title: Visual cortex excitability increases during visual mental imagery--a TMS study in healthy human subjects.
abstract: Previous neuroimaging studies provided evidence that visual mental imagery relies, in part, on the primary visual cortex. We hypothesized that, analogous to the finding that motor imagery increases the excitability of motor cortex, visual imagery should increase visual cortex excitability, as indexed by a decrease in the phosphene threshold (PT). In order to test visual cortex excitability, the primary visual cortex was stimulated with transcranial magnetic stimulation (TMS), so as to elicit phosphenes in the right lower visual quadrant. Subjects performed a visual imagery task and an auditory control task. We applied TMS with increasing intensity to determine the PT for each subject. Independent of the quadrant in which subjects placed their visual images, imagery decreased PT compared to baseline PT; in contrast, the auditory task did not change PT. These findings demonstrate for the first time a short-term, task-dependent modulation of PT. These results constitute evidence that early visual areas participate in visual imagery processing.
authors.affiliation: Laboratory for Magnetic Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02214, USA.
authors.forename: Roland
authors.initials: R
authors.lastname: Sparing
authors.forename: Felix M
authors.initials: FM
authors.lastname: Mottaghy
authors.forename: Giorgio
authors.initials: G
authors.lastname: Ganis
authors.forename: William L
authors.initials: WL
authors.lastname: Thompson
authors.forename: Rudolf
authors.initials: R
authors.lastname: Töpper
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Kosslyn
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D019018:Imagery, Psychotherapy; D008280:Magnetics; D008297:Male; D010719:Phosphenes; D012016:Reference Values; D014793:Visual Cortex / Q000502:physiology*