Spatial evolution in temporal dynamics of hemodynamic response function in human superior colliculi with...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• The superior colliculus (SC) is vital for visual processing, attention, and oculomotor control.
• A rostro-caudal functional gradient is proposed for the SC, with rostral regions for fixation and caudal regions for saccades.
• Limited evidence exists on whether this functional gradient is preserved in the human SC.

Purpose of the Study:

• To investigate the functional organization of the human superior colliculus (SC) using functional magnetic resonance imaging (fMRI).
• To examine the spatial distribution of hemodynamic responses along the rostro-caudal axis of the SC during a visual-motor task.

Main Methods:

• Utilized a sequence-following visual-motor task to activate the SC.
• Employed ultra-high-field blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI).
• Measured hemodynamic response functions (HRFs) to assess neural activity.

Main Results:

• Demonstrated a spatial gradient of positive BOLD HRFs (pHRFs) along the rostro-caudal axis of the human SC.
• Observed pHRFs predominantly in the rostral SC, weakening towards the caudal SC where negative HRFs (nHRFs) were detected.
• Found consistent rostro-caudal HRF evolution across subjects, aligning with prior electrophysiological findings.

Conclusions:

• Confirmed the existence of a functional rostro-caudal gradient in the human SC.
• Highlighted the feasibility of using ultra-high-field fMRI for non-invasive investigation of subcortical neurovascular dynamics.
• Provided evidence supporting the SC's role in oculomotor coordination and visual processing gradients.