410 research outputs found
Off-shell renormalization of the massive QED in the unitary gauge
Despite its simplicity, the unitary gauge is not a popular choice for
practical loop calculations in gauge theories, due to the lack of off-shell
renormalizability. We study the renormalization properties of the off-shell
Green functions of the elementary electron fields in the massive QED, in order
to elucidate the origin and structure of the extra ultraviolet divergences
which exist only in the unitary gauge. We find that all these divergences
affect the Green functions in a trivial way such that in coordinate space the
off-shell Green functions are in fact multiplicatively renormalizable. This
result may generalize to the abelian and non-abelian Higgs theories, for which
the unitary gauge might bring much simplification to the loop calculations.Comment: LaTeX2e, 7 pages, no figure, minor revision in the introductory
paragrap
Child Advocacy Studies (CAST): A National Movement to Improve the Undergraduate and Graduate Training of Child Protection Professionals
Oscillatory neural networks underlying resting-state, attentional control and social cognition task conditions in children with ASD, ADHD and ASD+ADHD
Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are common and impairing neurodevelopmental disorders that frequently co-occur. The neurobiological mechanisms involved in ASD and ADHD are not fully understood. However, alterations in large-scale neural networks have been proposed as core deficits in both ASD and ADHD and may help to disentangle the neurobiological basis of these disorders and their co-occurrence. In this study, we examined similarities and differences in large-scale oscillatory neural networks between boys aged 8-13 years with ASD (n = 19), ADHD (n = 18), ASD + ADHD (n = 29) and typical development (Controls, n = 26). Oscillatory neural networks were computed using graph-theoretical methods from electroencephalographic (EEG) data collected during an eyes-open resting-state and attentional control and social cognition tasks in which we previously reported disorder-specific atypicalities in oscillatory power and event-related potentials (ERPs). We found that children with ASD showed significant hypoconnectivity in large-scale networks during all three task conditions compared to children without ASD. In contrast, children with ADHD showed significant hyperconnectivity in large-scale networks during the attentional control and social cognition tasks, but not during the resting-state, compared to children without ADHD. Children with co-occurring ASD + ADHD did not differ from children with ASD when paired with this group and vice versa when paired with the ADHD group, indicating that these children showed both ASD-like hypoconnectivity and ADHD-like hyperconnectivity. Our findings suggest that ASD and ADHD are associated with distinct alterations in large-scale oscillatory networks, and these atypicalities present together in children with both disorders. These alterations appear to be task-independent in ASD but task-related in ADHD, and may underlie other neurocognitive atypicalities in these disorders. [Abstract copyright: Copyright © 2019 Elsevier Ltd. All rights reserved.
Uncovering neurodevelopmental paths to Autism Spectrum Disorder through an integrated analysis of developmental measures and neural sensitivity to faces
Background: Autism Spectrum Disorder (ASD) is highly
heterogeneous in etiology and manifestation. The
neurobiological processes underlying ASD development are
reflected in multiple features, from behavior and cognition to
brain functioning. An integrated analysis of these features
may optimize the identification of these processes.
Methods: We examined cognitive and adaptive functioning, and
ASD symptoms between 8 and 36 months in 161 infants at
familial high-risk for ASD (HR) and 71 low-risk controls (LR),
and neural sensitivity to eye-gaze at 8 months in a subsample
of 140 HR and 61 LR. We used linked independent component
analysis to extract patterns of variation across domains and
development, and selected the patterns significantly
associated with clinical classification at 36 months.
Results: An early process at 8 months, indicating high levels
of functioning and low levels of symptoms linked to higher
attention to gaze shifts, was reduced in infants who developed
ASD. A longitudinal process of increasing functioning and low
levels of symptoms was reduced in infants who developed ASD,
while another process suggesting a stagnation in cognitive
functioning at 24 months was increased in infants who
developed ASD.
Limitations: Although results show a clear significant trend
relating to clinical classification, there was substantial
overlap between groups.
Conclusions: We uncovered underlying processes acting together
early in development and associated with clinical outcome.
Results highlight the complexity of emerging ASD, which goes
beyond the borders of clinical categories. Future work should
integrate genetic data to investigate the specific genetic
risks linked to these processes
Sea anemones may thrive in a high CO2 world
Increased seawater pCO 2, and in turn 'ocean acidification' (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef-forming corals (Class: Anthozoa) that appear particularly susceptible to OA via reduced net calcification. However, here we show that OA-like conditions can simultaneously enhance the ecological success of non-calcifying anthozoans, which not only play key ecological and biogeochemical roles in present day benthic ecosystems but also represent a model organism should calcifying anthozoans exist as less calcified (soft-bodied) forms in future oceans. Increased growth (abundance and size) of the sea anemone (Anemonia viridis) population was observed along a natural CO 2 gradient at Vulcano, Italy. Both gross photosynthesis (P G) and respiration (R) increased with pCO 2 indicating that the increased growth was, at least in part, fuelled by bottom up (CO 2 stimulation) of metabolism. The increase of P G outweighed that of R and the genetic identity of the symbiotic microalgae (Symbiodinium spp.) remained unchanged (type A19) suggesting proximity to the vent site relieved CO 2 limitation of the anemones' symbiotic microalgal population. Our observations of enhanced productivity with pCO 2, which are consistent with previous reports for some calcifying corals, convey an increase in fitness that may enable non-calcifying anthozoans to thrive in future environments, i.e. higher seawater pCO 2. Understanding how CO 2-enhanced productivity of non- (and less-) calcifying anthozoans applies more widely to tropical ecosystems is a priority where such organisms can dominate benthic ecosystems, in particular following localized anthropogenic stress. © 2012 Blackwell Publishing Ltd
Autism diagnosis differentiates neurophysiological responses to faces in adults with tuberous sclerosis complex
- Background: Autism spectrum disorder (ASD) is a common and highly heritable neurodevelopmental disorder that is likely to be the outcome of complex aetiological mechanisms. One strategy to provide insight is to study ASD within tuberous sclerosis complex (TSC), a rare disorder with a high incidence of ASD, but for which the genetic cause is determined. Individuals with ASD consistently demonstrate face processing impairments, but these have not been examined in adults with TSC using event-related potentials (ERPs) that are able to capture distinct temporal stages of processing.
- Methods: For adults with TSC (n = 14), 6 of which had a diagnosis of ASD, and control adults (n = 13) passively viewed upright and inverted human faces with direct or averted gaze, with concurrent EEG recording. Amplitude and latency of the P1 and N170 ERPs were measured.
- Results: Individuals with TSC + ASD exhibited longer N170 latencies to faces compared to typical adults. Typical adults and adults with TSC-only exhibited longer N170 latency to inverted versus upright faces, whereas individuals with TSC + ASD did not show latency differences according to face orientation. In addition, individuals with TSC + ASD showed increased N170 latency to averted compared to direct gaze, which was not demonstrated in typical adults. A reduced lateralization was shown for the TSC + ASD groups on P1 and N170 amplitude.
- Conclusions: The findings suggest that individuals with TSC + ASD may have similar electrophysiological abnormalities to idiopathic ASD and are suggestive of developmental delay. Identifying brain-based markers of ASD that are similar in TSC and idiopathic cases is likely to help elucidate the risk pathways to ASD
Association of Polygenic Liability for Autism with face-sensitive cortical responses from infancy
This cohort study investigates whether N290 latency to faces vs nonfaces is associated with autism polygenic scores and cross-disorder polygenic scores in infants with and without a family history of autism
Event-Related Potentials and Emotion Processing in Child Psychopathology
In recent years there has been increasing interest in the neural mechanisms underlying altered emotional processes in children and adolescents with psychopathology. This review provides a brief overview of the most up-to-date findings in the field of Event-Related Potentials (ERPs) to facial and vocal emotional expressions in the most common child psychopathological conditions. In regards to externalising behaviour (i.e. ADHD, CD), ERP studies show enhanced early components to anger, reflecting enhanced sensory processing, followed by reductions in later components to anger, reflecting reduced cognitive-evaluative processing. In regards to internalising behaviour, research supports models of increased processing of threat stimuli especially at later more elaborate and effortful stages. Finally, in autism spectrum disorders abnormalities have been observed at early visual-perceptual stages of processing. An affective neuroscience framework for understanding child psychopathology can be valuable in elucidating underlying mechanisms and inform preventive intervention
Internal representations, external representations and ergonomics: towards a theoretical integration
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