p073fig02.22 An on-center off-surround network is capable of computing input ratios.<BR>||  Computing with patterns.<TABLE border="1"><TR><TD>How to compute the pattern-sensitive variable: </td><TD>θi = Ii / sum[k=1 to n: Ik]?</td></tr><TR><TD>Needs interactions! What type? </td><TD>θi = Ii / sum[k ≠ i: Ik]</td></tr></table>Ii↑ ⇒ θi↑ excitation, Ik↑ ⇒ θk↓, k ≠ i  inhibition<BR>On-center off-surround network.