[Transcranial magnetic stimulation: contributions to the study of the visual pathway]

Most of our impressions of the world and our memory are based on sight. Being able to look around us and recognise our surroundings involves the activity of several processing pathways in the brain that interact with each other and integrate information until it becomes conscious. Little is known about all these mechanisms today and therefore new tools must be developed and employed to enable us to further our understanding in this field.

The visual system is one of the most complex sensory systems. An important part of what we do know about how it is organised derives from studies carried out in animals or from clinical findings in patients with visual problems caused by local lesions. In recent years, advances in neurophysiological recording and stimulation techniques have made it possible to study visual functioning in a far more direct manner. Transcranial magnetic stimulation (TMS) is one of these new techniques and can be used to assess the excitability of the occipital cortex, induce conscious visual perceptions, produce 'virtual lesions' and even carry out direct manipulation of several visuoperceptual tasks. In this work we present the main applications of TMS in the study of the visual pathway, its most significant technical aspects and its clinical usefulness from the diagnostic point of view and within the field of visual rehabilitation.

TMS is a safe technique with important clinical and therapeutic implications, which offers valuable data about the mechanisms underlying the processing of visual information, and it is therefore becoming a very useful tool within the areas of neuroscience and clinical neurology.