At 09:49 14/10/99 PDT, Rod wrote: >Carrol. I can not disagree with anything that you said. (except that EEG's >measure electric fields not chemical changes.) There is much ignorance about >the subject (I read somewhere that there are over one hundred message >bearing chemicals in the brain and scientist understand the purpose of five >or six) and a lot of what is said even by the experts is pure guesswork. It >is clear that the "materialist" purely chemical explanation leaves a lot to >be desired. There is something more there than chemistry but we don't yet >know what it is. (And, No! I am not a dualist.) Not a mere hundred, a *thousand* chemical neurotransmitters have been identified in the brain. These are the chemicals released in tiny pulses across the synapses to stimulate or destimulate the likelihood of a depolarisation spreading to the next neurone. And of those neurochemical transmitters that have been studied in detail such as serotonin and dopamine they have each half a dozen of sub-types of receptor. Emergent properties are well modelled in complexity theory, but they do have to have simple processes of interaction between the component cells for an emergent property to occur. I am not sure that the example of mechanical electrical clocks wired together is really analogous with nature. In the marxian critique of classical economics value is an emergent property of the interaction of millions of commodity exchanges. Marx did not use the word emergent, he just analysed the dynamic at both the cellular and the macro level. A recent paper in Nature has an intriguing bridge between the cellular level of brain function and the dynamic level of mind function in the analysis of magnetic imaging in relation to the perception of objects. All that has to be predicated is that the perception of an object makes the perception of one of its related attributes more likely. And that applies equally well if the object is an object or, as in the usage of object relations theory, a human being with whom one has an important emotional investment. >"Object Relations" is the terminology deriving from Freud's usage of the >internal representation of important relationships with people. >Unfortunately in English the word object implies something that is not human. > >The following study published in Nature this month, October 1999, gives an >intriguing account of how physical objects may be attended to by the >physical brain as whole objects. >This is through attention to one attribute of an object enhancing the >attention to other attributes. > >Assuming this is replicable, it would apply to any objects from a glass, to >a haystack, to a tin of tuna fish. But interestingly one of the objects the >experimenters chose was a face, a representation of what could be an object >in the Freudian internalised sense. > >And the mechanism could well fit that too like a glove. The mechanism there >is described here at the level of organisation of the brain, could also be >described at the level of the mind. > >Indeed to form a cartesian split between the brain and the mind, with these >examples is quite unnecessary. > >Chris Burford > >London > >_____________________________ > >fMRI evidence for objects as the units of attentional selection > >KATHLEEN M. O'CRAVEN, PAUL E. DOWNING & NANCY KANWISHER > >Contrasting theories of visual attention emphasize selection by spatial >location, visual features (such as motion or colour) or whole objects. Here >we used functional magnetic resonance imaging (fMRI) to test key >predictions of the object-based theory, which proposes that pre-attentive >mechanisms segment the visual array into discrete objects, groups, or >surfaces, which serve as targets for visual attention. Subjects viewed >stimuli consisting of a face transparently superimposed on a house, with >one moving and the other stationary. In different conditions, subjects >attended to the face, the house or the motion. The magnetic resonance >signal from each subject's fusiform face area, parahippocampal place area >and area MT/MST provided a measure of the processing of faces, houses and >visual motion, respectively. > >Although all three attributes occupied the same location, attending to one >attribute of an object (such as the motion of a moving face) enhanced the >neural representation not only of that attribute but also of the other >attribute of the same object (for example, the face), compared with >attributes of the other object (for example, the house). > >These results cannot be explained by models in which attention selects >locations or features, and provide physiological evidence that whole >objects are selected even when only one visual attribute is relevant. > > - > - > - --- from list [EMAIL PROTECTED] --- >
