Lexical Diversity and Other Linguistic Measures in Schizophrenia: Associations With Negative Symptoms and Neurocognitive Performance.

ABSTRACT: Straightforward linguistic measures may be indicators of reduced language production and lexical diversity among individuals with schizophrenia with negative symptoms and neurocognitive impairments. We compared 98 patients with schizophrenia to 101 unaffected controls on six language variables ( e.g. , number of relationships between objects, use of complex transitions in the narrative structure), number of words produced, and lexical diversity computed as the moving average type-token ratio from both speaking and writing tasks. Patients differed from controls on nearly all of the linguistic measures; number of words produced had the strongest effect, with an average Cohen's d of 0.68; values pertaining to lexical diversity were 0.50 and 0.32, respectively, for the speaking tasks and the writing tasks. Most measures were correlated with alogia and other domains of negative symptoms (including avolition-apathy and anhedonia-asociality), as well as with diverse neurocognitive domains, especially those pertaining to working memory, verbal learning, and verbal category fluency. Further work is needed to understand longitudinal changes in these linguistic variables, as well as their utility as measures of alogia.

Computational linguistic analysis applied to a semantic fluency task: A replication among first-episode psychosis patients with and without derailment and tangentiality.

Automated tools do not yet exist to measure formal thought disorder, including derailment and tangentiality, both of which can be subjectively rated using the Scale for the Assessment of Positive Symptoms after a clinical research interview. CoVec, a new automated tool, measures the semantic similarity among words averaged in a five- and ten-word window (Coherence-5 and Coherence-10, respectively). One prior report demonstrated that this tool was able to differentiate between patients with those types of thought disorder and patients without them (and controls). Here, we attempted a replication of the initial findings using data from a different sample of patients hospitalized for initial evaluation of first-episode psychosis. Participants were administered a semantic fluency task and the animal lists were analyzed with CoVec. In this study, we partially replicated the prior findings, showing that first-episode patients with derailment had significantly lower Coherence-5 and Coherence-10 compared with patients without derailment. Further research is warranted on this and other highly reliable and objective methods of detecting formal thought disorder through simple assessments such as semantic fluency tasks.

Computational linguistic analysis applied to a semantic fluency task to measure derailment and tangentiality in schizophrenia.

Although rating scales to assess formal thought disorder exist, there are no objective, high-reliability instruments that can quantify and track it. This proof-of-concept study shows that CoVec, a new automated tool, is able to differentiate between controls and patients with schizophrenia with derailment and tangentiality. According to ratings from the derailment and tangentiality items of the Scale for the Assessment of Positive Symptoms, we divided the sample into three groups: controls, patients without formal thought disorder, and patients with derailment/tangentiality. Their lists of animals produced during a one-minute semantic fluency task were processed using CoVec, a newly developed software that measures the semantic similarity of words based on vector semantic analysis. CoVec outputs were Mean Similarity, Coherence, Coherence-5, and Coherence-10. Patients with schizophrenia produced fewer words than controls. Patients with derailment had a significantly lower mean number of words and lower Coherence-5 than controls and patients without derailment. Patients with tangentiality had significantly lower Coherence-5 and Coherence-10 than controls and patients without tangentiality. Despite the small samples of patients with clinically apparent thought disorder, CoVec was able to detect subtle differences between controls and patients with either or both of the two forms of disorganization.

The aprosody of schizophrenia: Computationally derived acoustic phonetic underpinnings of monotone speech.

OBJECTIVE: Acoustic phonetic methods are useful in examining some symptoms of schizophrenia; we used such methods to understand the underpinnings of aprosody. We hypothesized that, compared to controls and patients without clinically rated aprosody, patients with aprosody would exhibit reduced variability in: pitch (F0), jaw/mouth opening and tongue height (formant F1), tongue front/back position and/or lip rounding (formant F2), and intensity/loudness. METHODS: Audiorecorded speech was obtained from 98 patients (including 25 with clinically rated aprosody and 29 without) and 102 unaffected controls using five tasks: one describing a drawing, two based on spontaneous speech elicited through a question (Tasks 2 and 3), and two based on reading prose excerpts (Tasks 4 and 5). We compared groups on variation in pitch (F0), formant F1 and F2, and intensity/loudness. RESULTS: Regarding pitch variation, patients with aprosody differed significantly from controls in Task 5 in both unadjusted tests and those adjusted for sociodemographics. For the standard deviation (SD) of F1, no significant differences were found in adjusted tests. Regarding SD of F2, patients with aprosody had lower values than controls in Task 3, 4, and 5. For variation in intensity/loudness, patients with aprosody had lower values than patients without aprosody and controls across the five tasks. CONCLUSIONS: Findings could represent a step toward developing new methods for measuring and tracking the severity of this specific negative symptom using acoustic phonetic parameters; such work is relevant to other psychiatric and neurological disorders.

Speech deficits in serious mental illness: a cognitive resource issue?

Speech deficits, notably those involved in psychomotor retardation, blunted affect, alogia and poverty of content of speech, are pronounced in a wide range of serious mental illnesses (e.g., schizophrenia, unipolar depression, bipolar disorders). The present project evaluated the degree to which these deficits manifest as a function of cognitive resource limitations. We examined natural speech from 52 patients meeting criteria for serious mental illnesses (i.e., severe functional deficits with a concomitant diagnosis of schizophrenia, unipolar and/or bipolar affective disorders) and 30 non-psychiatric controls using a range of objective, computer-based measures tapping speech production ("alogia"), variability ("blunted vocal affect") and content ("poverty of content of speech"). Subjects produced natural speech during a baseline condition and while engaging in an experimentally-manipulated cognitively-effortful task. For correlational analysis, cognitive ability was measured using a standardized battery. Generally speaking, speech deficits did not differ as a function of SMI diagnosis. However, every speech production and content measure was significantly abnormal in SMI versus control groups. Speech variability measures generally did not differ between groups. For both patients and controls as a group, speech during the cognitively-effortful task was sparser and less rich in content. Relative to controls, patients were abnormal under cognitive load with respect only to average pause length. Correlations between the speech variables and cognitive ability were only significant for this same variable: average pause length. Results suggest that certain speech deficits, notably involving pause length, may manifest as a function of cognitive resource limitations. Implications for treatment, research and assessment are discussed.

Phonetic measures of reduced tongue movement correlate with negative symptom severity in hospitalized patients with first-episode schizophrenia-spectrum disorders.

BACKGROUND: Aprosody, or flattened speech intonation, is a recognized negative symptom of schizophrenia, though it has rarely been studied from a linguistic/phonological perspective. To bring the latest advances in computational linguistics to the phenomenology of schizophrenia and related psychotic disorders, a clinical first-episode psychosis research team joined with a phonetics/computational linguistics team to conduct a preliminary, proof-of-concept study. METHODS: Video recordings from a semi-structured clinical research interview were available from 47 first-episode psychosis patients. Audio tracks of the video recordings were extracted, and after review of quality, 25 recordings were available for phonetic analysis. These files were de-noised and a trained phonologist extracted a 1-minute sample of each patient's speech. WaveSurfer 1.8.5 was used to create, from each speech sample, a file of formant values (F0, F1, F2, where F0 is the fundamental frequency and F1 and F2 are resonance bands indicating the moment-by-moment shape of the oral cavity). Variability in these phonetic indices was correlated with severity of Positive and Negative Syndrome Scale negative symptom scores using Pearson correlations. RESULTS: A measure of variability of tongue front-to-back position-the standard deviation of F2-was statistically significantly correlated with the severity of negative symptoms (r=-0.446, p=0.03). CONCLUSION: This study demonstrates a statistically significant and meaningful correlation between negative symptom severity and phonetically measured reductions in tongue movements during speech in a sample of first-episode patients just initiating treatment. Further studies of negative symptoms, applying computational linguistics methods, are warranted.

Social context influences the vocalizations of a home-raised African Grey parrot (Psittacus erithacus erithacus).

Home-raised African Grey parrots (Psittacus erithacus erithacus) exhibit strong social bonding with their human companions. We examined how 1 parrot's vocal production (speech and nonword sounds) changed with social context with respect to descriptive measures of the vocalizations and their thematic content. We videotaped the parrot in 4 social conditions: subject home alone, subject and owner in the same room, owner in a separate room within hearing range, and owner and experimenter conversing in the same room as the parrot but ignoring her. Linguistic analysis revealed the parrot's repertoire consisted of 278 "units" ranging in length from 1 to 8 words or sounds. Rate of vocalization and vocabulary richness (i.e., the number of different units used) differed significantly, and many vocalizations were context-specific. For example, when her owner was in the room and willing to reciprocate communication, the parrot was more likely to use units that, in English, would be considered solicitations for vocal interaction (e.g., "Cosmo wanna talk"). When she and her owner were in separate rooms, the subject was significantly more likely to use units that referenced her spatial location and that of her owner (e.g., "Where are you"), suggesting she uses specific units as an adaptation of the wild parrot contact call. These results challenge the notion that parrots only imitate speech and raise interesting questions regarding the role of social interaction in learning and communicative competence in an avian species.

Meaningful confusions and confusing meanings in communication in schizophrenia.

Unconventional discourse in schizophrenia has been speculated to be attributable to the mixing up of symbols and signs. We illustrate how a series of scientific images, cartoons, and prose are used by a patient to weave disparate-and objectively unrelated-concepts. The resulting prose is incoherent science.

Automatic measurement of propositional idea density from part-of-speech tagging.

The Computerized Propositional Idea Density Rater (CPIDR, pronounced "spider") is a computer program that determines the propositional idea density (P-density) of an English text automatically on the basis of part-of-speech tags. The key idea is that propositions correspond roughly to verbs, adjectives, adverbs, prepositions, and conjunctions. After tagging the parts of speech using MontyLingua (Liu, 2004), CPIDR applies numerous rules to adjust the count, such as combining auxiliary verbs with the main verb. A "speech mode" is provided in which CPIDR rejects repetitions and a wider range of fillers. CPIDR is a user-friendly Windows .NET application distributed as open-source freeware under GPL. Tested against human raters, it agrees with the consensus of two human raters better than the team of five raters agree with each other [r(80) = .97 vs. r(10) = .82, respectively].

Does ketamine mimic aspects of schizophrenic speech?

Speech disturbances are well-known symptoms contributing to the diagnosis of schizophrenia. Subanesthetic doses of the N-methyl-D-aspartate (NMDA) antagonist ketamine have been reported to produce positive and negative symptoms and cognitive impairments consistent with those seen in schizophrenia. Insofar as this is true, it constitutes evidence that the NMDA system is involved in schizophrenia. It is therefore of interest to know whether ketamine produces speech disturbances like those of schizophrenia. Quantitative computer-aided analysis of apparently normal speech can detect clinically relevant changes and differences that are not noticeable to the human observer. Accordingly, in this study, speech samples were analysed for repetitiousness, idea density, and verb density using software developed by the authors. The samples came from two experiments, a within-subjects study of healthy volunteers given intravenous ketamine versus placebo, and a between-groups study of patients diagnosed with schizophrenia and comparable healthy controls.Our primary hypothesis was that in both schizophrenia and ketamine, repetitiousness would increase, since perserverative speech is a well-known symptom of schizophrenia. Our secondary hypotheses were that in both schizophrenia and ketamine, idea density and verb density would decrease as indicators of cognitive impairment. The primary hypothesis was confirmed in the schizophrenia experiment (between groups) and the ketamine experiment (within subjects). The secondary hypotheses were disconfirmed except that in the ketamine experiment, verb density was significantly lowered. Reduced use of verbs apparently reflects a cognitive impairment of a different type than repetitiousness, and further investigation is needed to determine whether this impairment occurs in psychosis.

Schizophrenia and the structure of language: the linguist's view.

Patients with schizophrenia often display unusual language impairments. This is a wide ranging critical review of the literature on language in schizophrenia since the 19th century. We survey schizophrenic language level by level, from phonetics through phonology, morphology, syntax, semantics, and pragmatics. There are at least two kinds of impairment (perhaps not fully distinct): thought disorder, or failure to maintain a discourse plan, and schizophasia, comprising various dysphasia-like impairments such as clanging, neologism, and unintelligible utterances. Thought disorder appears to be primarily a disruption of executive function and pragmatics, perhaps with impairment of the syntax-semantics interface; schizophasia involves disruption at other levels. Phonetics is also often abnormal (manifesting as flat intonation or unusual voice quality), but phonological structure, morphology, and syntax are normal or nearly so (some syntactic impairments have been demonstrated). Access to the lexicon is clearly impaired, manifesting as stilted speech, word approximation, and neologism. Clanging (glossomania) is straightforwardly explainable as distraction by self-monitoring. Recent research has begun to relate schizophrenia, which is partly genetic, to the genetic endowment that makes human language possible.