Extracting spacing-derived estimates of rod density in healthy retinae

Quantification of the rod photoreceptor mosaic using adaptive optics scanning light ophthalmoscopy (AOSLO) remains challenging. Here we demonstrate a method for deriving estimates of rod density and rod:cone ratio based on measures of rod spacing, cone numerosity, and cone inner segment area. Twenty-two AOSLO images with complete rod visualization were used to validate this spacing-derived method for estimating density. The method was then used to estimate rod metrics in an additional 105 images without complete rod visualization. The spacing-derived rod mosaic metrics were comparable to published data from histology. This method could be leveraged to develop large normative databases of rod mosaic metrics, though limitations persist with intergrader variability in assessing cone area and numerosity

Optical Coherence Tomography Artifacts Are Associated With Adaptive Optics Scanning Light Ophthalmoscopy Success in Achromatopsia

Purpose: To determine whether artifacts in optical coherence tomography (OCT) images are associated with the success or failure of adaptive optics scanning light ophthalmoscopy (AOSLO) imaging in subjects with achromatopsia (ACHM). / Methods: Previously acquired OCT and non-confocal, split-detector AOSLO images from one eye of 66 subjects with genetically confirmed achromatopsia (15 CNGA3 and 51 CNGB3) were reviewed along with best-corrected visual acuity (BCVA) and axial length. OCT artifacts in interpolated vertical volumes from CIRRUS macular cubes were divided into four categories: (1) none or minimal, (2) clear and low frequency, (3) low amplitude and high frequency, and (4) high amplitude and high frequency. Each vertical volume was assessed once by two observers. AOSLO success was defined as sufficient image quality in split-detector images at the fovea to assess cone quantity. / Results: There was excellent agreement between the two observers for assessing OCT artifact severity category (weighted kappa = 0.88). Overall, AOSLO success was 47%. For subjects with OCT artifact severity category 1, AOSLO success was 65%; for category 2, 47%; for category 3, 11%; and for category 4, 0%. There was a significant association between OCT artifact severity category and AOSLO success (P = 0.0002). Neither BCVA nor axial length was associated with AOSLO success (P = 0.07 and P = 0.75, respectively). / Conclusions: Artifacts in OCT volumes are associated with AOSLO success in ACHM. Subjects with less severe OCT artifacts are more likely to be good candidates for AOSLO imaging, whereas AOSLO was successful in only 7% of subjects with category 3 or 4 OCT artifacts. These results may be useful in guiding patient selection for AOSLO imaging. / Translational Relevance: Using OCT to prescreen patients could be a valuable tool for clinical trials that utilize AOSLO to reduce costs and decrease patient testing burden

Examining Whether AOSLO-Based Foveal Cone Metrics in Achromatopsia and Albinism Are Representative of Foveal Cone Structure

Purpose: Adaptive optics scanning light ophthalmoscopy (AOSLO) imaging in patients with achromatopsia (ACHM) and albinism is not always successful. Here, we tested whether optical coherence tomography (OCT) measures of foveal structure differed between patients for whom AOSLO images were either quantifiable or unquantifiable. Methods: The study included 166 subjects (84 with ACHM; 82 with albinism) with previously acquired OCT scans, AOSLO images, and best-corrected visual acuity (BCVA, if available). Foveal OCT scans were assessed for outer retinal structure, outer nuclear layer thickness, and hypoplasia. AOSLO images were graded as quantifiable if a peak cone density could be measured and/or usable if the location of peak density could be identified and the parafoveal mosaic was quantifiable. Results: Forty-nine percent of subjects with ACHM and 57% of subjects with albinism had quantifiable AOSLO images. Older age and better BCVA were found in subjects with quantifiable AOSLO images for both ACHM (P = 0.0214 and P = 0.0276, respectively) and albinism (P = 0.0073 and P < 0.0004, respectively). There was a significant trend between ellipsoid zone appearance and ability to quantify AOSLO (P = 0.0028). In albinism, OCT metrics of cone structure did not differ between groups. Conclusions: Previously reported AOSLO-based cone density measures in ACHM may not necessarily reflect the degree of remnant cone structure in these patients. Translational Relevance: Until AOSLO is successful in all patients with ACHM and albinism, the possibility of the reported data from a particular cohort not being representative of the entire population remains an important issue to consider when interpreting results from AOSLO studies

A Generalized Framework for Quantifying the Dynamics of EEG Event-Related Desynchronization

Brains were built by evolution to react swiftly to environmental challenges. Thus, sensory stimuli must be processed ad hoc, i.e., independent—to a large extent—from the momentary brain state incidentally prevailing during stimulus occurrence. Accordingly, computational neuroscience strives to model the robust processing of stimuli in the presence of dynamical cortical states. A pivotal feature of ongoing brain activity is the regional predominance of EEG eigenrhythms, such as the occipital alpha or the pericentral mu rhythm, both peaking spectrally at 10 Hz. Here, we establish a novel generalized concept to measure event-related desynchronization (ERD), which allows one to model neural oscillatory dynamics also in the presence of dynamical cortical states. Specifically, we demonstrate that a somatosensory stimulus causes a stereotypic sequence of first an ERD and then an ensuing amplitude overshoot (event-related synchronization), which at a dynamical cortical state becomes evident only if the natural relaxation dynamics of unperturbed EEG rhythms is utilized as reference dynamics. Moreover, this computational approach also encompasses the more general notion of a “conditional ERD,” through which candidate explanatory variables can be scrutinized with regard to their possible impact on a particular oscillatory dynamics under study. Thus, the generalized ERD represents a powerful novel analysis tool for extending our understanding of inter-trial variability of evoked responses and therefore the robust processing of environmental stimuli

Governing the Global Land Grab: Multipolarity, Ideas and Complexity in Transnational Governance

Since 2008, a series of new regulatory initiatives have emerged to address large-scale land grabs. These initiatives are occurring simultaneously at multiple levels of social organization instead of a single, overarching institutional site. A significant portion of this activity is taking place at the transnational level. We suggest that transnational land governance is indicative of emerging shifts in the practice of governance of global affairs. We analyze such shifts by asking two related questions: what does land grabbing tell us about developments in transnational governance, particularly with regard to North-South relations, and what do these developments in transnational governance mean for regulating land grabbing?Desde 2008, ha surgido una serie de nuevas iniciativas regulatorias para tratar acaparamientos de tierra a gran escala. Estas iniciativas est&aacute;n sucediendo simult&aacute;neamente a niveles m&uacute;ltiples de la organizaci&oacute;n social en vez de un lugar institucional predominante. Una porci&oacute;n importante de esta actividad est&aacute; tomando lugar al nivel transnacional. Sugerimos que la gobernanza de tierras trasnacionales es indicativa de los cambios que est&aacute;n surgiendo en la pr&aacute;ctica de gobernanza de los asuntos globales. Analizamos tales cambios haciendo dos preguntas relacionadas: &iquest;qu&eacute; nos dice el acaparamiento de tierras sobre los desarrollos en la gobernanza trasnacional, particularmente con las relaciones norte-sur?, y &iquest;qu&eacute; significan estos desarrollos en gobernanza trasnacional para regular el acaparamiento de tierras

Describing the sleep EEG with an Adaptive Autoregressive Model.

The spectral information of the sleep EEG is an important indicator for the sleep stage 1. Adaptive autoregressive parameters can describe the time-varying spectrum. The AR spectrum is

Delivering difference? Four neglected issues in China's aid to Africa

China's dramatic engagement in the international development landscape in this century has led to a debate on a possible alternative set of development ideology, theory, and practice, raising both hope and concern for the industrialization and revitalization of the Global South. Ideologically, the emerging power has begun as a 'norms maker' to challenge the current North-South donor-recipient relations and the financial and trade dominance behind the scenes. 1 It praises the inherent legitimacy and rationality of South-South Cooperation (SSC), 2 aims at reforms in the established global financial and trade systems, and is creating ‘parallel structures' to counterweigh the West's reluctance to change international institutions. 3 Regarding development theory, both the Chinese government and academia have shown their confidence in exporting China's successful development story to the developing world, purportedly known as the 'China Model'. 4 Infrastructure-led growth, industry parks with a focus on the labour-intensive manufacture, and knowledge transfer (particularly in agriculture) are among the indispensable experiences that have been theorized and that China wishes to promote worldwide