Graph theory applied to speech: insights on cognitive deficit diagnosis and dream research

In the past ten years, graph theory has been widely employed in the study of natural and technological phenomena. The representation of the relationships among the units of a network allow for a quantitative analysis of its overall structure, beyond what can be understood by considering only a few units. Here we discuss the application of graph theory to psychiatric diagnosis of psychoses and dementias. The aim is to quantify the flow of thoughts of psychiatric patients, as expressed by verbal reports of dream or waking events. This flow of thoughts is hard to measure but is at the roots of psychiatry as well as psychoanalysis. To this end, speech graphs were initially designed with nodes representing lexemes and edges representing the temporal sequence between consecutive words, leading to directed multigraphs. In a subsequent study, individual words were considered as nodes and their temporal sequence as edges; this simplification allowed for the automatization of the process, effected by the free software Speech Graphs. Using this approach, one can calculate local and global attributes that characterize the network structure, such as the total number of nodes and edges, the number of nodes present in the largest connected and the largest strongly connected components, measures of recurrence such as loops of 1, 2, and 3 nodes, parallel and repeated edges, and global measures such as the average degree, density, diameter, average shortest path, and clustering coefficient. Using these network attributes we were able to automatically sort schizophrenia and bipolar patients undergoing psychosis, and also to separate these psychotic patients from subjects without psychosis, with more than 90% sensitivity and specificity. In addition to the use of the method for strictly clinical purposes, we found that differences in the content of the verbal reports correspond to structural differences at the graph level. When reporting a dream, healthy subjects without psychosis and psychotic subjects with bipolar disorder produced more complex graphs than when reporting waking activities of the previous day; this difference was not observed in psychotic subjects with schizophrenia, which produced equally poor reports irrespective of the content. As a consequence, graphs of dream reports were more efficient for the differential diagnosis of psychosis than graphs of daily reports. Based on these results we can conclude that graphs from dream reports are more informative about mental states, echoing the psychoanalytic notion that dreams are a privileged window into thought.2019-07-3

The effects of early biliteracy on thought organisation and syntactic complexity in written production by 11-year-old children

The study investigates the effects of bilingualism and biliteracy on thought organisation, and syntactic complexity in the written production in a group of fifty 11-year-old children (M = 10.7) enrolled in 5th and 6th grades in a bilingual school in the south of Brazil. The children’s home and community language is Portuguese, and they have been exposed to English at school for 10 hours a week for at least five years. Participants were asked to create a narrative based on a sequence of five images (Cambridge Assessment, 2018), being one in English and one in Portuguese, in a counterbalanced order. Thought organisation (connectivity) was measured through the analysis of graph trajectories performed with the computational tool Speech Graphs (Mota et al., 2014, 2016, 2019) and the analysis of syntactic complexity involved the assessment of T-Units (Hunt, 1965). Results indicated a moderate positive correlation in the attributes of thought connectivity and the levels of syntactic complexity in both languages, demonstrating that, as children advance in the development of more complex writing strategies in Portuguese, they progress in their written production in English to the same extent

Speech structure links the neural and socio-behavioural correlates of psychotic disorders

Background: A longstanding notion in the concept of psychosis is the prominence of loosened associative links in thought processes. Assessment of such subtle aspects of thought disorders has proved to be a challenging task in clinical practice and to date no surrogate markers exist that can reliably track the physiological effects of treatments that could reduce thought disorders. Recently, automated speech graph analysis has emerged as a promising means to reliably quantify structural speech disorganization. Methods: Using structural and functional imaging, we investigated the neural basis and the functional relevance of the structural connectedness of speech samples obtained from 56 patients with psychosis (22 with bipolar disorder, 34 with schizophrenia). Speech structure was assessed by non-semantic graph analysis. Results: We found a canonical correlation linking speech connectedness and i) functional as well as developmentally relevant structural brain markers (degree centrality from resting state functional imaging and cortical gyrification index) ii) psychometric evaluation of thought disorder iii) aspects of cognitive performance (processing speed deficits) and iv) functional outcome in patients. Of various clinical metrics, only speech connectedness was correlated with biological markers. Speech connectedness filled the dynamic range of responses better than psychometric measurements of thought disorder. Conclusions: The results provide novel evidence that speech dysconnectivity could emerge from neurodevelopmental deficits and associated dysconnectivity in psychosis

A Naturalistic Assessment of the Organization of Children’s Memories Predicts Cognitive Functioning and Reading Ability

To explore the relationship between memory and early school performance, we used graph theory to investigate memory reports from 76 children aged 6–8 years. The reports comprised autobiographical memories of events days to years past, and memories of novel images reported immediately after encoding. We also measured intelligence quotient (IQ) and theory of mind (ToM). Reading and Mathematics were assessed before classes began (December 2013), around the time of report collection (June 2014), and at the end of the academic year (December 2014). IQ and ToM correlated positively with word diversity and word-to-word connectivity, and negatively with word recurrence. Connectivity correlated positively with Reading in June 2014 as well as December 2014, even after adjusting for IQ and ToM. To our knowledge, this is the first study demonstrating a link between the structure of children’s memories and their cognitive or academic performance.To explore the relationship between memory and early school performance, we used graph theory to investigate memory reports from 76 children aged 6–8 years. The reports comprised autobiographical memories of events days to years past, and memories of novel images reported immediately after encoding. We also measured intelligence quotient (IQ) and theory of mind (ToM). Reading and Mathematics were assessed before classes began (December 2013), around the time of report collection (June 2014), and at the end of the academic year (December 2014). IQ and ToM correlated positively with word diversity and word-to-word connectivity, and negatively with word recurrence. Connectivity correlated positively with Reading in June 2014 as well as December 2014, even after adjusting for IQ and ToM. To our knowledge, this is the first study demonstrating a link between the structure of children’s memories and their cognitive or academic performance

The History of Writing Reflects the Effects of Education on Discourse Structure: Implications for Literacy, Orality, Psychosis and the Axial Age

Background: Graph analysis detects psychosis and literacy acquisition. Bronze Age literature has been proposed to contain childish or psychotic features, which would only have matured during the Axial Age (∼800-200 BC), a putative boundary for contemporary mentality. Method: Graph analysis of literary texts spanning ∼4,500 years shows remarkable asymptotic changes over time. Results: While lexical diversity, long-range recurrence and graph length increase away from randomness, short-range recurrence declines towards random levels. Bronze Age texts are structurally similar to oral reports from literate typical children and literate psychotic adults, but distinct from poetry, and from narratives by preliterate preschoolers or Amerindians. Text structure reconstitutes the “arrow-of-time”, converging to educated adult levels at the Axial Age onset. Conclusion: The educational pathways of oral and literate traditions are structurally divergent, with a decreasing range of recurrence in the former, and an increasing range of recurrence in the latter. Education is seemingly the driving force underlying discourse maturation.Fil: Pinheiro, Sylvia. Universidade Federal do Rio Grande do Norte; BrasilFil: Mota, Natália Bezerra. Universidade Federal de Pernambuco; Brasil. Universidade Federal do Rio Grande do Norte; BrasilFil: Sigman, Mariano. Universidad Torcuato Di Tella; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fernandez Slezak, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigación en Ciencias de la Computación. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigación en Ciencias de la Computación; ArgentinaFil: Guerreiro, Antonio. Universidade Estadual de Campinas; BrasilFil: Tófoli, Luís Fernando. Universidade Estadual de Campinas; BrasilFil: Cecchi, Guillermo. No especifíca;Fil: Copelli, Mauro. No especifíca;Fil: Ribeiro, Sidarta. Universidade Federal do Rio Grande do Norte; Brasi

Risk factors for death among critically ill elderly patients

OBJETIVO: A população idosa está aumentando em todo o mundo, assim como a necessidade de cuidados intensivos para os idosos. Existem poucos estudos que investiguem os fatores de risco para óbito em pacientes idosos gravemente enfermos. Este estudo teve o objetivo de investigar os fatores associados ao óbito em uma população de pacientes idosos gravemente enfermos admitidos a uma unidade de terapia intensiva no Brasil. MÉTODOS: Estudo retrospectivo de coorte que incluiu todos os pacientes idosos (idade &#8805; 60 anos) admitidos a uma unidade de terapia intensiva em Fortaleza, Brasil, de janeiro a dezembro de 2007. Foi realizada uma comparação entre os sobreviventes e os não sobreviventes, e os fatores de risco para óbito foram investigados por meio de análise univariada e multivariada. RESULTADOS: Foi incluído um total de 84 pacientes, com uma média de idade de 73 ± 7,6 anos, sendo 59% do gênero feminino. A mortalidade foi de 62,8%. A principal causa de morte foi disfunção de múltiplos órgãos (42,3%), seguido por choque séptico (36,5%) e choque cardiogênico (9,7%). As complicações durante a permanência na unidade de terapia intensiva associadas com óbito foram insuficiência respiratória (OR = 61; p<0.001), lesão renal aguda (OR =23, p<0,001), sepse (OR = 12; p<0,001), acidose metabólica (OR = 17; p<0,001), anemia (OR = 8,6; p<0,005), distúrbios da coagulação (OR = 5,9; p<0,001) e fibrilação atrial (OR = 4,8; P<0,041). Os fatores de risco independentes para óbito foram idade (OR = 1,15; p<0,005), coma (OR = 7,51; p<0,003), hipotensão (OR = 21,75; p=0,003), insuficiência respiratória (OR = 9,93; p<0,0001), e lesão renal aguda (OR = 16,28; p<0,014). CONCLUSÕES: A mortalidade é elevada em pacientes idosos gravemente enfermos. Os fatores associados ao óbito foram idade, coma, hipotensão, insuficiência respiratória e lesão renal aguda.BACKGROUND: The elderly population is increasing all over the world. The need of intensive care by the elderly is also increasing. There is a lack of studies investigating the risk factors for death among critically ill elderly patients. This study aims to investigate the factors associated with death in a population of critically ill elderly patients admitted to an intensive care unit in Brazil. METHODS: This is a retrospective cohort study including all elderly patients (&gt;60 years) admitted to an intensive care unit in Fortaleza, Brazil, from January to December 2007. A comparison between survivors and nonsurvivors was done and the risk factors for death were investigated through univariate and multivariate analysis. RESULTS: A total of 84 patients were included, with an average age of 73 ± 7.6 years; 59% were female. Mortality was 62.8%. The main cause of death was multiple organ dysfunction (42.3%), followed by septic shock (36.5%) and cardiogenic shock (9.7%). Complications during intensive care unit ICU stay associated with death were respiratory failure (OR=61, p<0.001), acute kidney injury (OR=23, p<0.001), sepsis (OR=12, p<0.001), metabolic acidosis (OR=17, p<0.001), anemia (OR=8.6, p<0.005), coagulation disturbance (OR=5.9, p<0.001) and atrial fibrillation (OR=4.8, p<0.041). Independent risk factors for death were age (OR=1.15, p<0.005), coma (OR=7.51, p<0.003), hypotension (OR=21.75, p=0.003), respiratory failure (OR=9.93, p<0.0001) and acute kidney injury (OR=16.28, p<0.014). CONCLUSION: Mortality is high among critically ill elderly patients. Factors associated with death were age, coma, hypotension, respiratory failure and acute kidney injury.CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológic

Imagetic and affective measures of memory reverberation diverge at sleep onset in association with theta rhythm

The ‘day residue’ - the presence of waking memories into dreams - is a century-old concept that remains controver- sial in neuroscience. Even at the psychological level, it remains unclear how waking imagery cedes into dreams. Are visual and affective residues enhanced, modified, or erased at sleep onset? Are they linked, or dissociated? What are the neural correlates of these transformations? To address these questions we combined quantitative se- mantics, sleep EEG markers, visual stimulation, and multiple awakenings to investigate visual and affect residues in hypnagogic imagery at sleep onset. Healthy adults were repeatedly stimulated with an affective image, allowed to sleep and awoken seconds to minutes later, during waking (WK), N1 or N2 sleep stages. ‘Image Residue’ was objectively defined as the formal semantic similarity between oral reports describing the last image visualized before closing the eyes (‘ground image’), and oral reports of subsequent visual imagery (‘hypnagogic imagery). Similarly, ‘Affect Residue’ measured the proximity of affective valences between ‘ground image’ and ‘hypnagogic imagery’. We then compared these grounded measures of two distinct aspects of the ‘day residue’, calculated within participants, to randomly generated values calculated across participants. The results show that Image Residue persisted throughout the transition to sleep, increasing during N1 in proportion to the time spent in this stage. In contrast, the Affect Residue was gradually neutralized as sleep progressed, decreasing in proportion to the time spent in N1 and reaching a minimum during N2. EEG power in the theta band (4.5-6.5 Hz) was inversely correlated with the Image Residue during N1. The results show that the visual and affective aspects of the ‘day residue’ in hypnagogic imagery diverge at sleep onset, possibly decoupling visual contents from strong negative emotions, in association with increased theta rhythm.Neuroimag

Psychosis and the control of lucid dreaming

Dreaming and psychosis share important features, such as intrinsic senseperceptions independent of external stimulation, and a general lack of criticism that is associated with reduced frontal cerebral activity. Awareness of dreaming while a dream is happening defines lucid dreaming (LD), a state in which the prefrontal cortex is more active than during regular dreaming. For this reason, LD has been proposed to be potentially therapeutic for psychotic patients. According to this view, psychotic patients would be expected to report LD less frequently, and with lower control ability, than healthy subjects. Furthermore, psychotic patients able to experience LD should present milder psychiatric symptoms, in comparison with psychotic patients unable to experience LD. To test these hypotheses, we investigated LD features (occurrence, control abilities, frequency, and affective valence) and psychiatric symptoms (measure by PANSS, BPRS and automated speech analysis) in 45 subjects with psychotic symptoms (25 with Schizophrenia (S) and 20 with Bipolar Disorder (B) diagnosis) versus 28 non-psychotic control (C) subjects. Psychotic lucid dreamers reported control of their dreams more frequently (67% of S and 73% of B) than non-psychotic lucid dreamers (only 23% of C; S > C with p=0. 0283, B > C with p=0.0150). Importantly, there was no clinical advantage for lucid dreamers among psychotic patients, even for the diagnostic question specifically related to lack of judgment and insight. Despite some limitations (e.g. transversal design, large variation of medications), these preliminary results support the notion that lucid dreaming is associated with psychosis, but falsify the hypotheses that we set out to test. A possible explanation is that psychosis enhances the experience of internal reality in detriment of external reality, and therefore lucid dreamers with psychotic symptoms would be more able to control their internal reality than non-psychotic lucid dreamers. Training dream lucidity is likely to produce safe psychological strengthening in a non-psychotic population, but in a psychotic population LD practice may further empower deliria and hallucinations, giving internal reality the appearance of external reality