Against Division: Consciousness, Information and the Visual Streams (original) (raw)
Related papers
Streams and consciousness: visual awareness and the brain
Trends in Cognitive Sciences, 1998
Al though our understanding of human consciousness remains at a very preliminary stage, the enthusiasm for trying to study it scientifically has advanced very rapidly indeed. Accordingly, we have seen a plethora of new journals in the past few years that are devoted to such attempts (and to evaluations of the enterprise itself); among them are Psyche, Consciousness and Cognition and The Journal of Consciousness Studies. In addition, the number of recent books on the subject, by both philosophers and neuroscientists, is rising even more rapidly. According to two recent books 1,2 , one of the most promising areas of empirical investigation is the study of visual perception. In part, this optimism is due to the visual system having the best documented neuroanatomy and neurophysiology of any functional system in the primate brain. Thus, we have detailed information not only on the geniculo-striate and the colliculo-pulvinar pathways 3,4 , but also on the cortical elaborations of these two major input routes. We have a wiring diagram far more complex than any known urban subway system, in which some 30 areas in
Psyche, 2007
The aim of the present article is three-fold. First, it aims to show that perception requires action. This is most evident for some types of visual percept (e.g. space perception and action perception). Second, it aims to show that the distinction of the cortical visual processing into two streams is insufficient and leads to possible misunderstandings on the true nature of perceptual processes. Third, it aims to show that the dorsal stream is not only responsible for the unconscious control of action, but also for the conscious awareness of space and action.
Phenomenology and the Cognitive Sciences, 2012
Perception, Action, and Consciousness is a volume devoted to exploring the tensions and potential routes for reconciliation between two types of approaches to visual perception: the sensorimotor, action-oriented view of perception 1 and the two visual systems hypothesis. 2 These views hold conflicting positions as to the contribution that action makes to the qualitative character of a perceptual event. The actionoriented or sensorimotor views represented here, to varying degrees, hold that action plays a central, even constitutive, role in determining the phenomenal character of visual experience. 3 In contrast, the two visual systems model is committed to the idea that action and visual perception are processed independently and thus remain functionally distinct. Accordingly, the two visual systems model holds that the dorsal stream, which is responsible for processing vision for action, has no direct impact on conscious perceptual experience, which is processed separately by the ventral stream. This volume is essential reading for any philosopher of perception or vision researcher interested in the relationship between action and perception. The volume contains several contributions, which both frame and advance the debate between the two systems theorists and the adherents of the sensorimotor view. This book is exceptional in several ways that relate to interaction and communication: (1) this is a truly interdisciplinary volume with contributions from philosophers, psychologists, neurologists, and cognitive neuroscientists, and (2) theorists and scientists are Phenom Cogn Sci
Consciousness and the Flow of Attention
2012
Visual phenomenology is highly illusive. One attempt to operationalize or to measure it is to use ‘cognitive accessibility’ to track its degrees. However, if Ned Block is right about the overflow phenomenon, then this way of operationalizing visual phenomenology is bound to fail. This thesis does not directly challenge Block’s view; rather it motivates a notion of cognitive accessibility different from Block’s one, and argues that given this notion, degrees of visual phenomenology can be tracked by degrees of cognitive accessibility. Block points out that in the psychology literature, ‘cognitive accessibility’ is often regarded as either all or nothing. However, the notion motivated in the thesis captures the important fact that accessibility comes in degrees (consider the visual field from fovea the periphery). Different legitimate notions of accessibility might be adopted for different purposes. The notion of accessibility motivated here is weaker than Block’s ‘identification’ (2007) but is stronger than Tye’s ‘demonstration’ (2007). The moral drawn from the discussion of Block can be applied to the debate between Dretske and Tye on the speckled-hen style examples. Dretske’s view is even stronger than Block’s, but his arguments from various figures he provides do not support his conclusion since he does not have right ideas about fixation and attention. Tye’s picture is more plausible but his notion of accessibility is so weak that he reaches the excessive conclusion that accessibility overflows phenomenology. Three ramifications might be considered in the final part of the thesis. The first is the relation between this debate and the one concerning higher-order/same-order theories of consciousness. The second is about John McDowell’s early proposal about demonstrative concepts in visual experiences. The third is the relation between the interpretation of the Sperling case proposed here and McDowell new view of experiential contents, i.e., his story about how we carve out conceptual contents out of intuitional contents without falling pray to the Myth of the Given.
Toward a Theory of Visual Consciousness
Consciousness and Cognition, 1999
The visual brain consists of several parallel, functionally specialized processing systems, each having several stages (nodes) which terminate their tasks at different times; consequently, simultaneously presented attributes are perceived at the same time if processed at the same node and at different times if processed by different nodes. Clinical evidence shows that these processing systems can act fairly autonomously. Damage restricted to one system compromises specifically the perception of the attribute that that system is specialized for; damage to a given node of a processing system that leaves earlier nodes intact results in a degraded perceptual capacity for the relevant attribute, which is directly related to the physiological capacities of the cells left intact by the damage. By contrast, a system that is spared when all others are damaged can function more or less normally. Moreover, internally created visual percepts-illusions, afterimages, imagery, and hallucinations-activate specifically the nodes specialized for the attribute perceived. Finally, anatomical evidence shows that there is no final integrator station in the brain, one which receives input from all visual areas; instead, each node has multiple outputs and no node is recipient only. Taken together, the above evidence leads us to propose that each node of a processing-perceptual system creates its own microconsciousness. We propose that, if any binding occurs to give us our integrated image of the visual world, it must be a binding between microconsciousnesses generated at different nodes. Since any two microconsciousnesses generated at any two nodes can be bound together, perceptual integration is not hierarchical, but parallel and postconscious. By contrast, the neural machinery conferring properties on those cells whose activity has a conscious correlate is hierarchical, and we refer to it as generative binding, to distinguish it from the binding that might occur between the microconsciousnesses.