22 * yx

yxxy

Notice:1) The peak of the function =1 (its an autocorrelation)2) The triangular shape is a

result of zero padding3) The secondary peaks

mean the signal has some repetition

Autocorrelation calculated by:

retinal ganglion cell responses to a fluctuating light stimulus

The peaks of the cross correlation functions using Matlab’s “xcorr”

Offt, On

Offs, On

Offs, Offt

Offt, Offs

Time (ms)

cros

s co

rrel

atio

n co

effic

ient

A = fft (signal a)B = fft (signal b)Fourier Cross Correlation = ifft(A*conj(B))

Using the Fourier transform to calculate the cross correlation