Fig. 2.

Competition between sickness and maternal motivational states. In the experiments illustrated in this figure the sickness motivational state was maintained constant thanks to a fixed dose of lipopolysaccharide (LPS) sufficient to cause apathy and disinterest toward its pups in a lactating dam while the strength of the incentive stimuli for maternal behavior was gradually increased. The left figure represents the normal behavior of a dam with its litter. The figure in the middle shows what happens when the nest is removed and replaced by cotton wool and the pups are dispersed in the cage. The sick dam emerges from its lethargy and engages in pup retrieval but not in nest building when tested at 24 °C. The figure in the right shows what happens when the ambient temperature decreased from 24 to 6 °C. In this case the sick dam engages in both pup retrieval and nest building [3].