Evidence for a push-pull interaction between superior colliculi in monocular dynamic vision mode

Abstract

Visual perception can operate in two distinct vision modes - static and dynamic - that have been associated with different neural activity regimes in the superior colliculus (SC). The static vision mode (low flashing frequencies) is associated with strong SC activation modulated by cortical gain and inhibitory intertectal effects, while the dynamic vision mode (high flashing frequencies) evokes the continuity illusion, with associated suppression of SC neural activity. However, the pathway-wide mechanisms underpinning the dynamic vision mode remain poorly understood, especially in terms of corticotectal and tectotectal feedback. Here, we harness rat functional MRI combined with brain lesions to investigate whole-pathway interactions in the dynamic vision mode. In the SC, we find contralateral suppression of activity opposing positive ipsilateral neural activation upon monocular visual stimulation in the dynamic vision mode. A cortical amplification effect was confirmed for both static and dynamic vision modes through cortical lesions, while further lesioning ipsilateral SC led to a boost in the contralateral negative signals, suggesting an active push-pull interaction between ipsilateral and contralateral SCs during the dynamic vision mode regime. This push-pull interaction is specific to the dynamic vision mode; in the static vision mode, both SCs show similar response polarities. These results highlight hitherto unreported frequency-dependent modulations in the tectotectal pathway and further challenge the contemporary notion that intertectal connections solely serve as reciprocal inhibitory mechanisms for avoiding visual blur during saccade occurrence. One Sentence SummaryOpposing signals between superior colliculi in the dynamic vision mode suggest an active push-pull interaction within the tectotectal commissural pathway.