It is known that the effects of brain injury are not necessarily limited to the specific functions supported by damaged brain regions. This is often because brain injuries, particularly traumatic injuries, tend not to be specific to discrete areas. Recent research may have uncovered another reason why individuals experience numerous cognitive difficulties after injury.
In order for our brains to successfully support cognitive demands, different brain regions are linked together via complex neuronal connections and co-ordinate their activity in functional networks. These networks are considered integral to the way in which our brains process information. In a recent study, Gratton et al. (2012) used functional magnetic resonance imaging (fMRI) to look at such networks in stroke, traumatic brain injury and tumour patients and compared them with healthy controls.
The results showed that damage to areas important for communicating between different networks (as opposed to within a single network) appears to cause more diverse difficulties. The findings may go some way to indicating why the effects of brain injury can be so widespread and why it is so difficult to predict the effects based solely on areas of damage. For example, language tends to be localised to areas of the left hemisphere in most people. However, if areas of the right hemisphere connected to the language networks are damaged then speech and understanding can also be affected, even if the left hemisphere is intact.
Reference
Gratton, C., Nomura, E. M., Pérez, F. & D'Esposito, M. (2012) Focal brain lesions to critical locations cause widespread disruption of the modular organization of the brain.Journal of Cognitive Neuroscience. 24(6), 1275-1285.
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