Aging, intelligence, and anatomical segregation in the frontal lobes

In this paper we propose a specific neuroanatomical theory of cognitive agi ng. We review evidence supporting the growing consensus that normal adult a ge changes reflect differential deterioration of the frontal lobes of the b rain. Important differences in the pattern of spared and impaired abilities classically linked to aging or frontal lesions are highlighted. Capitalizi ng on neuropsychological and neuroimaging findings, the notion of functiona l and anatomical segregation within the frontal lobes is introduced, sugges ting that the frontal cortex is not equipotential. In particular, the dorso lateral and orbitoventral prefrontal regions are called upon by distinct co gnitive and behavioral functions. A detailed analysis of the literature sug gests that only functions associated with dorsolateral regions are impaired with age, while orbitoventral functions are spared. The hypothesis is adva nced that cognitive aging could be better interpreted in terms of changes i n dorsolateral prefrontal cortex rather than an all-encompassing "frontal" deterioration. Finally, the role of modularity in cognitive aging and front al lobe function is discussed.