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Recent advances in computational psychiatry have provided unique insights into the neural and cognitive underpinnings of psychotic symptoms. In particular, a host of new data has demonstrated the utility of computational frameworks for understanding how hallucinations might arise from alterations in typical perceptual processing. Of particular promise are models based in Bayesian inference that link hallucinatory perceptual experiences to latent states that may drive them. In this piece, we move beyond these findings to ask: how and why do these latent states arise, and how might we take advantage of heterogeneity in that process to develop precision approaches to the treatment of hallucinations? We leverage specific models of Bayesian inference to discuss components that might lead to the development of hallucinations. Using the unifying power of our model, we attempt to place disparate findings in the study of psychotic symptoms within a common framework. Finally, we suggest directions for future elaboration of these models in the service of a more refined psychiatric nosology based on predictable, testable, and ultimately treatable information processing derangements., (Copyright © 2022 Elsevier B.V. All rights reserved.)

We constantly exploit the statistical regularities in our environment to help guide our perception. The hippocampus has been suggested to play a pivotal role in both learning environmental statistics, as well as exploiting them to generate perceptual predictions. However, it is unclear how the hippocampus balances encoding new predictive associations with the retrieval of existing ones. Here, we present the results of two high resolution human fMRI studies (N = 24 for both experiments) directly investigating this. Participants were exposed to auditory cues that predicted the identity of an upcoming visual shape (with 75% validity). Using multivoxel decoding analysis, we find that the hippocampus initially preferentially represents unexpected shapes (i.e., those that violate the cue regularities), but later switches to representing the cue-predicted shape regardless of which was actually presented. These findings demonstrate that the hippocampus is involved both acquiring and exploiting predictive associations, and is dominated by either errors or predictions depending on whether learning is ongoing or complete., (© 2022. The Author(s).)

The way we perceive the world is strongly influenced by our expectations. In line with this, much recent research has revealed that prior expectations strongly modulate sensory processing. However, the neural circuitry through which the brain integrates external sensory inputs with internal expectation signals remains unknown. In order to understand the computational architecture of the cortex, we need to investigate the way these signals flow through the cortical layers. This is crucial because the different cortical layers have distinct intra- and interregional connectivity patterns, and therefore determining which layers are involved in a cortical computation can inform us on the sources and targets of these signals. Here, we used ultra-high field (7T) functional magnetic resonance imaging (fMRI) to reveal that prior expectations evoke stimulus-specific activity selectively in the deep layers of the primary visual cortex (V1). These findings are in line with predictive processing theories proposing that neurons in the deep cortical layers represent perceptual hypotheses and thereby shed light on the computational architecture of cortex., Competing Interests: The authors have declared that no competing interests exist.

Perception is a process of inference, integrating sensory inputs with prior expectations. However, little is known regarding the temporal dynamics of this integration. It has been proposed that expectation plays a role early in the perceptual process, biasing sensory processing. Alternatively, others suggest that expectations are integrated only at later, postperceptual decision-making stages. The current study aimed to dissociate between these hypotheses. We exposed human participants (male and female) to auditory cues predicting the likely direction of upcoming moving dot patterns, while recording neural activity using magnetoencephalography (MEG). Participants' reports of the moving dot directions were biased toward the direction predicted by the cues. To investigate when expectations affected sensory representations, we used inverted encoding models to decode the direction represented in early sensory signals. Strikingly, the cues modulated the direction represented in the MEG signal as early as 150 ms after visual stimulus onset. While this may not reflect a modulation of the initial feedforward sweep, it does reveal a modulation of early sensory representations. Exploratory analyses showed that the neural modulation was related to perceptual expectation effects: participants with a stronger perceptual bias toward the predicted direction also revealed a stronger reflection of the predicted direction in the MEG signal. For participants with this perceptual bias, a correlation between decoded and perceived direction already emerged before visual stimulus onset, suggesting that the prestimulus state of the visual cortex influences sensory processing. Together, these results suggest that expectations play an integral role in the neural computations underlying perception. SIGNIFICANCE STATEMENT Perception can be thought of as an inferential process in which our brains integrate sensory inputs with prior expectations to make sense of the world. This study investigated whether this integration occurs early or late in the process of perception. We exposed human participants to auditory cues that predicted the likely direction of visual moving dots, while recording neural activity with millisecond resolution using magnetoencephalography. Participants' perceptual reports of the direction of the moving dots were biased toward the predicted direction. Additionally, the predicted direction modulated the neural representation of the moving dots just 150 ms after they appeared. This suggests that prior expectations affected sensory processing at early stages, playing an integral role in the perceptual process., (Copyright © 2020 Aitken, Turner et al.)

Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type thermodynamic equation of state, which relates the free volume of solvated electrons to temperature, density, and phase dependent internal pressure. The model is first calibrated against known electron mobility reference data along the saturated vapor pressure line and then validated to reproduce the existing mobility literature values as a function of pressure and temperature with at least 10% accuracy. Four different electron mobility regimes are identified: (1) Landau critical velocity limit (T ≈ 0), (2) mobility limited by thermal phonons (T < 0.6 K), (3) thermal phonon and discrete roton scattering ("roton gas") limited mobility (0.6 K < T < 1.2 K), and (4) the viscous liquid ("roton continuum") limit (T > 1.2 K) where the ion solvation structure directly determines the mobility. In the latter regime, the Stokes equation can be used to estimate the hydrodynamic radius of the solvated electron based on its mobility and fluid viscosity. To account for the non-continuum behavior appearing below 1.2 K, the temperature and density dependent Millikan-Cunningham factor is introduced. The hydrodynamic electron bubble radii predicted by the present model appear generally larger than the solvation cavity interface barycenter values obtained from density functional theory (DFT) calculations. Based on the classical Stokes law, this difference can arise from the variation of viscosity and flow characteristics around the electron. The calculated DFT liquid density profiles show distinct oscillations at the vacuum/liquid interface, which increase the interface rigidity.

Evidence for helium excimers (He 2 * ) in the lowest allowed rotational quantum state in liquid helium is presented. He 2 * was generated by a corona discharge in the gas and normal liquid phases. Fluorescence spectra recorded in the visible region between 3.8 and 5.0 K and 0.2 and 5.6 bar showed the rotationally resolved d 3 Σ u + → b 3 Π g transition of He 2 * . Analysis of the pressure and temperature dependence of lineshifts and line intensities showed features of solvated He 2 * superimposed on its gas-phase spectrum and, in the liquid phase only, pressure-induced rotational cooling. These findings suggest that He 2 * can be used to investigate bulk helium in different phases at the nanoscale.

The Orsay-Trento bosonic density functional theory model is extended to include dissipation due to the viscous response of superfluid (4)He present at finite temperatures. The viscous functional is derived from the Navier-Stokes equation by using the Madelung transformation and includes the contribution of interfacial viscous response present at the gas-liquid boundaries. This contribution was obtained by calibrating the model against the experimentally determined electron mobilities from 1.2 K to 2.1 K along the saturated vapor pressure line, where the viscous response is dominated by thermal rotons. The temperature dependence of ion mobility was calculated for several different solvation cavity sizes and the data are rationalized in the context of roton scattering and Stokes limited mobility models. Results are compared to the experimentally observed "exotic ion" data, which provides estimates for the corresponding bubble sizes in the liquid. Possible sources of such ions are briefly discussed.

Medical dosimetry education occupies a specialized branch of allied health higher education. Noted international shortages of health care workers, reduced university funding, limitations on faculty staffing, trends in learner attrition, and increased enrollment of nontraditional students force medical dosimetry educational leadership to reevaluate current admission practices. Program officials wish to select medical dosimetry students with the best chances of successful graduation. The purpose of the quantitative ex post facto correlation study was to investigate the relationship between applicant characteristics (cumulative undergraduate grade point average (GPA), science grade point average (SGPA), prior experience as a radiation therapist, and previous academic degrees) and the successful completion of a medical dosimetry program, as measured by graduation. A key finding from the quantitative study was the statistically significant positive correlation between a student׳s previous degree and his or her successful graduation from the medical dosimetry program. Future research investigations could include a larger research sample, representative of more medical dosimetry student populations, and additional studies concerning the relationship of previous work as a radiation therapist and the effect on success as a medical dosimetry student. Based on the quantitative correlation analysis, medical dosimetry leadership on admissions committees could revise student selection rubrics to place less emphasis on an applicant׳s undergraduate cumulative GPA and increase the weight assigned to previous degrees., (Copyright © 2016 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.)

Positively charged ions were produced in supercritical helium at temperatures from 6 to 10 K and up to 2 MPa using a corona discharge. Their mobility was measured via current-voltage curves, and the hydrodynamic radius was derived using Stokes law. An initial increase and subsequent decrease of hydrodynamic radius was observed and interpreted in terms of growth, compression and solidification of ion clusters. The mobility was modeled using a van der Waals-type thermodynamic state equation for the ion-in-helium mixed system and a temperature-dependent Millikan-Cunningham factor, describing experimental data both in the Knudsen and the Stokes flow region. Regions of maximum hydrodynamic radius and large compressibility were interpreted as boiling points. These points were modeled over a large range of pressures and found to match the Frenkel line of pure helium up to 0.7 MPa, reflecting similarity of density fluctuations in pure supercritical helium and gas-liquid phase transitions of ionic helium clusters.

Positively charged helium clusters, also called 'snowballs', have been investigated within normal liquid helium. Thermodynamic state equations for ionic helium clusters in liquid helium have been developed, allowing us to discern the 'hydrodynamic' radius for a wide range of hydrostatic pressures and temperatures. The mobilities derived from the cluster sizes using stokes law match experimental data with unsurpassed accuracy. For low pressures the compressibility of the cluster ions was found to be distinctly larger than the compressibility of solid helium suggesting that in this pressure range clusters are fully or partially liquid.

Electron mobilities in supercritical and liquid helium were investigated as a function of the density. The mobilities were derived from I(V) curves measured in a high-pressure cryogenic cell using a corona discharge in point-plane electrode geometry for charge generation. The presented data spans a wide pressure and temperature range due to the versatility of our experimental set-up. Where data from previous investigations is available for comparison, very good agreement is found. We present a semi-empirical model to calculate electron mobilities both in the liquid and supercritical phase. This model requires the electron-helium scattering length and thermodynamic state equations as the only input and circumvents any need to consider surface tension. Our semi-empirical model reproduces experimental data very well, in particular towards lower densities where transitions from localised to delocalised electron states were observed.

The experimental results reported in this paper mainly concern the two first transient pressure waves emitted after a fast (approximately ns) and localized (approximately micron) injection of electrical energy Wi in insulating liquids. The influence of various parameters (hydrostatic pressure P infinity, injected energy Wi, etc.) on the relative amplitude of these two transient pressure waves are presented and discussed. The analysis shows clearly a difference of behavior, in particular their dependence as a function of hydrostatic pressure, between these two waves. Basically, the physical processes leading to their emission are quite different. The first pressure transient is a consequence of the plasma relaxation, whereas the second one is due to the bubble collapse. According to these results, the chronology of the events is more improved, as well as the theoretical analysis.

Ultrasound scans were performed on 6 adult males with simple ureteroceles, 2 of which were detected on primary scanning of patients in renal failure and 4 after excretory urography. Two complications were also detected--obstruction with hydro-ureter formation and tumour formation in a ureterocele. A scheme is proposed for differentiating ureteroceles from other causes of bladder filling defects using ultrasound examination.

Forty-seven newborn infants who had umbilical arterial catheterisation were studied prospectively to determine the incidence of arterial thrombus formation. Pull-out angiography was performed on 30 patients at the time of removal of the catheter. Arterial thrombus formation was demonstrated in 9 of the 30, i.e. 30%. No clinical signs referable to thrombus formation were present. There was no statistically significant difference in birthweight or duration of catheterisation between infants who showed thrombus formation and those who did not. At sutopsy, arterial thrombus was found in 5 infants out of 8. The major aortic tributaries were localised by angiography, and the need for the correct placement of the catheter is emphasised.