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Having found by the use of a new method for examining perception without attention that grouping and texture segregation do not seem to occur (see Mack, Tang, Tuma, Kahn, & Rock (1992) Cognitive Psychology, 24, we go on to ask what is perceived without attention using this new method. Our subjects receive only one inattention trial in a sequence of trials(More)
A staging series for retinal histogenesis is described for Xenopus laevis. It is based on scanning EM studies of intact eyes and serial section analysis of silver-stained preparations. Retinal development is arbitrarily divided into twelve stages (I--XII) based on distinct morphological and histological changes. In general, four different phases of retinal(More)
We studied the time of origin, development and location of glial elements in the developing optic nerve of Xenopus with light and electron microscopy. The first cells acting as a primitive glia are ependymal cells lying dorsal to the chiasmatic optic nerve (CON) at Nieuwkoop & Faber (1956) NF stage 39. Later (stage 47/48), immature astrocyte cell bodies(More)
The normal retinotectal path in the diencephalon of Xenopus tadpoles is widely distributed in the form of a wedge of fibres extending from the central grey to the outer margin of the diencephalon. Regenerating optic nerve fibres were shown, by silver-staining and proline autoradiography, to follow an abnormal path up the extreme lateral edge of the(More)
The ontogeny of optic fiber patterns within the Xenopus laevis retina has been studied in silver-stained serial sections and whole mounts. Ganglion cell axons ("pioneers") appear much earlier than previously recognized, at Nieuwkoop-Faber ('56) Stage 28. Fibers fasciculate into bundles as they arise in the retina and reach the chiasma by NF Stage 32.(More)
The rotated eye paradigm has been a major experimental test of the neuronal specificity model for the development of ordered retinotectal connections in amphibians. In most studies, however, no optic fiber pathways were traced from rotated eyes and correlated with visuotectal projections. As an initial approach to this question, optic fibers from eyes(More)
Growth and guidance behavior of Xenopus embryonic (ER) (optic vesicle stage 25/26) and regenerating retinal fibers (stage 47/50 newly regenerating NR, and actively regenerating RR, respectively) have been studied in vitro on a variety of substrates in serum-free media. RR retinas receive a prior conditioning lesion 12-14 days before explantation while NR(More)
The development of the tectum and diencephalon in Xenopus has been investigated in relation to recent descriptions of the establishment of the retinotectal projection. Tritiated thymidine autoradiography and bromodeoxyuridine immunohistology were used to identify the stages at which cells became postmitotic. Cells in the diencephalon were found to become(More)
During development of the retina in mammals and birds, most retinal ganglion cells (RGC) that are produced are eliminated later in development by cell death. In lower vertebrates, however, such massive cell death has not been observed; total ganglion cell number increases linearly during most of development. Using 3H-thymidine or 5-bromodeoxyuridine(More)