A perspective on the mechanism of the light-rise of the electro-oculogram

The light-rise of the electro-oculogram is believed to originate from a substance released from the rods after dark adaptation. The identity of this 'elusive' light-rise substance has not been demonstrated and therefore a new perspective on the light-rise is presented. The light-rise is caused by the depolarization of the basolateral membrane of the retinal pigment epithelium has become clearer in the last decade with the identification of calcium as the intracellular secondary messenger and the role of bestrophin as a regulator of intracellular stores of calcium and controlling the cytosolic calcium levels through L-type calcium channels. The light-rise depends upon a change from darkness to light which triggers the intracellular cascade resulting in the depolarization of the basolateral membrane. The same intracellular signalling molecules- notably calcium and inositol tri-phosphate (IP3) are strongly implicated in this cascade. Recent studies have now led to a clearer understanding of the roles and functions of the ion channels and their contribution to the light-rise with IP3 regulating the release of calcium for intracellular stores. Given that calcium and IP3 are also regulators of phagocytosis, and that the initiation of rod outer segment phagocytosis is initiated with light-onset, it may be that the light-rise is generated in response to this physiological event. Therefore, the putative light-rise substance may not be released by the rods but follows directly from IP3 release from the RPE's phospholipid membrane following the onset of light and the initiation of phagocytosis- The light rise substance, could be considered to be light itself

Crowding and visual search in high functioning adults with autism spectrum disorder

Purpose: Individuals with autism spectrum disorder have demonstrated faster reaction times when searching for objects in a visual scene. One possible explanation for this observation is that the influence of crowding may not be as strong within this group compared to typically developing individuals. Subjects and methods: We recruited 16 participants with and without a diagnosis of autism spectrum disorder in the age range of 20–58 years. The main experiments focused on determining the critical spacing for the correct identification of an ellipse’s orientation in the periphery when flanked by two circles with 81% correctly identified. The second experiment was an attempt to replicate previous studies that had demonstrated superior visual search in autism using reaction time, set-size slopes and intercepts as measures of search efficiency and pre-attentive processes. Results: There were no significant group differences in the critical spacings for the crowded ellipses in the periphery (P = 0.358) or in the elliptical discrimination thresholds (P = 0.477). In addition there were no significant differences between groups in reaction times (P = 0.083), accuracy (P = 0.658) and set-size slopes (P = 0.976), however the intercept for the set-size slope function was significantly lower for the comparison group (P = 0.016). Conclusions: The individuals we tested demonstrated neither immunity to crowding nor any advantage in the visual search task. Therefore, we failed to confirm that enhanced discrimination underlies superiority in visual search in adults with high functioning autism spectrum disorder. This finding may be associated with the older age group investigated compared to previous studies and suggests that the underlying mechanism of superior visual search may not be a persistent feature of autism spectrum disorder

Investigations into the underlying cellular mechanism of the alcohol-electro-oculogram

The aim of this study was to determine the underlying cellular mechanism by which ethanol alters the standing potential of the human eye (the ethanol electro-oculogram). Using chamber experiments using animal explants of retinal pigment epithelium and retina, as well as cultured retinal pigment epithelial cells grown on filter inserts, were conducted to determine whether the retinal pigment epithelium was the target for ethanol. The human retinal pigment epithelial cell line, ARPE-19 was used to investigate changes in intracellular calcium concentration in response to ethanol. Human studies involving patients with cystic fibrosis were performed to determine the likely ionic channel involved in the ethanol-electro-oculogram. Results indicated that ethanol was capable of elevating intracellular calcium concentration but that the source was from the extracellular pools. The likely ionic channel responsible for the light evoked electro-oculogram is the L-type calcium channel and this channel could be the route through which ethanol mediates the calcium-signal based on this finding. The amplitude of the ethanol evoked electro-oculogram was not dependent upon one functional chloride channel affected in cystic fibrosis and regulated by cyclic adenosine monophosphate dependent protein kinase A. This finding supports the role of a calcium-gated basolateral chloride channel being responsible for the ethanol-electro-oculogram. The fast oscillations in the cystic fibrosis subjects also showed higher or normal responses which are supportive of a recent finding in an animal model of this condition. The findings of this study indicate that the ethanol-electro-oculogram is dependent upon calcium signalling. The earlier clinical studies have also shown that the ethanol-electro-oculogram is affected more than the light electro-oculogram in early retinal degenerations. Therefore, the results presented would suggest that calcium signalling is impaired in early retinal degenerations

Non-Abelian BIonic Brane Intersections

We study "fuzzy funnel" solutions to the non-Abelian equations of motion of the D-string. Our funnel describes n^6/360 coincident D-strings ending on n^3/6 D7-branes, in terms of a fuzzy six-sphere which expands along the string. We also provide a dual description of this configuration in terms of the world volume theory of the D7-branes. Our work makes use of an interesting non-linear higher dimensional generalization of the instanton equations.Comment: 17 pages uses harvmac; v2: small typos corrected, refs adde

Dependent Types for Pragmatics

This paper proposes the use of dependent types for pragmatic phenomena such as pronoun binding and presupposition resolution as a type-theoretic alternative to formalisms such as Discourse Representation Theory and Dynamic Semantics.Comment: This version updates the paper for publication in LEU

Open-Closed Duality at Tree Level

We study decay of unstable D-branes in string theory in the presence of electric field, and show that the classical open string theory results for various properties of the final state agree with the properties of closed string states into which the system is expected to decay. This suggests a duality between tree level open string theory on unstable D-branes and closed strings at high density.Comment: LaTeX file, 10 page

AdS Branes Corresponding to Superconformal Defects

We investigate an AdS_4 x L_2 D5-brane in AdS_5 x X_5 space-time, in the context of AdS/dCFT correspondence. Here, X_5 is a Sasaki-Einstein manifold and L_2 is a submanifold of X_5. This brane has the same supersymmetry as the 3-dimensional N=1 superconformal symmetry if L_2 is a special Legendrian submanifold in X_5. In this case, this brane is supposed to correspond to a superconformal wall defect in 4-dimensional N=4 super Yang-Mills theory. We construct these new string backgrounds and show they have the correct supersymmetry, also in the case with non-trivial gauge flux on L_2. The simplest new example is AdS_4 x T^2 brane in AdS_5 x S^5. We construct the brane solution expressing the RG flow between two different defects. We also perform similar analysis for an AdS_3 x L_3 M5-brane in AdS_4 x X_7, for a weak G_2 manifold X_7 and its submanifold L_3. This system has the same supersymmetry as 2-dimensional N=(1,0) global superconformal symmetry, if L_3 is an associative submanifold.Comment: 22 pages, LaTeX, 3 figures. v2: typos corrected, references added. v3: typos correcte