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From Colour to Perception to Neuroscience Arne Valberg Norwegian University of Science and Technology Section of Biophysics and Medical Physics Trondheim, Norway. Newton and optical phenomena. The nature of colours (Leonardo da Vinci about 1500)
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Norwegian University of Science and Technology
Section of Biophysics and Medical Physics
(Leonardo da Vinci about 1500)
”There are six simple colours…. White is the first among the simple colours, yellow the second, green the third, blue the fourth, red the fifth, and black the sixth”
Leonardo da Vinci: Traktat von der Malerei. Jena, Diederichs 1925, p.85.
” In the eye there are three types of nerve fibres. Stimulation of the first one excites the sensation of red, stimulation of thre second the sensation of green, stimulation of the third the sensation of violet”and he continues”…(the essence of Young’s hypothesis is) that the sensations of colour are imagined as composed of three mutually and completely independent processes in th neural substrate.” Hermann von Helmholtz, 1860/1911
Young-Helmholtz’ view on colour vision
Distribution of cone receptors.(no rods and no S-cones in the central fovea).
λmax= 570 nm (yellow), 545 nm (yellow-green), and 445 nm (violet)
Figur fra Valberg, 2005
James Clerk Maxwell (1831 – 1879)
and the colour top
”… it is not necessary to specify any given colours as typical for these primary sensations. … any of three colours might have been chosen, provided that white resulted from their combination in proper proportions”
CIE chromaticity diagram
Symmetric hue circle
Registration of nerve pulses from a nerve cell with a microelectrode
MC-cells respond to contours
and how to simulate them
Data base: Single cell recordings from the LGN of macaque monkeys (done at Max Planck Institute for biophysical Chemistry, Göttingen (D)) .
Collaborators: Barry B. Lee, Thorstein Seim, and Jo Tryti.
How do we arrive at a model for colour scaling?A possible (theoretical) combination of the different cone opponent cell responses along orthogonal axes.(response to the white adapting stimulus subtracted)
Movement and direction of movement (MC)
Contour (PC, KC)
Opponent combination (difference) of cone signals,
for instance VM and VL:
● Perception. Opponent unique colours red-green, yellow-blue, white-black. Mechanisms unknown.
● The spectrum
● Colour matches. Photoreceptors L, M, and S (retina).
● Opponent ganglion cells: ’L-M’, ’M-L’, ’M-S’, ’S-L’. Incr. & Decr. cells (retina, LGN).
● Simulation of cell responses (retina, LGN)/model (V1?). Scaling.
● ”Bottom up” (retina, LGN) versus ”top down” (V4, V2...).
● Unique colours and surround effects (simultaneous contrast, adaptation, ”colour constancy”) unexplained.
in colour vision
How did colour vision evolve?
What is the neural code for colour?
How is colour organized in the cortex?
How are colour differences scaled?
How to explain the aesthetics of colour?
How does the eye adapt to light and colour?
Which are the cone inputs to cone-opponent cells?
What is the significance of colour?
How do colour qualia come into being?
How do colour opponent neurons interact?
How many colour vision deficiencies are there?
How are cone-opponent cells spatially organized?
What is the status of elementary (opponent) colours?
Which are the most important non-linearity in colour vision?
What are the neural correlates for white and black?
What is the genetic basis of colour vision deficiencies?
How can colour constancy and adaptation be explained?
How does neural activity correlate with colour perception?
How many (shifted) visual pigments can a photoreceptor have?
How many dimensions do colour perception have (modes of appearance)?
How is the relation between receptor specificity and pigments established?
How do ganglion cells pick receptors for receptive field centre and surround?
Is a receptor identity (as L or M type) established solely by its pigment (or cant here
with an M pigment?)
Eye dominance and orientation sensitive columns
The knots (corresponding to the circles in fig.A) are colour sensitive
Model stages and important parameters.
Stimulus → sensory response → neural representation →perception
Stimulus: Spectral distribution of interference filters, Intensity, Size, Spatial contrast. 5 log units of intensity
Sensory response: Receptors (L,M,S), Light absorption and non- linearity, Standing potentials, Adaptation
Neural representations: Firing frequency, Receptive field,Increment- and Decrement opponent cells (ON & OFF),
Adaptation (retina and LGN)
Perceptual properties: Elementary colours (Y, R, B, G)
Hue, Colour strength, Relative lightness (black, grey, white), Brightness.
Object colours and light colours (reflecting and emitting sources of colour), Colour scaling
Albert Einstein, 1950
”Nothing can exist in conscioussness without having first passed the senses.”