Face recognition ability is manifest in early dynamic decoding of face-orientation selectivity – evidence from multi-variate pattern analysis of the neural response

Although humans are considered to be face experts, there is a well-established reliable variation in the degree to which neurotypical individuals are able to learn and recognise faces. While many behavioural studies have characterised these differences, studies that seek to relate the neuronal response to standardised behavioural measures of ability remain relatively scarce, particularly so for the time-resolved approaches and the early response to face stimuli. In the present study we make use of a relatively recent methodological advance, multi-variate pattern analysis (MVPA), to decode the time course of the neural response to faces compared to other object categories (inverted faces, objects). Importantly, for the first time, we directly relate metrics of this decoding assessed at the individual level to gold-standard measures of behavioural face processing ability assessed in an independent task. Thirty-nine participants completed the behavioural Cambridge Face Memory Test (CFMT), then viewed images of faces and houses (presented upright and inverted) while their neural activity was measured via electroencephalography. Significant decoding of both face orientation and face category were observed in all individual participants. Decoding of face orientation, a marker of more advanced face processing, was earlier and stronger in participants with higher levels of face expertise, while decoding of face category information was earlier but not stronger for individuals with greater face expertise. Taken together these results provide a marker of significant differences in the early neuronal response to faces from around 100ms post stimulus as a function of behavioural expertise with faces

Infrared absorption spectra, radiative efficiencies, and global warming potentials of perfluorocarbons: Comparison between experiment and theory

Experimentally and theoretically determined infrared spectra are reported for a series of straight-chain perfluorocarbons: C2F6, C3F8, C4F10, C5F12, C6F14, and C8F18. Theoretical spectra were determined using both density functional (DFT) and ab initio methods. Radiative efficiencies (REs) were determined using the method of Pinnock et al. (1995) and combined with atmospheric lifetimes from the literature to determine global warming potentials (GWPs). Theoretically determined absorption cross sections were within 10% of experimentally determined values. Despite being much less computationally expensive, DFT calculations were generally found to perform better than ab initio methods. There is a strong wavenumber dependence of radiative forcing in the region of the fundamental C-F vibration, and small differences in wavelength between band positions determined by theory and experiment have a significant impact on the REs. We apply an empirical correction to the theoretical spectra and then test this correction on a number of branched chain and cyclic perfluoroalkanes. We then compute absorption cross sections, REs, and GWPs for an additional set of perfluoroalkenes

Effects of expectation on face perception and its association with expertise

Perceptual decisions are derived from the combination of priors and sensorial input. While priors are broadly understood to reflect experience/expertise developed over one’s lifetime, the role of perceptual expertise at the individual level has seldom been directly explored. Here, we manipulate probabilistic information associated with a high and low expertise category (faces and cars respectively), while assessing individual level of expertise with each category. 67 participants learned the probabilistic association between a color cue and each target category (face/car) in a behavioural categorization task. Neural activity (EEG) was then recorded in a similar paradigm in the same participants featuring the previously learned contingencies without the explicit task. Behaviourally, perception of the higher expertise category (faces) was modulated by expectation. Specifically, we observed facilitatory and interference effects when targets were correctly or incorrectly expected, which were also associated with independently measured individual levels of face expertise. Multivariate pattern analysis of the EEG signal revealed clear effects of expectation from 100 ms post stimulus, with significant decoding of the neural response to expected vs. not stimuli, when viewing identical images. Latency of peak decoding when participants saw faces was directly associated with individual level facilitation effects in the behavioural task. The current results not only provide time sensitive evidence of expectation effects on early perception but highlight the role of higher-level expertise on forming priors

Transmitting and decoding facial expressions of emotion during healthy aging: more similarities than differences

Older adults tend to perform more poorly than younger adults on emotional expression identification tasks. The goal of the present study was to test a processing mechanism that might explain these differences in emotion recognition – specifically, age-related variation in the utilization of specific visual cues. Seventeen younger and 17 older adults completed a reverse correlation emotion categorization task (Bubbles paradigm), consisting of a large number of trials in each of which only part of the visual information used to convey an emotional facial expression was revealed to participants. The task allowed us to pinpoint the visual features each group used systematically to correctly recognize the emotional expressions shown. To address the possibility that faces of different age groups are differently processed by younger and older adults, we included younger, middle-aged, and older adult face models displaying happy, fearful, angry, disgusted, and sad facial expressions. Our results reveal strong similarity in the utilization of visual information by younger and older adult participants in decoding the emotional expressions from faces across ages – particularly for happy and fear emotions. These findings suggest that age-related differences in strategic information use are unlikely to contribute to the decline of facial expression recognition skills observed in later life

Disturbed YouTube for kids: characterizing and detecting inappropriate videos targeting young children

A large number of the most-subscribed YouTube channels target children of very young age. Hundreds of toddler-oriented channels on YouTube feature inoffensive, well produced, and educational videos. Unfortunately, inappropriate content that targets this demographic is also common. YouTube’s algorithmic recommendation system regrettably suggests inappropriate content because some of it mimics or is derived from otherwise appropriate content. Considering the risk for early childhood development, and an increasing trend in toddler’s consumption of YouTube media, this is a worrisome problem. In this work, we build a classifier able to discern inappropriate content that targets toddlers on YouTube with 84:3% accuracy, and leverage it to perform a first-of-its-kind, large-scale, quantitative characterization that reveals some of the risks of YouTube media consumption by young children. Our analysis reveals that YouTube is still plagued by such disturbing videos and its currently deployed counter-measures are ineffective in terms of detecting them in a timely manner. Alarmingly, using our classifier we show that young children are not only able, but likely to encounter disturbing videos when they randomly browse the platform starting from benign videos.Accepted manuscrip

Disturbed YouTube for kids: characterizing and detecting inappropriate videos targeting young children

A large number of the most-subscribed YouTube channels target children of very young age. Hundreds of toddler-oriented channels on YouTube feature inoffensive, well produced, and educational videos. Unfortunately, inappropriate content that targets this demographic is also common. YouTube’s algorithmic recommendation system regrettably suggests inappropriate content because some of it mimics or is derived from otherwise appropriate content. Considering the risk for early childhood development, and an increasing trend in toddler’s consumption of YouTube media, this is a worrisome problem. In this work, we build a classifier able to discern inappropriate content that targets toddlers on YouTube with 84:3% accuracy, and leverage it to perform a first-of-its-kind, large-scale, quantitative characterization that reveals some of the risks of YouTube media consumption by young children. Our analysis reveals that YouTube is still plagued by such disturbing videos and its currently deployed counter-measures are ineffective in terms of detecting them in a timely manner. Alarmingly, using our classifier we show that young children are not only able, but likely to encounter disturbing videos when they randomly browse the platform starting from benign videos.Accepted manuscrip

Variability in face recognition ability: insights from social motivation, early perception and neural correlates

Face perception is arguably the most important aspect of non-verbal social cognition. Over the last decade, it has become increasingly apparent that between those with prosopagnosia and so called ‘super recognisers’, exists a normally distributed continuum of face recognition ability, within the wider neurotypical population. This thesis explores potential drivers of this variability and associated neural underpinnings. Chapter One investigates the theoretical background of these claims, in addition to discussing the current literature that motivates subsequent empirical Chapters. In Chapter Two, the assumption that socially motivated behaviour, which in turn, mediates increased experience and therefore, expertise with faces, is explored. Across two experiments, a behavioural economics style paradigm is utilised; first, in a large cohort, at the London Science Museum and subsequently repeated (AsPredicted#11359), in a smaller, but highly controlled laboratory setting. Here, the assumption that increased social motivation is associated with better face recognition performance is tested. In Chapter Three, the claim that early perceptual filtering mechanisms are related to face recognition ability is investigated. Here, a breaking Continuous Flash Suppression paradigm is utilised, to explore whether better face recognisers experience preferential access to awareness when compared with worse face recognisers. Findings are then replicated and extended in a second experiment. In Chapter Four, I review recent evidence that suggests that a greater reliance on the eye-region is a predictor of face recognition ability. Across two experiments, I again utilise a behavioural economic style key-pressing paradigm, this time employed to investigate motivated viewing behaviour, for individual face features. Again, a replication (AsPredicted#17150) and extension is attempted using more robust control conditions. In Chapter Five, I review the literature pertaining to possible neural correlates associated with face recognition variability. Here, across two electroencephalography experiments, I combine traditional Event Related Potential techniques (targeting the N170 & P100), with sophisticated multivariate pattern analysis machine learning. In experiment one, classifiers are trained to decode face orientation, independently, in better and worse face recognisers. In a second experiment, I again utilise machine learning to train classifiers to decode between face-parts and corresponding house parts, again, across face recognition groups. Chapter Six summarises the experiments presented in this thesis, identifies common themes and outlines their implications regarding potential contributory factors of face recognition variability as well as potential limitations and future research directions

Relative and absolute quantification of aberrant and normal splice variants in hbb^{ivsi−110 (G > a)} β-thalassemia

The β-thalassemias are an increasing challenge to health systems worldwide, caused by absent or reduced β-globin (HBB) production. Of particular frequency in many Western countries is HBBIVSI−110(G > A) β-thalassemia (HGVS name: HBB:c.93-21G > A). Its underlying mutation creates an abnormal splice acceptor site in the HBB gene, and while partially retaining normal splicing of HBB, it severely reduces HBB protein expression from the mutant locus and HBB loci in trans. For the assessment of the underlying mechanisms and of therapies targeting β-thalassemia, accurate quantification of aberrant and normal HBB mRNA is essential, but to date, has only been performed by approximate methods. To address this shortcoming, we have developed an accurate, duplex reverse-transcription quantitative PCR assay for the assessment of the ratio and absolute quantities of normal and aberrant mRNA species as a tool for basic and translational research of HBBIVSI−110(G > A) β-thalassemia. The method was employed here to determine mRNA ratios and quantities in blood and primary cell culture samples and correlate them with HBB protein levels. Moreover, with its immediate utility for β-thalassemia and the mutation in hand, the approach can readily be adopted for analysis of alternative splicing or for quantitative assays of any disease-causing mutation that interferes with normal splicing

Unravelling the Complexity of the +33 C>G [HBB:c.-18C>G] Variant in Beta Thalassemia

The +33 C>G variant [NM_000518.5(HBB):c.-18C>G] in the 5′ untranslated region (UTR) of the β-globin gene is described in the literature as both mild and silent, while it causes a phenotype of thalassemia intermedia in the presence of a severe β-thalassemia allele. Despite its potential clinical significance, the determination of its pathogenicity according to established standards requires a greater number of published cases and co-segregation evidence than what is currently available. The present study provides an extensive phenotypic characterization of +33 C>G using 26 heterozygous and 11 compound heterozygous novel cases detected in Cyprus and employs computational predictors (CADD, RegulomeDB) to better understand its impact on clinical severity. Genotype identification of globin gene variants, including α- and δ-thalassemia determinants, and rs7482144 (XmnI) was carried out using Sanger sequencing, gap-PCR, and restriction enzyme digestion methods. The heterozygous state of +33 C>G had a silent phenotype without apparent microcytosis or hypochromia, while compound heterozygosity with a β+ or β0 allele had a spectrum of clinical phenotypes. Awareness of the +33 C>G is required across Mediterranean populations where β-thalassemia is frequent, particularly in Cyprus, with significant relevance in population screening and fetal diagnostic applications