Adaptation 1.Adaptation – examples and definitions 2.Adaptation as efficient coding 3.A tradeoff between sensitivity and efficiency 4.Adaptation and perception.

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