It is obviously true that the nature of a journey depends on where it began, and on the places visited along the way. Thus cognitive function is shaped by factors operating across the whole of the life course, with implications for the accumulation of cognitive reserve and risk of cognitive impairment. These factors begin with genes but include the uterine environment and the highly malleable stage of infancy; they then appear through the school years and during transition into the adult word of work and lifestyle choices; finally, they are still evident in later life, when the effects of normal and abnormal brain ageing are increasingly important. Behind these influences, cognitive function itself tracks across the life course, although it is not always clear whether level of prior cognition influences rate of cognitive decline in later life, or simply the level from which such decline begins. Nevertheless, to the extent that cognition does track, it follows that influences on cognition at any stage of the life course are capable of indirectly influencing cognitive functioning at subsequent stages. This talk will offer a broad overview of this framework and key supporting evidence.