The Clinical Science of
Neurologic Rehabilitation,
Second Edition
BRUCE H. DOBKIN, M.D.
OXFORD UNIVERSITY PRESS
ix
Contents
Part I. Neuroscientific Foundations for Rehabilitation
1. ORGANIZATIONAL PLASTICITY IN SENSORIMOTOR AND
COGNITIVE NETWORKS 3
SENSORIMOTOR NETWORKS 4
Overview of Motor Control • Cortical Motor Networks • Somatosensory Cortical
Networks • Pyramidal Tract Projections • Subcortical Systems • Brain Stem
Pathways • Spinal Sensorimotor Activity
STUDIES OF REPRESENTATIONAL PLASTICITY 39
Motor Maps • Sensory Maps
BASIC MECHANISMS OF SYNAPTIC PLASTICITY 44
Hebbian Plasticity • Cortical Ensemble Activity • Long-Term Potentiation and
Depression • Molecular Mechanisms • Growth of Dendritic Spines • Neurotrophins •
Neuromodulators
COGNITIVE NETWORKS 52
Overview of the Organization of Cognition • Explicit and Implicit Memory Network •
Working Memory and Executive Function Network • Emotional Regulatory Network •
Spatial Awareness Network • Language Network
SUMMARY 64
2. BIOLOGIC ADAPTATIONS AND NEURAL REPAIR 76
TERMS FOR IMPROVEMENT AFTER INJURY 79
Compensation • Restitution and Substitution • Impairment and Disability
INTRINSIC BIOLOGIC ADAPTATIONS 81
Spontaneous Gains • Activity in Spared Pathways • Sensorimotor Representational
Plasticity • Spasticity and the Upper Motor Neuron Syndrome • Synaptogenesis •

Nerve Transection
TRAINING-INDUCED REORGANIZATION 176
Sensorimotor Training • Aphasia • Cognition • Cross-Modal Plasticity
NEUROPHARMACOLOGIC MODULATION 184
Monaminergic Agents • Other Agents
SUMMARY 185
4. NEUROSTIMULATORS AND NEUROPROSTHESES 193
PERIPHERAL NERVOUS SYSTEM DEVICES 194
Functional Neuromuscular Stimulation • Nerve Cuffs
CENTRAL NERVOUS SYSTEM DEVICES 198
Neuroaugmentation • Spinal Cord Stimulators • Brain–Machine Interfaces •
Sensory Prostheses
ROBOTIC AIDS 203
Upper Extremity • Lower Extremity
TELETHERAPY 206
SUMMARY 206
Part II. Common Practices Across Disorders
5. THE REHABILITATION TEAM 213
THE TEAM APPROACH 213
The Rehabilitation Milieu
Contents xi
PHYSICIANS 215
Responsibilities • Interventions
NURSES 218
Responsibilities • Interventions
PHYSICAL THERAPISTS 219
Responsibilities • Interventions for Skilled Action
OCCUPATIONAL THERAPISTS 231
Responsibilities • Interventions for Personal Independence
SPEECH AND LANGUAGE THERAPISTS 235

Instruments • Adjustment Scales • Style Of Questions
MEASURES OF HANDICAP 302
MEASURES OF COST-EFFECTIVENESS 303
STUDY DESIGNS FOR REHABILITATION RESEARCH 303
Ethical Considerations • Types of Clinical Trials • Confounding Issues in Research
Designs • Statistical Analyses
SUMMARY 314
8. ACUTE AND CHRONIC MEDICAL MANAGEMENT 323
DEEP VEIN THROMBOSIS 323
Prevention
ORTHOSTATIC HYPOTENSION 324
THE NEUROGENIC BLADDER 325
Pathophysiology • Management
BOWEL DYSFUNCTION 329
Pathophysiology • Management
NUTRITION AND DYSPHAGIA 330
Pathophysiology • Assessment • Treatment
PRESSURE SORES 334
Pathophysiology • Management
PAIN 336
Acute Pain
• Chronic Central Pain • Weakness-Associated Shoulder Pain • Neck,
Back, and Myofascial Pain
DISORDERS OF BONE METABOLISM 348
Heterotopic Ossification • Osteoporosis
SPASTICITY 348
Management
CONTRACTURES 357
MOOD DISORDERS 358
Posttraumatic Stress Disorder • Depression

Traumatic Spinal Cord Injury • Nontraumatic Disorders
MEDICAL REHABILITATIVE MANAGEMENT 458
Time of Onset to Start of Rehabilitation • Specialty Units • Surgical Interventions •
Medical Interventions
SENSORIMOTOR CHANGES AFTER PARTIAL AND
COMPLETE INJURY 466
Neurologic Impairment Levels • Evolution of Strength and Sensation • Changes in
Patients with Paraplegia • Changes in Patients with Quadriplegia • Mechanisms of
Sensorimotor Recovery
FUNCTIONAL OUTCOMES 473
Self-Care Skills • Ambulation
TRIALS OF SPECIFIC INTERVENTIONS 477
Mobility • Strengthening and Conditioning • Upper Extremity Function • Neural
Prostheses • Spasticity
LONG-TERM CARE 485
Aging • Sexual Function • Employment • Marital Status • Adjustment and Quality
of Life
SUMMARY 489
xiv Contents
11. TRAUMATIC BRAIN INJURY 497
EPIDEMIOLOGY 498
Economic Impact • Prevention
PATHOPHYSIOLOGY 499
Diffuse Axonal Injury • Hypoxic-Ischemic Injury • Focal Injury • Neuroimaging
NEUROMEDICAL COMPLICATIONS 503
Nutrition • Hypothalamic-Pituitary Dysfunction • Pain • Seizures • Delayed-Onset
Hydrocephalus • Acquired Movement Disorders • Persistent Vegetative State
ASSESSMENTS AND OUTCOME MEASURES 510
Stages of Recovery • Disability
PREDICTORS OF FUNCTIONAL OUTCOME 513

SUMMARY 571
INDEX 579
PART I
NEUROSCIENTIFIC
FOUNDATIONS
FOR REHABILITATION
class="bi x10 ybf w5 hb"
Chapter 1
Organizational Plasticity
in Sensorimotor and
Cognitive Networks
SENSORIMOTOR NETWORKS
Overview of Motor Control
Cortical Motor Networks
Somatosensory Cortical Networks
Pyramidal Tract Projections
Subcortical Systems
Brain Stem Pathways
Spinal Sensorimotor Activity
STUDIES OF REPRESENTATIONAL
PLASTICITY
Motor Maps
Sensory Maps
BASIC MECHANISMS OF SYNAPTIC
PLASTICITY
Hebbian Plasticity
Cortical Ensemble Activity
Long-Term Potentiation and Depression
Molecular Mechanisms
Growth of Dendritic Spines

nect their feedforward and feedback pro-
jections. The victims of neurologic disorders
often improve, however. Mechanisms of
activity-dependent learning within spared mod-
ules of like-acting neurons are a fundamental
property of the neurobiology of functional gains.
Rehabilitation strategies can aim to manipulate
the molecules, cells, and synapses of networks
that learn to represent some of what has been
lost. This plasticity may be no different than
what occurs during early development, when a
new physiologic organization emerges from in-
trinsic drives on the properties of neurons and
their synapses. Similar mechanisms drive how
living creatures learn new skills and abilities.
3
4 Neuroscientific Foundations for Rehabilitation
Activity-dependent plasticity after a CNS or
PNS lesion, however, may produce mutability
that aids patients or mutagenic physiology that
impedes functional gains.
Our understanding of functional neu-
roanatomy is a humbling work in progress. Al-
though neuroanatomy and neuropathology
may seem like old arts, studies of nonhuman
primates and of man continue to reveal the
connections and interactions of neurons. The
brain’s macrostructure is better understood
than the microstructure of the connections be-
tween neurons. It is just possible to imagine

animal research and the functional neu-
roanatomy of people with and without CNS le-
sions. These computerized techniques offer in-
sights into where the coactive assemblies of
neurons lie as they simultaneously, in parallel
and in series, process information that allows
thought and behavior. Neuroimaging has both
promise and limitations (see Chapter 3).
What neuroscientists have established about
the molecular and morphologic bases for learn-
ing motor and cognitive skills has become more
critical for rehabilitationists to understand.
Neuroscientific insights relevant to the restitu-
tion of function can be appreciated at all the
main levels of organization of the nervous sys-
tem, from behavioral systems to interregional
and local circuits, to neurons and their den-
dritic trees and spines, to microcircuits on ax-
ons and dendrites, and most importantly, to
synapses and their molecules and ions. Expe-
rience and practice lead to adaptations at
all levels. Knowledge of mechanisms of this
activity-dependent plasticity may lead to the
design of better sensorimotor, cognitive, phar-
macologic, and biologic interventions to en-
hance gains after stroke, traumatic brain and
spinal cord injury, multiple sclerosis, and other
diseases.
SENSORIMOTOR NETWORKS
Motor control is tied, especially in the rehabil-

activity within and between these systems is the
very essence of brain function.” He proposed:
“The remarkable capacity for improvement of
Plasticity in Sensorimotor and Cognitive Networks 5
function after partial brain lesions is viewed as
evidence for the adaptive capacity of such dis-
tributed systems to achieve a goal, albeit slowly
and with error, with the remaining neural
apparatus.”
2
A distributed system represents a collection
of separate dynamic assemblies of neurons with
anatomical connections and similar functional
properties.
3
The operations of these assemblies
are linked by their afferent and efferent mes-
sages. Signals may flow along a variety of path-
ways within the network. Any locus connected
within the network may initiate activity, as both
externally generated and internally generated
signals may reenter the system. Partial lesions
within the system may degrade signaling, but
will not eliminate functional communication so
long as dynamic reorganization is possible.
What are some of the “essences” of brain and
spinal cord interplay relevant to understanding
how patients reacquire the ability to move with
purpose and skill?
No single theory explains the details of the

of the batter’s box, and how networks respond
to changes in input to update a view of the en-
vironment for goal-directed behaviors, such as
catching the baseball 400 feet away while on
the run.
4
A wiring diagram for hauling in a fly
ball, especially with rapidly changing weights
and directions of synaptic activity, seems im-
possibly complex. Researchers have begun,
however, to describe some clever solutions for
rapid and accurate responses that evolve within
interacting, dynamic systems such as the CNS.
5
Each theory contains elements that describe,
physiologically or metaphorically, some of the
processes of motor control. These theories lead
to experimentally backed notions that help ex-
plain why rehabilitative therapies help patients.
GENERAL THEORIES OF
MOTOR CONTROL
Sherrington proposed one of the first physio-
logically based models of motor control. Sen-
sory information about the position and veloc-
ity of a limb moving in space rapidly feeds back
information into the spinal cord about the cur-
rent position and desired position, until all
computed errors are corrected. Until the past
decade or two, much of what physical and oc-
cupational therapists practiced was described

equally well by one’s hand, shoulder, or foot.
This approach, however, needs some elabora-
tion to explain how contingencies raised by the
environment and the biomechanical character-
istics of the limbs interact with stored programs
or with chains of reflexes. A more elegant the-
ory of motor control, perhaps first suggested
by Bernstein in the 1960s, tried to account for
how the nervous system manages the many de-
grees of freedom of movement at each joint.
7
He hypothesized that lower levels of the CNS
control the synergistic movements of muscles.
Higher levels of the brain activate these syn-
ergies in combinations for specific actions.
Other theorists added a dynamical systems
model to this approach. Preferred patterns of
movement emerge in part from the interaction
of many elements, such as the physical prop-
erties of muscles, joints, and neural connec-
tions. These elements self-organize according
to their dynamic properties. This model says
little about other aspects of actions, including
how the environment, the properties of objects
such as their shape and weight, and the de-
mands of the task all interact with movement,
perception, and experience.
Most experimental studies support the ob-
servations of Mountcastle and others that the
sensorimotor system learns and performs with

functional groups with preferred lines of com-
munication.
8
Thus, goal-oriented learning, as
opposed to mass practice of a simple and repet-
itive behavior, ought to find an essential place
in rehabilitation strategies.
Several experimentally based models sug-
gest how the brain may construct movements.
Target-directed movements can be generated
by motor commands that modulate an equilib-
rium point for the agonist and antagonist mus-
cles of a joint.
9
During reaching movements,
for example, the brain constructs motor com-
mands based on its prediction of the forces the
arm will experience. Some forces are external
loads and need to be learned. Other forces de-
pend on the physical properties of muscle, such
as its elasticity. The computations used by neu-
rons to compose the motor command may be
broadly tuned to the velocity of movements.
10
Using microstimulation of closely related re-
gions of the lumbar spinal cord, Bizzi and col-
leagues have also defined fields of neurons in
the anterior horns that store and represent spe-
cific movements within the usual workspace of
a limb, called primitives.

or the control of mechanical properties of mus-
cles and joints.
15
Other theories suggest how
ever larger groups of neurons may interact to
carry out a learned or novel action.
16,17
Motor programs can also be conceptualized
as cortical cell assemblies stored in the form of
strengthened synaptic connections between
pyramidal neurons and their targets, such as
the basal ganglia and spinal cord for the prepa-
ration and ordered sequence of movements.
18
Indeed, multiple representations of aspects of
movement are found among the primary and
secondary sensorimotor cortices. The neurons
of each region have interconnections and cell
properties that promote some common re-
sponses, such as being tuned in a graded and
preferred fashion to the direction or velocity of
a reaching movement, to perceived load, and
to other visual and proprioceptive information,
including external stimuli such as food.
19
Many
other frames of reference, such as shoulder
torques, the equilibrium points of muscle
movements mentioned above, and the position
of the eyes and head also elicit neuronal dis-

and goals that formulate a particular action via
a large variety of movement strategies. The dis-
tributed and modular organization of the sen-
sorimotor neurons of the brain and spinal cord
provide neural substrates that arrange or repre-
sent particular patterns of movement and are
highly adaptable to training.
No single unifying principle for all aspects
of motor control is likely. The one certain fact
that must be accounted for in theories about
motor control for rehabilitation is that the nerv-
ous system, above all, learns by experience. The
rehabilitation team must determine how a per-
son best learns after a brain injury. At a cellu-
lar level, activity-dependent changes in synap-
tic strength are closely associated with motor
learning and memory. Later in the chapter, we
will examine molecular mechanisms for learn-
ing such as long-term potentiation (LTP),
which may be boosted by neuropharmacologic
interventions during rehabilitation. After a
neurologic injury, these forms of adaptability
or neural plasticity, superimposed upon the re-
maining intact circuits that can carry out task
subroutines, can be manipulated to lessen im-
pairments and allow functional gains.
To consider the neural adaptations needed
to gain a motor skill or manage a cognitive task,
I selectively review some of the anatomy, neu-
rotransmitters, and physiology of the switches

ability within the neuronal assemblies and
distributed pathways that may be called upon to
improve walking in hemiparetic and paraparetic
patients and to enhance the use of a paretic arm.
Cortical Motor Networks
PRIMARY MOTOR CORTEX
Neurophysiologic and functional imaging stud-
ies point to intercoordinated, functional as-
semblies of cells distributed throughout the
neuraxis that initiate and carry out complex
movements. These neuronal sensorimotor as-
semblies show considerable plasticity as maps
of the dermatomes, muscles, and movements
that they represent. In addition, they form mul-
tiple parallel systems that cooperate to manage
the diverse information necessary for the rapid,
precise, and yet highly flexible control of mul-
tijoint movements. This organization subsumes
many of the neural adaptations that contribute
to the normal learning of skills and to partial
recovery after a neural injury.
The primary motor cortex (M1) in Brod-
mann’s area (BA) 4 (Fig. 1–2), lies in the cen-
tral sulcus and on the precentral gyrus. It
receives direct or indirect input from the adja-
cent primary somatosensory cortex (S1) and re-
ceives and reciprocates direct projections to
the secondary somatosensory cortex (SII), to
nonprimary motor cortices including BA 24,
the supplementary motor area (SMA) in BA 6,

multijoint synergistic movements needed for
reaching and grasping.
23
This arrangement also
is a structural source for modifications in the
strength and distribution of connections among
neurons that work together as a skill is learned.
Some individual neurons overlap in their con-
trol of muscles of the wrist, elbow, and shoul-
der.
24,25
In addition, representations for move-
ments of each finger overlap with other fingers
and with patches of neurons for wrist ac-
tions.
26,27
They, too, are mutable controllers and
a mechanism for neuroplasticity.
Figure 1–2. Brodmann’s areas cytoar-
chitectural map over the (A) lateral and
(B) medial surfaces of the cortex.
10 Neuroscientific Foundations for Rehabilitation
A single corticospinal neuron from M1 may
project to the spinal motoneurons for different
muscles to precisely adjust the amount of mus-
cle coactivation.
28
Branching M1 projections,
however, rarely innervate both cervical and
lumbar cord motor pools. Strick and colleagues

confined to the hand region of M1 tends to af-
fect distal joints more than proximal ones and
tends to involve all fingers approximately equally
(see Color Fig. 3–5 in separate color insert).
The M1 encodes specific movements and
acts as an arranger that pulls movements to-
gether. The relationships of the motoneurons
for representations of movements are dynam-
ically maintained by ongoing use. Horizontal
and vertical intracortical and corticocortical
connections modulate the use-dependent inte-
grations of these ensembles.
32
Intermingled
functional connections among these small en-
sembles of neurons offer a distributed organi-
zation that provides a lot of flexibility and stor-
age capacity for aspects of movement. These
assemblies manage the coordination of multi-
joint actions, the velocity and direction of
movements, and process the order of stimuli
on which a motor response will be elicited to
carry out a task.
16
The assemblies also make
rapid and slow synaptic adaptations during
learning.
Thus, a cortical motoneuron can activate a
small field of target muscles; and an assembly
of interacting motoneurons within M1 can rep-

tions, rather than a map of muscles or of par-
ticular movement patterns.
19
Its overlapping
organization contributes to the control of the
complex muscle synergies needed for fine co-
ordination and forceful contractions.
35
After le-
sioning M1 in a monkey, the upper extremity
is initially quite impaired. The hand can be re-
trained, however, to perform simple move-
ments and activate single muscles. This reha-
bilitation leads to flexion and extension of the
wrist, but the monkey cannot learn to make
smooth diagonal wrist movements using mus-
cles for flexion and radial deviation.
28
The an-
imal accomplishes this motion only in a step-
wise sequence. The M1, then, activates and
inactivates muscles in a precise spatial and tem-
poral pattern, including the controllers for frac-
tionated finger movements. Using some clever
hand posture tasks to dissociate muscle activ-
ity, direction of movement at the wrist, and the
direction of movement in space, Kakei and col-
leagues showed that substantial numbers of
Plasticity in Sensorimotor and Cognitive Networks 11
neurons in M1 represent both muscles and di-

tense for reaching at a particular magnitude
and direction of force.
14
The direction of an
upper extremity movement may be coded by
the sum of the vectors of the single cell activ-
ities in motor cortex in the direction of the
movement.
40
The activity of a single corticomotoneuron
can differ from the activity of an assembly of
neighboring motoneurons. When a small as-
sembly of cells becomes active, the discharge
pattern of a neuron within that population may
change with the task. As the active population
evolves to include cells that had not previously
participated or to exclude some of the cells that
had been active, the assembly becomes a
unique representation of different information
about movement.
Thus, M1 is involved in many stages of guid-
ing complex actions that require the coordina-
tion of at least several muscle groups. The M1
computes the location of a target, the hand tra-
jectory, joint kinematics, and torques to reach
and hold an object—the patterns of muscle ac-
tivation needed to grasp the item—and relates
a particular movement to other movements of
the limb and body. These parameters may be
manipulated by therapists during retraining

tex represented particularly the space in front
of the monkey’s chest. Premotor cortex stimu-
lation always included a gripping posture of the
fingers when the hand-to-mouth pattern was
evoked, presumably related to the action of
feeding. All the evoked postures suggested typ-
ical behaviors such as feeding, a defensive
movement, reaching, flinching, and others.
Evoked postures were also found for the leg,
in which stimulation elicited movements that
converged the foot from different starting
positions to a single final location within its
ordinary workspace, much like what has
been found with lumbar spinal cord micros-
timulation (see section, Spinal Sensorimotor
Activity).
Functional imaging studies reveal a small ac-
tivation in ipsilateral motor cortex during sim-
ple finger tapping. A study by Cramer and col-
leagues found a site of ipsilateral activation
when the right finger taps to be shifted ap-
proximately 1 cm anterior, ventral, and lateral
to the site in M1 activated by tapping the left
finger.
41
This bilateral activity may be related
to the uncrossed corticospinal projection, to an
aspect of motor control related to bimanual ac-
tions, or to sensory feedback. The M1 in mon-
12 Neuroscientific Foundations for Rehabilitation

their synaptic relationships in remarkably flex-
ible ways during behavioral training. Future ex-
perimental studies of the details of these com-
putations, of the neural correlates for features
of upper extremity function, and of the rela-
tionships between neuronal assemblies in dis-
tributed regions during a movement will have
practical implications for neurorehabilitation
training and pharmacologic interventions.
The Primary Motor Cortex
and Locomotion
Supraspinal motor regions are quite active in
humans during locomotion.
45,46
In electro-
physiologic studies of the cat, motoneurons in
M1 discharge modestly during locomotion over
a flat surface under constant sensory condi-
tions. The cells increase their discharges when
a task requires more accurate foot placement,
e.g., for walking along a horizontally positioned
ladder, compared to overground or treadmill
locomotion. Changing the trajectory of the
limbs to step over obstacles also increases cor-
tical output.
47
As expected, then, M1 is needed
for precise, integrated movements.
Some pyramidal neurons of M1 reveal rhyth-
mical activity during stepping. The cells fire es-

the leg enough to clear the foot, when cortical
influences have been lost, is to evoke a flexor
reflex withdrawal response.
For voluntary tasks that require attention to
the amount of motor activity of the ankle
movers, M1 motoneurons appear equally
linked to the segmental spinal motor pools of
the flexors and extensors.
49
This finding sug-
gests that the activation of M1 is coupled to the
timing of spinal locomotor activity in a task-
dependent fashion, but may not be an essen-
tial component of the timing aspects of walk-
ing, at least not while walking on a treadmill
belt. Spinal segmental sensory inputs, de-
scribed later in this chapter, may be more crit-
ical to the temporal features of leg movements
during walking. The extensor muscles of the
leg, such as the gastrocnemius, especially de-
pend on polysynaptic reflexes during walking
modulated by sensory feedback for their anti-
gravity function.
50
Primary motor cortex neu-
rons also represent the contralateral paraspinal
muscles and may innervate the spinal motor
pools for the bilateral abdominal muscles.
51
Potential overlapping representations between

in functional imaging studies tends to be
smaller than what is found with finger tapping
(see Fig. 3–7). With an isometric contraction
of the tibialis anterior or gastocnemius mus-
cles, the bilateral superior parietal (BA 7) and
premotor BA 6 become active during PET
scanning, probably as a result of an increase in
cortical control of initiation and maintenance
of the contraction.
55
Greater exertion of force
and speed of movement give higher activations,
similar to what occurs in M1 when finger and
wrist movements are made faster or with
greater force. When walking on uneven sur-
faces and when confronted by obstacles, BA6
and 7, S1, SMA, and the cerebellum partici-
pate even more for visuomotor control, bal-
ance, and selective movements of the legs. An
increase in cortical activity in moving from
rather stereotyped to more skilled lower ex-
tremity movements also evolves as a hemi-
paretic or paraparetic person relearns to walk
with a reciprocal gait (see Fig. 3–8).
NONPRIMARY MOTOR CORTICES
The premotor cortex and SMA exert what
Hughlings Jackson called “the least automatic”
control over voluntary motor commands.
These cortical areas account for approximately
50% of the total frontal lobe motoneuron con-

functional, rather than an anatomical repre-
sentation.
59
For example, the toe and foot have
access to the motor program for the hand for
cursive writing, even though the foot may never
have practiced writing. An fMRI study that
compared writing one’s signature with the
dominant index finger and ipsilateral big toe
revealed that both actions activated the intra-
parietal sulcus and premotor cortices over the
convexity in the hand representation.
59
The
finding that one limb can manage a previously
learned task from another limb may have im-
plications for compensatory and retraining
strategies after a focal brain injury.
Premotor Cortex
Whereas M1 mediates the more elementary as-
pects of the control of movements, the pre-
motor networks encode motor acts and pro-
gram defined goals by their connections with
the frontal cortical representations for goal-di-
rected, prospective, and remembered actions.
BA 6 has been divided into a dorsal area, in
and adjacent to the precentral and superior
frontal sulcus, and a ventral area in and adja-
cent to the caudal bank of the arcuate sulcus
at its inferior limb. In the dorsal premotor area,

400
5200
6
Total frontal lobe
46
15
9
7
4
17
2
CS projections
(%)
Functional movement roles Execute action Self-initiated
Movement
Reward-based Visually guided Grasp by visual
selection;
sequence
motor
reaching guidance
learned from
memory
selection
sequence;
Bimanual action
M1, primary motor cortex; SMA, supplementary motor area; CS, corticospinal.
Source: Adapted from data from Cheney et al., 2000.
396
Plasticity in Sensorimotor and Cognitive Networks 15
separate arm and leg representations are found

tribute to upper extremity movements, short of
coordinated cocontractions and fractionated
wrist and finger actions.
28
Lesions of the SMA
cause akinesia and impaired control of biman-
ual and sequential movements, especially
of the digits, consistent with its role in motor
planning.
61
The SMA plays a particularly intriguing role
within the mosaic of anatomically connected
cortical areas involved in the execution of
movements. Electrical stimulation of the SMA
produces complex and sequential multijoint,
synergistic movements of the distal and proxi-
mal limbs. Surface electrode stimulation over
the mesial surface of the cerebral cortex in hu-
mans prior to the surgical excision of an epilep-
tic focus has revealed the somatotopy within
SMA and suggests that it is involved not only
in controlling sequential movements, but also
in the intention to perform a motor act.
As an example of hemispheric asymmetry,
stimulation of the right SMA produced both
contralateral and ipsilateral movements,
whereas left-sided stimulation led mostly to
contralateral activity.
62
In humans, the SMA is

The posterior portion of BA 24 in cin-
gulate cortex sends dense projections to the
spinal cord, to M1, and to the caudal part of
SMA.
65
This BA 24 subregion also interacts
with BA 6. The rostral portion targets the SMA.
Functional imaging studies usually reveal acti-
vation of the mesial cortex during motor learn-
ing and planning, bimanual coordination of
movements, and aspects of the execution of
movements, more for the hand than the foot.
Limited evidence from imaging in normal sub-
jects suggests that all the nonprimary motor re-
gions are activated, often bilaterally to a mod-
est degree, by even simple movements such as
finger tapping.
44
The activations increase as be-
havioral complexity increases. As noted, after a
CNS injury, greater activity may evolve in M1
and nonprimary motor cortices when simple
movements become more difficult to produce.
The portion of the corticospinal tract from
the anterior cingulate projects to the interme-
diate zone of the spinal cord. The anterior cin-
gulate cortex also has reciprocal projections
with the dorsolateral prefrontal cortex, dis-
cussed later in this chapter in relation to work-
ing memory and cognition. The anterior cin-

havior has to be modified in a novel or chal-
lenging situation. The region may be especially
important for enabling new strategies for mo-
tor control in patients during rehabilitation.
SPECIAL FEATURES OF
MOTOR CORTICES
Rehabilitationists can begin to consider the
contribution of the cortical nodes in the motor
system to motor control, to anticipate how the
activity of clusters of neurons may vary in re-
lation to different tasks, to test for their dys-
function, and to adapt appropriate interven-
tions. For example, patients with lesions that
interrupt the corticocortical projections from
somatosensory cortex to the primary motor cor-
tex might have difficulty learning new motor
skills, but they may be able to execute existing
motor skills.
67
The lateral premotor areas, es-
pecially BA 46 and 9, receive converging visual,
auditory, and other sensory inputs that inte-
grate planned motor acts. As discussed later in
the section on working memory (see Working
Memory and Executive Function Network,
these regions have an important role in the
temporal organization of behaviors, including
motor sets and motor sequences.
68
In the pres-

Motor imagery activates approxi-
mately 30% of the M1 neurons that would ex-
ecute the imagined action. Observation and
imitation of a simple finger movement by the
right hand preferentially activated two motor-
associated regions during an fMRI study by Ia-
coboni and colleagues: (1) Broca’s ventral pre-
motor area that encodes the observed action in
terms of its motor goal, i.e., lift the finger, and
(2) the right anterior superior parietal cortex
that encodes the precise kinesthetic aspects of
the movement formed during observation of
the movement, i.e., how much the finger
should be raised.
72
Mirror neurons are a sub-
set of the neurons activated by both the ob-
servation of a goal-directed movement, e.g.,
another person’s hand reaching for food, and
by the subject’s action in reaching for an item.
Mirror neurons represent action goals more
than movements. They may be critical for the
earliest learning of movements from parents.
Thus, the brain’s representation of a movement
includes the mental content that relates to the
goal or consequences of an action, as well as
the neural operations that take place before the
action starts (see Experimental Case Study
1–1). In a sense, the cognitive systems of the
brain can be thought of as an outgrowth of the

Mirror Mapping, Mental Imagery and the Dance
I have watched my wife learn a new dance—the movements of a ballet, a modern dance, a center piece
tango for the Los Angeles production of Evita back in 1980. How is she able to observe the choreog-
rapher’s actions and immediately reproduce what seem to me like an infinite number of head, torso,
arm and leg movements that flow and rapidly evolve with practice? What she sees resonates with her
sensorimotor system. She knows a vocabulary of movement from 20 years of studio classes and stage
performance. She understands the choreographer’s movements by mapping what she observes onto a
sensorimotor representation of each phrase of what she observes. Her ability to imitate is almost auto-
matic. As the choregrapher sweeps into action, she watches intently. Her body winks abbreviated ges-
tures that start to replicate the fuller movement she observes. She is making a direct match
81
between
the observation and the execution of a vocabulary of motion. This imitation calls upon mirror neurons
that are active with observation of goal-oriented movement. Indeed, the choreographer learns from her.
He observes and imitates some of the movement variations that she injects into the dance. He almost
unconsciously imitates those added movements, she imitates his. Back and forth they go, building the
dance.
Her image of the dance gains an internal representation, engaging the same neural structures for ac-
tion that were engaged during perception. Standing in a line at the supermarket, stirring a sauce, sit-
ting at the edge of the studio, standing in the wings of the theatre just before a performance, her im-
agery rerepresents the vision and affective components of the dance. Mental practice multiplies the
number of repetitions of dance movements, extending her physical practice. Cerebral reiteration may
prime and facilitate her performance, perhaps not as efficiently as the full movements with their ki-
naesthetic feedback, but good enough for her to be aware that she possesses explicit knowledge of the
dance.
She practices during sleep. I know this. I am kicked abruptly in our bed several times a night when-
ever she is learning a dance or dreams of dance. Stages of sleep may reactivate and consolidate the rep-
resentation of her movements. Whether asleep or in the moments before she glides onto the stage, she
engages her systems of imagery and imitation to practice, soundly building associations among auditory,
visual, visuospatial, and sensorimotor nodes of inferior frontal, right anterior parietal, and parietal op-