[Closing-in phenomena observed in patients with Alzheimer's disease--analysis of drawing behavior and eye movements].

'Closing-in' symptom is defined as a tendency to close-in on the model while performing constructive tasks. This unique symptom is one of the constructional apraxia often observed in Alzheimer's disease (AD), which is considered to be involved in visuospatial dysfunctions. However, little is known about the nature of the symptom and pathophysiology underlying the symptom. In this study, we examined drawing behavior, eye movements of AD (n = 19), multi-infarct dementia (n = 8) and age matched healthy subjects (n = 10). 1) In AD, contrary to age matched healthy subjects, the patients drew slowly with apparent difficulty and drawing behavior was disorganized. The copied figures were incomplete and often fragmented. The spatial relationships of the parts were lost each other during copying a Necker's cube. 2) The characteristic eye movements were observed in AD patients with apraxia, and closing-in symptom. These were consisted of gaze apraxia, and disorders of visual attention appeared similar to Bàlint's syndrome. 3) The eye movements of the AD patients with closing-in symptoms were classified into wandering of fixation, locking of fixation, and mixed types. The 'closing-in' symptoms in copied figures were classified into three types, overlap, adherent, and near types. Then, the wandering type was seen both in near and adherent types, whereas the fixation type was only found in the overlap type. 4) SPECTs showed reduced RI activities in the parieto-occipital and in the frontal regions of AD patients with apraxia and closing-in symptoms. Our results suggest that AD patients may have a difficulty to create abstract space from concrete space. This may also imply regression to a primitive undifferentiated stage where gnostic and practic behavior is not differentiated in terms of space appreciation.