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Background: The entorhinal cortex (EC) is the first cortical region affected by tauopathy in Alzheimer's disease (AD) and is implicated in path integration. In early stages of AD, path integration deficits could be present, even before overt memory deficits. Furthermore, path integration deficits are found among older individuals at risk for AD, such as APOE ε4 carriers. We investigated whether this deficit was related to AD pathology or to APOE genotype using a pure path integration task, the "Apple Game" (Bierbrauer et al. 2020). Method: Participants navigated through a virtual arena and were asked to drop a basket to its initial location after visiting one intermediate location. We recruited 175 clinically normal participants (MMSE>24/30, median age = 65). We genotyped the APOE gene and classified participants as ε4 carriers (n = 60) or non‐carriers (n = 115). We measured the plasma ratio of Aβ42 and Aβ40 using Simoa. We defined a threshold of Aβ42/Aβ40 with a gaussian mixture model to classify participants as Aβ+ (Aβ42/Aβ40<0.047, n = 54) or Aβ‐ (Aβ42/Aβ40> = 0.047, n = 121). We analyzed path integration performance depending on APOE genotype and amyloid status with a linear mixed model including age as covariate. A subset of participants (n = 49) underwent a second generation Tau‐PET (18F‐MK‐6240). Task performance was related to EC tauopathy using a linear mixed model. Results: The path integration performance was lower among older individuals Aβ+ compared to Aβ‐ (Fig.1, p = 0.04). There was no APOE effect after taking Aβ into account. This indicates that path integration performance was more related to Aβ pathology than to APOE genotype. In participants with Tau‐PET, we observed that the angular error, a component of the task performance, increased with the EC Tau signal (Fig.2, p = 0.05). Conclusion: We detected a path integration deficit among clinically normal older individuals that depended on Aβ. Furthermore, path integration performance was related to tauopathy in the EC, possibly reflecting impairment of grid cells. These observations suggest that path integration deficits observed in older individuals carrying an APOE ε4 allele are related to incipient AD pathology. [ABSTRACT FROM AUTHOR]

Estimating sex from burnt human remains is a challenging task in bioanthropology, mainly due to their high level of alteration and fragmentation. Protected within the petrous part of the temporal bone, the bony labyrinth may be particularly valuable for assessing the sex of burnt remains. This prospective study aims at testing predictive models, already found reliable on unburnt bony labyrinths, to burnt specimens. Six discriminant functions were applied on six bony labyrinths of donated adult cadavers of known sex, before and after outdoor burning experiments. Comparisons between unburnt and burnt measurements were executed using Mann–Whitney U tests while shape and size differences induced by fire exposure were examined through a geometric morphometrics (GM) analysis. Predicted sex on unburnt bony labyrinths was consistent with known sex in five cases while a systematic misclassification for males was highlighted on burnt specimens. Higher values of shrinkage were found in males for two measurements included in the equations. GM analysis revealed significant differences in centroid size among males after calcination. Visualization of mean consensus of both female and male bony labyrinths evidenced a reduction in cochlear size and variations in the width and length of semicircular canals of burnt specimens. This exploratory study seems to confirm that designing sex estimation standards specifically for burnt bony labyrinth may be advisable. Understanding how the burning process could impact its morphology is highly recommended through further experiments on larger samples and in controlled environments. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) is associated with cognitive impairment, including spatial disorientation. Disorientation may be an early indicator of AD because spatial navigation relies on entorhinal cortex, the first cortical region affected by AD pathology. To test the hypothesis that spatial navigation declines in preclinical AD, we investigated age and genotype effects on a virtual path integration task, the "Apple Game" (Bierbrauer et al. 2020). Method: Participants navigated in a virtual field and had to drop a basket to their initial location. Difficulty varied according to two parameters: (1) the number of interim locations (distractor) participants had to visit (0, 1, or 2); and (2) the presence or absence of a landmark. We recruited 145 clinically normal participants (MMSE>24/30, median age= 64). We genotyped the apolipoproteinE (APOE) gene, the ε4 allele of which is a risk factor for AD. We classified participants as E4 (n=41) if they had at least one ε4 allele and E3 (n=104) otherwise (table 1). We used linear mixed models to predict the drop error, i.e., the Euclidean distance between the correct and the actual drop location. The two components of the drop error, the angle and distance errors, were analyzed. Results: The drop error increased with age. In trials with no distractor and no landmark, we observed higher drop error for E4 than E3 participants older than 70 years (fig.1), suggesting a deficit in pure path integration for oldest E4 carriers. This deficit was due to higher angle error (fig.2) rather than distance error (fig.3). In trials with distractors, performance dropped to chance level for all participants above 50 years (fig.4), suggesting the task was too difficult in general. In trials with landmark, the error was not influenced by the APOE genotype. Conclusion: This spatial navigation task detected a deficit in pure path integration in elderly E4 carriers, when the task was not too difficult. The deficit may reflect an impairment in grid cells localized in the entorhinal cortex. Indeed, this group has probably the most AD neuropathology brain deposit. By contrast, landmark‐based navigation was impaired with age but not related to AD risk. [ABSTRACT FROM AUTHOR]

In forensic anthropology, sex estimation is a fundamental step in assessing individual biological profiles when analyzing human skeletons. Yet, current methods are not reliable enough to allow an accurate sex identification of highly fragmented, burnt, or subadult remains. This paper aims to investigate sexual dimorphism of the bony labyrinth on both identified subadult and adult individuals. The bony labyrinth is of particular interest for sex estimation since it is alleged to complete size and maturation pre‐pubertally and is located inside the petrous part of the temporal bone which protects it from taphonomic processes. The study was performed on 93 CT scans of identified individuals from two Belgian osteological collections (19–20th century) and from current pediatric images (Erasme hospital, Brussels). Linear and angular measurements were taken on 2D slices of right bony labyrinths. Intra‐ and interobservers error measurements were calculated. Statistical tests were used to unravel any morphological variations between subadult and adult bony labyrinths and to highlight differences between females and males, separately in subadults and adults. Linear discriminant functions were established by cross‐validation and tested on an independent sample from Belgium. Some measurements were significantly different between subadults and adults, and between females and males within both subadult and adult samples. Univariate functions achieved 72.7% in subadults and 68.4% in adults whereas multivariate equations increased accuracy respectively up to 84.9% and 78.4%. This study entails promising results to design a sex estimation method suitable for fragmented and/or subadult remains. Further metric approaches are needed to explore bony labyrinth sexual dimorphism. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The frequently used prediction equations of body mass do not seem appropriate for elderly individuals. Here, we establish the relationship between femoral dimensions and known body mass in elderly individuals in order to develop prediction formulas and identify the factors affecting their accuracy. Materials and Methods: The body mass linear least‐squares regression is based on 17 femoral dimensions, including femoral volume, and 66 individuals. Body proportion and composition effects on accuracy are analyzed by means of the body mass index (BMI) and on a subset sample (n = 25), by means of the masses of adipose, bone and muscle tissues. Results: Most variables significantly reflect body mass. Among them, six dimensions (e.g., biepicondylar breadth, femoral volume, and head femoral diameter) present percent standard errors of estimate ranging from 9.5 to 11% (r = 0.72–0.81) in normal BMI samples. Correlations are clearly lower in samples with normal and abnormal BMI [r = 0.38–0.58; % of standard error of estimate (SEE) = 17.3–19.6%] and not significantly correlated in females (femoral volume) who present high proportions of abnormal BMI and adipose tissue. In the subset, femoral volume is well correlated with bone mass (r = 0.88; %SEE = 7.9%) and lean body mass (r = 0.67; %SEE = 17.2%). Discussion: Our body mass estimation equations for elderly individuals are relevant since relatively low correlations are recurrent in studies using younger individuals of known body mass. However, age, sex, lifestyle, and skeleton considerations of studied populations can provide information about the relevance of the body mass estimation, which is dependent on the BMI classification and the proportion of adipose tissue. Our general considerations can be used for studies of younger individuals. [ABSTRACT FROM AUTHOR]

Keywords: alcohol; bowling; eye movements; pupil; saccades; smooth pursuit EN alcohol bowling eye movements pupil saccades smooth pursuit 1017 1018 2 02/17/21 20210215 NES 210215 Most of us already experienced the consequences of alcohol consumption, if only by observing it. This study sheds new light on the influence of alcohol on human behaviour by reporting a very robust and significant effect of alcohol at ultra-low blood-alcohol levels on eye movements. Alcohol, bowling, eye movements, pupil, saccades, smooth pursuit. [Extracted from the article]

Selective impairment of face recognition following brain damage, as in acquired prosopagnosia, may cause a dramatic loss of diagnosticity of the eye area of the face and an increased reliance on the mouth for identification (Caldara et al., 2005). To clarify the nature of this phenomenon, we measured eye fixation patterns in a case of pure prosopagnosia (PS, Rossion et al., 2003) during her identification of photographs of personally familiar faces (27 children of her kindergarten). Her age-matched colleague served as a control. Consistent with previous evidence, the normal control identified the faces within two fixations located just below the eyes (central upper nose). This pattern (location and duration) of fixations remained unchanged even by increasing difficulty by presenting anti-caricatures of the faces. In contrast, the great majority of the patient's fixations, irrespective of her accuracy, were located on the mouth. Overall, these observations confirm the abnormally reduced processing of the upper area of the face in acquired prosopagnosia. Most importantly, the prosopagnosic patient also fixated the area of the eyes spontaneously in between the first and last fixation, ruling out alternative accounts of her behaviour such as, for example, avoidance or failure to orient attention to the eyes, as observed in autistic or bilateral amygdala patients. Rather, they reinforce our proposal of a high-level perceptual account (Caldara et al., 2005), according to which acquired prosopagnosic patients have lost the ability to represent multiple elements of an individual face as a perceptual unit (holistic face perception). To identify a given face, they focus very precisely on local features rather than seeing the whole of a face from its diagnostic centre (i.e. just below the eyes). The upper area of the face is particularly less attended to and less relevant for the prosopagnosic patient because it contains multiple features that require normal holistic perception in order to be the most diagnostic region. Consequently, prosopagnosic patients develop a more robust representation of the mouth, a relatively isolated feature in the face that may contain more information than any single element of the upper face area, and is thus sampled repeatedly for resolving ambiguity in the process of identification. [ABSTRACT FROM AUTHOR]

Saccades and smooth pursuit eye movements are two different modes of oculomotor control. Saccades are primarily directed toward stationary targets whereas smooth pursuit is elicited to track moving targets. In recent years, behavioural and neurophysiological data demonstrated that both types of eye movements work in synergy for visual tracking. This suggests that saccades and pursuit are two outcomes of a single sensorimotor process that aims at orienting the visual axis. [ABSTRACT FROM AUTHOR]

Selective impairment of face recognition following brain damage, as in acquired prosopagnosia, may cause a dramatic loss of diagnosticity of the eye area of the face and an increased reliance on the mouth for identification (Caldara et al., 2005). To clarify the nature of this phenomenon, we measured eye fixation patterns in a case of pure prosopagnosia (PS, Rossion et al., 2003) during her identification of photographs of personally familiar faces (27 children of her kindergarten). Her age-matched colleague served as a control. Consistent with previous evidence, the normal control identified the faces within two fixations located just below the eyes (central upper nose). This pattern (location and duration) of fixations remained unchanged even by increasing difficulty by presenting anti-caricatures of the faces. In contrast, the great majority of the patient's fixations, irrespective of her accuracy, were located on the mouth. Overall, these observations confirm the abnormally reduced processing of the upper area of the face in acquired prosopagnosia. Most importantly, the prosopagnosic patient also fixated the area of the eyes spontaneously in between the first and last fixation, ruling out alternative accounts of her behaviour such as, for example, avoidance or failure to orient attention to the eyes, as observed in autistic or bilateral amygdala patients. Rather, they reinforce our proposal of a high-level perceptual account (Caldara et al., 2005), according to which acquired prosopagnosic patients have lost the ability to represent multiple elements of an individual face as a perceptual unit (holistic face perception). To identify a given face, they focus very precisely on local features rather than seeing the whole of a face from its diagnostic centre (i.e., just below the eyes). The upper area of the face is particularly less attended to and less relevant for the prosopagnosic patient because it contains multiple features that require normal holistic perception in order to be the most diagnostic region. Consequently, prosopagnosic patients develop a more robust representation of the mouth, a relatively isolated feature in the face that may contain more information than any single element of the upper face area, and is thus sampled repeatedly for resolving ambiguity in the process of identification.