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Adaptation
1. Adaptation – examples and definitions
2. Adaptation as efficient coding
3. A tradeoff between sensitivity and efficiency
4. Adaptation and perception
5. Adaptation occurs over multiple timescales
6. Adaptation involves multiple mechanisms
Mori, Sasakura, & Kuhara, 2007
Adaptation with 302 neurons
C. elegans
Adaptation with thousands (?) of neurons
Rhodes, Jeffery, Watson, Clifford, & Nakayama 2003
human psychophysics
exposed to compressive distortion exposed to expansive distortion
Adaptation with millions (?) of neurons
How does this explain that?Why might this be useful?
stimulus
Smirnakis & Meister, 1997
Adaptation
1. Adaptation – examples and definitions
2. Adaptation as efficient coding
3. A tradeoff between sensitivity and efficiency
4. Adaptation and perception
5. Adaptation occurs over multiple timescales
6. Adaptation involves multiple mechanisms
The idea of efficient coding
1. Each neuron should use all parts of its dynamic range with roughly equal frequency.
2. Information encoded in the spike train of one neuron should not be duplicated in the spike train of another neuron.
1. Each neuron should use all parts of its dynamic range with roughly equal frequency.
The idea of efficient coding
Encoding a natural distribution efficiently
Dunn and Rieke, 2006
Laughlin 1981redrawn in Wark & Fairhall 2007
Encoding a natural distribution efficientlyEqual areas of probability density should correspond to equal segments of dynamic range.
Laughlin 1981redrawn in Wark & Fairhall 2007
Changing stimulus statistics
Laughlin 1981redrawn in Wark & Fairhall 2007
Changing stimulus statistics
Laughlin 1981redrawn in Wark & Fairhall 2007
Efficient coding of a changing distribution
Adaptation
Adaptation
1. Adaptation – examples and definitions
2. Adaptation as efficient coding
3. A tradeoff between sensitivity and efficiency
4. Adaptation and perception
5. Adaptation occurs over multiple timescales
6. Adaptation involves multiple mechanisms
Enroth-Cudgell & Lennie, 1975
An example:light adaptation in the retina
cat RGC
spatial integratorhigh redundancy
spatial edge detectorlow redundancy
An adaptive change in receptive field
low luminance(low signal-to-noise)
high luminance(high signal-to-noise)
An adaptive change in receptive field
temporal edge detectorlow redundancy
high luminance(high signal-to-noise)
temporal integratorhigh redundancy
low luminance(low signal-to-noise)
Adaptation
1. Adaptation – examples and definitions
2. Adaptation as efficient coding
3. A tradeoff between sensitivity and efficiency
4. Adaptation and perception
5. Adaptation occurs over multiple timescales
6. Adaptation involves multiple mechanisms
Repulsive perceptual adaptation
http://homepages.inf.ed.ac.uk/jbednar/tae.html
Repulsive perceptual adaptation
Bacon & Murphey 1984see http://www.biol.sc.edu/~vogt/courses/neuro/neurolabs.html
The cricket cercal system
cell 1 cell 2 cell 3 cell 4
wind direction (degrees)
r / rmax
Theunissen & Miller 1991Salinas & Abbott 1994
v
Attractive neural adaptation
macaque MT
adaptingstimulus
adaptingstimulus○ before
● after
Kohn and Movshon, 2004
Kohn and Movshon, 2004
Attractive neural adaptation can explain repulsive perceptual adaptation
Adaptation
1. Adaptation – examples and definitions
2. Adaptation as efficient coding
3. A tradeoff between sensitivity and efficiency
4. Adaptation and perception
5. Adaptation occurs over multiple timescales
6. Adaptation involves multiple mechanisms
Adaptation on many timescalesin the same neuron
Smirnakis et al. 1997salamander RGC
Adaptation on many timescalesin the same neuron
velocity
Fairhall et al. 2001blowfly H1
Adaptation on many timescalesin the same neuron
single exponential process
cascade of exponential processes
Drew and Abbott, 2006model
Adaptation
Adaptation
1. Adaptation – examples and definitions
2. Adaptation as efficient coding
3. A tradeoff between sensitivity and efficiency
4. Adaptation and perception
5. Adaptation occurs over multiple timescales
6. Adaptation involves multiple mechanisms
Mechanisms of adaptation:intrinsic mechanisms
Lancaster and Nicoll, 1987
Vm
Iinj
Mechanisms of adaptation:synaptic mechanisms
Tsodyks & Markram 1997
Mechanisms of adaptation:circuit mechanisms
Hosoya et al., 2005
Costs of adaptation
Adaptation worsens the ability of a system to encode the absolute magnitude of a stimulus.
Noise in the signals controlling gain can produce noisy fluctuations in gain.
input output
