Sunday, 2 March 2008

Our plastic brain - a game of give and take?

Neuroplasticity refers to our brains ability to change and reorganise itself through forming new neural connections. This is clearly at the heart of the learning process but also shows itself in the remarkable ability to move and redevelop brain function in the event of injury or damage.

Indeed, as we specialise and become experts in a specific skill or knowledge area, then the brain area used most to support this activity grows. As an example, this comparative study of London taxi and bus drivers (Maguire, Woollet and Spiers, 2006) found:

...that compared with bus drivers, taxi drivers had greater gray matter volume in mid-posterior hippocampi and less volume in anterior hippocampi. Furthermore, years of navigation experience correlated with hippocampal gray matter volume only in taxi drivers, with right posterior gray matter volume increasing and anterior volume decreasing with more navigation experience. This suggests that spatial knowledge, and not stress, driving, or self-motion, is associated with the pattern of hippocampal gray matter volume in taxi drivers.

Taxi drivers navigate around a city demanding constant recall of the spatial area, adapting constantly to traffic flow, passenger preferences and other factors. Bus drivers, on the other hand follow a more limited set of routes.

Another study (Draganski et al, 2006) focused on German medical students demonstrating that extensive learning of abtract information in preparing for an exam (and comparing them with students not being examed), showed that:

During the learning period, the gray matter increased significantly in the posterior and lateral parietal cortex bilaterally. These structural changes did not change significantly toward the third scan during the semester break 3 months after the exam. The posterior hippocampus showed a different pattern over time: the initial increase in gray matter during the learning period was even more pronounced toward the third time point.

I wonder whether this suggests that cramming intensively - usually frowned upon but still a very common practice - has a more lasting impact on future learning and memory retrieval than we have assumed to date?

But then how does this sit with the other finding from Maguire's study that the brains ability to change to suit the tasks and activities we engage in, comes at a cost to other brain areas not used as intensively? In this case, they found that the ability to acquire new visuo-spatial information was worse for taxi drivers than bus drivers. This is the effect of the anterior hippocampus decreasing in size.


With the growing use of MRI and voxel-based morphometry we'll be seeing more and more of these types of study informing our understanding of how we actually learn.

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