Spatial Stereoresolution for Depth Corrugations May Be Set in Primary Visual Cortex

Stereo “3D” depth perception requires the visual system to extract binocular disparities between the two eyes' images. Several current models of this process, based on the known physiology of primary visual cortex (V1), do this by computing a piecewise-frontoparallel local cross-correlation between the left and right eye's images. The size of the “window” within which detectors examine the local cross-correlation corresponds to the receptive field size of V1 neurons. This basic model has successfully captured many aspects of human depth perception. In particular, it accounts for the low human stereoresolution for sinusoidal depth corrugations, suggesting that the limit on stereoresolution may be set in primary visual cortex. An important feature of the model, reflecting a key property of V1 neurons, is that the initial disparity encoding is performed by detectors tuned to locally uniform patches of disparity. Such detectors respond better to square-wave depth corrugations, since these are locally flat, than to sinusoidal corrugations which are slanted almost everywhere. Consequently, for any given window size, current models predict better performance for square-wave disparity corrugations than for sine-wave corrugations at high amplitudes. We have recently shown that this prediction is not borne out: humans perform no better with square-wave than with sine-wave corrugations, even at high amplitudes. The failure of this prediction raised the question of whether stereoresolution may actually be set at later stages of cortical processing, perhaps involving neurons tuned to disparity slant or curvature. Here we extend the local cross-correlation model to include existing physiological and psychophysical evidence indicating that larger disparities are detected by neurons with larger receptive fields (a size/disparity correlation). We show that this simple modification succeeds in reconciling the model with human results, confirming that stereoresolution for disparity gratings may indeed be limited by the size of receptive fields in primary visual cortex

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Not AvailableStudy was conducted to determine the biochemical constituents in coconut (Cocos nucifera L.) haustorium, a spongy tissue formed during coconut germination. Results indicated that 100g of dried coconut haustorium contained 1.05 ± 0.2% ash, 44.2 ± 4.6% soluble sugar, 24.5 ± 3.2% starch, 5.50 ± 0.3% protein, 1.99 ± 0.9% fat, 5.72 ± 0.4% soluble dietary fibre, 20.3 ± 1.9% insoluble dietary fibre, and 146 ± 14.3 mg phenolics. Mineral profiling showed that it contained 145 ± 8.6, 104 ± 9.6, 33.9 ± 8.2, 30.9 ± 1.9, 9.45 ± 2.1, 0.292 ± 0.1, 2.53 ± 0.2 and 1.20 ± 0.1 mg of K, Mg, Ca, P, Mn, Cu, Fe and Zn, respectively. Antioxidant activity assay indicated that 100g haustorium was equivalent to 1918 ± 173, 170 ± 20.4, 72.8 ± 14.7 and 860 ± 116 mg of Trolox as measured by CUPRAC, FRAP, DPPH and ABTS, respectively. Amino acid score indicated that methionine + cysteine (57.6%), phenylalanine + tyrosine (32.6%), leucine (45.7%) and isoleucine (68%) are found less in haustorium. Further studies needed in developing nutritionally balanced formulations using coconut haustorium, which will be useful for lactose intolerant children.Not Availabl

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Not AvailableCoconut testa, a brown skin covering of a coconut endosperm, is a rich source of phenolics. It is one of the byproducts obtained in the coconut processing industries and currently underutilized despite being rich in phenolic compounds. A study was conducted to identify the suitable solvent system for maximum extractability of total phenolic content (TPC) and total flavonoid content (TFC) with antioxidant potential from the testa. Individual phenolic acids and flavonoids of different solvent extracts were also determined using UPLC-H class coupled with TQD-MS/MS. The TPC and TFC ranged from 4.9 to 167 mg GAE/g and 8.84–115 mg QE/g defatted testa, respectively; significant differences were observed for various solvent systems studied. Acidification of solvents significantly increased the extractability of TPC and reduced the extractability of TFC. A total of 28 phenolics comprising 16 phenolic acids and 12 flavonoids were identified. Protocatechuic acid, p-coumaric acid and ferulic acid are the major phenolic acids identified whereas, catechin, apigenin and kaempferol are the major flavonoids identified. In summary, this study proved that coconut testa is a natural source of multiple phenolics acids and flavonoids with potent antioxidant capacity, and it can be used as a natural source of antioxidants.Not Availabl