Standard Teaching on Apraxia
André Roch Lecours Jean-Luc Nespoulous Pierre Desaulniers
This chapter deals with a somewhat renewed conception of apraxia. The subject matter has long been and, to a large extent, remains classical standard teaching on apraxia. In a preliminary section, we summarize a not-so-standard although equally classical conception of human motility and its neuroanatomical substratum, and thereafter define apraxia by reference to this conception. Also as a preliminary, and in order to define what apraxia is not (at least in the context of this chapter), we briefly discuss the various forms of motility disorders that can be observed in clinical neurology. The last and main section bears on apraxia, more precisely on upper limbs apraxia.
Most of us can conceive of the world as having two sides, the right one and the left one, which can be apprehended because we have two eyes, two ears, and so forth, and upon which we can act because we have two hands (among other reasons), the right one and the left one, the clever one and the clumsy one. And most of us also agree that there are two halves to the human brain, an assertion which one can choose to consider in either of two manners. On the one hand, one might state that there are the anterior or prerolandic, as opposed to the posterior or retrolandic halves: and one might thereafter insist that the former is the executive half and the latter the cognitive one. Or else, on the other hand, one might state that there is the left or dominant half or hemisphere ("dominant" because it governs language behaviors as well as the activities of the clever hand), as opposed to the right or nondominant half: and one might thereafter insist that each constitutes the biological substratum of one of two modes of human cognition, the analytic or deductive mode for the left hemisphere, and the holistic or inductive mode for the right one.