2. 7.5- Interaction between COM motion (characterized by velocity on
the y axis and displacement on the x-axis) and type of response
used to recover stability following an external perturbation.
3. • Shaded area indicates when the COM will
cause a step in order to maintain stability
• First movement the COM stays within the
limits and person uses ankle strategy
• The second trajectory puts the COM outside
the stability limits forcing the step
• The third trajectory requires a step because
the initial COM velocity is high and the
movement is short
5. • Shows typical synergy w/ loss of balance and
use of ankle strategy; used for small
perturbations
• Muscles react 90-100 msec after perturbation
w/o synergy of hamstring and paraspinal
muscles, indirect effect of gastroc. Ankle
torque on prox body segments would result in
forward motion of trunk mass relative to lower
extremities
• Muscles are activated distal to proximal
• Responses have been hypothesized to be
activated in response to visual and vestibular
inputs referred to as M3 responses
6. 7.10: Muscle synergy and body motions
associated with hip strategy for controlling
forward and backward sway
7. • A)The typical synergistic muscle activity
associated w/ hip strategy
• Motion of the platform in the backward
direction causes the subject to sway forward
• Muscles activity begins @ about 90 to 100
msec after perturbation onset in the
abdominal muscles followed by activation of
quads
• B)muscle pattern associated with hip strategy
correcting for backward sway
• Used to restore equilibrium in response to
larger, faster perturbations
8. 7.15 the six sensory conditions used to test how people
adapt the senses to changing sensory conditions during
maintenance of stance
9. • Conditions 4 to 6 are identical to 1 to 3
except that the support surface now
rotates with body sway
• Difference in amount of body sway in
these conditions determine subjects
ability to adapt
• Children over the age of 7 adapt easily
11. • Subject of experimenter lifted a 1 kg weight from
subject forearm in active unloading by subject,
there's a prepatory bicep inhibition to keep arm from
moving upward when it was unloaded
• Anticipatory reduction in bicep EMG of arm holding
load was time-locked with the onset of activation of
the biceps of lifting arm
• This reduction is not seen during passive unloading
• Postural adjustments are organized at the
bulbospinal level and the pyramidal tract activates
these pathways as it send descending commands to
the prime mover
• While the basic mechanisms for postural adjustment
may be organized at this level, they appear to be
modulated by several parts of the nervous system
including the cerebellum
12.
13. 9.11- single and dual task paradigms. Postural
and cognitive task performance is measured in
isolation
14. • A. single vs dual task
• B. Contraction onset for the gastroc muscle
for young, healthy adults and balance
impaired older adults
• All three groups show delays in the dual task
vs single
• EMG magnitude of the gastroc
• Healthy and balance impaired older adults
show a reduction of response amplitude in
the dual task conditions
16. • Parkinsons disease coactivates antagonistic
muscles around hip and knee
• This activation results in a stiffening of the
body and is very inefficient for recovery
balance
• Rigidity and loss of balance found in patients
during tilt tests imply equilibrium reactions
were absent
• Patients respond to dis equilibrium but the
pattern of muscle activity is eneffective in
recovering balance
17. 10.13: EMG activity in controls (A) versus
persons with anterior lobe cerebellar
degeneration
18. • Hypermetric postural responses found in
people w/ anterior-lobe cerebellar damage
• Responses in people w/ cerebellar disease
are LARGER in amplitude & longer in
duration than controls
• Hypermetric muscle activity resulted in
excess torque and overcorrection in sway
during recovery of stability
• Multidirectional perturbations postural
responses are LARGER than normal in
people w/ MS--> to compensate for delayed
onset of contraction
• The larger postural responses seen in MS
subjects were similar but not as large as the
hypermetric postural responses seen in
20. • PD= inability to change movement strategies quickly
to adapt to changes in support surface characteristic
• PD subjects had to maintain balance in various
situations
• Control group was able to modify postural muscle
responses quickly in response to changing task
demands; PD couldn’t
• Results show that basal ganglia functions to prime or
set the nervous system to achieve goal
• PD had difficulty changing from 1 movement to
another
• Reduced ability to modify postural strategies has
been shown in response to multidirectional surface
perturbations and resonse to changing stance width
21. 12.5 brain and spinal cord showing different sites of
lesions used in the study of the contributions of different
neural sub-systems to gait
22. 12.8- Hip, knee, & ankle trajectories of the swing limb
observed in response to a trip during early swing phase
of walking, showing the elevation strategy. Normal
stride= solid line, perturbed trial= dashed, arrow=
contact of foot w/ obstacle, vertical solid line= normal
heel contact, dashed= perturbed heel contact
23. • Type of strategy depends on where in swing
phase trip occurs
• Early- elevating strategy of the swing limb w/
muscle responses occurring @ 60 to 140 msec
• Shows the increased flexion @ hip, knee, &
ankle after obstacle contact compared w/ control
trial
• Elevating strategy- flexor torque component of
the swing limb, w/ the temporal sequencing of the
swing limb biceps femoris occurring prior to the
swing limb rectus femoris to remove the limb
from the obstacle before accelerating the limb
over it
• An extensor torque component in the stance limb
generated an early heel off to increase the height
of the body
24. 12.9- hip, knee, & ankle trajectories of the swing
limb observed in response to the late swing
phase of walking, showing the lowering
strategies
25. • Lowering strategy was used
• Early plantar flexion of the ankle
• Accomplished by inhibitory responses in
the swing limb vastus lateralis & an
excitatory response of the swing limb
biceps femoris, resulting in a shortened
step length
26.
27. • Initiation of gait is really just a fall, and regaing one’s
balance
• Prior to movement, COP is just posterior to ankle and
midway btw both feet
• As movement beings, COP first makes posterior and
laterally toward the swing limb and then shifts
towards the stance limb
• COP toward the stance limb occurs simultaneously
w/ hip and knee flexion and ankle dorsifelxion as
swing limb prepares for toe off. Then the COP moves
toward the stance limb
• Toe off swing limb occurs w/ COP shifting from lateral
to forward
• RTO is where COP is when the right toe is off the
ground
• RHS is COP when the right heel strikes
28. 13.2- stick figured taken from motion
analysis of one step cycle of walking in an
infant vs. adult
29. • Locomotor pattern changes over the first 2
years of development
• Synchronous pattern of joint movements in
newborn stepping to a more adult like
dissociated pattern of joint motion by the end
of the 1st year
• Heel strike begins to occur in the front of the
body
• Shows kinematics of neonatal vs adult
stepping
• Infant shows high levels of hip flexion
• Neonate: high degree of synchronized activity
(extensor muscle were active simultaneously
& coactivation of agonist & antagonist
muscles
30. 8.10- responses from one child during the emergence of
coordinated muscle activity in the leg and trunk muscles
in response to platform perturbances
31. • EMG responses from one child during the
mergence of coordinated muscle activity in
the leg & trunk muscles in response to a fall
backward
• 2-6 month before pull to stand behavior and
beginning of pull to stand did not show
coordinated muscle response organization in
response to threats to balance
• As behavior progressed--> showed
directionally appropriate responses in ankle
muscles, muscles in thigh segment were
added, consistent distal-to-proximal
sequence
• Independent stance/walk: trunk muscles
activated--> complete synergy
32. 9.5- graph showing COP trajectory from perturbation
onset to 2 sec after the perturbations for young stable
and unstable older adults. Arrow indicates perturbation
onset
33. • Platform perturbation= efficient return to the
COP to a stable positoin, whereas the stable
& ustable older adults each showed more
COP oscillation before coming to a stable
position
• Unstable group showing the largest excursion
of the COP & increase time for the COP to
come to stabilization
• NO differences in peak COM displacements
• Each group aimed @ keeping a low COM
displacement & when it went beyond, older
adults shifted strategies and took a step
34. 13.8- nine phases of prone progression & graphs for
each phase showing the ages at which the behavior
was seen and percentage of children in which it was
observed
35. • 9 phases that take infant from the prone
position to creeping/crawling & span months
from birth to 10 to 13 months
• 1) low extremity flexion& extension in a
primarily flexed position
• 2) spinal extension begins and head control
• 3) spinal extension continues
cephalocaudally, reaching thoracic
• 4 &5) propulsion movements & arms and legs
• 6) creeping position
• 7) disorganized attempts @ progression
• 8 & 9) organized propulsion in the creeping
position
36. 13.12- A--> stick figures taken from motion analysis of
the movements of a young and an older adult
responding to a forward slip at heel strike
37. • Adults were less stable after a slip--> when
recovering adults tripped more as the advancing
swing limb caught on the surface
• Occurred 66% adults, 15% younger adults
• Older- greater trunk hyperextension & higher arm
elevation in response to the slip; backward extension
of the trunk & raising 1 arm
• Had earlier contralateral foot strike & shortened stride
length--> more conservative balance strategy
• Longer onset latencies & smaller magnitudes in the
postural muscle activated in balance recovery (TA,
rectus femoris, abs)
• To compensate they showed longer muscle response
burst--> duration & arms in recovery, longer
coactivation
• Midstance slip and heel strike response are the same
size--> no adaptation b/c reduced response capacity
38.
39. • A. effect of a motor, cognitive, and
combined task on gait speed
• Step length
41. • A. initial input is feedforward (using
vision), while final input is feedback
(using somatosensory inputs from the
arm/hand)
• B. angular changes in the elbow and
wrist and muscle responses (rectified
surface electromyograms)
43. • Velocity profiles & movement durations of a
reach vary depending on the goal of the task
• Grasp- movement duration of the reach was
longer than to point & hit a target preparing to
grasp
• Acceleration phase of the reaching
movement was much shorter than the
deceleration phase, but hitting a target w/ the
index finger
• Acceleration phase was longer than
deceleration phase w/ the subject hitting the
target @ a relatively high velocity
• Movement times were shorter for grasp and
throw versus grasp and fit
44. 16.4- reaching and manual- estimation tasks, grasping-
A, manual estimation- B, maximum grip aperature
versus manual estimation size --> C
45. • Reached for a disk placed in the center of one of the
2 sets of circles (hypothesized dorsal stream) or
manually estimate the size of a disk (hypothesized
ventral stream)
• Results: manually estimated disk size as different,
although they are the same size
• Grip size was scaled to actual target size rather than
apparent size
• 16.14C- difference in max grip and manual estimated
for disk
• Max grip was greater for large disks, though subjects
reported they were identical in size
• Ventral stream of projections to the temporal cortex
play a major role in the perceptual identification of
objects
• Dorsal stream- parietal cortex mediates the required
sensorimotor transformations for usually guided
actions directed @ those objects
46. 16.9- in A: solid= position, dotted=
velocity, B: solid= 55 mm diameter,
dotted= 2mm
47. • When reaching forward to grasp an object, shaping of
hand for grasping occurs during transportation
component of reach
• The graph shows changes in velocity and grip size
• The pre grasp is under visual control
• Two categories of properties affecting the shape:
intrinsic (object size, shape, texture) and extrinsic
(objects orientation, distance from body)
• Size of grip opening is proportional to size of object
(seen in part B). Each increased 1 cm in object size
is associated with a max grip size of 0.77 cm.
• Fingers change with opening while thumb stays still
• Increase arm= stretched fingers and distance btw
thumb and fingers is largest during final slow
approach phase
• Increase relationship is not due to neural constraints
but may be most efficient way to reach
49. • A. comparison of reaction time and the
number of response alternatives available
• RT increases nonlineraly with the number of
response alternatives
• Information processing model, three stages
between stimulus input and movement output
• RT during successive blocks of trials when
responding to a predictable (a) versus a
nonpredictable (b) stimulus
• RT decreases with predictable condition and
does not change with random stimuli
50. 17.4- hand paths used by one infant
at 4 ages compared to adults
51. • Infant reaches are curved @ early ages &
become straighter by 2-3 years (straightness
ratio)
• About 2 @ reach onset & decrease to 1.3 to
1.4 by 2-3 years
• Still less straight than adults (1)
• Increase of smoothness
• Max hand speed during reach occurs closer
to the beginning of reach w/ development
being @ .35 to .5 and moving to .2 to .4 of the
reach by 2-3 years
• Average reaching speed does not increase
during this time period
53. • 5 year olds use highest level of bollistic
patterns
• 7 year olds use high levels of step tramp
patterns
• 9-11 year olds use highest level of ballistic
patterns w/ smooth decelerations, indicationg
primary use of visual feedback at end of
movement
• This may be due to increased use of
proprioceptive feedback in 7 year olds and
restriction of feedback control in the homing-
in phase in older children--> result of
increased efficiency of breaking system
54. 17.11- graph showing the relationship between
movement time and the index of difficulty of a
task, for four age groups of children
55. • The intercept of the line w/ the y-axis reflects
the general efficiency of the motor system
• The slope reflects the amount of info that can
be processed per second by the motor
system
• Y-intercept decreases with age (increased
efficiency)
• Age improvements depend on task and are
more evident in discrete versus serial
movements
56. 17.14- grasp force traces from a young subject and on
older adult showing typical grasp force patterns when
lifting an object w/ nonslippery versus slippery surface
57. • Adults have a decrease in manual dexterity
• Becomes apparent in tasks such as buttoning
a shirt or tying shoelaces
• Time to complete increases by 25-40%
• 81+ year used grasp forces that were two
times as large than young adults
• They take longer to adapt to the final grasp
force for the rayon
58. 18.2- a comparison of wrist path in a control vs a
subject w/ cerebellar pathology moving is slow accurate
and fast accurate conditions
59. • Control: slow accurate condition line is wrist
trajectory solid dot is target circles are finger
endpoint
• Control: fast accurate condition
• Cerebellar: slow accurate condition in regular
and unnecessary wrist movement
• Cerebellar: fast (no so) accurate condition
much less consistency with wrist movement
not accurate
61. • Participant set-up, ball dropped and impact-
displacement values are plotted
• Control: catches a light ball, adapts within two
trials to catching a heavy ball, first trial of light
ball again and there is a large negative
impact displacement
• Cerebellar pathology: reduces a persons
ability to adjust to novel loads through trial-
and-error practice
• Requires 22 trials to adapt to heavy ball
• Has no negative impact displacement on first
light ball again
63. • A vs D multijoint shoulder and elbow
coordination with a free vs constrained
shoulder
• B & E control made few errors in either
condition
• Cerebellar pathology patients made
large end-point errors in free condition
• F but no so in the constrained condition
