title: Activation of SC during electrical stimulation of LGN: retinal antidromic stimulation or corticocollicular activation?
abstract: We have recently used combined electrostimulation, neurophysiology, microinjection and functional magnetic resonance imaging (fMRI) to study the cortical activity patterns elicited during stimulation of cortical afferents in monkeys. We found that stimulation of a site in lateral geniculate nucleus (LGN) increases the fMRI signal in the regions of primary visual cortex receiving input from that site, but suppresses it in the retinotopically matched regions of extrastriate cortex. Intracortical injection experiments showed that such suppression is due to synaptic inhibition. During these experiments, we have consistently observed activation of superior colliculus (SC) following LGN stimulation. Since LGN does not directly project to SC, the current study investigated the origin of SC activation. By examining experimental manipulations inactivating the primary visual cortex, we present here evidence that the robust SC activation, which follows the stimulation of LGN, is due to the activation of corticocollicular pathway.
authors.affiliation: Max-Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany. yusuke.murayama@tuebingen.mpg.de
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Murayama
authors.forename: Mark
authors.initials: M
authors.lastname: Augath
authors.forename: Nikos K
authors.initials: NK
authors.lastname: Logothetis
mesh_terms: D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D001931:Brain Mapping; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D012160:Retina / Q000502:physiology*; D013477:Superior Colliculi / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*