Lecture slides

advertisement
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 with 302 neurons
C. elegans
Mori, Sasakura, & Kuhara, 2007
Adaptation with thousands (?) of neurons
Adaptation with millions (?) of neurons
exposed to compressive distortion
human psychophysics
exposed to expansive distortion
Rhodes, Jeffery, Watson, Clifford, & Nakayama 2003
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.
The idea of efficient coding
1. Each neuron should use all parts of its dynamic range with
roughly equal frequency.
Encoding a natural distribution efficiently
Dunn and Rieke, 2006
Encoding a natural distribution efficiently
Equal areas of probability density should correspond to equal segments of dynamic range.
Laughlin 1981
redrawn in Wark & Fairhall 2007
Changing stimulus statistics
Laughlin 1981
redrawn in Wark & Fairhall 2007
Changing stimulus statistics
Laughlin 1981
redrawn in Wark & Fairhall 2007
Efficient coding of a changing distribution
Laughlin 1981
redrawn in Wark & Fairhall 2007
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
An example:
light adaptation in the retina
cat RGC
Enroth-Cudgell & Lennie, 1975
An adaptive change in receptive field
low luminance
(low signal-to-noise)
high luminance
(high signal-to-noise)
spatial integrator
high redundancy
spatial edge detector
low redundancy
An adaptive change in receptive field
low luminance
(low signal-to-noise)
high luminance
(high signal-to-noise)
temporal integrator
high redundancy
temporal edge detector
low redundancy
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
Repulsive perceptual adaptation
http://homepages.inf.ed.ac.uk/jbednar/tae.html
The cricket cercal system
see http://www.biol.sc.edu/~vogt/courses/neuro/neurolabs.html
Bacon & Murphey 1984
cell 1
cell 2
cell 3
cell 4
r / rmax
wind direction (degrees)
v
Theunissen & Miller 1991
Salinas & Abbott 1994
Attractive neural adaptation
○ before
● after
adapting
stimulus
adapting
stimulus
macaque MT
Kohn and Movshon, 2004
Attractive neural adaptation can explain
repulsive perceptual adaptation
Kohn and Movshon, 2004
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 timescales
in the same neuron
salamander RGC
Smirnakis et al. 1997
Adaptation on many timescales
in the same neuron
velocity
blowfly H1
Fairhall et al. 2001
Adaptation on many timescales
in the same neuron
cascade of exponential processes
single exponential process
model
Drew and Abbott, 2006
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
Vm
Iinj
Lancaster and Nicoll, 1987
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
Download
Related flashcards

Muscle relaxants

58 cards

Epilepsy

15 cards

Create Flashcards