The nature of constructional apraxia in senile dementia
Cameron, Ian A.
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1. The performance of a series of 13 visuo- constructive tasks by 40 patients with senile dementia (mean age 77.87 years) and 20 aged control subjects (mean age 77.55 years) is studied. The aim of the investigation is to define the nature of constructional defect within the patient group.2. The wide heterogeneity of problems posed by conventional testing of constructional ability is discussed.3. In the consideration of results an attempt has been made to isolate major common factors. Executive and gestalt failures are defined as occurring under three conditions of direct copying, spontaneous construction and reproduction from immediate memory, and the patient and control groups are contrasted.4. Other aspects of response not isolated as common features are described discursively.5. In the discussion of results it is concluded that the morbid group under study fail to construct diamond- orientated rather than square - orientated design. They fail to construct design which has no line of symmetry, rather than design which has, and they fail to construct design which has a diagonal line of symmetry rather than a vertical one.6. Patients in faulty response show a tendency to reduce design to symmetry and to the vertical, when it should properly be asymmetrical and non -vertical.7. Horizontal design poses more difficulty to the experimental group than vertical, but not so much as diagonal design.8. Where complexity as defined in this study is beyond perceptual capacity, those aspects of the design which are diamond -orientated are those which fail to be perceived and constructed; though they may be perceived and constructed in less complex designs.9. Failure of visual recognition of design can alone be a cause of faulty construction in seniles.10. In senile patients the need to consider a large number of variables, in a task, in itself may inhibit the best performance the patient is capable of in respect of any one of these variables.11. The identification of the class to which a design belongs, and the analysis of the dimensions of a particular design within that class, are perceptual tasks of a different order differentially affected in senile dementia.12. in spontaneous construction recall fails. In reproduction from imnediate memory retention fails when the task of construction is still in progress.13. Patient group is worse than control group performance in every test. There are 6 'superior' patients whose performance falls within the control range. Qualitative differences between control and patient groups are discussed.14. In more complex construction control subjects show defects similar to those described as occurring in constructional apraxia of focal origin.15. The patient group in this study shows evidence of a specific spatial defect which is similar to that described by authors considering constructional apraxia as an outcome of focal brain damage. In this study other general causes of constructional failure have also been defined. It is suggested that the specific spatial perceptual defect determines failure in the constructional act even before purely motor manipulation activity begins.16. It is tentatively suggested that the spatial defect outlined in this study may be a consequence of loss of awareness of body verticality, allowing the mainly square or vertical orientation of objects in the environment to exert an undue influence upon the patients' perceptual function.