The role of spatial and temporal information in biological motion perception

Point-light biological motion stimuli provide spatio-temporal information about the structure of the human body in motion. Manipulation of the spatial structure of point-light stimuli reduces the ability of human observers to perceive biological motion. A recent study has reported that interference with the spatial structure of pointlight walkers also reduces the evoked eventrelated potentials over the occipitotemporal cortex, but that interference with the temporal structure of the stimuli evoked event-related potentials similar to normal biological motion stimuli. We systematically investigated the influence of spatial and temporal manipulation on 2 common discrimination tasks and compared it with predictions of a neurocomputational model previously proposed. This model first analyzes the spatial structure of the stimulus independently of the temporal information to derive body posture and subsequently analyzes the temporal sequence of body postures to derive movement direction. Similar to the model predictions, the psychophysical results show that human observers need only intact spatial configuration of the stimulus to discriminate the facing direction of a point-light walker. In contrast, movement direction discrimination needs a fully intact spatiotemporal pattern of the stimulus. The activation levels in the model predict the observed eventrelated potentials for the spatial and temporal manipulations

The PDZ domain of the SpoIVB serine peptidase facilitates multiple functions

During spore formation in Bacillus subtilis, the SpoIVB protein is a critical component of the sigma (K) regulatory checkpoint. SpoIVB has been shown to be a serine peptidase that is synthesized in the spore chamber and which self-cleaves, releasing active forms. These forms can signal proteolytic processing of the transcription factor sigma (K) in the outer mother cell chamber of the sporulating cell. This forms the basis of the sigma (K) checkpoint and ensures accurate sigma (K)-controlled gene expression. SpoIVB has also been shown to activate a second distinct process, termed the second function, which is essential for the formation of heat-resistant spores. In addition to the serine peptidase domain, SpoIVB contains a PDZ domain. We have altered a number of conserved residues in the PDZ domain by site-directed mutagenesis and assayed the sporulation phenotype and signaling properties of mutant SpoIVB proteins. Our work has revealed that the SpoIVB PDZ domain could be used for up to four distinct processes, (i) targeting of itself for trans proteolysis, (11) binding to the protease inhibitor BofC, (iii) signaling of pro-sigma (K) processing, and (iv) signaling of the second function of SpoIVB

Increased toxin expression in a Clostridium difficile mfd mutant

BACKGROUND: The symptoms of Clostridium difficile infection are mediated primarily by two toxins, TcdA and TcdB, the expression of which is governed by a multitude of factors including nutrient availability, growth phase and cell stress. Several global regulators have been implicated in the regulation of toxin expression, such as CcpA and CodY. RESULTS: During attempts to insertionally inactivate a putative secondary cell wall polysaccharide synthesis gene, we obtained several mutants containing off-target insertions. One mutant displayed an unusual branched colony morphology and was investigated further. Marker recovery revealed an insertion in mfd, a gene encoding a transcription-coupled repair factor. The mfd mutant exhibited pleiotropic effects, in particular increased expression of both toxin A and B (TcdA and TcdB) compared to the parental strain. Western blotting and cellular cytotoxicity assays revealed increased expression across all time points over a 24 h period, with inactivation of mfd resulting in at least a 10 fold increase in cell cytotoxicity. qRT-PCR demonstrated the upregulation of both toxins occurred on a transcriptional level. All effects of the mfd mutation were complemented by a plasmid-encoded copy of mfd, showing the effects are not due to polar effects of the intron insertion or to second site mutations. CONCLUSIONS: This study adds Mfd to the repertoire of factors involved in regulation of toxin expression in Clostridium difficile. Mfd is known to remove RNA polymerase molecules from transcriptional sites where it has stalled due to repressor action, preventing transcriptional read through. The consistently high levels of toxin in the C. difficile mfd mutant indicate this process is inefficient leading to transcriptional de-repression

In-Space Propulsion: Connectivity to In-Space Fabrication and Repair

The connectivity between new in-space propulsion technologies and the ultimate development of an in-space fabrication and repair infrastructure are described in this Technical Memorandum. A number of advanced in-space propulsion technologies are being developed by NASA, many of which are directly relevant to the establishment of such an in-space infrastructure. These include aerocapture, advanced solar-electric propulsion, solar-thermal propulsion, advanced chemical propulsion, tethers, and solar photon sails. Other, further-term technologies have also been studied to assess their utility to the development of such an infrastructure

Psychological characteristics of children with visual impairments: learning, memory and imagery

The performance of children (and sometimes adults) with visual impairments (VI) on a range of tasks that reflect learning, memory and mental imagery is considered in this article. Sometimes the evidence suggests that there are impairments in performance in comparison with typically developing children with vision and sometimes some advantages emerge. The author’s aim is to describe some of her own and others’ findings and explore what they tell us about the cognitive characteristics of such children, so that progress with practical interventions can be advanced through understanding. The article starts by focusing on social-cognitive development and in particular considers the potential benefits of language in that development. This is followed by a review of some studies of learning and memory performance which provide a coherent picture of development without vision and finally ends with a consideration of spatial mental imagery

Influences of Neural Pathway Integrity on Children's Response to Reading Instruction

As the education field moves toward using responsiveness to intervention to identify students with disabilities, an important question is the degree to which this classification can be connected to a student's neurobiological characteristics. A few functional neuroimaging studies have reported a relationship between activation and response to instruction; however, whether a similar correlation exists with white matter (WM) is not clear. To investigate this issue, we acquired high angular resolution diffusion images from a group of first grade children who differed in their levels of responsiveness to a year-long reading intervention. Using probabilistic tractography, we calculated the strength of WM connections among nine cortical regions of interest and correlated these estimates with participants’ scores on four standardized reading measures. We found eight significant correlations, four of which were connections between the insular cortex and angular gyrus. In each of the correlations, a relationship with children's response to intervention was evident

Direct and indirect contributions of executive function to word decoding and reading comprehension in kindergarten

Extant research is increasingly recognizing the contribution of executive function (EF) to reading comprehension alongside established predictors like word decoding and oral language. The nature of the association between EF and reading comprehension is commonly investigated in older children and in those with reading impairments. However, less is known about this relationship in emerging readers in kindergarten, where word decoding and reading comprehension are highly intertwined. Moreover, a better understanding of the mechanisms by which EF influences reading comprehension is needed. The present study investigated direct contributions of EF to reading comprehension, as well as indirect contributions via word decoding in 97 kindergarteners. Results indicated that there was a significant indirect effect of EF on reading comprehension, with word decoding mediating this association. The direct contribution of EF to reading comprehension was not significant. Implications for reading instruction and intervention for early readers are discussed.NICHDUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD) [R01HD078351, R01HD086168, R01HD096261, R01HD094834, P50HD052120]; National Science FoundationNational Science Foundation (NSF) [NSF-1540854]; University of California Office of the President Multicampus Research Programs and Initiatives AwardUniversity of California System [MRP-17-454925]; Oak Foundation [ORIO-16-012, OCAY-19-215]; UCSF Dyslexia Center; Dyslexia Training Institute; The Potter Family; ALTA; San Mateo County of Education; IMBES; SfN; Hyde Park Day School; University of Chicago Laboratory Schools24 month embargo; published online: 25 September 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Detecting the direction of a signal on high-dimensional spheres: Non-null and Le Cam optimality results

We consider one of the most important problems in directional statistics, namely the problem of testing the null hypothesis that the spike direction $\theta$ of a Fisher-von Mises-Langevin distribution on the $p$-dimensional unit hypersphere is equal to a given direction $\theta_0$. After a reduction through invariance arguments, we derive local asymptotic normality (LAN) results in a general high-dimensional framework where the dimension $p_n$ goes to infinity at an arbitrary rate with the sample size $n$, and where the concentration $\kappa_n$ behaves in a completely free way with $n$, which offers a spectrum of problems ranging from arbitrarily easy to arbitrarily challenging ones. We identify various asymptotic regimes, depending on the convergence/divergence properties of $(\kappa_n)$, that yield different contiguity rates and different limiting experiments. In each regime, we derive Le Cam optimal tests under specified $\kappa_n$ and we compute, from the Le Cam third lemma, asymptotic powers of the classical Watson test under contiguous alternatives. We further establish LAN results with respect to both spike direction and concentration, which allows us to discuss optimality also under unspecified $\kappa_n$. To investigate the non-null behavior of the Watson test outside the parametric framework above, we derive its local asymptotic powers through martingale CLTs in the broader, semiparametric, model of rotationally symmetric distributions. A Monte Carlo study shows that the finite-sample behaviors of the various tests remarkably agree with our asymptotic results.Comment: 47 pages, 4 figure