A Bayesian account of 'hysteria'

This article provides a neurobiological account of symptoms that have been called 'hysterical', 'psychogenic' or 'medically unexplained', which we will call functional motor and sensory symptoms. We use a neurobiologically informed model of hierarchical Bayesian inference in the brain to explain functional motor and sensory symptoms in terms of perception and action arising from inference based on prior beliefs and sensory information. This explanation exploits the key balance between prior beliefs and sensory evidence that is mediated by (body focused) attention, symptom expectations, physical and emotional experiences and beliefs about illness. Crucially, this furnishes an explanation at three different levels: (i) underlying neuromodulatory (synaptic) mechanisms; (ii) cognitive and experiential processes (attention and attribution of agency); and (iii) formal computations that underlie perceptual inference (representation of uncertainty or precision). Our explanation involves primary and secondary failures of inference; the primary failure is the (autonomous) emergence of a percept or belief that is held with undue certainty (precision) following top-down attentional modulation of synaptic gain. This belief can constitute a sensory percept (or its absence) or induce movement (or its absence). The secondary failure of inference is when the ensuing percept (and any somatosensory consequences) is falsely inferred to be a symptom to explain why its content was not predicted by the source of attentional modulation. This account accommodates several fundamental observations about functional motor and sensory symptoms, including: (i) their induction and maintenance by attention; (ii) their modification by expectation, prior experience and cultural beliefs and (iii) their involuntary and symptomatic nature

A positive diagnosis of functional (psychogenic) tics

BACKGROUND AND PURPOSE: Functional tics, also called psychogenic tics or pseudo-tics, are difficult to diagnose because of the lack of diagnostic criteria and their clinical similarities to organic tics. The aim of the present study was to report a case series of patients with documented functional tics and to describe their clinical characteristics, risk factors and psychiatric comorbidity. Also clinical tips are suggested which might help the differential diagnosis in clinical practice. METHODS AND RESULTS: Eleven patients (mean age at onset 37.2, SD 13.5; three females) were included with a documented or clinically established diagnosis of functional tics, according to consultant neurologists who have specific expertise in functional movement disorders or in tic disorders. Adult onset, absent family history of tics, inability to suppress the movements, lack of premonitory sensations, absence of pali-, echo- and copro-phenomena, presence of blocking tics, the lack of the typical rostrocaudal tic distribution and the coexistence of other functional movement disorders were common in our patients. CONCLUSIONS: Our data suggest that functional tics can be differentiated from organic tics on clinical grounds, although it is also accepted that this distinction can be difficult in certain cases. Clinical clues from history and examination described here might help to identify patients with functional tics

Symptom severity in patients with functional motor symptoms : patient's perception and doctor's clinical assessment

BACKGROUND: Beliefs and expectations about symptoms and an abnormal direction of attention towards the body have been proposed as important mechanistic factors in the pathophysiology of functional motor symptoms (FMS). We therefore aimed to evaluate patients' awareness/perception of the presence and severity of their own symptoms before and while watching themselves in a video and to compare this with doctors' assessment of the presence and severity of FMS, based on video evaluation. METHODS: We evaluated 16 patients affected by FMS. Patients were invited to give a "subjective evaluation" of their symptoms. Afterwards, patients were invited to watch a video of themselves and to judge the presence of symptoms in the different body parts and, if so, to rate the severity. Patients' videos were also assessed by a rater with expertise in FMS. RESULTS: Patients judged their symptoms to be more severe on subjective evaluation than when viewing a video of themselves (p = 0.002; t = 3.656). Subjective evaluation of symptom severity by patients was higher than that of raters viewing a video of the patient (p < 0.001, t = 4.860), but there was only a trend towards a difference between video ratings of severity by patients and independent raters (p = 0.017, t = 2.962 with p set at 0.016 according to Bonferroni correction). CONCLUSIONS: Our study shows that patients with FMS tend to overestimate the severity of their symptoms compared independent rating. However, when viewing a video of themselves they rated their symptoms as less severe and closer to those of independent raters

Development of SRC-I product analysis. Volume 2. Evaluation of analytical techniques for SRC-I characterization, recycle solvent studies, and product fractionation studies

A data analysis was performed to determine the relationship between the Wilsonville Solvent Quality test result and SRC liquefaction process parameters. The data base studied covers the years 1979 to 1982, Wilsonville runs 133 to 234. Only process-defined material balance data sets were included to best represent steady-state operation. Each material balance period provided 48 variables from which common process conditions were selected by imposing a range of acceptable deviations from a norm, e.g., a reactor hydrogen pressure of 2000 +- 100 psi. Data for all variables vs. solvent quality were plotted, and in some cases variables were compared with each other to determine common trends, e.g. gas production vs. hydrogen consumption. The plotted data produced no discernible trends. Separating the data by coal type (mine location) and identifying common process conditions with coal types still provided no absolute correlations with solvent quality. However, the effect of the weight percent pyrite present in the feed coal produced a consistent trend. A coal containing more than 1.2% pyrite and less than 0.1% sulfate sulfur yielded results in which any one correlation would cluster about a central point. It was observed that, on average, Kentucky Fies and Pyro mine coal and Indiana V coal clustered together, while Kentucky Lafayette and Dotiki mine coals clustered together. These data point clusters for the variables tested were nearly independent of reactor pressure, space rate, and temperature. One unusual observation of all the data points, independent of process conditions, was that at each change of feed coal, the sum of hydrocarbon and heteroatom gas production was greatest for the first 30 days, after which gas production reached a steady state dependent on process conditions, primarily temperature

Development of SRC-I product analysis. Volume 3. Documentation of procedures

This section documents the BASIC computer program written to simulate Wilsonville's GC-simulated distillation (GCSD) results at APCI-CRSD Trexlertown. The GC conditions used at APCI for the Wilsonville GCSD analysis of coal-derived liquid samples were described in the SRC-I Quarterly Technical Report, April-June 1981. The approach used to simulate the Wilsonville GCSD results is also from an SRC-I Quarterly Technical Report and is reproduced in Appendix VII-A. The BASIC computer program is described in the attached Appendix VII-B. Analysis of gases produced during coal liquefaction generates key information needed to determine product yields for material balance and process control. Gas samples from the coal process development unit (CPDU) and tubing bombs are the primary samples analyzed. A Carle gas chromatographic system was used to analyze coal liquefaction gas samples. A BASIC computer program was written to calculate the gas chromatographic peak area results into mole percent results. ICRC has employed several analytical workup procedures to determine the amount of distillate, oils, asphaltenes, preasphaltenes, and residue in SRC-I process streams. The ASE procedure was developed using Conoco's liquid column fractionation (LC/F) method as a model. In developing the ASE procedure, ICRC was able to eliminate distillation, and therefore quantify the oils fraction in one extraction step. ASE results were shown to be reproducible within +- 2 wt %, and to yield acceptable material balances. Finally, the ASE method proved to be the least affected by sample composition