Behavioral

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

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.

An impairment in the build-up and use of context has been proposed as a core feature of schizophrenia. The current study tested the hypothesis that schizophrenia patients show impairments in building up context within sentences because of abnormalities in combining semantic with syntactic information. Schizophrenia patients and healthy controls read and made acceptability judgments about sentences containing verbs that were semantically associated with individual preceding words but that violated either the meaning (animacy/semantic constraints) or the syntactic structure (morphosyntactic constraints) of their preceding contexts. To override these semantic associations and determine that such sentences are unacceptable, participants must integrate semantic with syntactic information. These sentences were compared with congruous and pragmatically/semantically violated sentences that imposed fewer semantic-syntactic integration demands. At sentence-final words and decisions, patients showed smaller reaction time differences than controls to animacy/semantically violated or morphosyntactically violated sentences relative to pragmatically/semantically violated or nonviolated sentences. The relative insensitivity to these violations in patients with schizophrenia may arise from impairments in combining semantic and syntactic information to build up sentence context.

Prediction or expectancy is thought to play an important role in both music and language processing. However, prediction is currently studied independently in the two domains, limiting research on relations between predictive mechanisms in music and language. One limitation is a difference in how expectancy is quantified. In language, expectancy is typically measured using the cloze probability task, in which listeners are asked to complete a sentence fragment with the first word that comes to mind. In contrast, previous production-based studies of melodic expectancy have asked participants to sing continuations following only one to two notes. We have developed a melodic cloze probability task in which listeners are presented with the beginning of a novel tonal melody (5-9 notes) and are asked to sing the note they expect to come next. Half of the melodies had an underlying harmonic structure designed to constrain expectations for the next note, based on an implied authentic cadence (AC) within the melody. Each such ’authentic cadence’ melody was matched to a ’non-cadential’ (NC) melody matched in terms of length, rhythm and melodic contour, but differing in implied harmonic structure. Participants showed much greater consistency in the notes sung following AC vs. NC melodies on average. However, significant variation in degree of consistency was observed within both AC and NC melodies. Analysis of individual melodies suggests that pitch prediction in tonal melodies depends on the interplay of local factors just prior to the target note (e.g., local pitch interval patterns) and larger-scale structural relationships (e.g., melodic patterns and implied harmonic structure). We illustrate how the melodic cloze method can be used to test a computational model of melodic expectation. Future uses for the method include exploring the interplay of different factors shaping melodic expectation, and designing experiments that compare the cognitive mechanisms of prediction in music and language.

BackgroundPeople 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.MethodsTo 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.ResultsWe 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.ConclusionsThese 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.

In people with schizophrenia and related disorders, impairments in communication and social functioning can negatively impact social interactions and quality of life. In the present study, we investigated the cognitive basis of a specific aspect of linguistic communication—lexical alignment— in people with schizophrenia and bipolar disorder. We probed lexical alignment as participants played a collaborative picture-naming game with the experimenter, in which the two players alternated between naming a dual-name picture (e.g., rabbit/bunny) and listening to their partner name a picture. We found evidence of lexical alignment in all three groups, with no differences between the patient groups and the controls. We argue that these typical patterns of lexical alignment in patients were supported by preserved—and in some cases increased—bottom-up mechanisms, which balanced out impairments in top-down perspective-taking.