Applications of tuning curves 2

APPLICATIONS OF TUNING CURVES

IN NEUROSCIENCE

Tyler Coye

Alfred University

NEUROSCIENCE

A branch of science that deals with the anatomy, physiology, biochemistry,

or molecular biology of nerves and nervous tissue and especially their

relation to behavior and learning

-Merriam-Webster

Dictionary

http://upload.wikimedia.org/wikipedia/commons/d/db/Structural.gif

TUNING CURVE

Tuning curves are widely used to characterize the

responses of sensory neurons to external stimuli.

http://www.cogsci.bme.hu/~ikovacs/latas2005/prepI_3_1_files/c_fig6.jpg

NEURON CELLS

A neuron is an electrically

excitable cell that processes

and transmits information by

electrical and chemical

signaling.

There are several stimuli that

can activate a neuron leading

to electrical activity, including

pressure, stretch, chemical

transmitters, and changes of

the electric potential across

the cell membrane.

http://upload.wikimedia.org/wikipedia/en/a/a6/Chemical_synapse_schema.jpg

NEURON RECORDING

Single-Cell Recording is a technique used in research to

observe changes in voltage or current in a neuron.

Microelectrode is inserted into the skull and into a neuron in

the area of the brain that is of interest.

http://www.cogsci.bme.hu/~ikovacs/latas2005/prepI_3_1.html

GAUSSIAN TUNING CURVE

0

10

20

30

40

50

60

-60 -40 -20 0 20 40 60

F(H

z)

S (orientation angle in degrees)

APPLICATION OF THE GAUSSIAN TUNING CRUVE

Modeling neuron activation in the primary visual cortex (V1) of a cat

shown bars of light that moved across the receptive field of a cell at

different angles.

(Data points from Henry et al., 1974)

COSINE TUNING CURVE

APPLICATION OF THE COSINE TUNING GURVE

Applied to the primary motor cortex of a monkey that performed an arm-

reaching task.

(Data points from Georgopulos et al,

1982)

SIGMOIDAL TUNING CURVE

0

5

10

15

20

25

30

35

40

-1.5 -1 -0.5 0 0.5 1 1.5

F(H

z)

S (retinal disparity in degrees)

APPLICATION OF THE SIGMOIDAL TUNING CURVE

Applied to data gathered from V1 neuronal activation of a cat shown

separate bars of light in each eye.

(Data points from Poggio and Talbot,

1981)

DESCRIBING A STIMULUS

WEBER-FECHNER LAWErnst

Weber

http://en.wikipedia.org/wiki/File

:Ernst_Heinrich_Weber.jpg

Gustav Theodor

Fechner

http://en.wikipedia.org/wiki/File

:Gustav_Fechner.jpg

Question:

A blind man is holding a weight. The weight

is gradually increased over time. What is the

smallest incrememental change that can be

made in the amount of weight being held

before the man perceives the difference?

Weber found that the smallest noticeable

difference was proportional to the initial

value of the weight.

dp : differential change in perception,

dS: differential increase in the stimulus,

S: stimulus at an instant in time.

K: is an experimentally determined factor.

WEBER-FECHNER LAW

We know that

Integrating we get

Where C is a constant. Setting p (perception) equal to 0 and

solving for C we get

Because perception is 0, S0 is the threshold below which a

stimulus is not perceived. Finally, through substitution we

get

STEVEN’S POWER LAW

Stevens, S. S. (1957)

Stanley Smith Stevens proposed the more

mathematically plausible power-law relation of

sensation to intensity.

I: Intensity of the stimulus

ψ(I) :psychophysical function relating to the Intensity

of the sensation evoked by the stimulus

a: exponent which is stimulation-dependent

For example: when sensation is heaviness

and stimulation is weight, a=1.45.

K: constant which is stimulation and units-dependent.

THE END