The **Sequence** choice variable is used to select the method of correlation. The mathematics behind these functions is described in the Tina memos and published papers.

**compare** initiates the comparison between the image sequence and the
stimulus function. The stimulus function is selected using the stimulus
choice variable and the comparison performed using the technique selected
with the sequence choice variable. The resultant correlation image is stored
on the top of the image stack.

The 3 correlation functions are given below. is the image pixel at the current location taken from the 'th image from a sequence of , is the mean value of the image sequence, is the 'th value from the stimulus function and is the mean value of the stimulus sequence.

(19.1) |

(19.2) |

(19.3) |

These statisitcal measures are our interpretation of the basic statistical approaches taken in the GBAM software, STIMULATE software and by Friston's group (Tina memo 2001-002).