Decision-making and apathy in early stage of Alzheimer's disease and in mild cognitive impairment

Abstract

Decision-making and apathy have common neuropsychological processes and neuroanatomical substrates. However, their links in mild cognitive impairment (MCI) and Alzheimer's disease (AD) remain unclear. in order to evaluate these links, we compared 3 groups of 20 control subjects to 20 patients with MCI and 20 patients with mild AD. All participants completed the mini mental state examination (MMSE), the Lille apathy rating scale (LARS, a multidimensional scale of apathy), the game of dice task (GDT, assessing decision under risk) and the Iowa gambling task (IGT, assessing decision under ambiguity). 60% of patients in both clinical groups were apathetic versus 5% of control subjects. In both clinical groups the IGT and GDT net scores were comparable (respectively: p = 0.76 and p = 0.84), while the control group had higher scores than MCI and AD's groups (respectively, GDT p < 0.02 and p < 0.05; IGT: p < 0.05 and p < 0.05). Cognitive impairment increased the risk of disadvantageous choices in decision under risk (× 6), and under ambiguity (× 3.5). No global contribution of apathy was found for decision-making performances (all PS > 0.05), but on the LARS, the "intellectual curiosity" (cognitive dimension) was a predictor for the performances on GDT's (OR = 1.73, p = 0.05), while the "action initiation" (behavioral dimension) was a predictor of those on IGT (OR = 1.57, p = 0.05). these results highlight the behavioral and the cognitive sensitivity of the IGT and the GDT, and are analyzed according to Levy and Dubois's model of apathy, and to the three steps of the decision-making process of Gleichgerrcht et al. (2010). However, more researches are necessary to explain the causality links between action initiation and decision under ambiguity.