Apraxia: the rise, fall and resurrection of diagrams to explain how the brain works

The purpose of brains is to make movement. A brain has to identify what is going on in the environment and in its attached body and generate movements to stay alive and procreate to keep the species going. Movements of a person, which includes speech, are all that other people know of another person. The repertoire of movements that people can make is very broad, and even most ordinary movements are complex. Eating and dressing, for example, involve multiple body parts making a series of coordinated multi-joint movements. The movements of highly skilled athletes and musicians are so well tuned that most persons cannot match them. These complex movements that form the behaviour of everyday life are praxis movements. Their failure is apraxia. To call such a failure apraxia, of course, requires that the deficit cannot be explained by a more basic abnormality such as weakness, sensory loss, ataxia or aphasia. The range of capability of the brain to make movement is so large that there can be many types of failures. This has generated different classification schemes with a variety of different terms, sometimes with the same term meaning something else in a different classification. The book by Goldenberg on apraxia contains a comprehensive description of different manifestations of apraxia and addresses the different classifications. Chapters 6 through 14 deal with topics such as imitation, body part specificity, and use of single tools. Chapters 1 to 5 give the historical background and set the stage for the rest of the book. I found the historical part particularly interesting, both as relates to apraxia but also ideas as to how the brain works. While there were some historical precedents, the first well described cases of apraxia and pathological explanation were from Hugo Liepmann from 1900 to 1908 (Fig. 1). On …