Topography of Covert Visual Attention in Human Superior Colliculus

Abstract

Experiments were performed to examine the topography of covert visual attention signals in human superior colliculus (SC), both across its surface and in its depth. We measured the retinotopic organization of SC to direct visual stimulation using a 90° wedge of moving dots that slowly rotated around fixation. Subjects (n = 5) were cued to perform a difficult speed-discrimination task in the rotating region. To measure the retinotopy of covert attention, we used a full-field array of similarly moving dots. Subjects were cued to perform the same speed-discrimination task within a 90° wedge-shaped region, and only the cue rotated around fixation. High-resolution functional magnetic resonance imaging (fMRI, 1.2 mm voxels) data were acquired throughout SC. These data were then aligned to a high-resolution T1-weighted reference volume. The SC was segmented in this volume so that the surface of the SC could be computationally modeled and to permit calculation of a depth map for laminar analysis. Retinotopic maps were obtained for both direct visual stimulation and covert attention. These maps showed a similar spatial distribution to visual stimulation maps observed in rhesus macaque and were in registration with each other. Within the depth of SC, both visual attention and stimulation produced activity primarily in the superficial and intermediate layers, but stimulation activity extended significantly more deeply than attention.

On the Role of Suppression in Spatial Attention: Evidence from Negative BOLD in Human Subcortical and Cortical Structures

“…By alternating stimulation from one hemifield to the other, without a baseline condition, the approach used by could capture both modest attention-dependent increases (Schneider and Kastner, 2009), along with perhaps larger effects reflecting a release from suppression that we measure here. We did, however, detect an attention-dependent increase in the superior colliculus contralateral to the stimulus, consistent with literature highlighting an attentional role of this structure (Schneider and Kastner, 2009;Katyal et al, 2010;Lovejoy and Krauzlis, 2010;Krauzlis et al, 2013;Katyal and Ress, 2014).…”

Altered visual processing in a rodent model of Attention-Deficit Hyperactivity Disorder

“…However, several lines of evidence support a role for the SC in ADHD. Firstly, people with ADHD have difficulty inhibiting saccades (Klein et al, 2003;O'Driscoll et al, 2005) and shifts in covert attention (Swanson et al, 1991), consistent with collicular dysfunction (Ignashchenkova et al, 2004;Katyal et al, 2010;Robinson and Bucci, 2014). Secondly, collicular dysfunction has been reported in rodent models of ADHD.…”

Neural correlates of spatial orienting in the human superior colliculus

“…The prominent blood vessels of the upper brain stem induce pulsatile movement artifact, which can contaminate the recorded signal if not circumvented. Despite these difficulties, it has been possible to retinotopically map the human SC (DuBois and Cohen 2000; Katyal et al 2010;Schneider and Kastner 2005), record visual responses to static and moving stimuli (Schneider and Kastner 2005;Sylvester et al 2007), and demonstrate attentional modulations (Gitelman et al 2002;Himmelbach et al 2007;Katyal et al 2010;Schneider and Kastner 2009), all with functional magnetic resonance imaging (fMRI). However, despite the critical role the SC plays in oculomotor control, very few studies have attempted to record oculomotor signals from the human SC (Anderson et al 2008;Krebs et al 2010aKrebs et al , 2010bPetit and Beauchamp 2003).…”