Advances in neuroscience implicate reentrant signaling as the predominant form of communication between brain areas. This principle was used in a series of masking experiments that defy explanation by feed-forward theories. The masking occurs when a brief display of target plus mask is continued with the mask alone. Two masking processes were found: an early process affected by physical factors such as adapting luminance and a later process affected by attentional factors such as set size. This later process is called (...) masking by object substitution, because it occurs whenever there is a mismatch between the reentrant visual representation and the ongoing lower level activity. Iterative reentrant processing was formalized in a computational model that provides an excellent fit to the data. The model provides a more comprehensive account of all forms of visual masking than do the long-held feed-forward views based on inhibitory contour interactions. (shrink)

Voluntary acts are preceded by electrophysiological (RPs). With spontaneous acts involving no preplanning, the main negative RP shift begins at about200 ms. Control experiments, in which a skin stimulus was timed (S), helped evaluate each subject's error in reporting the clock times for awareness of any perceived event.

_Behavioral and Brain Sciences_ , 15, 183-247, 1992. Reprinted in _The Philosopher's Annual_ , Grim, Mar and Williams, eds., vol. XV-1992, 1994, pp. 23-68; Noel Sheehy and Tony Chapman, eds., _Cognitive Science_ , Vol. I, Elgar, 1995, pp.210-274.

IntroductionIt is at least a bit embarrassing, perhaps even scandalous, that debate should still rage over the sheer existence of qualia, but they continue to find able defenders after decades of being attacked as relics of ghostly substances, epiphenomenal non-entities, nomological danglers and the like; the intensity of the current confrontation is captured vividly by Daniel Dennett:What are qualia, exactly? This obstreperous query is dismissed by one author by invoking Louis Armstrong's legendary reply when asked what jazz was: “If you (...) gotta ask, you ain't never gonna get to know.” … If I succeed in my task, this move … will look as quaint and insupportable as a jocular appeal to the ludicrousness of a living thing-a living thing, mind you! -doubting the existence of elan vital. (shrink)

Owen Flanagan argues that we are on the way to understanding consciousness and its place in the natural order.

Review of T. S. Kuhn's The Essential Tension.

Damasio remarks, it "informs virtually all research on mind and brain, explicitly or implicitly." Indeed, serial information processing models generally run this risk (Kinsbourne, 1985). The commentaries provide a wealth of confirming instances of the seductive power of this idea. Our sternest critics Block, Farah, Libet, and Treisman) adopt fairly standard Cartesian positions; more interesting are those commentators who take themselves to be mainly in agreement with us, but who express reservations or offer support with arguments that betray a continuing (...) allegiance to one or another tenet of the view we sought to discredit. (shrink)

Oliver Sacks MD, Clinical Professor of Neurology at the Albert Einstein College of Medicine in New York, talked with Anthony Freeman during his visit to London in January 1995 to publicize his recently published book An Anthropologist on Mars. The interview is preceded by an overview of the book.

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The human self model comprises essential features such as the experiences of ownership, of body-centered spatial perspectivity, and of a long-term unity of beliefs and attitudes. In the pathophysiology of schizophrenia, it is suggested that clinical subsyndromes like cognitive disorganization and derealization syndromes reflect disorders of this self model. These features are neurobiologically instantiated as an episodically active complex neural activation pattern and can be mapped to the brain, given adequate operationalizations of self model features. In its unique capability of (...) integrating external and internal data, the prefrontal cortex (PFC) appears to be an essential component of the neuronal implementation of the self model. With close connections to other unimodal association cortices and to the limbic system, the PFC provides an internally represented world model and internal milieu data of the organism, both serving world orientation. In the pathophysiology of schizophrenia, it is the dysfunction of the PFC that is suggested to be the neural correlate for the different clinical schizophrenic subsyndromes. The pathophysiological study of psychiatric disorders may contribute to the theoretical debate on the neuronal basis of the self model. (shrink)