neuroscience Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, development ...

the bridge locus for a particular sensory

percept Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...

is a hypothetical set of

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...

s whose activity is the basis of that sensory percept. The term was introduced by D.N. Teller and E.Y. Pugh Jr. in 1983, and has been sparingly used. Activity in the bridge locus neurons is postulated to be

necessary and sufficient In logic and mathematics, necessity and sufficiency are terms used to describe a conditional or implicational relationship between two statements. For example, in the conditional statement: "If then ", is necessary for , because the truth of ...

for sensory perception: if the bridge locus neurons are not active, then the sensory perception does not occur, regardless of the actual sensory input. Conversely if the bridge locus neurons are active, then sensory perception occurs, regardless of the actual sensory input. It is the highest neural level of a sensory perception. So, for example,

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

l neurons are not considered a bridge locus for visual perception because stimulating

visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...

can give rise to visual percepts. Not all scholars believe in such a neural correlate of consciousness. Pessoa et al., for example, argue that there is no necessity for a bridge locus, basing their argument on the requirement of an isomorphism between neural states and conscious states. Thompson argues that there are good reasons to think that the notion of a bridge locus, which he calls a "localizationist approach", is misguided, questioning the premise that there has to be one particular neural stage whose activity forms the immediate substrate of perception. He argues, based upon work by Zeki & Shipp, DeYoe & Van Essen, and others, that brain regions are not independent stages or modules but have dense forward and backward projections that act reciprocally, and that visual processing is highly interactive and context-dependent. He also argues that cells in the visual cortex "are not mere 'feature detectors, and that neuroscience has revealed that the brain in fact employs distributed networks, rather than centralized representations. He equates the notion of a bridge locus to a

Cartesian theatre "Cartesian theater" is a derisive term coined by philosopher and cognitive scientist Daniel Dennett to refer pointedly to a defining aspect of what he calls Cartesian materialism, which he considers to be the often unacknowledged remnants of Carte ...

and suggests that as a notion it should be abandoned.

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