Age dependent de-differentiation across functional domains

Introduction: There is evidence that functional specialisation of the human cerebral cortex decreases with age (Park et al., 2004). Evidence for this process, known as de-differentiation, was provided so far only by examination of individual functional networks (Park et al. 2010). On the other hand, little is known about similar mechanisms during cross-modal processing. The present study examined potential age related de-differentiation across two cognitive domains by assessing aging effects of motor control and selective attention.

Methods: 101 right-handed healthy adults (49 female) with a balanced age distribution between 21 and 71 were scanned (3T Tim-TRIO, Siemens). Functional (BOLD) images were obtained using an EPI sequence while subjects performed an experimental paradigm consisting of two conditions: Self-paced alternating left/right index finger tapping (TAP) and a letter counting task keeping track of the number of E's in a stream of letters (COUNT).

Results: The activation pattern for both tasks were largely differentiated into two seperate networks. Thus, a classification in task specific components was feasible. Two areas in those components showed age related recruitment patterns: In the TAP component, activation in right parietal opercular area OP1 (Fig.1 green arrow) was negatively correlated with age during TAP and positively correlated during COUNT. Superior parietal area 7A of the COUNT component (Fig.1 red arrows) showed the opposite pattern.

Conclusions: We here demonstrated for the first time a functional activation shift in the elderly across different domains. With respect to the de-differentiation hypothesis, which reflects a breakdown of neural specificity, the results suggest that a loss of neural specificity in one region can alter to compensatory over-recruitment depending on the functional context. This functional activation shift suggests an adaptive character of functional integration in the healthy aging brain.

Literatur: Park DC, Polk TA, Park R, Minear M, Savage A, Smith MR (Aging reduces neural specialization in ventral visual cortex. Proc Natl Acad Sci U S A 101:13091-13095.2004). Park J, Carp J, Hebrank A, Park DC, Polk TA (Neural specificity predicts fluid processing ability in older adults. J Neurosci 30:9253-9259.2010).