Abstract
Detecting imminent collision is essential for survival. Recent studies revealed subcortical circuits responding to looming stimulus in rodents. Little is known about how human subcortical visual pathways process collision information. Using fMRI, we studied how the superior colliculus (SC) and pulvinar of thalamus respond to potential collision information. Visual stimuli depicting an incoming ball towards the subject were presented with 3D LED monitors. The incoming ball appeared in one of the four quadrants of visual field. Within each quadrant, the trajectory of incoming ball varied slightly to either hit the center of face, hit the eye, near-miss or miss the head of observers. subjects responded whether the ball was on a collision course with their head or not. Behavioral results show that subjects performed slightly better detecting collision (hit vs. miss) for stimuli in the upper visual field than in the lower visual field. FMRI data showed that the superficial layers of the SC were sensitive to the looming information from the contralateral visual field, especially when the looming object came from the upper visual field and was on a collision course leading to a direct hit at the center of the subject head. A sub-region in the ventral Pulvinar was also sensitive to the incoming object on a collision course from the contralateral side, showing the strongest response when the incoming object would hit the subjects' contralateral eye (on the same side of the incoming object). These results suggest that human SC and Pulvinar are closely involved in processing incoming objects potentially on a collision course.
Meeting abstract presented at VSS 2017