Transcranial magnetic stimulation as an investigative tool in the study of visual function.

Transcranial magnetic stimulation (TMS) is a novel and powerful probe to study the relationship between human brain function and behavior. TMS is being widely used to investigate memory, language, attention, learning, and motor function and is even being utilized therapeutically in the treatment of depression. Some of the earliest applications of TMS have been directed toward the investigation of human visual perception. For example, a strong TMS pulse delivered to the occipital cortex in a sighted or even blind individual can evoke the sensation of perceiving light (visual phosphenes). TMS can also be used to suppress visual perception and investigate the timing of visual information processing. Furthermore, the functional connectivity between different brain areas can be mapped using TMS, thus establishing a causal link between visual cortical function and visual perception. The present article is meant as an overview of the technique of TMS and a review of the literature as it pertains to the study of visual function. The application of TMS in the diagnosis as well as possible therapeutic use in various visual disorders is also discussed.