Decoding the dynamic representation of facial expressions of emotion in explicit and incidental tasks

Faces transmit a wealth of important social signals. While previous studies have elucidated the network of cortical regions important for perception of facial expression, and the associated temporal components such as the P100, N170 and EPN, it is still unclear how task constraints may shape the representation of facial expression (or other face categories) in these networks. In the present experiment, we used Multivariate Pattern Analysis (MVPA) with EEG to investigate the neural information available across time about two important face categories (expression and identity) when those categories are either perceived under explicit (e.g. decoding facial expression category from the EEG when task is on expression) or incidental task contexts (e.g. decoding facial expression category from the EEG when task is on identity). Decoding of both face categories, across both task contexts, peaked in time-windows spanning 91–170 ms (across posterior electrodes). Peak decoding of expression, however, was not affected by task context whereas peak decoding of identity was significantly reduced under incidental processing conditions. In addition, errors in EEG decoding correlated with errors in behavioral categorization under explicit processing for both expression and identity, but only with incidental decoding of expression. Furthermore, decoding time-courses and the spatial pattern of informative electrodes showed consistently better decoding of identity under explicit conditions at later-time periods, with weak evidence for similar effects for decoding of expression at isolated time-windows. Taken together, these results reveal differences and commonalities in the processing of face categories under explicit Vs incidental task contexts and suggest that facial expressions are processed to a richer degree under incidental processing conditions, consistent with prior work indicating the relative automaticity by which emotion is processed. Our work further demonstrates the utility in applying multivariate decoding analyses to EEG for revealing the dynamics of face perception

Requests for malaria prevention advice to Public Health England, Malaria Reference Laboratory: a retrospective observational study.

BACKGROUND: The Malaria Reference Laboratory (MRL) provides a specialist advisory service for complex queries from healthcare professionals. This study was conducted to examine the types of queries that general practitioners and nurses ask around malaria prophylaxis, to identify issues which are not obvious from existing easily available sources. METHODS: We reviewed all the faxed requests received over a period of 6 months at the MRL. RESULTS: There were a total of 608 queries (104 concerning children) relating to 450 travellers. 98% of requests were from general practice (GP or practice nurse). The most common enquiries were about travellers to multiple destinations (95/529, 17.96%), prolonged duration of travel (70/529, 13.23%), the immunosuppressed (38/529, 7.18%), potential drug interactions (69/529, 13.04%), pregnancy and conception (36, 6.81%). 79/529 queries related to patients with multiple conditions requiring expert advice from the MRL. 27% of the enquiries could have been answered by consulting the UK malaria prophylaxis guidelines available on the MRL site. CONCLUSION: Most queries where practitioners requested help were not easily answered with existing guidelines. Pregnancy and epilepsy are areas where guidance needs strengthening. Difficulties for practitioners were multifactorial, it would be difficult to address all scenarios in guidelines without making them unwieldy

Distinct information critically distinguishes judgments of face familiarity and identity

Accurately determining the familiarity of another and correctly establishing their identity are vital social skills. A considerable body of work has explored their perceptual and neural underpinnings and debate remains regarding whether they are dissociable, i.e., separable parts of a dual process, or different aspects of a common retrieval process. Less is known about the specific visual information that guides familiarity judgments and how this compares to the information used to identify a face by name. Here we sought to establish the critical information underlying participants’ judgments of facial familiarity and identification. We created a new standardized stimulus set comprising 6 personally familiar and 12 unfamiliar faces and applied the Bubbles reverse-correlation methodology to establish the information driving correct performance in each task. Results revealed that markedly different information underlies familiarity and identity judgments. When categorizing familiarity, participants relied more upon lower spatial-frequency, broad facial cues (eye and face shape) than when categorizing identity, which relied on fine details in the internal features (eyes and mouth). These results provide novel evidence of qualitatively distinct information use in familiarity and identification judgments and emphasize the importance of considering the task set for participants and their processing strategy when investigating face recognition

Understanding strategic information use during emotional expression judgments in Williams syndrome

Detailed analysis of expression judgments in Williams syndrome reveals that successful emotion categorization need not reflect ‘classic’ information processing strategies. These individuals draw upon a distinct set of featural details to identify happy and fearful faces that differ from those used by typically developing comparison groups: children and adults. The diagnostic visual information is also notably less interlinked in Williams syndrome, consistent with reports of diminished processing of configural information during face identity judgments. These results prompt reconsideration of typical models of face expertise by revealing that an age-appropriate profile of expression performance can be achieved via alternative routes

Distinct profiles of information-use characterize identity judgments in children and low-expertise adults

Face processing abilities vary across the lifespan: increasing across childhood and adolescence, peaking around 30 years of age, and then declining. Despite extensive investigation, researchers have yet to identify qualitative changes in face processing during development that can account for the observed improvements on laboratory tests. The current study constituted the first detailed characterization of face processing strategies in a large group of typically developing children and adults (N=200) using a novel adaptation of the Bubbles reverse correlation technique (Gosselin & Schyns, 2001). Resultant classification images reveal a compelling age-related shift in strategic information-use during participants’ judgments of face identity. This shift suggests a move from an early reliance upon high spatial frequency details around the mouth, eye-brow and jaw-line in young children (~8yrs) to an increasingly more interlinked approach, focused upon the eye region and the center of the face in older children (~11yrs) and adults. Moreover, we reveal that the early vs. late phases of this developmental trajectory correspond with the profiles of information-use observed in weak vs. strong adult face processors. Together, these results provide intriguing new evidence for an important functional role for strategic information-use in the development of face expertise

DIRECT ESTIMATION OF ABOVEGROUND FOREST PRODUCTIVITY THROUGH HYPERSPECTRAL REMOTE SENSING OF CANOPY NITROGEN

The concentration of nitrogen in foliage has been related to rates of net photosynthesis across a wide range of plant species and functional groups and thus represents a simple and biologically meaningful link between terrestrial cycles of carbon and nitrogen. Although foliar N is used by ecosystem models to predict rates of leaf‐level photosynthesis, it has rarely been examined as a direct scalar to stand‐level carbon gain. Establishment of such relationships would greatly simplify the nature of forest C and N linkages, enhancing our ability to derive estimates of forest productivity at landscape to regional scales. Here, we report on a highly predictive relationship between whole‐canopy nitrogen concentration and aboveground forest productivity in diverse forested stands of varying age and species composition across the 360 000‐ha White Mountain National Forest, New Hampshire, USA. We also demonstrate that hyperspectral remote sensing can be used to estimate foliar N concentration, and hence forest production across a large number of contiguous images. Together these data suggest that canopy‐level N concentration is an important correlate of productivity in these forested systems, and that imaging spectrometry of canopy N can provide direct estimates of forest productivity across large landscapes

Developmental changes in the processing of faces as revealed by EEG decoding

Rapidly and accurately processing information from faces is a critical human function that is known to improve with developmental age. Understanding the underlying drivers of this improvement remains a contentious question, with debate continuing as to the presence of early vs. late maturation of face-processing mechanisms. Recent behavioural evidence suggests an important ‘hallmark’ of expert face processing – the face inversion effect – is present in very young children, yet neural support for this remains unclear. To address this, we conducted a detailed investigation of the neural dynamics of face processing in children spanning a range of ages (6 – 11 years) and adults. Uniquely, we applied multivariate pattern analysis (MVPA) to the electroencephalogram signal (EEG) to test for the presence of a distinct neural profile associated with canonical upright faces when compared both to other objects (houses) and to inverted faces. Results revealed robust discrimination profiles, at the individual level, of differentiated neural activity associated with broad face categorization and further with its expert processing, as indexed by the face inversion effect, from the youngest ages tested. This result is consistent with an early functional maturation of broad face processing mechanisms. Yet, clear quantitative differences between the response profile of children and adults is suggestive of age-related refinement of this system with developing face and general expertise. Standard ERP analysis also provides some support for qualitative differences in the neural response to inverted faces in children in contrast to adults. This neural profile is in line with recent behavioural studies that have reported impressively expert early face abilities during childhood, while also providing novel evidence of the ongoing neural specialisation between child and adulthood

Investigation and validation of FDTD weighting function modelling for microwave radiometric temperature measurement

Microwave radiometry can provide a non-invasive, non-destructive and inherently safe method of temperature measurement suitable for a range of medical and industrial applications. The measured radiometric signal is formed by a convolution of the actual material temperature distribution with a coupling spatial response, or weighting function, over the viewed volume of material. The form of this weighting function depends on both the electromagnetic coupling structure (either antenna or cavity) and on the geometry and dielectric properties of the material. Through reciprocity, the weighting function can be found by computation or measurement of the power dissipation distribution (also known as the specific absorption rate (SAR)) when the coupling structure is actively excited. Knowledge of the weighting function is used to interpret the measured radiometric temperature. Chapter 1 introduces the method of microwave radiometry, its range of applications and considers the key features of weighting function determination. The suitability and validity of finite difference time domain (FDTD) SAR and weighting function modelling was investigated for the largely travelling - wave fields appropriate to surface contact antennas. An FDTD simulator, the Basic Electromagnetic Simulation Tool [3], was used to computationally model a range of antenna configurations that could then be compared directly with experimental results. Chapter 2 introduces several numerical techniques and justifies the choice of FDTD modelling. An introduction to the theory of the FDTD technique and a description of the BEST software is also given. Simulations of systems where electromagnetic field distributions are known (or can be determined experimentally) allowed the direct comparison of simulation results with theoretical predictions. Chapters 3 and 4 consider various validation examples; a monopole radiator above ground plane and TEOl waveguide in chapter 3, experimental field determination in lossy dielectrics using the non-resonant perturbation method in chapter 4. In all cases considered, simulation and experiment agree within a reasonable magnitude of error. With the successful validation of its microwave modeling capabilities, the BEST program was then used to predict the weighting functions expected for practical radiometer antennas for microwave temperature measurement. Of primary importance are the variations of the effective coupling distance into the viewed material with dielectric changes, particularly those due to water content, and with measurement frequency. Knowledge of this behaviour is essential for estimating, at one extreme, relatively small but physiologically important temperature gradients within the human body, and at the other extreme, the large and rapidly varying temperature patterns induced during industrial processes. By measuring the microwave temperature at different microwave frequencies, it is possible to retrieve information on the temperature at varying depths within the material. To aid in the interpretation of these measurements, the BEST program was used to ascertain the form of the weighting function at two frequencies, 1.35 GHz and 3.2 GHz, for a specific dual - frequency antenna in a range of phantom materials. The phantom materials were composed of a mixture of water, protein and salts, with the intention being to simulate common biological materials. To consider foodstuffs a mashed potato phantom was used. Chapter 5 includes the design of this dual frequency antenna and its application to measuring the radiometric temperature of non-isothermal mashed potato mixtures. The specific manipulation of the potato mixture (through heating and cooling) to produce known temperature profiles (quasi-linear and quasi-quadratic) is also considered in this chapter. Further validation of the BEST weighting function determination is possible by comparison with these experimental temperature measurements. Chapter 6 initially covers the modelling of the dielectric properties of the mashed potato and protein / saline mixtures. In particular, a model of the variation of the dielectric constant and loss factor of the mashed potato material, covering a wide range of temperatures at 1.35GHz and 3.2GHz, is presented and shown to agree with published literature. The effects on the computed weighting function of variation of several key factors, including measurement frequency and material temperature, are then considered for both phantom types. Further, limitations in the computational modelling in terms of finite bounds and the modelling of layers are investigated. Finally, techniques for obtaining the physical temperature distribution from multi - frequency microwave readings are considered in chapter 7 and their applicability at two frequencies is discussed. By making use of the data collected from the dual - frequency antenna and simulated microwave temperatures, the various methods of temperature profile retrieval are compared

Physical Activity Reduces Hippocampal Atrophy in Elders at Genetic Risk for Alzheimer\u27s Disease

We examined the impact of physical activity (PA) on longitudinal change in hippocampal volume in cognitively intact older adults at varying genetic risk for the sporadic form of Alzheimer\u27s disease (AD). Hippocampal volume was measured from structural magnetic resonance imaging (MRI) scans administered at baseline and at an 18-month follow-up in 97 healthy, cognitively intact older adults. Participants were classified as High or Low PA based on a self-report questionnaire of frequency and intensity of exercise. Risk status was defined by the presence or absence of the apolipoprotein E-epsilon 4 (APOE-ε4) allele. Four subgroups were studied: Low Risk/High PA (n = 24), Low Risk/Low PA (n = 34), High Risk/High PA (n = 22), and High Risk/Low PA (n = 17). Over the 18 month follow-up interval, hippocampal volume decreased by 3% in the High Risk/Low PA group, but remained stable in the three remaining groups. No main effects or interactions between genetic risk and PA were observed in control brain regions, including the caudate, amygdala, thalamus, pre-central gyrus, caudal middle frontal gyrus, cortical white matter (WM), and total gray matter (GM). These findings suggest that PA may help to preserve hippocampal volume in individuals at increased genetic risk for AD. The protective effects of PA on hippocampal atrophy were not observed in individuals at low risk for AD. These data suggest that individuals at genetic risk for AD should be targeted for increased levels of PA as a means of reducing atrophy in a brain region critical for the formation of episodic memories