Linking the 'why' and 'how' of ageing: evidence for somatotropic control of long-term memory function in the pond snail .

Organisms live on a budget; hence, they cannot maximize all their activities at the same time. Instead, they must prioritize how they spend limiting resources on the many processes they rely on in their lives. Among others, they are thought to economize on the maintenance and repair processes required for survival in favour of maximizing reproduction, with ageing as a consequence. We investigate the biological mechanisms of neuronal ageing. Using , we have previously described various aspects of age-associated neuronal decline and appetitive long-term memory failure. In view of postulated trade-offs between somatic maintenance and reproduction, we tested for interactions between resource allocation mechanisms and brain function. We show that removal of the lateral lobes, which are key regulators of energy balance in , increases body mass and enhances appetitive learning, raising the possibility that the lateral lobes are one of the sites where the 'why' and 'how' of (neuronal) ageing meet.