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Discussion forum
Apraxia: A conceptual meta-analysis Discussion forum on ‘Apraxia, the cognitive side of motor control’ by Georg Goldenberg Paul Eling* Donders Institute for Brain, Cognition and Behavior, Radboud University Nijmegen, Nijmegen, The Netherlands
Since the nineteen sixties, cognitive models have become fashionable to explain all sorts of phenomena in the domain of language, perception, memory and motor behavior. Many experimental psychologists rejected the behaviorist idea that we should develop theories that are based on stimuluseresponse associations and avoid mentalistic terms. In order to understand behavior, we have to assume that input is processed in some systematic way. Unraveling this ‘systematic way’ is the key problem and requires assumptions, concepts and theories that can do the job. And of course, the brain, an enormously complex network of cells with their fibers, plays a crucial role in this process. Anatomical and physiological features of this organ put some limits on the kind of explanations that may be valid, but it is unlikely that looking at the brain for a long time is going to be helpful in generating process models. The marriage between cognitive psychology and neuropsychology was therefore wise and fruitful: specific behavioral deficits following a brain lesion may reveal something about the underlying functional processes. The rise of modern neuropsychology can, to a large extent, be ascribed to the stimulating activities of Norman Geschwind. He discovered, early in his career, the work of Wernicke and his many influential pupils (Geschwind, 1963; Kean, 1993). It was not Wernicke’s area that triggered Geschwind, but his ‘paradigm’: the description of a (mental) process, language, in the brain in terms of centers and connections (Geschwind, 1965a, 1965b). Wernicke ‘drew’ centers on specific spots on the cortex, but soon there were only circles and connections: these were functional models. With this ‘constructional material’ one can build theories that aim to explain phenomena
that can be observed in a neurological clinic, in patients that seem to be impaired, in a more or less systematic way, in terms of language production and language perception. Physicians could discuss the nature of the processes, assumed to take place in a given center, about the validity of a presumed connection, or the routes through the network. Others, like Bastian (1869), Marshall (1993), Baginsky (1871) and Eling (2005) had preceded Wernicke with this way of thinking (and also leaving out the brain in their figures). However, it was, apparently, Wernicke who convinced his fellow Neuropsychiatrists of the usefulness of this approach. Soon Wernicke’s ‘paradigm’ was used by others to explain other language modalities (Kussmaul, 1877; Lichtheim, 1885), problems in processing music (Knoblauch, 1888), visual recognition problems (Lissauer, 1890) and problems in performing actions (Liepmann, 1900). The German papers from Lichtheim and Knoblauch were translated in English and published in Brain. But soon the British were warned for these ‘diagram makers’ by John Hughlings-Jackson and his pupil, Henry Head (Head, 1926): it was better to abstain from localization of mental functions. An advantage of this kind of theorizing, i.e., producing diagrams, was that it allowed for a further analysis of a ‘faculty’. For centuries the mind had been described in terms of perception, judgment and memory, language being part of memory. Around 1800, Franz Joseph Gall strongly argued against such a psychology and introduced new faculties, closely related to behavioral patterns, such as propagation, attachment, sense of property, memory of things and facts, sense of locality, faculty of spoken language and the faculty of imitation (Gall & Spurzheim, 1810e1819; Lesky, 1979).
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Please cite this article in press as: Eling, P., Apraxia: A conceptual meta-analysis, Cortex (2014), http://dx.doi.org/10.1016/ j.cortex.2014.02.005
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Ecologically valid, one could say. Gall also argued that these faculties have their seat in the cortex and for this more general claim he produced important neuroanatomical evidence. The Experimental Physiologist Jean Pierre Flourens admired Gall for his anatomical work, including a number of discoveries, and he also agreed with the general claim: faculties are localized in the brain. But he strongly opposed to his psychology! Gall’s claim of multiple faculties was silly, the mind is a unity like Descartes had stated, Flourens (1846) and Lelut (1837) argued (see Clarke and Jacyna, 1987). Without much debate about the unity of the mind, Wernicke presented his psychological theory: he assumed that language is subserved by several specialized centers as well as the rest of the cortex, where all sorts of representations necessary for communication are stored. Apparently, honorable scientists could now think about multiple faculties, and they did. A dangerous property of diagrams is the temptation to speculate about the localization of such a functional center in a specific spot in the brain. Wernicke, of course, had started out tracing the auditory nerve to the temporal lobe before he began his project on receptive aphasia and concluded that Broca was not completely right (Keyser, 1993). For Wernicke, localization in the brain was crucial: he rejected the contribution of Baginsky since the latter had only a psychological model and no neuropathological data supporting it (Eling, 2005; Wernicke, 1974). For many, it was (and, in my view, still is) difficult to distinguish between the functional and localization claims of such diagrams. In the beginning of the twentieth century, diagrams were more generally rejected because the belief in strict localization was lost, rather than because the functional models led to erroneous predictions. Kurt Goldstein, however, indeed argued for a completely different psychology. The revival of neuropsychology due to Geschwind’s plea for analyzing disconnections (Geschwind, 1965a, 1965b; Catani & ffytche, 2005), resulted in new diagrams, now with boxes rather than circles, in line with the then current convention of describing computer software programs. Many were influenced by Geschwind’s example, for instance, Damasio and Heilman, to mention a few who contributed to the study of apraxia. But more than ever, it remains important to distinguish between the functional and localization aspects of such theories. In modern studies on neuropsychological topics like aphasia, agnosia and apraxia it is quite common to find a reference to the early ‘neuropsychological’ literature. In ‘the old days’, authors had the opportunity to describe their ideas in much detail and often these articles are quite long. Summarizing these old studies with just a few sentences often does not do justice to the opinions expressed therein, with the risk that important arguments, considerations or limitations are missed. Consequently, earlier theories have been neglected to some extent and new proposals have been formulated with relatively little integration of insights, developed over time, into a coherent conceptual framework. Science is not about producing many papers with many data, with a supplementary meta-analysis that simply combines data from different studies in the hope to get a more reliable result; it is about understanding. The study of apraxia involves the proper description of patients with remarkable patterns of
dissociations, and these observations should be used for testing the validity of our understanding of how actions, or perhaps classes of actions, are performed by different people and under different conditions. Goldenberg studied for nearly 30 years with his colleagues many aspects of apraxia, for instance, tool use, pantomime, communicative gestures and the role of handedness and hemispheric asymmetries and interactions. He has now produced an excellent conceptual meta-analysis of both the old and current work on apraxia. He describes in great detail the views of forerunners with a keen eye for theoretical details that are important for understanding how a person produces a movement, without or with an object, which may be familiar or new to him. Combining his own extensive empirical basis with a thorough analysis of concepts and theoretical claims, he is able to illustrate the pendulum movement in theory development (between cognitive and motor control type of explanations), to reveal limitations or inadequacies of some of these theories, and to provide a cognitive analysis of various forms of apraxia in a coherent way. But then he argues (e.g., Goldenberg, 2013, p. 82 and p. 218) that this distinction between cognitive and motor control level explanations ultimately refer to the mindebody dichotomy. This seems to me to be an unfortunate step. A cognitive explanation implies the notion that the performance of actions involves some planning (‘generation’), the integration of information on goals and external and internal conditions that are relevant for attaining that goal, in a plan that is not directly formulated in terms of muscle movements. The body or body parts may play a role in such plans but not in the form of overlearned motor programs. And indeed, a cognitive plan has to be transformed in concrete actions. But that is not the same as bridging the gap between Descartes’ mind and body, just like we would not normally consider the planning of an utterance as ‘mind’ and articulation as ‘body’. There is no dichotomy: determining the goal and the road towards it just require various types of calculations.
references
Baginsky, A. (1871). Aphasie in Folge schwerer Nierenerkrankung (uraemia). Berliner Klinische Wochenschrift, 8(428e431), 439e443. Bastian, H. C. (1869). On the various forms of loss of speech in cerebral disease. British and Foreign Medico-Chirurgical Journal, 43, 209e236. Catani, M., & ffytche, D. H. (2005). The rises and falls of disconnection syndromes. Brain, 128, 2224e2239. Clarke, E., & Jacyna, L. S. (1987). Nineteenth-century origins of neuroscientific concepts. Berkeley, CA: University of California Press. Eling, P. (2005). Baginsky on aphasia. Journal of Neurolinguistics, 18, 301e315. Flourens, M.-J.-P. (1846). Phrenology examined. Philadelphia, PA: Hogan & Thompson. Gall, F. J., & Spurzheim, J. (1810e1819). Anatomie et Physiologie du Syste`me Nerveux en Ge´ne´ral, et du Cerveau en Particulier. Paris: F. Schoell. Geschwind, N. (1963). Carl Wernicke, the Breslau School and the history of aphasia. In E. C. Charterette (Ed.), Brain function: Vol. III. Speech, language and communication. Berkeley: University of Berkeley Press.
Please cite this article in press as: Eling, P., Apraxia: A conceptual meta-analysis, Cortex (2014), http://dx.doi.org/10.1016/ j.cortex.2014.02.005
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Geschwind, N. (1965a). Disconnexion syndromes in animals and man. Brain, 88, 237e294. Geschwind, N. (1965b). Disconnexion syndromes in animals and man. Brain, 88, 585e644. Goldenberg, G. (2013). Apraxia. The cognitive side of motor control. Oxford: Oxford University Press. Head, H. (1926). Aphasia and kindred disorders of speech (Vol. 1). Cambridge: Cambridge. University Press. Kean, M.-L. (1993). Norman Geschwind (1926e1984). In P. Eling (Ed.), Reader in the history of aphasia. Amsterdam: Benjamins. Keyser, A. (1993). Carl Wernicke (1848e1905). In P. Eling (Ed.), Reader in the history of aphasia. Amsterdam: Benjamins. Knoblauch, A. (1888). Ueber Sto¨rungen der musikalischen Leistungsfa¨higkeit infolge von Gehirnla¨sionen [On disorders of the musical capacity from cerebral disease]. Deutsches Archiv fu¨r Klinische Medezin, 43, 331e352. Kussmaul, A. (1877). Die Sprache der Sto¨rungen. Versuch einer der Sprache Pathology. Leipzig: FCW Vogel. Lelut, L. F. (1837). Qu’est-ce-que la phre´nologie. In ou Essai sur la signification et la valeur des syste`mes de psychologie en ge´ne´ral et de celui de Gall, en particulier. Paris: Trinquart.
Lesky, E. (1979). Franz Joseph Gall (1758e1828). Naturforscher und Anthropologe. Bern: Huber. Lichtheim, L. (1885). Ueber Aphasie. Aus der medicinischen Klinik in Bern. Deutsches Archiv fu¨r Klinische Medizin, 36, 204e268. Liepmann, K. H. (1900). Das Krankheitsbild der Apraxie (‘motorischen Asymbolie’) auf Grund eines Falles von einseitiger Apraxie. Monatsschrift fu¨r Psychiatrie und Neurologie, 8, 15e44. Lissauer, H. (1890). Ein Fall von Seelenblindheit, nebst einem Beitrag zur Theorie derselben. Archiv fur Psychiatrie und Nervenkrankheiten, 21, 222e270. Marshall, J. C. (1993). Henry Charlton Bastian (1837e1915). In P. Eling (Ed.), Reader in the history of aphasia. Amsterdam: Benjamins. Wernicke, C. (1974). Der aphasische Symptoms Complex. In Eine psychologische Studie auf eine Anatomischer Basis. Breslau: Cohen.
Received 29 January Reviewed 03 February Revised 5 February Accepted 7 February
2014 2014 2014 2014
Please cite this article in press as: Eling, P., Apraxia: A conceptual meta-analysis, Cortex (2014), http://dx.doi.org/10.1016/ j.cortex.2014.02.005