nick ward ucl institute of neurology
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Neuroplasticity: does it occur in the older brain?. NICK WARD UCL INSTITUTE OF NEUROLOGY. British Geriatrics Society , BMA House, London 27 th January 2011. What is different about the older brain?. What do we mean by plasticity? Motor system changes with ageing - PowerPoint PPT PresentationTRANSCRIPT
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NICK WARD
UCL INSTITUTE OF NEUROLOGY
Neuroplasticity: does it occur in the older brain?
British Geriatrics Society, BMA House, London 27th January 2011
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1. What do we mean by plasticity?
2. Motor system changes with ageing
3. Motor system changes after stroke
What is different about the older brain?
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Plasticity! Hold on ….. the cortex is not capable of change but is hardwired and immutable. Once damage occurs, cortical neurons either die or at best do not change their projection patterns…..”
1. ‘Neural changes in response to activity’
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Dendritic growth in vivo (600:1 time lapse)
Niell et al., Nat Neurosci 2004; 7: 254-260
Axon arborisation in vivo (600:1 time lapse)
Hua et al., Nature 2005; 434: 1022-1026
1. ‘Neural changes in response to activity’
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Dendritic growth in vivo (600:1 time lapse)
Niell et al., In vivo imaging of synapse formation on a growing dendritic arbor. Nat Neurosci 2004; 7: 254-260
1. ‘Neural changes in response to activity’
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from Kolb 1995
1. ‘Neural changes in response to activity’
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In humans it will not be the synapses per se but the neural circuits in which they participate which will be the appropriate explanatory level to understand plasticity
Continuous change in structure and ultimately function throughout a lifetime (Bryan Kolb, 1995)
Increments in synaptic efficacy occur when firing of one neuron repeatedly produces firing in another neuron to which it is connected (Hebb’s postulate, 1947)
System level plasticity = state- and history-dependent change in connection strength between areas.
1. ‘Neural changes in response to activity’
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1. ‘Neural changes in response to activity’
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scan1 scan 2 scan 3
Draganski B et al., Nature. 2004 ;427:311-2
1. ‘Neural changes in response to activity’
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Task: button press sequence
Training related increases in grey matter
1. ‘Neural changes in response to activity’
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“…..the cortex is not capable of plasticity but is hardwired and immutable. Once damage occurred, cortical neurons either died or at best did not change their projection patterns…..”
The structure of the brain is constantly changing – this is the basis of learning both in health and disease
However, it requires ‘activity’ to take advantage of these processes and create new connections and networks
1. ‘Neural changes in response to activity’
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|
2. Imaging cerebral reorganisation - Ageing
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GRIP
REST
BO
LD S
IGN
AL
TIME
40 secs
GR
IP F
OR
CE
GRIP GRIP GRIP
30%20%
40%
40 secs
2. Imaging cerebral reorganisation - Ageing
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fMRI – main effects
right hand15
10
5
t-score
forc
e
time
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ipsilateral cerebellum (lobule VI) contralateral superior cingulate sulcuscontralateral central sulcus
fMRI – activity during force modulationfo
rce
time
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fMRI – normal motor system activation
BF1
BG = average effect of all hand grips
BF = increase in BOLD signal with increasing peak force
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Ipsilateral M1 activity related to increasing age
Ward et al., Neurobiol Aging 2007
Main effect of hand grip
2. Imaging cerebral reorganisation - Ageing
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right
leftcM1 iM1
cPMd iPMd
cPMv iPMv
IHI
2. Imaging cerebral reorganisation - Ageing
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fig 5
Ward et al., Neurobiol Aging 2007
Increasing response to force modulation in inferior frontal gyrus /
BA44 with advancing age
2. Imaging cerebral reorganisation - Ageing
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right
leftcM1 iM1
cPMd iPMd
cPMv iPMv
excitability
2. Imaging cerebral reorganisation - Ageing
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M1
PMv
SMA
PMd
M1
PMv
SMA
PMd
2. Imaging cerebral reorganisation - Ageing
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M1
PMv
SMA
PMd
M1
PMv
SMA
PMd
2. Imaging cerebral reorganisation - Ageing
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M1
PMv
SMA
PMd
M1
PMv
SMA
PMd
2. Imaging cerebral reorganisation - Ageing
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Heuninckx et al. 2005
ISO
NONISO
For other tasks there may be different cognitive or ‘network’
solutions
2. Imaging cerebral reorganisation - Ageing
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Wu & Hallett 2005
Subjects learned a sequence of button presses
Older took longer than younger to become automatic
‘Equal’ performance by time of scanning
old v young young v old
2. Imaging cerebral reorganisation - Ageing
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3. Imaging cerebral reorganisation - Stroke
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Disruption to CST leads to a shift of activity away from primary to secondary motor areas
These areas can take on new and functionally relevant roles
They are important in supporting recovered function
affected hemisphere
3. Imaging cerebral reorganisation - Stroke
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less CS damagemore CS damage
Increasing ‘main effect’ of left hand gripaffected hemisphere
Ward et al., Brain 2006 CSS Integrity CSS Integrity
CSS Integrity
3. Imaging cerebral reorganisation - Stroke
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A
B
infarct3 months
post stroke17 days
post stroke24 days
post stroke31 days
post stroke
OUTCOMES Barthel ARAT GRIP NHPT
Patient A 20/20 57/57 98.7% 78.9%
Patient B 20/20 57/57 64.2% 14.9%
10 days post stroke
affected side
affected side
3. Imaging cerebral reorganisation - Stroke
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4. Implications for neurorehabilitation: Increase ‘practice’?
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• Cortical stimulation with task oriented training e.g. rTMS or TCDC strimulation
• Motor imagery, action observation
• Pharmacotherapy e.g. amphetamine, DA agonists, FLAME
• Pharmacotherapy e.g. plasticity modifying drugs
4. Implications for neurorehabilitation: Modify plasticity
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Ward and Cohen, Arch Neurol 2004
input
input
input
input
4. Implications for neurorehabilitation: Stratify?
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affected unaffected
+ +- -
affected unaffected
4. Implications for neurorehabilitation: Stratify?
a measurable change (in the brain) which characterises the ability to benefit from a particular treatment
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Greater gains predicted by:
1. Less impairment at baseline
2. Lower M1 activity at baseline
4. Implications for neurorehabilitation: Stratify?
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Brain reorganisation – is there a limit?
1. Age related changes and stroke related changes in motor system organisation are qualitatively similar
2. ‘Reorganising’ treatments will work differently
3. If stroke related changes are adaptive, does this mean older patents have less reserve?
4. Or does it mean that there is ‘reserve’ elsewhere?
5. Older brains are ‘changeable’ but with more effort
6. Is this a dose problem or a strategy problem?
7. Chronological age is not the same as biological age
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FIL:
Richard Frackowiak
Jennie Newton
Peter Aston
Eric Featherstone
Will Penny
SOBELL DEPARTMENT :
John Rothwell
Penny Talelli
Sven Bestmann
Orlando Swayne
Hartwig Siebner
Acknowledgements
ABIU/NRU:
Richard Greenwood
Alan Thompson
Martin Brown
Diane Playford
Katie Sutton
All nurses, physios, OTs, SLTs
FUNDING:
Neuroplasticity: does it occur in the older brain?