Eye-specific termination bands in tecta of three-eyed frogs.
ABSTRACT An extra eye primordium was implanted into the forebrain region of embryonic Rana pipiens. During development both normal and supernumerary optic tracts terminated within a single, previously uninnervated tectal lobe. Autoradiographic tracing of either the normal or supernumerary eye's projection revealed distinct, eye-specific bands of radioactivity running rostrocaudally through the dually innervated tectum. Interactions among axons of retinal ganglion cells, possibly mediated through tectal neurons, must be invoked to explain this stereotyped disruption of the normally continuous retinal termination pattern.
- SourceAvailable from: Christoph von der Malsburg[Show abstract] [Hide abstract]
ABSTRACT: Ontogenetic development of ocularity domains--stripes, patches and layers in cortex, colliculus superior and lateral geniculate nucleus--is the result of organization that may either be intrinsic to the postsynaptic structure or induced to it by the afferents. A specific type of axonal growth behaviour that was recently proposed as a basis for ontogenetic development of retinotopy is sufficient to account also for ocularity domains. No intrinsic organization in the postsynaptic structure is required. The latter merely serves as a propagating medium for markers carried by the presynaptic terminals. Computer simulations demonstrate the mechanism to be complete and consistent.Biological Cybernetics 03/1979; 32(1):49-62. DOI:10.1007/BF00337452 · 1.93 Impact Factor
Article: Deconstructing neural constructivism[Show abstract] [Hide abstract]
ABSTRACT: Activity-dependent processes play an active role in shaping the structure of neuronal circuitry and therefore contribute to neural and cognitive development. Neural constructivism claims to be able to account for increases in the complexity of cognitive representations in terms of directed growth of neurons. This claim is overstated, rests on biased nterpretations of the evidence, and is based on serious misapprehensions of the nature of somatic variation and selection.Behavioral and Brain Sciences 11/1997; 20(04):576 - 577. DOI:10.1017/S0140525X97461587 · 14.96 Impact Factor
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ABSTRACT: Neural organization raises, in an especially clear way, a major problem confronting contemporary cognitive science. The problem (the “big issue” of my title) is: What is the relation between the strategies used to solve basic problems of perception and action and those used to solve more abstract or “cognitive” problems? Is there a smooth, incremental route from what Arbib et al. call “instinctual schemas” to higher-level kinds of cognitive prowess? I argue that, despite some suggestive comments, Arbib et al. do not resolve this issue.Behavioral and Brain Sciences 07/2000; 23(04):536 - 537. DOI:10.1017/S0140525X0026336X · 14.96 Impact Factor