A source of despair in consciousness studies is the way in which popular science writers continue to plough ahead making pronouncements that are flatly contradicted by the neuroscientific data of recent years. In particular, consciousness students might be forgiven for screaming every time Libet’s veteran 1980s experiment is trundled out. Halligan and Oakley writing in a recent issue of ‘New Scientist’ go down this predictable route. The brain prepares for actions such as reaching out prior to awareness of the intention to reach.
Posts Tagged ‘ventral stream’
Thoughts on Reality An insubstantial pageant The one thing we can be reasonably sure of is that what we see has nothing to do with reality. Physics tells us as much as that; that there are no things and there is no colour green. Visual information is delivered to the retina by photons fluctuating at varying frequencies. The photons are either reflected from or produced by ‘objects’, which can in their turn be understood as quantum particles held together by the charges of the electromagnetic Read more […]
The Focus magazine’s reply to this question leaves considerable gaps in terms of the present century’s neuroscience. Benjamin Libet’s experiment from the 1980s is once again confidently quoted as a refutation of the concept of freewill. This veteran experiment showed that brain activity could be detected before the conscious awareness of the intention to perform an action, and has ever after been trundled out as a refutation of freewill.
Even at the very early stage of the retina, an important division arises between two parallel visual streams, the dorsal stream and the ventral stream. The dorsal stream projects to the parietal cortex, and is responsible for movements in relation to objects, many of them of a routine or reflex nature. It is also seen as an answer to the ‘where is it?’ location question. The processing of the dorsal is unconscious, and is faster than the consciousness-related processing of the ventral stream.
Spatial coordinates and phenomenology in the two visual systems model Pierre Jacob & Frederique de Vignemont, Institut Jean Nicod & New York University In:- Perception, Action & Consciousness (2010) – Eds. – Gangopadhyay, N., Madary, M. & Spicer, F. Goodale and Milner introduced the concept of the ‘two visual systems’ model in 1992. This involves a functional distinction between vision used for perception, involving the separation of an object from its background, and Read more […]
The First Half Second Eds. Haluk Ogmen & Bruno Breitmeyer MIT Press (2006) Summary and review of the above book This book aims to look at the brain’s visual processing from the initial stimuli to the eventual outcome of the subject’s behaviour. Responses to stimuli emerge only after a measurable period of time, usually between 250 and 500 ms, referred to as ‘latency’. The book looks particularly at how unconscious processing in the thalamus and primary cortex became a conscious representation Read more […]
Cortical visual systems for perception and action David Milner & Melvyn Goodale, University of Durham and University of Western Ontario In:- Perception, Action and Consciousness – Eds. Gangopadhyay, N., Madary, M. & Spicer, F. Keywords: ventral stream, dorsal stream, Milner & Goodale, Aglioti, Biegstraaten The authors had previously proposed a model in which there are distinct paths for vision for perception and vision for action. This involves to pathways the ventral Read more […]
Sight Unseen Melvyn Goodale & David Milner, University of Ontario & University of Durham Oxford University Press INTRODUCTION: Goodale and Milner’s work points to a ventral stream in the brain that produces conscious visual perception and a separate dorsal stream supporting non-conscious visuomotor orientations and movements. For consciousness studies, this is important in that it appears to refute the simplistic, but often well-received contention, that consciousness is just what Read more […]