MOVEMENT PLANNING IN
DEVELOPMENTAL COORDINATION
DISORDER
KATE WILMUT, MAIA BYRNE AND ANNA BARNETT
ACTION SEQUENCES
• Actions are composed of a string of movements,
each movement taking into account the next
• Internal forward modelling allows anticipation of
motor consequences prior to execution (Wolpert & Kawato,
1998)
• Allows a spatially and temporally optimal movement
(Haggard, 1998; Rosenbaum, Vaughan, Barnes, & Jorgensen, 1992)
INTENDED ACTION
• Intended action also effects initial kinematics of the
reach-to-grasp when initial demands of a reach
component are identical
• In adults
• Elongated deceleration phase for a fit vs. a throw action
(Marteniuk et al. 1987)
• Larger peak aperture and larger peak deceleration for a
throwing/placing action vs. a lift action (Armbruster & Spijkers, 2006)
• In children
• 10 month-old infants: higher peak velocity when reaching to
throw vs. place (Claxton, Keen, & McCarty, 2003)
• 4 years of age: elongated deceleration period when reaching
to fit vs. reaching to throw (Chen & Yang, 2007).
INTENDED ACTION IN DCD
• DCD: explained by a deficit in the internal modelling
of movement? (Maruff et al., 1999; Smits-Engelsman et al. 2007; Williams et al.,
2006).
• Difficulty predicting the outcome of action
• If so we would not expect these individuals to tailor a
movement to an onward action.
• Aim: To consider whether children and adults with
DCD tailor a movement to the onward action
PARTICIPANTS
• All reported current motor difficulties and none indicated
any neurological deficit or comorbid condition that would
explain their motor difficulties
Adults
Children
TD
DCD
TD
DCD
N
Mean age
Gender ratio f:m
18
24:11
7:11
18
25:00
7:11
24
9:01
4:20
24
9:01
4:20
MABC-2 percentile
All > 20th
All < 5th
All > 20th
All < 5th
BOT-2 percentile
ADC
Childhood
Adulthood
All < 15th
6.6
All < 10
17.2
All < 40
23.3
(all > 18)
47.6
(7 > 62)
• Grasped a cylinder and:
•
•
•
•
Tight place (hole x1)
Loose hole (hole x2)
Lift
Throw
• A Vicon 3D motion capture
system was used to track
the movement of the
thumb, index finger,
knuckle and wrist of the
dominant hand.
METHOD
RESULTS: MOVEMENT DURATION
• DCD group showed a longer movement duration
compared to the TD individuals.
• TD – developmental improvement
• DCD – no difference
• Effect of action type:
• TD group: Lift > tight place = loose place
• DCD group: Lift > Throw
RESULTS: PROPORTION TIME IN
DECELERATION
• DCD group spent a longer proportion of MT
decelerating
• TD – developmental improvement, DCD – no
difference
62
60
Effect of action type:
• Adults:
• TD: tight >loose=lift>throw
• DCD: tight=loose=lift>throw
• Children:
• TD: tight=loose=lift>throw
• DCD: no effect
58
56
54
52
50
48
46
44
Children: TD
Children: DCD
Adults: TD
Adults: DCD
Tight
Loose
Lift
Throw
EFFECTS OF ACTION TYPE
TD adults
1. Shortened proportion of time spent
decelerating for a throw action as
compared to a place or lift movement
2. Discriminated between the tight and
loose place action
TD Children
1. Shortened proportion of movement time
in deceleration when throwing as
compared to the other three actions
2. No discrimination between the place
action
Adults with DCD
1. Same pattern as the TD children
Children with DCD
1. Difference in the movement duration,
longer for a lift vs. a throw action.
2. No other differences.
EFFECTS OF ACTION TYPE
• Adults and children with DCD are able to concatenate
actions and account for the onward action.
• DCD group able to use internal forward modelling, even
if it is not as sophisticated as that seen in TD adults.
• Does it ever reach a fully mature level?
• Is it driven by different underlying mechanism(s)?
• Control of action in DCD is actually different to the
typically developing population rather than simply
delayed.
MOVEMENT OUTCOME
• To some extent all of the groups tailored initial reach
movement to the intended action
• Does this result in a more functional movement?
• For place movements:
• How long spent adjusting prior to placing.
MOVEMENT OUTCOME
Calculated % change
in proportion of
movement time spent
decelerating from a
tight place to a loose
place
Compared to the
average adjustment
time across tight and
loose place trials.
MOVEMENT OUTCOME
• Significant relationship for the TD adults, r=-0.532
p=0.023
• Pp who showed a greater discrimination in deceleration
period from tight to loose place showed a shorter overall
adjustment time
• Not significant for the TD children, the adults with
DCD or the children with DCD.
FUNCTIONALITY OF MOVEMENT
• If the children and adults with DCD are failing (even
if only in some respects) to concatenate movement
does this actually matter?
• Seems to be a functionality to predicting onward
action
• TD adults: relationship between the degree to which they
discriminated between the two place actions during the
initial reach phase and the time spent adjusting
CONCLUSIONS
• Both adults and children with DCD seem able to use
forward modelling of inverse models to anticipate
movement and concatenate action.
• Not as sophisticated as that seen in typically
developing adults.
• Underlying forward anticipation of action may be
different, rather than simply delayed in DCD.
THANK-YOU FOR
LISTENING
ANY QUESTIONS?