2 Neuroscience2.10 Neurodevelopment and neuroplasticity
2.10.4 Neuroplasticity
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Written by Resident Doctor Committee · Published
Definition
Neuroplasticity is activity-dependent or experience-dependent change in the structure or function of the nervous system. It supports development, learning and recovery, but also persistent pain, fear and habit.
Long-term potentiation and depression
Long-term potentiation strengthens a synapse when presynaptic release and postsynaptic depolarisation coincide: calcium enters through NMDA receptors, kinases such as CaMKII act, and AMPA receptors are inserted.
Long-term depression follows a smaller, more prolonged calcium rise: phosphatases such as calcineurin act, and AMPA receptors are internalised.
Synaptic pruning
Synaptic pruning is the programmed elimination of surplus synapses and receptors between early childhood and the end of adolescence.
Cortical and striatal D2 receptor density falls through adolescence, and pruning continues late in the prefrontal cortex.
Pruning is developmental, whereas receptor downregulation and desensitisation are adaptations to exposure to a ligand.
Brain-derived neurotrophic factor (BDNF)
Form | Receptor | Effect |
|---|---|---|
Mature BDNF | TrkB | Survival, growth and synaptic strengthening |
ProBDNF | p75NTR with sortilin | Apoptosis and synaptic weakening |
Neurogenesis and ECT
Adult neurogenesis in the dentate gyrus is well established in animals, but its extent in adult humans is disputed.
Exercise, enrichment, antidepressants and electroconvulsive stimulation increase it, while ageing, chronic stress and glucocorticoids reduce it.
The most replicated structural change after a course of electroconvulsive therapy (ECT) is an increase in hippocampal volume, a sign of neuroplasticity rather than damage. It correlates poorly with clinical improvement.