General and specific age effects on brain activity

Aging is one of the most relevant challenges for our society. For this reason high-quality research in this field is highly relevant, since age impacts on cognitive processes and brain activations in several ways. Some cognitive functions are known to develop with age, others remain relatively stable across adulthood and others decline with age. The same is true for brain activation associated with cognitive functions. In more complex cognitive tasks, several cognitive functions and their neuroanatomical correlates are recruited. In such tasks one can expect age to have a more pronounced detrimental influence on specific stages of information processing combined with an unspecific effect on other stages of information processing. For this reason, one should distinguish between specific and general effects of age on cognitive processes. While general effects of age are common to different aspects of cognitive functioning, specific effects of age affect given cognitive functions in a unique way. In the present study, specific and general effects of age on interference processing as well as number magnitude representation will be examined. The working hypothesis for the current study is partly based upon previous findings (Kaufmann et al., 2005, 2006, Wood et al., in press). From the results of a previous study (Wood et al., in press), we expect general effects of age on interference processing and number magnitude: activation patterns in a more distributed prefrontal network should be recruited by elderly participants in response to interference processing, while magnitude processing as involved in number comparison tasks should be the strongest in intraparietal regions in younger adults. Moreover, specific effects of age should be found in brain areas associated with the adoption of age-related compensatory strategies. Overall, this study aims at elucidating the following questions: Which brain regions are sensitive to age effects on interference and magnitude processing? In those regions sensitive to age effects, can specific age effects be differentiated from general ones? When a differentiation is possible, how relevant are specific age effects in comparison to general ones in the regions sensitive to age effects?

Aging is one of the most relevant challenges for our society. For this reason, high-quality research in this field is highly relevant, since age impacts on cognitive processes and brain activations in several ways. Some cognitive functions are known to develop with age, others remain relatively stable across adulthood and others decline with age. The same is true for brain activation associated with cognitive functions. In more complex cognitive tasks, several cognitive functions and their neuroanatomical correlates are recruited. In such tasks, one can expect age to have a more pronounced detrimental influence on specific stages of information processing combined with an unspecific effect on other stages of information processing. For this reason, we aimed at disentangling specific and general effects of age on cognitive processes. While general effects of age are common to different aspects of cognitive functioning, specific effects of age affect given cognitive functions in a unique way. In the present study, specific and general effects of age on interference processing as well as number magnitude representation were examined. General effects of age on interference processing and number magnitude were found in large brain regions including frontoparietal networks. Specific effects of age on different cognitive tasks could not be found after controlling for brain structure and brain activity parameters. Overall, this study showed that the contribution of neuroanatomical and functional aspects of the brain to cognitive function seem to affect a number of cognitive functions in a similar way.Key words: size-congruity effect, counting Stroop, aging, fMRI, structural equation models