Eye tracking using markov models

We propose an eye detection and tracking method based on color and geometrical features of the human face using a monocular camera. In this method a decision is made on whether the eyes are closed or not and, using a Markov chain framework to model temporal evolution, the subject's gaze is determined. The method can successfully track facial features even while the head assumes various poses, so long as the nostrils are visible to the camera. We compare our method with recently proposed techniques and results show that it provides more accurate tracking and robustness to variations in view of the face. A procedure for detecting tracking errors is employed to recover the loss of feature points in case of occlusion or very fast head movement. The method may be used in monitoring a driver's alertness and detecting drowsiness, and also in applications requiring non-contact human computer interaction

Identifying important individual‐ and country‐level predictors of conspiracy theorizing: a machine learning analysis

Psychological research on the predictors of conspiracy theorizing—explaining important social and political events or circumstances as secret plots by malevolent groups—has flourished in recent years. However, research has typically examined only a small number of predictors in one, or a small number of, national contexts. Such approaches make it difficult to examine the relative importance of predictors, and risk overlooking some potentially relevant variables altogether. To overcome this limitation, the present study used machine learning to rank-order the importance of 115 individual- and country-level variables in predicting conspiracy theorizing. Data were collected from 56,072 respondents across 28 countries during the early weeks of the COVID-19 pandemic. Echoing previous findings, important predictors at the individual level included societal discontent, paranoia, and personal struggle. Contrary to prior research, important country-level predictors included indicators of political stability and effective government COVID response, which suggests that conspiracy theorizing may thrive in relatively well-functioning democracies

Automated Posterior Cranial Fossa Volumetry by MRI: Applications to Chiari Malformation Type I

BACKGROUND AND PURPOSE: Quantification of PCF volume and the degree of PCF crowdedness were found beneficial for differential diagnosis of tonsillar herniation and prediction of surgical outcome in CMI. However, lack of automated methods limits the clinical use of PCF volumetry. An atlas-based method for automated PCF segmentation tailored for CMI is presented. The method performance is assessed in terms of accuracy and spatial overlap with manual segmentation. The degree of association between PCF volumes and the lengths of previously proposed linear landmarks is reported. MATERIALS AND METHODS: T1-weighted volumetric MR imaging data with 1-mm isotropic resolution obtained with the use of a 3T scanner from 14 patients with CMI and 3 healthy subjects were used for the study. Manually delineated PCF from 9 patients was used to establish a CMI-specific reference for an atlas-based automated PCF parcellation approach. Agreement between manual and automated segmentation of 5 different CMI datasets was verified by means of the t test. Measurement reproducibility was established through the use of 2 repeated scans from 3 healthy subjects. Degree of linear association between PCF volume and 6 linear landmarks was determined by means of Pearson correlation. RESULTS: PCF volumes measured by use of the automated method and with manual delineation were similar, 196.2 ± 8.7 mL versus 196.9 ± 11.0 mL, respectively. The mean relative difference of −0.3 ± 1.9% was not statistically significant. Low measurement variability, with a mean absolute percentage value of 0.6 ± 0.2%, was achieved. None of the PCF linear landmarks were significantly associated with PCF volume. CONCLUSIONS: PCF and tissue content volumes can be reliably measured in patients with CMI by use of an atlas-based automated segmentation method

Normobaric hypoxia and symptoms of acute mountain sickness: Elevated brain volume and intracranial hypertension

Objective The study was undertaken to determine whether normobaric hypoxia causes elevated brain volume and intracranial pressure in individuals with symptoms consistent with acute mountain sickness (AMS). Methods Thirteen males age�=�(26 (sd 6)) years were exposed to normobaric hypoxia (12% O2) and normoxia (21% O2). After 2 and 10 hours, AMS symptoms were assessed alongside ventricular and venous vessel volumes, cerebral blood flow, regional brain volumes, and intracranial pressure, using high-resolution magnetic resonance imaging. Results In normoxia, neither lateral ventricular volume (R2�=�0.07, p�=�0.40) nor predominance of unilateral transverse venous sinus drainage (R2�=�0.07, p�=�0.45) was related to AMS symptoms. Furthermore, despite an increase in cerebral blood flow after 2 hours of hypoxia (hypoxia vs normoxia: �148ml/min�1, 95% confidence interval [CI]�=�58 to 238), by 10 hours, when AMS symptoms had developed, cerebral blood flow was normal (��51ml/min�1, 95% CI�=��141 to 39). Conversely, at 10 hours brain volume was increased (�59ml, 95% CI�=�8 to 110), predominantly due to an increase in gray matter volume (�73ml, 95% CI�=�25 to 120). Therefore, cerebral spinal fluid volume was decreased (��40ml, 95% CI�=��67 to �14). The intracranial pressure response to hypoxia varied between individuals, and as hypothesized, the most AMS-symptomatic participants had the largest increases in intracranial pressure (AMS present, �7mmHg, 95% CI�=��2.5 to 17.3; AMS not present, ��1mmHg, 95% CI�=��3.3 to 0.5). Consequently, there was a significant relationship between the change in intracranial pressure and AMS symptom severity (R2�=�0.71, p�=�0.002). Interpretation The data provide the strongest evidence to date to support the hypothesis that the �random� nature of AMS symptomology is explained by a variable intracranial pressure response to hypoxia. ANN NEUROL 201

Knockdown of type 3 iodothyronine deiodinase severely perturbs both embryonic and early larval development in zebrafish

Exposure to appropriate levels of thyroid hormones (THs) at the right time is of key importance for normal development in all vertebrates. Type 3 iodothyronine deiodinase (D3) is the prime TH-inactivating enzyme, and its expression is highest in the early stages of vertebrate development, implying that it may be necessary to shield developing tissues from overexposure to THs. We used antisense morpholino knockdown to examine the role of D3 during early development in zebrafish. Zebrafish possess 2 D3 genes, dio3a and dio3b. Here, we show that both genes are expressed during development and both contribute to in vivo D3 activity. However, dio3b mRNA levels inembryosare higher, and the effects of dio3b knockdownonD3activityandonthe resulting phenotype are more severe. D3 knockdown induced an overall delay in development, as determined by measurements of otic vesicle length, eye and ear size, and body length. The time of hatching was also severely delayed in D3-knockdown embryos. Importantly, we also observed a severe disturbance of several aspects of development. Swim bladder development and inflation was aberrant as was the development of liver and intestine. Furthermore, D3-knockdown larvae spent significantly less time moving, and both embryos and larvae exhibited perturbed escape responses, suggesting that D3 knockdown affects muscle development and/or functioning. These data indicate that D3 is essential for normal zebrafish embryonic and early larval development and show the value of morpholino knockdown in this model to further elucidate the specific role of D3 in some aspects of vertebrate development. Copyrigh