Doron Todder1, Sofia Avissar2, Gabriel Schreiber3. 1. Ben Gurion University of the Negev Psychiatry Department Beer Sheva Israel 84105. 2. Ben Gurion University of the Negev Clinical Pharmacology Department Beer Sheva Israel 84105. 3. Ben Gurion University of the Negev Faculty of Health Sciences Beer Sheva Israel 84105.
Abstract
UNLABELLED: "Language is a form and not a substance" - Ferdinand de Saussure Objective: Analyses of speech processes in schizophrenia are invariably focused on words as vocal signals. The results of such analyses are, however, strongly related to content, and may be language- and culture-dependent. Little attention has been paid to a pure measure of the form of speech, unrelated to its content: inter-words time intervals. METHOD: 15 patients with schizophrenia and 15 healthy volunteers are recorded spontaneously speaking for 10-15 min. Recordings are analyzed for inter-words time intervals using the following non-linear dynamical methods: unstable periodic orbits, correlation dimension, bi-spectral analysis, and symbolic dynamics. RESULTS: The series of inter-word time intervals in normal speech have the characteristics of a low-dimensional chaotic attractor with a correlation dimension of [Formula: see text]. Deconstruction of the attractor appears in psychosis with re-establishment after anti-psychotic treatment. Shannon entropy, a measure of the complexity in the time series, calculated from symbolic dynamics, is higher for psychotic speech, which is also characterized by higher levels of phase coupling: higher bicoherence, obtained using bi-spectral analysis. CONCLUSION: Non-linear dynamical methods applied to ITIs thus enable a content-independent, pure measure of the form of normal thought, its distortion in psychosis, and its restoration under treatment.
UNLABELLED: "Language is a form and not a substance" - Ferdinand de Saussure Objective: Analyses of speech processes in schizophrenia are invariably focused on words as vocal signals. The results of such analyses are, however, strongly related to content, and may be language- and culture-dependent. Little attention has been paid to a pure measure of the form of speech, unrelated to its content: inter-words time intervals. METHOD: 15 patients with schizophrenia and 15 healthy volunteers are recorded spontaneously speaking for 10-15 min. Recordings are analyzed for inter-words time intervals using the following non-linear dynamical methods: unstable periodic orbits, correlation dimension, bi-spectral analysis, and symbolic dynamics. RESULTS: The series of inter-word time intervals in normal speech have the characteristics of a low-dimensional chaotic attractor with a correlation dimension of [Formula: see text]. Deconstruction of the attractor appears in psychosis with re-establishment after anti-psychotic treatment. Shannon entropy, a measure of the complexity in the time series, calculated from symbolic dynamics, is higher for psychotic speech, which is also characterized by higher levels of phase coupling: higher bicoherence, obtained using bi-spectral analysis. CONCLUSION: Non-linear dynamical methods applied to ITIs thus enable a content-independent, pure measure of the form of normal thought, its distortion in psychosis, and its restoration under treatment.
Entities:
Keywords:
Schizophrenia; cognitive neuroscience; inter-words time intervals (ITIs); nonlinear dynamics; psychotic speech; speech form
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