Temporal preparation in aging: a functional MRI study

Young and elderly adults performed a choice-RT task while scanned with functional magnetic resonance imaging. A foreperiod separated a warning and a response signal. In the variable condition, the foreperiod varied randomly between 1 and 3s. In the fixed conditions, it was kept constant at either 1 or 3s. Elderly subjects responded slower than controls in both task conditions. An interaction was observed between age and foreperiod in the variable condition only: in the young group, RT decreased with longer foreperiods, whereas the elderly participants showed the opposite tendency. This was accompanied by difference in brain activation. Right lateral prefrontal regions were more activated in the young than in the elderly group in the variable vs. fixed foreperiod contrast. These findings unveil the neural substrate of age-related preparation deficits, and confirm that the involvement of right lateral prefrontal cortex is essential for strategic preparation under uncertain timing conditions.