Peripheral nerve injury/tissue inflammation triggers maladaptive plastic changes along the somatosensory system so that altered nociceptive signal processing, represented by tactile allodynia occurs.It is suggested that early afferent barrage can drive subsequent alterations in the central nervous system, including the cortex, that in turn contribute to neuropathic/cbronic pain.Recent advance in imaging techniques, e.g.functional MRI and PET, allows us to understand the activation of various higher brain areas in case of chronic pain.