title: Endogenous attention signals evoked by threshold contrast detection in human superior colliculus.
abstract: Human superior colliculus (SC) responds in a retinotopically selective manner when attention is deployed on a high-contrast visual stimulus using a discrimination task. To further elucidate the role of SC in endogenous visual attention, high-resolution fMRI was used to demonstrate that SC also exhibits a retinotopically selective response for covert attention in the absence of significant visual stimulation using a threshold-contrast detection task. SC neurons have a laminar organization according to their function, with visually responsive neurons present in the superficial layers and visuomotor neurons in the intermediate layers. The results show that the response evoked by the threshold-contrast detection task is significantly deeper than the response evoked by the high-contrast speed discrimination task, reflecting a functional dissociation of the attentional enhancement of visuomotor and visual neurons, respectively. Such a functional dissociation of attention within SC laminae provides a subcortical basis for the oculomotor theory of attention.
authors.affiliation: Departments of Neuroscience and Psychology, The University of Texas at Austin, Austin, Texas 78712.
authors.forename: Sucharit
authors.initials: S
authors.lastname: Katyal
authors.forename: David
authors.initials: D
authors.lastname: Ress
mesh_terms: D001288:Attention / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D013477:Superior Colliculi / Q000502:physiology*
keywords: attention; contrast detection; fMRI; midbrain; optic tectum; superior colliculus