Which parts of the brain are most resilient to change (that is, the least ‘plastic’ parts of the brain) and which are the least?
Your question is a fascinating one because we are still in the early stages of understanding the complexities of our fabulous brain. Is there one area that is more ‘plastic’ than others? Short answer: maybe. The reason is that the brain is composed of neurons, and as long as there are neurons, there is a potential for neuronal plasticity. Let’s define neuroplasticity. Basically, neuroplasticity is the ability of elements in the brain to show structural and functional changes in response to internal and external events. Neuroplasticity occurs at different levels: structural plasticity (new neurons born, growth and shrinkage of neurons), functional synaptic plasticity (enhancing/diminishing the functional connection between neurons) and all the molecular and cellular mechanisms that accompany these changes. You can even think of three main players in the brain: the drivers (grey matter), the highways (white matter) and the city planners (support structures, including glia). At all times, these players are constantly changing, just like a city grows and changes, with traffic increasing and decreasing between different areas.
Currently, there is no evidence that any part of the adult brain is not plastic, and the brain is ‘plastic’ for life, meaning the possibility of neuroplasticity exists throughout our whole life — you can say goodbye to that old saying, ‘can’t teach an old dog new tricks’! That said, we are still discovering robust neuroplasticity in areas that haven’t been as extensively researched as the hippocampus or cortex. For instance, the thalamus, which is a major highway of information into our cortex, also shows plasticity. That said, certain brain areas tend to be more ‘sensitive’ to stressors that ultimately affect our brain’s plastic powers. The areas most researched in this field are the cortex, amygdala and hippocampus – areas critical for learning and memory. So perhaps a way to think about this is that the brain tends to show remarkable plasticity throughout, but some areas are more susceptible to experience-based changes than others.
The growth and pruning of neuronal connections are opposing processes that are constant and necessary, but it is our experience that changes the balance between the two.