Mutual inhibition is when two or more neurones (artifical or biological) inhibit one another, that is when one being active makes the others less so. This can be direct nodes A and B each inhibit one another, or involve larger cycles, for example A inhibits B inhibits C inhibits A.. If the mutual inhibition is strong, this can lead to a 'winner takes all' situations, for example during disambiguation of an object in an image where, in the end, there is a single classification. Mutual inhibition can also lead to rhythmic behaviour, and can be found in the motor control of animals and insects.
Used on Chap. 6: pages 123, 124