Figure 1. Altered functional activation of brain systems during brain ageing.

Functional imaging of brain activation during task performance shows a change in activation patterns as the human brain ages. a, Top: functional magnetic resonance imaging scans show simultaneous activation of the medial prefrontal cortex (mPFC), posterior cingulate (pC) and lateral parietal cortex (LP) in young adults, but this temporal correlation of activity is considerably reduced in aged individuals. (Images reproduced, with permission, from ref. 2.) Bottom: hypothetical connections between areas of the mPFC, pC and LP may mediate the coordinated activation in young adults, whereas declining function of such connections could underlie the observed disruption in coordinated activity in ageing brains. (Images courtesy of C. Koch, California Institute of Technology, Pasadena.) b, Positron emission tomography shows that young adults performing a memory test exhibit right-lateralized brain activation. Aged adults with poor performance in this test also had right-lateralized PFC activity, but aged adults with good performance showed bilateral activation. Thus, recruitment of additional brain areas may compensate for age-dependent functional decline in the primary areas subserving cognitive abilities (3, 5). (Images reproduced, with permission, from ref. 5.)