idea of a dysfunction in the reflexive system (hyper-priming) as a core deficit in language processing in schizophrenia.

Language Processing and Human Voice Perception in Schizophrenia: A Functional Magnetic Resonance Imaging Study

Neuroimaging studies have demonstrated either reduced left-lateralized activation or reversed language dominance in schizophrenia. These findings of left hemispheric dysfunction could be attributed to language processing tasks, which activate mainly left hemispheric function. Recent functional magnetic resonance imaging studies reported right-lateralized temporal activation by human voice perception, but few studies have investigated activation by human voice in schizophrenia. We aimed to clarify the cerebral function of language processing in schizophrenia patients by considering cerebral activation of human voice perception. Fourteen right-handed schizophrenia patients and 14 right-handed controls with matched handedness, sex, and education level were scanned by functional magnetic resonance imaging while listening to sentences (SEN), reverse sentences (rSEN), and identifiable non-vocal sounds (SND). Under the SEN-SND and SEN-rSEN contrasts including language processing, patients showed less activation of the left hemisphere than controls in the language-related fronto-tempo-parietal region, hippocampus, thalamus and cingulate gyrus. Under the rSEN-SND contrast including human voice perception, patients showed less activation than controls in the right-lateralized temporal cortices and bilateral posterior cingulate. Our results indicate that schizophrenia patients have impairment of broader bilateral cortical-subcortical regions related to both the semantic network in the left hemisphere and the voice-specific network in the right hemisphere.

Electrophysiological insights into language processing in schizophrenia

Deficits in language comprehension in schizophrenia were examined using event-related potentials (ERPs). Schizophrenic and healthy participants read sentences in which the first clause ended with a homograph, and the second clause started with a target word that was semantically related to the homograph's dominant meaning (e.g., 1. Diving was forbidden from the bridge because the river had rocks in it. or 2. The guests played bridge because the river had rocks in it.). Processing of the targets (e.g., "river") was expected to be primarily influenced by the preceding overall sentence context (congruent in 1; incongruent in 2) in healthy participants, but to be inappropriately affected by the dominant meaning of homographs (e.g., the "structure" meaning of "bridge") in sentences like 2 in schizophrenic patients. The N400 ERP component that is known to be sensitive to contextual effects during language processing confirmed these predictions. This showed that language abnormalities in schizophrenia may be related to deficient processing of context-irrelevant semantic representations of words from the discourse.

Modulation of language processing in schizophrenia: effects of context and haloperidol on the event-related potential

Background: Disturbances in language associations were among the first clinical symptoms reported for individuals described as schizophrenic (Bleuler 1911/1950). Currently, associative language disturbance is a diagnostic feature of schizophrenia (American Psychiatric Association 1994); however, the mechanisms that produce this symptom remain unknown. In the present study, two candidate psychological functions were examined: sensitivity to semantic context and expectancy (attention). Methods: Visual event-related potentials were recorded during a lexical decision task in which semantic relationship and expectancy (relatedness proportions) were varied. Semantic priming processes were compared between 34 male normal control subjects tested once and 37 male schizophrenic inpatients evaluated during their participation in a double-blind haloperidol maintenance therapy and placebo replacement protocol. Results: Schizophrenic patients failed to discriminate between associated and unassociated words, as measured by the amplitude of the N400 component (i.e., absence of the N400 priming effect); however, the overall mean amplitude of N400 did not differ between patients and control subjects. In addition, patients and control subjects did not differ significantly in the amplitude of N400 elicited to associated words or to unassociated words. Finally, the effect of expectancy-based processing on the magnitude of the N400 priming effect did not differ between patients and control subjects. Conclusions: On the basis of these findings, a tentative hypothesis is suggested that schizophrenic patients are characterized by a pattern of indiscriminate or random spread of activation in their semantic network during the processing of single-word semantic contexts.

ERP assessment of visual and auditory language processing in schizophrenia.

Language disturbance in schizophrenia has been recently attributed to disturbed priming mechanisms. In the present study, event-related potentials (ERPs), were recorded to final words in sentences presented to 13 chronic patients with schizophrenia and 12 normal controls. Half of the final words fit a sentence context and another half did not. The N400 (the ERP sensitive to language) latency was prolonged, and its amplitude was more negative to both correct and incorrect sentence endings in the group with schizophrenia relative to the group of normal controls. The early ERP components, N100 and P200, were similar in both groups. These results suggest that language abnormalities in schizophrenia are related to a dysfunction in the language system and not to a general cognitive dysfunction, and may be related to poor use of context in patients with schizophrenia.

Anomalous cerebral asymmetry and language processing in schizophrenia.

Reversal or reduction of normal structural cerebral asymmetries may be related to the pathogenesis of schizophrenia, but this relationship remains controversial. We review the literature and describe a further study designed to detect whether anomalous asymmetries are present early in the illness (at the first episode), whether they predict deficits in language processing, and whether they may be related to a genetic predisposition for schizophrenia. Asymmetries of brain widths and segments of the sylvian fissure were assessed in a magnetic resonance imaging study of 87 patients with a first episode of schizophrenia and 52 normal controls. These asymmetries were correlated with specific measures of language processing, memory, and hand skill. An independent group of 14 pairs of siblings with schizophrenia were also evaluated for evidence of heritability to cerebral asymmetries. Width asymmetries were reduced in patients compared with controls in the posterior (p = 0.02) and occipital (p = 0.05) regions. Brain horizontal length, on the other hand, was significantly more asymmetrical in patients (left > right; p = 0.04). For sylvian fissure measurements, asymmetries in controls (left > right) were greatest for the horizontal component; this asymmetry tended to detect differences in patients by comparison with controls (p < 0.06). In a range of tests of language and memory, few significant correlations between performance and cerebral asymmetries were detected either in patients or controls, although patients consistently scored poorer than controls in the majority of tests. In 14 pairs of psychotic siblings, within-pair correlations for the horizontal sylvian fissure asymmetry were significantly greater than between-pair correlations. These findings are consistent with the early presence (possibly genetic) of anomalous cerebral asymmetry. However, the functional correlates of reduced asymmetry remain obscure.

ERP assessment of visual and auditory language processing in schizophrenia.

Language disturbance in schizophrenia has been recently attributed to disturbed priming mechanisms. In the present study, event-related potentials (ERPs), were recorded to final words in sentences presented to 13 chronic patients with schizophrenia and 12 normal controls. Half of the final words fit a sentence context and another half did not. The N400 (the ERP sensitive to language) latency was prolonged, and its amplitude was more negative to both correct and incorrect sentence endings in the group with schizophrenia relative to the group of normal controls. The early ERP components, N100 and P200, were similar in both groups. These results suggest that language abnormalities in schizophrenia are related to a dysfunction in the language system and not to a general cognitive dysfunction, and may be related to poor use of context in patients with schizophrenia.

Evoked potential measures of language processing in schizophrenia

The Continuous Performance Test (CPT) has been used extensively in studies concerned with attentional deficits in schizophrenia, however, the cognitive subprocesses underlying CPT performance are poorly understood. Startle eyeblink modification (gEM) is a psychophysiological measure which has the potential to separately evaluate discrete stages of information processing. When a nonstartling prepulse precedes a startleeliciting stimulus by a short interval (250 ms or less), the startle reflex is reliably inhibited. This prepuise inhibition is thought to reflect the early stages of information processing associated with sensory gating. When the interval is longer (1000 ms or greater), gEM is thought to reflect later stages of information processing. This study employed the gEM technique to index early and later stages of attentional processing during a visual memory-load version of the CPT with auditory (tone) distractors. Relatively remitted schizophrenic outpatients (n-20) and matched normal controls (n-18) viewed a series of single digits some of which served as prepulses for a startle.eliciting noise burst. Subjects were instructed to press a button after the digit 7 of each 3-7 sequence. The noise burst was presented either 120 or 1200 ms following the onset of preselected Target (i.e., Y'), Nontarget (non-3, non-7 digits), and Target plus Distractor (Y' and simultaneous tone distractor) prepuises, as well as in the absence of a prepulse (baseline). Primary results indicate that for control subjects the Target prepulse produced significantly greater inhibition than the Nontarget prepulse at the 120 ms lead-interval, suggesting early stimulus discrimination and selective attention. Also, significant but nondifferential prepulse inhibition was observed following the Target prepulse and the Target plus Distraetor prepulse, suggesting that the controls effectively ignot~l the distractor. In contrast, the patients failed to show differential prepulse inhibition to the Target and Nontarget prepulses. However, they did show attentional modulation of gEM as they exhibited significantly greater prepulse inhibition following the Target plus Distractor prepulse. These findings suggest that CPT deficits in schizophrenia are associated with inefficient early controlled attentional processes. Together with animal models of prepulse inhibition, gEM offers a unique way to delineate the neural basis of information processing deficits in schizophrenia.