Unifying cognitive aging: From neuromodulation to representation to cognition

An integrative theory relating cognitive aging deficits observed at the beh avioral level with age-related deficiency in neuromodulation causing less d istinctive cortical representations is tested in a series of neural network simulations. Age-related attenuation of catecholaminergic function is simu lated by lowering the mean gain of the processing unit, which subsequently reduces responsivity and raises intra-network activation variability. Age d ifferences in learning rate, asymptotic performance, interference susceptib ility, complexity cost, intra- and interindividual variability, and ability dedifferentiation can all be modeled. Together, the simulations illustrate catecholamine's role in regulating the fidelity of neural information proc essing and subsequent effects leading to cognitive aging deficits. (C) 2000 Elsevier Science B.V. All rights reserved.