Lesion Studies Case Studies

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Lesion studies (which generate lesion data), localize human brain function by studying the correlation between a behavioural disorder and the location of brain injury. These studies have greatly advanced our understanding of brain function. In 1861, Paul Broca boldly suggested that the third convolution of the inferior frontal gyrus is involved with speech production. This study founded a long tradition of neuropychological research which is still relevant today. The advantages of this type study can be appreciated by considering the vast amount of knowledge on cognitive function that it has brought about. Carl Wernicke discovered that damage to the left posterior temporal cortex leads to difficulty in language comprehension. Beginning in…show more content…
First, lesion studies assume that discrete anatomical modules deal with different cognitive functions. This assumption is often referred to as the ‘modularity’ or ‘localization’ assumption. Unfortunately, many brain functions might be carried out in a distributed manner, with large portions of the brain working in a plastic fashion rather than each region having a fixed function. Most brain damage is not limited by the boundaries of the underlying functional modules: for example, the location and extent of strokes are typically constrained by the brain’s blood supply. . Disruption of this blood supply usually leads to a wide range of deficits, knocking out neighbouring regions that often have different functions16. On the other hand, owing to the redundancy of the human brain, small lesions that only partially damage a module might not lead to any obvious behavioural…show more content…
However, the brain shows great anatomical differences between individuals and also shows plasticity, with different regions changing their function in response to damage to one area17. The lesion method usually assumes that after a focal lesion, the intact regions of the brain continue to function in the same manner as before the lesion. However, with tasks controlled by distributed and plastic circuits, the brain can start to reconfigure rapidly following damage. This reconfiguration is helpful for recovery, but makes it difficult to infer the original function of the healthy brain The lesion method also faces the challenge of differential vulnerability: some areas of the cortex are particularly likely to be damaged by stroke18. Therefore, the locations of brain damage are not randomly distributed in the brain: the design of the brain, its blood supply and the surrounding skull mean that some regions of the brain are damaged more often than others. This makes it difficult to interpret lesion overlay plots. For example, are the regions highlighted in FIG. 2 specifically involved with aphasia and with spatial neglect, or are they simply commonly damaged

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