FURTHER ANALYSES OF CLOCK DRAWINGS AMONG DEMENTED AND NONDEMENTED OLDER SUBJECTS

In a previous article we described a 10-point scoring system (i.e., sc ale I) to grade clock drawings to command and copy with hands set for ''ten after 11'' among demented patients. Alzheimer's subjects (AD) im proved from the command to copy conditions, whereas subjects with isch aemic vascular dementia (IVD) did not. To investigate the underlying c ognitive deficits responsible for this profile, an additional scale wa s developed (scale 2) that tallied errors in graphomotor functioning, hand/number placement, and executive control. On an independent sample of subjects, AD subjects, again, made significant improvement on scal e I from the command to copy condition, whereas no such improvement oc curred among the IVD subjects. On scale 2, IVD subjects made more grap homotor errors in the command condition, and more executive control an d more total errors in the copy conditions than AD subjects. A number of positive correlations were noted between tests of language and memo ry on scale 1. By contrast, scares on tests of executive control decli ned as scale 2 errors increased. In addition, a principal component an alysis indicated that scale 2 test performance loaded on a factor with other tests related to executive control. These results suggest that impairment in frontal systems functioning may explain why IVD subjects do not improve from the command to copy conditions on scale 1. Such a pattern of performance in clock drawing may also be helpful in making a differential diagnosis between AD and IVD.