Apraxia

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f
g, D
disconnected from cortical areas directing the muscles that
implement the intended actions.
meaningful gestures. He postulated that aphasia is regularly
cient motor control as the source of these difficulties. He
wrote: “It is not themovement of the limbs which is inhibited,
but the relationship between the movements and the object
used”. His conclusion that “this apraxia is an obvious
apraxia were overridden by “holistic” theories which denied
the validity of anatomical localisation for explaining mental
ia was considered as
undermines the au-
victim of stereotypic
routines and environmental influences.
he pendulum swung
renaissance of the
d resuscitated Liep-
motor skills and thus degraded the posterior to anterior
stream from amechanism for the government of the limbs by
the mind to a path for the transport of motor skills from their
storehouse to the place of execution.
* Krankenhaus Munchen-Bogenhausen, Neuropsychologische Abteilung, Englschalkingerstrasse 77, D-81925 Munchen, Germany.
Available online at www.sciencedirect.com
w.e
c o r t e x 5 7 ( 2 0 1 4 ) 2 7 0e2 7 4
E-mail address: Georg.Goldenberg@extern.lrz-muenchen.de.
upside-down and took hold of spoon and fork as if he had
never used them before. Steinthal explicitly excluded defi-
mann’s model of apraxia but replaced the multi-modal
mental images of intended actions by a stock of learned
accompanied by such problems because they are, like aphasia
itself, expression of an overarching “asymbolia”. The linguist
Steinthal described an aphasic patient who grasped the pen
In the last third of the 20th century t
back again and holism gave way to a
localising approach. Norman Geschwin
motor control. The psychiatrist Finkelnburg described diffi-
culties of aphasic patients with the production and compre-
hension of non-verbal signs like musical notes, numbers, or
implementation of motor control. Aprax
a weakness of voluntary control which
tonomy of action and renders the patient
The concepts of “asymbolia” and “apraxia” were grounded
in linguistics and psychology rather than in the anatomy of
symptoms of brain damage. Explanations referred to univer-
sal psychological principles rather than to the anatomical
memory traces of previous actions were either destroyed or In the middle of the 20th century Liepmann’s theories of
Discussion forum
Apraxia e The cognitive side o
Georg Goldenberg*
Krankenhaus Munchen-Bogenhausen, Neuropsychologische Abteilun
1. History
The beginning of research on apraxia is usually identifiedwith
the seminal writings of the German psychiatrist Hugo Karl
Liepmann in the first decades of the 20th century, but
disturbed mental control of deliberate movements had been
subject to clinical observation and theorizing before Liep-
mann. The clinical literature of the late 19th century recog-
nized three syndromes characterized by wrong or awkward
actions in spite of preservedmotor strength and coordination:
Mind-palsy, Asymbolia, and Apraxia.
The theoretical fundament of mind-palsy was the associ-
ationist reduction of mental processes to the anatomy of
modality specific cortical areas and their connections. Mind-
palsy was expected to arise when cortical areas storing
Journal homepage: ww
0010-9452/$ e see front matter ª 2013 Elsevier Ltd. All rights reserve
http://dx.doi.org/10.1016/j.cortex.2013.07.016
motor control
-81925 Munchen, Germany
amplification of aphasia” seems to be the first printed
appearance of the word “apraxia”.
Liepmann’s seminal model of apraxia unified the
anatomical with the psychological approach to apraxia. He
suggested that fibres connecting posterior brain regions with
the motor cortex are the substrate of a posterior to anterior
stream of action control that converts conscious mental im-
ages into motor commands. The stream thus leads from the
realm of psychology to the physiology of motor control.
Liepmann characterized its function as the “government of
the limbs by the mind”. He envisioned two possible loci of
breakdown: Disturbed mental images of intended actions
would lead to “ideational”, and interruption of the stream
from mental images to motor cortex to “ideo e kinetic”
apraxia.
lsevier.com/locate/cortex
d.
hemisphere dominance for different manifestations of
apraxia, and in the final chapter also the principles and suc-
Consequently it can accommodate not only familiar but also
novel gestures by turning them into combinations of familiar
c o r t e x 5 7 ( 2 0 1 4 ) 2 7 0e2 7 4 271
cess of therapy of apraxia. In this pre´cis I will discuss the core
manifestation, laterality and intra-hemispheric location of
responsible lesions, and the significance of kinematic abnor-
malities for understanding apraxia.
2. Imitation of gestures
Defective imitation had been a central argument for Liep-
mann’s distinction between “ideational” and “ideo e kinetic”
apraxia. He reasoned that for imitation the mental image of
the requested gesture is given by the demonstration and er-
rors thus testify a deficiency of motor execution. This argu-
ment has been invalidated by the observation of patients with
“visuo e imitative” apraxia who commit severe errors on
imitation but can demonstrate communicative gestures on
verbal command flawlessly (Goldenberg & Hagmann, 1997;
Peigneux et al., 2000; Rumiati et al., 2005). A defect of motor
execution should affect gestures regardless of whether they
are generated from visual demonstration or from knowledge
of their shapes and meaning.
The selective deficiency of imitation would be compatible
with damage to a direct route that links the perception of
motor action with motor execution of the same action.
Damage to this route would interrupt imitation but leave
intact the production of gestures stored in long-termmemory.
This proposal has recently attracted popularity from specu-
lations about “mirror neurons” that connect perception and
motor replication of action without interpolated cognitive
mediation, but it was called into question by the demonstra-
tion that patients with apraxia for imitation commit errors
The excursion into the history of apraxia reveals a basic
dichotomy shining through the theoretical accounts of
apraxia. It opposes a high mental or, in today’s terminology,
cognitive level to a lower motor level of action control. This
dichotomy was explicitly spelled out by Liepmann and un-
derlay his distinction between ideational and ideo-kinetic
apraxia. Other accounts did not explicitly elaborate such a
dichotomy but defended the supremacy of one level and
contested the importance of the other. Finkelnburg, Steinthal
and the holists attributed the symptoms of apraxia to perva-
sive psychological deficiencies and denied the relevance of
possible errors of motor execution. Conversely, the concept of
mind-palsy was developed in animal experiments. It took into
consideration only mechanisms of motor control which are
similar in dog and man and excluded consideration of spe-
cifically human psychological processes.
The opposition of a higher cognitive to a lower motor level
ofaction control is a leading threat of my review of modern
theories and empirical evidence of apraxia (Goldenberg, 2013).
Chapters are devoted to core manifestations of apraxia, that
is, imitation of gestures, use of single tool and objects, and
production of communicative gestures on command. Further
chapters discuss spontaneous gesturing, naturalistic multi-
step actions, kinematic analyses of apraxic errors, callosal
apraxia and intermanual conflicts, apraxia in left-handers,
also when replicating gestures on a manikin or selecting
matching photographs of gestures although the motor acts of
body parts. The supramodality of its function and the capacity
to cope with novelty qualify body part coding as a high level,
cognitive component of imitation.
Defective imitation in apraxia can be body part specific
affecting for example postures of the fingers but not of the
whole hand or vice versa. In the framework of the direct route
from perception to motor replication body part specificity has
been referred to the somatotopy of motor cortex. According to
this suggestion the distribution of defective imitation depends
on the location of the causal lesion with respect to the parti-
tion of primary motor cortex. Defective imitation of feet
posture should be associated with dorsal, hand postures with
middle, and finger postures with ventral lesions of the cere-
bral motor strip (Buccino et al., 2001). Results from systematic
studies of lesions underlying defective imitation do not
conform to this contention. They show that defective imita-
tion of hand postures is bound to left parietal lesions whereas
imitation of finger and feet postures can also result from left
frontal lesions and from lesions of the right hemisphere
(Goldenberg & Strauss, 2002; Goldenberg & Karnath, 2006). As I
argue in more detail in the book, this constellation of body
part specificity can be explained by the interplay of body part
coding with deployment of attention and with structural
properties of different body parts.
3. Use of tools and objects
Most authors agree that apraxia for use of single familiar ob-
jects is due to loss of knowledge about their correct use rather
than to insufficient motor execution, but there is controversy
about the nature and relative importance of different com-
ponents of such knowledge (Coccia, Bartolini, Luzzi,
Provinciali & Lambon Ralph, 2004; Silveri & Ciccarelli, 2009;
Vingerhoets, Vandekerckhove, Honore´, Vandemaele &
Achten, 2011; Osiurak, Jarry, & Le Gall, 2011).
One of them is functional knowledge retrieved from
semantic memory. It specifies the purpose, the recipient and
the movements of the prototypical use of familiar tools.
A popular opinion assumes the existence of a separate section
of semantic memory devoted to “manipulation knowledge”
manipulating a manikin or pointing to pictures are funda-
mentally different from those of imitation of the same ges-
tures. These and other inconsistencies of the direct route
account of imitation have led to the alternative proposal that
body part coding is interpolated between perception and
reproduction of gestures (Goldenberg, 1995; Goldenberg &
Karnath, 2006).
Body part coding decomposes the gestures into combina-
tions of a limited number of defined body parts. It applies
independently of whether the gesture is perceived or executed
and independently of the different perspectives and modal-
ities of perceiving one’s own and other bodies (including those
of a manikin). Body part coding constitutes a “generative
system” where a multitude of formations can be produced
from combination of a limited number of defined elements.
(Buxbaum& Saffran, 2002; Boronat et al., 2005; Pelgrims, Olivier
& Andres, 2011). Manipulation knowledge complements
and objects are segmented into functionally significant parts
and properties, and combinations of these parts and proper-
c o r t e x 5 7 ( 2 0 1 4 ) 2 7 0e2 7 4272
ties with parts and properties of other tools and objects are
used for construction of mechanical chains. Mechanical
problem solving can be considered as a generative system,
because a multitude of mechanical chains can be constructed
from a limited number ofmechanical elements. Since familiar
and unfamiliar objects are composed of the same repertoire of
functionally significant parts and properties, and since pro-
totypical and familiar applications of tools and objects obey to
the same physical regularities, mechanical problem solving
can accommodate novel tools and objects and detect alter-
native ways of using familiar tools and objects. Mechanical
problem solving can also be applied to the multi-part me-
chanical object that is the human body. For tool use the
integration of the body closes a mechanical chain that leads
from the proximal body to the distal recipient of tool action.
Manual grips and movements form part of this chain and are
selected according to their mechanical relationships with the
other parts. With exceptions for specialized manual skills
needed for handicrafts like knitting or type writing there is
little necessity for stored representations of tool specific
manual actions.
Mechanical problem solving applies as well to own motor
execution of tool use as to the comprehension and construc-
tion of external mechanical devices, and it can accommodate
novel tools and atypical applications of familiar tools. Supra-
modal validity and the capacity to cope with novelty qualify
mechanical problem solving as a cognitive component of tool
use.
4. Communicative gestures-pantomime of
tool use
Degradation of gestural communication had been central to
Finkelnburg’s postulate of a general asymbolia affecting
both verbal and gestural expressions of aphasic patients.
Liepmann integrated faulty performance of communicative
gestures in his system of apraxias but changed the focus of
interest from their communicative value to their motor
execution. Observation of spontaneous gestural communica-
tion was replaced by production of gestures on command and
the range of gestures restricted to emblems and pantomime of
tool use. Emblems are gestures with a conventional shape and
functional knowledge by specification of grip andmotor actions
of the hand during use of the tool (Daprati & Sirigu, 2006).
Manipulation knowledge is a descendent of Geschwind’s
storehouse of learned motor skills. Its restriction to the motor
modality and its dependence on previous experience qualify it
as a low level motor component of tool use.
An alternative position denies the importance of modality
specific motor representations for selection of manual grips
and actions (Goldenberg & Spatt, 2009; Osiurak et al., 2011).
Instead, it proposes that correct manipulation results from
mechanical problem solving. The elements of mechanical
problem solving are not the prototypical functions of entire
tools, but the functional compatibilities of their parts. Tools
meaning like o. k. or “silence”. Pantomimes of tool use are
frequently preferred over emblems because the instruction
can be conveyed by giving examples and showing pictures of
the tools. A theoretically more interesting motive for the
preference of pantomimes may be that they are communi-
cative manual actions derived from instrumental ones. They
thus promise insight into the relationship between instru-
mental and communicative functions of the hands.
A traditional belief holds that pantomime of tool use is
achieved by replaying the motor programs of real use
(Geschwind, 1975; Heilman, Rothie & Valenstein, 1982; Poizner
et al., 1995) and that apraxia for pantomime results from
destruction or inaccessibility of these programs. This modelis
an obvious variant of Geschwind’s storehouse of learned
motor skills. Arguments against its validity come from
observation of patients with apraxia and from simple exper-
iments with normal people.
A substantial proportion of patients who fail pantomime of
tool use can demonstrate tool use normally when they are
permitted to grasp the real tool and apply it to its recipient.
Obviously their motor program of use is sufficient for carrying
out the tool action. On the other hand, close analysis of the
pantomimes of healthy subjects reveals substantial aberra-
tions from motor programs of actual use. For example, when
taking up a glass for drinking, the hand is initially opened
wider than the width of the glass and closes to a firm grip only
when it approaches the glass. By contrast, when normal
subjects pantomime taking up a glass for drinking they open
the hand approximately to the width of the glass and move to
the pretended location of the glass without further changing
the aperture of the grip. There, the hand changes direction
and moves upwards to the mouth, still preserving constant
aperture (Goodale, Jakobson & Keillor, 1994; Laimgruber,
Goldenberg, & Hermsdo¨rfer, 2005). Closing the hand firmly
around the glass is an essential component of the motor
program of real use but is not necessary for a comprehensible
pantomime. Wide aperture of the grip and the interruption
and subsequent change of direction of the transport suffice for
indicating width and the position of the glass.
The independence of pantomime from motor programs of
use is corroborated by the common observation that people
can pantomime the use of tools and objects that they do not
master in reality like playing musical instruments. It is even
possible to produce comprehensible pantomimes of actions
that are out of the range of human motor competence. For
example, rhythmical up and down beat of both arms beside
the body will be recognized as a pantomime of flying like a
bird.
The motor programs of real use and of pantomime fulfil
fundamentally different purposes. Whereas the motor actions
of real tool use integrate manual configurations and move-
ments into mechanical chains that change the status of
external recipients, the motor actions of pantomime should
enable other human beings to recognize the pretended tools
and their actions. They are communicative rather than
instrumental. Creation of a pantomime may start with the
retrieval of a mental image depicting the object together with
the hand acting on it. Conversion of this image into recogniz-
able pantomimes requires segmentation of the compound
image of hand, tool, and action into distinct features and the
selection of only those features that can be demonstrated by
the configuration, themovement, and the position of the hand.
Selected features must then be combined to a continuous
movement sequence of the hand. Apraxia of pantomime can
emerge in spite of preserved actual use when patients are un-
able to select and combine crucial features for demonstration.
For being comprehensible, pantomimesmust demonstrate
also non-motor features like shape and size of the pretended
tools. Their creation thus transgresses the emphasis onmotor
features of the pretended action. Nor is pantomime bound to
motor experience with the object and its use. It is a generative
system that can accommodate non-routine, novel, and even
impossible actions. Transgression of the motor modality and
openness for novelty justify the classification of pantomime
as a high level cognitive achievement and consequently
apraxia for pantomime as a high level cognitive disturbance.
5. Laterality and intra-hemispheric
localization of apraxia
Apraxia is not a unitary disorder nor can its variants be sorted
into the slots of an all embracing “praxis e system” (Lewis,
2006; Frey, 2008). Fig. 1 gives an overview of disturbances
that are generally recognized as belonging to apraxia and of
the putative localizations of their causal lesions. Imitation of
untrained stimuli. Supramodal function and coping with
novelty assign them to the cognitive side of motor control.
aberrations and the scores on conventional apraxia testing
found no statistically significant correlations (Haaland, 1984;Multi-step actions
c o r t e x 5 7 ( 2 0 1 4 ) 2 7 0e2 7 4 273
Hand Postures
Pantomime of
tool use 
Imitation 
Finger Postures
Fig. 1 e A summary of locations of different manifestations
of apraxia: Shading of the whole hemisphere does not
exclude the possibility of more fine grained localizations
within the hemisphere, but indicates that there are no firm
hand postures, use of single mechanical tools, and panto-
mime of tool use stand out in that they are strictly bound to
left hemisphere lesions. I propose to consider these manifes-
tations as “core manifestations” of apraxia. They have in
common the creation of gestures by segmentation and com-
bination of defined elements. Segmentation and combination
are not confined to motor acts but include elements from
other modalities like body parts for imitation, mechanical
devices for tool use, and shape and size of objects for
Mechanical 
Problem Solving
Use of single
conventional tools 
Left
Hemisphere
Right 
Hemisphere
Functional 
Knowledge
grounds for delimiting the critical areas. Adapted from
Goldenberg (2007, p. 149) by permission of Elsevier.
Hermsdo¨rfer et al., 1996; Ietswaart, Carey & Della Sala, 2006;
Schaefer, Haaland & Sainburg, 2007; Hermsdo¨rfer, Li,
Randerath, Goldenberg & Johannsen, 2012).
There is thus no convincing evidence that the clinical
symptoms of apraxia derive from abnormalities of motor co-
ordination. It rather seems that these abnormalities are an
additional but in principle independent sequel of left brain
damage. They demonstrate that unilateral brain damage can
cause bilateral disturbances of motor coordination, but not
that apraxia is one of them. Apraxia retains its place on the
cognitive side of motor control.
Supplementary data
The proposal that imitation of hand postures, pantomime
of tool use, and use of single mechanical tools are core man-
ifestations of apraxia is not intended to deny any importance
of segmentation and combination to other manifestations of
apraxia like imitation of finger and foot postures or perfor-
mance of multi-step actions with multiple tools and objects. I
rather assume that for these variants of apraxia other factors,
like distribution of attention or capacity of working memory
are also important, and that damage to these additional
components can cause disturbances even when lesions spare
the substrate of the core manifestations.
6. Approaching apraxia from the motor side
Apraxia is diagnosed from observation of visible movements.
They derive from coordination of multiple muscular actions
with the biodynamic of joints and bones. Failure of this co-
ordination might itself escape visual observation but none-
theless be causal for the emergence of the visible apraxic
errors. Basically, two approaches have been tried for doc-
umenting and analysing deficits of motor coordination un-
derlying apraxic errors: Kinematic measurement of the
actions produced for the examination of apraxia, and experi-
mental investigation of more simple and “elemental” motor
actions like pointing or grasping (Poizner et al., 1995;
Hermsdo¨rfer et al., 1996; Haaland, Prestopnik, Knight & Lee,
2004; Mutha, Sainburg & Haaland, 2010). They largely agree
upon the existence of clinically imperceptible disturbances of
motor coordination that resemble apraxia in that they affect
the limbs ipsilateral to the damaged hemisphere which is
predominatelythe left. There are, however, substantial dif-
ferences between apraxia and these abnormalities. Whereas
apraxic errors are visible to the naked eye already on single
trials, they come to the fore only by fine grainedmeasurement
and statistical evaluation of multiple repeated trials. Studies
that looked for correlations between the severity of kinematic
pantomime. Their breakdown deprives subjects not only of
habitual motor routines but also of the ability to cope with
Supplementary data related to this article can be found at
http://dx.doi.org/10.1016/j.cortex.2013.07.016.
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	Apraxia – The cognitive side of motor control
	1 History
	2 Imitation of gestures
	3 Use of tools and objects
	4 Communicative gestures-pantomime of tool use
	5 Laterality and intra-hemispheric localization of apraxia
	6 Approaching apraxia from the motor side
	Appendix A Supplementary data
	References