The concept of the receptive field, first articulated by Hartline, is central to visual neuroscience. The receptive field of a neuron encompasses the spatial and temporal properties of stimuli that activate the neuron, and, as Hubel and Wiesel conceived of it, a neuron’s receptive field is static. This makes it possible to build models of neural circuits and to build up more complex receptive fields out of simpler ones. Recent work in visual neurophysiology is providing evidence that the classical receptive (...) field is an inaccurate picture. The receptive field seems to be a dynamic feature of the neuron. In particular, the receptive field of neurons in V1 seems to be dependent on the properties of the stimulus. In this paper, we review the history of the concept of the receptive field and the problematic data. We then consider a number of possible theoretical responses to these data. (shrink)
Ebbhinghaus, H., J. Flum, and W. Thomas. 1984. Mathematical Logic. New York, NY: Springer-Verlag. Forster, T. Typescript. The significance of Yablo’s paradox without self-reference. Available from http://www.dpmms.cam.ac.uk. Gold, M. 1965. Limiting recursion. Journal of Symbolic Logic 30: 28–47. Karp, C. 1964. Languages with Expressions of Infinite Length. Amsterdam.
In a recent paper, Ebbs has given an elegant statement of a notable puzzle that has recurred in the literature since the original publication of Putnam’s “The Meaning of ‘Meaning’.” The puzzle can be formulated, for a certain characteristic case, along the following lines. There are very strong intuitions in support of a thesis that Putnam has explicitly endorsed, namely, the thesis: The extension of the word ‘gold’, as we use it now, is the same as the extension of (...) ‘gold’, as it was used in 1650 (before the rise of molecular chemistry). However, strong convictions about language use and truth conditions also incline us to the view that the extension of a term, as it is used at a time t, is determined by facts about the use of the term in the language at or before t, together with the facts about the various items to which the term prospectively applied. This paper looks at the various issues involved regarding these matters. (shrink)
In this paper we describe a test for Nijhout's (1978, 1980a) hypothesis that the eyespot patterns on butterfly wings are the result of a threshold reaction of the epidermal cells to a concentration gradient of a diffusing degradable morphogen produced by focal cells at the centre of the future eyespot. The wings of the nymphalid butterfly, Bicyclus anynana, have a series of eyespots, each composed of a white pupil, a black disc and a gold outer ring. In earlier (...) extirpation and transplantation experiments (Nijhout 1980a; French and Brakefield, 1995) it has been established that these eyespots are indeed organised around groups of signalling cells active during the first hours of pupal development. If these cells were to supply the positional information for eyespot formation in accordance with Nijhout's diffusion-degradation gradient model, then, when two foci are close together, the signals should sum, and this effect should be apparent in the detailed shape of the resulting pigment pattern. We give an equation for the form of the contours that would be obtained in this manner. We use this to test the morphogen gradient hypothesis on measurements of the outlines of fused eyespots obtained either by grafting focal cells close together, or by using a mutation (Spotty) that produces adjacent fused eyespots. The contours of the fused patterns were found to satisfy our equation, thus corroborating Nijhout's hypothesis to the extent possible with this particular type of experiment. (shrink)
Gold & Stoljar's attempt to disentangle the body-mind problem in time for the end of the decade of the brain deserves praise for its diligence and courage in moving onto the treacherous ground of interdisciplinary discourse. In making their point, they should not have stopped half-way: a more clearly defined experimental paradigm seems necessary to solve this exciting and substantial problem.
Ethical mysticism, by S. Coit.--The ethical import of history, by D. S. Muzzey.--The tragic and heroic in life, by W. M. Salter.--Distinctive features of the ethical movement, by A. W. Martin.--Ethical experience as the basis of religious education, by H. Neumann.--"All men are created equal," by G. E. O'Dell.--How far is art an aid to religion? by P. Chubb.--Evolution and the uniqueness of man, by H. J. Bridges.--The spiritual outlook on life, by H. J. Golding.--The ethics of Abu'l Ala al (...) Ma'arri, by N. Schmidt.--Life's unused moral force, by H. Snell.--Is the ideal real? by G. A. Smith.--Some ethical tendencies in the professions, by R. D. Kohn.--On the art of living, by W. Boerner.--The relation of the ethical ideal to social reform, by J. L. Elliott.--Concerning tolerance, by R. F. Dewey.--Ethical culture in Germany after the war, by R. Penzig.--A confession of faith, by S. B. Weston.--"Hearing the witnesses," by J. Gutmann. (shrink)