Neuroplasticity PDF

Neuroplasticity Lois Stevens UWE Bristol  Content What is neuroplasticity? Why do rehabilitation therapists need to know about it? How does it take place?  Plasticity All living organisms have an ability to self- organize throughout life O...

Neuroplasticity Lois Stevens UWE Bristol  Content What is neuroplasticity? Why do rehabilitation therapists need to know about it? How does it take place?  Plasticity All living organisms have an ability to self- organize throughout life Organizational processes reflect the organism’s history – environment, experience, use TASK – INDIVIDUAL - ENVIRONMENT  Definition Capacity of the CNS to adapt to functional demands and therefore the system’s capacity to re-organise Brain processes are continually remodelled by our experiences throughout life and especially by the use to which we put the system Remodelling is a feature of the maturation of the nervous system not “hard-wired” dynamic: changes in ‘connectivity’ throughout life  Mechanisms Neuro-chemical Neuro-receptive Neuro-structural ▼ Enables capacity for change  Also, importantly….. The parallel and distributed nature of brain organisation plays a part in the brain’s capacity for flexibility and adaptation Functions are represented throughout the CNS – wide overlap in cortical neural networks targeting different body parts  Cortical Mapping -Training Effect Training has been shown in animals to lead to changes in the strength of existing neural connections and to the emergence of new connections E.g. training rats on specific reaching activity shown to increase selectively the dendritic arborisation in the forelimb representation of the motor and sensory cortices Isaacs et al 1992  Cortical Mapping preferred hand new preferred hand  Human Studies Functional changes have been demonstrated in the human brain associated with training and use Increased use of body part and / or sensory feedback from it Particularly so when increased use is associated with functional gain  Mental Practice Plastic changes can occur as a result of the mental practice of a novel task Lacourse et al 2004  Synaptic Effectiveness ‘Cells that wire together, fire together…’ Regulation of both transient and long term effectiveness of synapses occurs daily throughout life and is also determined by experience Receptors demonstrate plasticity – synaptic transmission < or > according to use Chemical Synapse 13 Long-term Potentiation (LTP) Long-term potentiation (LTP) is the long- lasting enhancement in communication between two neurons that results from stimulating them simultaneously  Long-term Potentiation By enhancing synaptic transmission LTP improves the ability of two neurons, one presynaptic and the other postsynaptic, to communicate with one another across a synapse.  Long-term Potentiation Enhanced communication is predominantly carried out by improving the postsynaptic cell's sensitivity to signals received from the presynaptic cell.  Long-term Potentiation LTP improves the postsynaptic cell's sensitivity to neurotransmitter in large part by increasing the activity of existing receptors and by increasing the number of receptors on the postsynaptic cell surface. Long-term depression (LTD) ‘use it or lose it…’ Long-term depression (LTD) is the weakening of a neuronal synapse Selectively weakens specific sets of synapses in order to make constructive use of synaptic strengthening caused by LTP Silent Synapses Relationship between form and function form function altered form --> altered function sustained change in demand on the cell --> change in form  The story so far… Humans have capacity to adapt or to reorganise, throughout life, in response to external demands – plasticity - learning Structural and functional CNS changes underpin plastic processes Plasticity has been shown to be enhanced by training, use/sensory feedback