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Recently, elongated comet-shaped receptive fields were discovered in the fourth extrastriate crescent (area V4A) of cats and monkeys. It was shown that the long axes of these receptive fields were oriented radially toward the centre of the retina. Such unusual "radial" organization of this extrastriate area led to the assumption that these neurons may contribute to the analysis of optic flow. To investigate this assumption we recorded activity of neurons in the V4A of cats during real motion in depth toward or away from a stationary visual scene. Responses of neurons in area V4A were compared with activity of neurons in area V2 under similar conditions of stimulation. Area V2 is known to be sensitive to motion but does not have radial organization. It was found that a substantial number of visual neurons in both areas did not fire at all when cats were exposed to motion in depth. Nevertheless, neurons with selective activation to direction of motion in depth were identified, but comparable numbers were found in both areas studied. We conclude that radial organization of the fourth extrastriate crescent does not provide any special advantage for the analysis of optic flow information.

Purpose: Reducing the undesirable systemic effect of photodynamic therapy (PDT) can be achieved by incorporating a photosensitizer in microparticles (MPs). This study is devoted to the preparation of biocompatible biodegradable MPs with the inclusion of the natural photosensitizer Radachlorin (RС) and an assessment of the possibility of their use for PDT. Methods: RC-containing MPs (RС MPs) with poly(lactic-co-glycolic acid) copolymer (PLGA) matrix were prepared by a double emulsion solvent evaporation methods. The size and morphology of RC MPs were surveyed using scanning electron microscopy, confocal laser scanning microscopy, and dynamic light scattering. The content of RC, its release from RC MPs, and singlet oxygen generation were evaluated by the optical spectroscopy. Cellular uptake and cytotoxic photodynamic effect of RC MPs were investigated with in vitro assays. Results: The average diameter of the prepared RC MPs was about 2-3 μm. The RC MPsprepared by the water/oil/oil method had a significantly higher inclusion of RC (1.74 μg/mg) then RC MPs prepared by the water/oil/water method (0.089 μg/mg). Exposure of the prepared RC MPs to PDT light radiation was accompanied by the singlet oxygen generation and a cytotoxic effect for tumor cells. The release of the RC from the RC MPs was prolonged and lasted at least two weeks. Conclusion: PLGA RC MPs were found to cause a photoactivated cytotoxic effect for tumor cells and can be used for local application in PDT of tumors.

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