Recent research has provided a better understanding of the localization of the neuro-anatomical abnormality in AD, and with the growing evidence for the role of these regions in different cognitive abilities, it is now becoming possible to design briefer approaches to diagnosis which target affected neurocognitive networks (Blackwell et al., 2004; Robert et al., 2003; Saling, Maccuspie-Moore et al., 2002; Solomon et al., 1998). There is increasing evidence regarding staging of the structural and functional changes in the MTL region and temporoparietal structures respectively. Understanding how damage to these areas affects performance first on new learning of arbitrary associations, and then on the integrity of the semantic system, suggests that tasks that tap into these abilities will be successful in screening for memory difficulties associated with DAT.
Clock-Anomalies Detection Task (CADT)
Consistent with the recently successful demonstration of the Clock-Anomalies Detection task as a strong predictor of membership in a group of mild to moderate dementia (Saling, Maccuspie-Moore et al., 2002b), this study investigated the utility of this task in screening for the earliest end of the dementia spectrum. As semantic processing was suggested to be mediated by temporoparietal structures, it seems reasonable to speculate that at the early stages of AD, when levels of temporoparietal hypometabolism are relatively low, the detection of clock anomalies will not be significantly impaired compared to a group of healthy elderly controls.
Object-Place Association Task
Recent studies have demonstrated the difficulty of DAT patients in forming and maintaining associations between objects placed in arbitrary locations using the computerized PAL task (Blackwell et al., 2004; Fowler et al., 2002). In the current study, a similar desktop version of the PAL task was evaluated, with the aim to reconfirm the value of this paradigm in the earliest stages of AD with the use of a non-computerized version. As some elderly individuals may feel intimidated by computerized tests, the desktop version might be better tolerated by some of these patients.
The Object-Place Association Task (OPAT) developed for this study measures the ability to form arbitrary associations between every-day objects and boxes located on a small board in which they are hidden. The task was administered with both an acquisition phase, and a delayed recall trial. These tasks rely on a demonstrated relationship with specific neurocognitive systems affected in early DAT. Further, the OPAT and CADT can be administered within a few minutes, with minimal professional knowledge, and are non-threatening. These features emphasize their potential value in clinical settings.