Three hypotheses were tested in the current study. Firstly, it was
hypothesized that patients with a diagnosis of very early DAT would
perform worse than a matched control group of non-demented individuals
on the Object-Place Association Task (OPAT):
1. On the delayed recall trial of the task, the patient group would be
more impaired in their ability to associate the objects with their
location.
2. In the acquisition phase, patients would show a slower improvement
than the control group, and therefore would require more trials to
arrive at a perfect performance.
Secondly, it was hypothesized that the Clock-Anomalies Detection Task
(CADT) would not be successful in discriminating between the groups at
an early stage of the disease, and therefore that no significant
difference would be found between the groups in detection of anomalies.
Thirdly, it was hypothesized that participants would be correctly
classified into either the patient group or the control group solely on
the basis of their performance on the CADT and the OPAT.
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.