Frontal Defects Contribute to the Genesis of Closing-in in Alzheimer's Disease Patients

Closing-in (CI) refers to copying drawings near to or superimposed on the original model, and is often observed in Alzheimer's disease (AD) patients. Contrasting hypotheses have been suggested to explain CI, but no prospective study has directly verified these interpretations. We evaluated the role of frontal/executive versus visuo-spatial impairments in a prospective sample of AD patients, and also explored whether different types of CI are related to specific neuropsychological tasks. We enrolled 64 AD patients who underwent copying tasks and an extensive neuropsychological assessment of visuo-spatial and visuo-constructional skills, frontal/executive abilities and anterograde memory. AD patients with CI showed more severe impairment on frontal/executive functions than AD patients without CI. Moreover, the tendency to produce copies superimposed on the model was selectively associated with poor inhibitory control for irrelevant responses. On this basis, we suggest that different CI phenomena could be ascribed to distinctive frontal/executive defects.