Studies of neuroplasticity with transcranial magnetic stimulation

In recent years, there has been increasing interest in studies of brain pla sticity. Although still loosely defined, this term describes the ability of the brain to change. Cortical plasticity encompasses a wide Variety of phe nomena and mechanisms, including modifications in cortical properties such as strength of internal connections, representational patterns, or neuronal modifications, either morphological or functional (Donoghue et al., 1996). We focus on the description of different ways in which transcranial magnet ic stimulation (TMS) can be used to study patterns of reorganization and so me of the mechanisms involved in these changes. Correlation between TMS and neuroimaging studies in humans and animal studies addressing similar quest ions is discussed. It is important to identify in each situation whether pl asticity plays a beneficial role or is maladaptive in terms of functional c ompensation. The understanding of patterns, mechanisms, and functional rele vance of cortical plasticity will hopefully lead to the design of effective strategies to enhance plasticity when it is beneficial and to down-regulat e it when it is maladaptive. An example of a possible strategy, using TMS, is discussed.