Schizophrenic Thought Disorder Research Articles

Semantic activation and verbal working memory maintenance in schizophrenic thought disorder: insights from electrophysiology and lexical ambiguity.

We have examined language processing using ambiguous words (homographs like panel or toast) and rapid or slow presentation rates while recording event-related brain potentials (ERPs). Homographs allow for tracking the train of thought at points of lexical ambiguity and detecting modulation of associative threads by previous context. Rapid presentation rates stress automatic semantic activation, and slow rates stress controlled verbal working memory contextual modulation. In conjunction with reaction times and performance, ERPs allow for objective measurement of activity related to language processing from word presentation through overt behavioral response. Smaller N400 to related and unrelated items at short stimulus onset asynchronies (SOAs), the presence of a semantic bias, and large N400 to related and unrelated items at long SOAs are present in schizophrenia. We describe a model of initial semantic memory hyper-priming and subsequent decay of information in verbal working memory stores, the activation-maintenance model of schizophrenic thought disorder hypothesized to underlie the thought disorder in schizophrenia.

Neural Evidence for Faster and Further Automatic Spreading Activation in Schizophrenic Thought Disorder

It has been proposed that the loose associations characteristic of thought disorder in schizophrenia result from an abnormal increase in the automatic spread of activation through semantic memory. We tested this hypothesis by examining the time course of neural semantic priming using event-related potentials (ERPs). ERPs were recorded to target words that were directly related, indirectly related, and unrelated to their preceding primes, while thought-disordered (TD) and non-TD schizophrenia patients and healthy controls performed an implicit semantic categorization task under experimental conditions that encouraged automatic processing. By 300-400 milliseconds after target word onset, TD patients showed increased indirect semantic priming relative to non-TD patients and healthy controls, while the degree of direct semantic priming was increased in only the most severely TD patients. By 400-500 milliseconds after target word onset, both direct and indirect semantic priming were generally equivalent across the 3 groups. These findings demonstrate for the first time at a neural level that, under automatic conditions, activation across the semantic network spreads further within a shorter period of time in specific association with positive thought disorder in schizophrenia.

Double-decision lexical tasks in thought-disordered schizophrenic patients: A path towards cognitive remediation?

It has been shown that schizophrenics have certain difficulties in the processing of semantic context. These difficulties have usually been evaluated using lexical decision tasks with semantic priming. In this study, we chose to examine the idea of an abnormality in the early stages of semantic context processing in thought-disordered schizophrenics using two double lexical decision tasks: one with a high (25%) and one with a low (15%) proportion of related words to assess the participants’ competency in controlled and possibly also more automatic context processing. The results obtained in 40 control participants and 40 schizophrenic patients revealed no significant differences in the amplitude of semantic priming between the two groups. These results suggest that, in the disorganized schizophrenic subjects evaluated in this study, the context processing processes mobilized by the employed tasks were unimpaired.

'Hyper-priming' in thought-disordered schizophrenic patients.

A number of studies have suggested that indirect semantic priming is enhanced in thought-disordered schizophrenics. However, research on direct semantic priming has produced conflicting results. The aim of the present study was to resolve some of the ambiguities of previous findings. For the present study, 44 schizophrenic patients were split according to the presence of associative loosening into a positive thought-disordered (TD) and non-positive thought-disordered (NTD) group. Thirty healthy subjects and 36 psychiatric patients served as controls. Schizophrenics displayed increased indirect semantic priming compared with psychiatric controls. When subtyping the sample, TD-patients exhibited significantly enhanced indirect semantic priming compared with healthy and psychiatric controls as well as NTD-patients. Overall slowing was found to be independent of priming effects. Medication, age and chronicity of the schizophrenic illness did not modulate priming. In line with Spitzer and Maher it is inferred that disinhibited semantic networks underlie formal thought disorder in schizophrenia. For future research, it would be appropriate to: employ indirect semantic priming rather than direct semantic priming conditions; and, pay more attention to potential moderators of the priming effect, most importantly, the prime display duration and the length of the stimulus onset asynchrony.

Sensitivity to linguistic anomalies in spoken sentences: a case study approach to understanding thought disorder in schizophrenia.

As a group, positively thought-disordered (TD) schizophrenic patients are relatively impaired in their ability to use linguistic context to process sentences online (Kuperberg et al. 1998). This study investigates the heterogeneity in the use of linguistic context both between individual TD patients and within the individual patients as severity of thought disorder changes over time. Seventeen TD schizophrenics performed an online word-monitoring task on four separate occasions. In each patient, baseline reaction time (RTs) to target words in normal sentences were subtracted from RTs to target words in pragmatically-, semantically- and syntactically-violated sentences to obtain a measure of online sensitivity to each type of linguistic violation, and these were compared with normative data of a healthy volunteer and a non-TD schizophrenic control group. In addition, the co-variation of severity of thought disorder and sensitivity to linguistic context within all individual TD patients over the four testing sessions, was examined. There was marked heterogeneity between individual TD patients in their sensitivity to different types of linguistic violations: some were selectively insensitive to pragmatic violations, while others were insensitive to semantic and syntactic (subcategorization) violations. There was also an inverse relationship between severity of thought disorder and sensitivity to linguistic violations within individual patients over the four sessions. It is likely that a single cognitive deficit does not account for all types of schizophrenic thought disorder, but rather that there are multiple deficits affecting specific levels of linguistic processing. In these schizophrenic patients, impairment in the use of linguistic context was related to the state, rather than the trait, of thought disorder.

Reduced sensitivity to linguistic context in schizophrenic thought disorder: evidence from on-line monitoring for words in linguistically anomalous sentences.

The use of linguistic context in positively thought-disordered (TD) schizophrenics was investigated through examination of their performance on an on-line word-monitoring task. Controls and non-TD schizophrenics took longer to recognize words preceded by linguistic anomalies compared with words in normal sentences. Compared with both other groups, TD schizophrenics showed significantly smaller differences in reaction time, suggesting that they were relatively insensitive to linguistic violations. TD schizophrenics were also less sensitive to linguistic violations in an off-line version of the task, in which they judged whether the sentences "made sense." Finally, these participants produced more errors on a verbal fluency task than did non-TD schizophrenics or normal controls. These findings are consistent with the theory that schizophrenic thought disorder arises from a deficit in the use of linguistic context to process and produce speech.

Formal thought disorder in schizophrenia. Linguistic, attentional, and intellectual correlates.

Formal thought disorder (i.e., abnormal utterances and communication problems) is a prominent feature of schizophrenia. To investigate the hypothesis that formal thought disorder in schizophrenics represents a disturbance of language functioning, we compared 21 thought-disordered and 16 non-thought-disordered schizophrenics on the Porch Index of Communicative Ability. The thought-disordered schizophrenics were significantly more impaired. We also examined nonlinguistic factors potentially impacting language performance in schizophrenics (e.g., disturbed attention, intellect, and/or thought content). Reduced attention was the best predictor of language performance in the thought-disordered group, whereas low intellect and reduced attention were predictive of language dysfunction in the non-thought-disordered group. Disturbed thought content was not predictive of language impairment in either group. These findings provide partial support for the idea that formal thought disorder in schizophrenics represents defective language functioning.

Investigating thought disorder in schizophrenia with the lexical decision task

Prior work has found evidence of hyperpriming in schizophrenics, which has been related to a persistence of associational activation in thought disorder. We extended this work by administering a lateralized version of the lexical decision task to 10 thought-disordered schizophrenics (TD), 10 non-thought-disordered schizophrenics (NTD), and 11 control subjects to localize the patterns of priming. All subjects were right-handed males. Associated, unassociated, and neutral prime-target pairs were displayed across seven stimulus location combinations: prime and target both presented to the center, left visual field (LVF), or right visual field (RVF); prime presented to the center with target presented to the LVF or RVF; and prime and target presented contralaterally. TD schizophrenics exhibited priming effects comparable to those of the other subject groups, suggesting intact semantic memory structures and memory processes that may be unimpaired under the conditions studied. It is believed that the associative process mediating priming effects found in schizophrenia are later in the sequence than those examined in this study.

P300 indexes thought disorder in schizophrenics, but allusive thinking in normal subjects.

Loosening of thinking as assessed by the Object Sorting Test (OST) has been found in a percentage of normal subjects but in a higher percentage of schizophrenics, and is familially transmitted in both groups. Loosening of thinking in normal subjects is not associated with evidence of impaired function or increased psychopathology, and in recognition of this, it was termed allusive thinking rather than thought disorder. Both OST-assessed loosening and concreteness of thinking were found to be present independently in a high percentage of schizophrenics, so that both were considered to contribute to schizophrenic thought disorder. The presence of OST-assessed loosening in schizophrenics would, therefore, be predicted to correlate partially rather than totally with measures of schizophrenic thought disorder. It has been suggested that OST-assessed loosening in normal subjects is due to a genetically determined reduction in strength of an inhibitory process that limits the spread of activation of semantic associations and results in a predisposition to schizophrenia. The brain event-related potential P300, which is, in part, under genetic control, may index this inhibitory process. Therefore, it was predicted that in normal subjects, P300 would correlate with OST-assessed loosening of associations. If schizophrenic thought disorder is due to a further weakening of this inhibitory process, it can be predicted that P300 in schizophrenics correlates only weakly with OST-assessed loosening of thinking, but more strongly with schizophrenic thought disorder. In a study in which P300 was elicited using a difficult selective attention task with 15 unmedicated schizophrenics and 22 healthy subjects, all three predictions were supported.

Object chaining and thought disorder in schizophrenic speech

The phenomenon of object chaining was investigated to determine its relationship to thought disorder in schizophrenia. Samples from thought-disordered schizophrenics (N = 12) and controls (10 non-thought-disordered schizophrenics and 10 normals) were analysed. Using the object subject ratio (OSR) to measure object chaining, we found higher OSRs in the speech of thought-disordered subjects than in that of subjects free of thought disorder. Object chaining correlated with low predictability of speech. We conclude that object chaining is associated with reduced speech comprehensibility and probably contributes to the judgement that thought disorder is present.

The grid test of schizophrenic thought disorder, and EPQ psychoticism, in non-clinical subjects

Intensity and consistency scores on the Grid Test of Schizophrenic Thought Disorder were positively correlated with each other and with test-retest reliability or ‘element consistency’ in 40 male and 48 female students. Element consistency was higher than observed previously in a psychiatric sample, but was negatively correlated with Psychoticism in the women and subjects overall. Grid Test performance indices reflect cognitive integrity but do not distinguish its features.

Semantic priming in thought disordered schizophrenic patients

Groups of thought disordered (TD) and non-thought disordered (NTD) schizophrenic patients, unipolar affective patients and normal controls performed a lexical decision task involving the recognition of words immediately preceded (primed) by either an associated or an unrelated word. Significant increments in recognition speed in the associated prime condition were found in all groups, with significantly greater gain by TD schizophrenics than by others. These findings are consistent with network models of associational activation and lend support to an attentional deficit hypothesis for schizophrenic language functioning.

Interrelationship of hypochondriacal, paranoid, depressive, and suicidal symptoms in Chinese psychiatric patients.

Data concerning 150 consecutive adult psychiatric patients treated by the authors in a general hospital psychiatric unit were analyzed. All patients with predominant hypochondriacal or paranoid symptoms were selected. The presence of depressed mood and suicidal ideas and their impact on prognosis were investigated. Finally, characteristics of patients with both hypochondriacal and paranoid symptoms were studied. We found that: (a) 79% of the patients with predominant hypochondriacal symptoms were depressed, but only 27% of these had suicidal ideas. These patients usually revealed a poor response to treatment. (b) Only 27% of the patients with paranoid symptoms only were depressed, but their suicidal risk was high. They usually had a good response to treatment. (c) Only 3% of the total sample exhibited both hypochondriacal and paranoid symptoms. They were all thought-disordered schizophrenics but had better prognosis than expected. The psychodynamic background of the results is discussed.

Role of the thalamus in language: is it related to schizophrenic thought disorder?

Crosson (1985) proposed a model for language production which integrated cortical with subcortical functions. The implications of this model for schizophrenia are explored. One conclusion is that neural systems, as opposed to a single neural focus, account for schizophrenic symptoms. In this light, data regarding dysfunction in the limbic system, nucleus accumbens, globus pallidus, and prefrontal cortex, which are often seen as contradictory, can be viewed as complementary. Another conclusion is that Crosson's model may have implications specific to schizophrenic thought disorder. Random triggering of semantic segments and inability to maintain contextual referents are discussed in the context of the language production theory.

The early course of schizophrenic thought disorder.

The current investigation studied the early course of positive thought disorder and its relationship to other aspects of schizophrenic outcome. Forty-eight schizophrenics diagnosed using the Research Diagnostic Criteria (RDC), 51 psychotic nonschizophrenics, and 67 nonpsychotic patients were studied at index hospitalization and at a 1.5-year followup. Most thought-disordered schizophrenics and other psychotic patients showed some reduction in thought pathology between index hospitalization and followup (p less than .02). A larger percentage of schizophrenics than other psychotic and nonpsychotic showed thought disorder at the acute phase and at followup assessment (p less than .05), although only a subgroup of 27 percent of the schizophrenics showed severe thought disorder at followup. At followup, severely thought-disordered schizophrenics showed residual signs of psychosis and poor functioning in other areas. Positive thought disorder in schizophrenics at followup most often occurred within the context of an unremitted illness and was less frequently due to a new, acute episode of disturbance. Continuously thought-disordered schizophrenics exhibited more severe impairments in life adjustment at 1.5-year followup than did episodic or nonthought-disordered schizophrenics (p less than .02). The results suggest that severe thought disorder is a persistent characteristic in a subgroup of early schizophrenics.

Schizophrenic thought disorder at followup: its persistence and prognostic significance.

To assess the prominence, persistence, and prognostic significance of positive thought disorder in schizophrenia, we studied a large sample of psychiatric inpatients at the acute phase and then followed them up twice--1 1/2-2 years and 4 years after hospital discharge. Positive thought disorder was more prominent at the acute phase in schizophrenic and manic patients than in other types of psychotic and nonpsychotic disorders. At followup, positive thought disorder did not persist for all schizophrenics, but a significantly larger percentage of schizophrenic than other psychotic and nonpsychotic patients followed a course in which positive thought disorder was either persistently or episodically present. Positive thought disorder, when seen after the acute phase, was related to concurrent functioning, and predicted subsequent poorer outcome and functioning for both schizophrenic and nonschizophrenic patients. Positive thought disorder was one of several central features of the active schizophrenic disorder. Among schizophrenics, it was related to other major types of psychopathology, especially delusions, another positive symptom with cognitive-ideational elements. Severe positive thought disorder after the acute phase indicated a sustained episode, and suggested a more severe type of schizophrenia with a poorer prognosis.

Repetition in schizophrenic speech.

Previous research on language with the Type-Token Ratio (TTR) indicates an increased repetitiousness in schizophrenics, specifically in thought-disordered schizophrenics. The present investigation involves an analysis of oral language samples utilizing a variety of repetition measures. Subjects were 40 schizophrenics, 20 affective disorder controls and 22 normal controls. Phrase repetitions were found to be more prevalent among the schizophrenic group, and especially among the TD subgroup, and indices of phrase repetition were positively correlated with dimensions of formal thought disorder. The frequency patterns of repeated words in schizophrenic language reflect a less common, but not unusual lexicon compared to controls, thereby supporting the view that word repetition in schizophrenic utterance is not a consequence of a restricted vocabulary range. The intervals between phrase repetitions were not different for schizophrenics and controls, indicating that simple perseveration is also not a likely explanation. Rather, repetitiousness, a major characteristic of schizophrenic speech, may be due to a unique, yet undetermined mechanism responsible for the language disturbances seen in this disorder.

Measuring consistency with the Grid Test.

It is argued that the Consistency score derived from the Grid Test of Schizophrenic Thought Disorder is not the most sensitive index of stability between the identical grid forms in identifying the pattern of relations between constructs. The SASD score is proposed as an alternative to the Consistency score. The present study indicates that the SASD score is a more valid measure of the stability between the identical grid forms.

Disordered thinking.

To evaluate formulations that thought disorder at the posthospital phase identifies a subgroup of nuclear schizophrenics with poor outcomes, 77 patients from a longitudinal project were followed up on major dimensions of psychopathology linked to nuclear schizophrenia. The data indicate that (1) schizophrenics were more thought disordered than were nonschizophrenics at the posthospital phase; (2) thought-disordered schizophrenics had only slightly poorer scores on classic prognostic indicators associated with poor outcomes; (3) a subgroup of early chronic schizophrenics were not severely thought disordered; (4) almost all severely thought-disordered schizophrenics demonstrated clear evidence of delusional activity at follow-up; and (5) thought-disordered schizophrenics had poorer outcomes. The overall results fit in with formulations that a severe thought disorder is one of several major features of schizophrenia. The data suggest that posthospital thought disorder identifies a subgroup of poor-outcome schizophrenics, although some non-thought-disordered schizophrenics also show poor outcomes.

An investigation of the construct validity of the Bannister-Fransella Grid Test of Schizophrenic Thought Disorder.

An attempt was made to demonstrate the construct validity of the Grid Test in a psychiatric population by showing that: (a) judgements of thought disorder based on the Grid Test were associated with judgements based on a clinical interview; (b) Grid Test scores were not associated with measures of other forms of psychopathology, intelligence, or memory. Results of a principal components factor analysis confirmed both hypothesis, supporting the validity of the Grid Test as a measure of thought disorder.