Neuropsychologia
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Moorlaas (1928) proposed that apraxic patients can identify objects and can remember the purpose they have been made for but do not know the way in which they must be used to achieve that purpose. Knowledge about the use of objects and tools can have two sources: It can be based on retrieval of instructions of use from semantic memory or on a direct inference of function from structure. The ability to infer function from structure enables subjects to use unfamiliar tools and to detect alternative uses of familiar tools. ⋯ Analysis of LBD patients' lesions suggested that frontal lobe damage does not disturb novel tool selection. Only LBD patients who failed on pantomime of object use and on novel tool selection committed errors in actual use of familiar tools. The finding that mechanical problem solving is invariably defective in apraxic patients who commit errors with familiar tools is in good accord with clinical observations, as the gravity of their errors goes beyond what one would expect as a mere sequel of loss of access to instruction of use.