 Details in the maps came later through microelectrode stimulation and recording techniques became commonly used in demonstrating somatotopic maps and later in the auditory and visual systems, both cortically and in subcortical structures such as the colliculi and geniculate nuclei of the thalamus.Single-cell recording, Transcranial magnetic stimulation(TMS), electrical stimulation of the cortex, and Functional magnetic resonance imaging(fMRI) are some of the techniques used to study maps in the brain.Many of the existing topographic maps have been further studied or refined using fMRI.