Biology subjects

Denninger, A. F.

Publications and source records attributed to Denninger, A. F..

3 recordsLinked to original sources

bioRxiv2026

A transient signal in foveal superior colliculus neurons for jumpstarting peripheral saccadic orienting

The superior colliculus (SC) both senses the environment and orients gaze within it. While the SCs sensory and motor bursts appear qualitatively similar to each other, population activity structure in the two processing regimes (visual and motor) is very different, necessitating a hitherto unexplored rapid representational transformation, occurring on the scale of only tens of milliseconds. Here, we first show that when a planned saccade is released with a go signal, peripheral SC neurons representing the saccade target location exhibit a transient, short-latency pause right before their motor bursts eventually emerge. This pause starts within [~]50 ms from the go signal; it is stimulus-dependent; and it is significantly weaker in purely visual SC neurons than in saccade-related ones. Foveal SC neurons, on the other hand, transiently burst, and their bursts lead the peripheral neurons pauses by [~]10 milliseconds. These transient foveal bursts also lead the same foveal neurons saccade-related pauses, which are time-locked to movement generation. Remarkably, during immediate visually-guided saccade tasks, requiring a transformation from visual to motor peripheral bursts in <50-100 ms, the transient foveal SC bursts still occur, resulting in simultaneous short-latency bursting at two disparate SC loci: one foveal; and one eccentric and responding to the visual appearance of the saccade target. Our results suggest that in classic saccade tasks used to investigate visual, motor, and cognitive processes in primate brains, a transient foveal SC signal precedes peripheral saccadic orienting, and may facilitate a necessary rapid representational transformation needed for SC saccade motor bursts to ensue. SignificanceSaccade control studies often involve behavioral paradigms dissociating stimulus presentation, deliberation epochs, and "go" instructions. While the stimulus presentation, deliberation, and actual movement aspects have been well studied, the "go" phases of trials are less considered. We show that foveal superior colliculus neurons exhibit transient activity bursts at the "go" instruction for saccades, likely enabling a rapid representational transformations from a visual to a motor regime in the extrafoveal collicular neurons driving the eye movements.

neuroscience↗

bioRxiv2024

Perisaccadic perceptual mislocalization strength depends on the visual appearance of saccade targets

We normally perceive a stable visual environment despite repetitive eye movements. To achieve such stability, visual processing integrates information across saccades, and laboratory hallmarks of such integration are robustly observed by presenting brief perimovement visual probes. In one classic phenomenon, perceived probe locations are grossly erroneous. This phenomenon is believed to depend, at least in part, on corollary discharge associated with saccade-related neuronal movement commands. However, we recently found that superior colliculus motor bursts, a known source of corollary discharge, can be different for different image appearances of the saccade target. Therefore, here we investigated whether perisaccadic perceptual mislocalization also depends on saccade-target appearance. We asked human participants to generate saccades to either low (0.5 cycles/deg) or high (5 cycles/deg) spatial frequency gratings. We always placed a high contrast target spot at grating center, to ensure matched saccades across image types. We presented brief perisaccadic probes, which were high in contrast to avoid saccadic suppression, and the subjects pointed (via mouse cursor) at their perceived locations. We observed stronger perisaccadic mislocalization for low spatial frequency saccade targets, and for upper visual field probe locations. This was despite matched saccade metrics and kinematics across conditions, and it was also despite matched probe visibility for the different saccade target images (low versus high spatial frequency gratings). To the extent that perisaccadic perceptual mislocalization depends on corollary discharge, our results suggest that such discharge might relay more than just spatial saccade vectors to the visual system; saccade-target visual features can also be transmitted. SignificanceBrief visual probes are grossly mislocalized when presented in the temporal vicinity of saccades. While the mechanisms of such mislocalization are still under investigation, one component of them could derive from corollary discharge signals associated with saccade movement commands. Here, we were motivated by the observation that superior colliculus movement bursts, one source of corollary discharge, vary with saccade-target image appearance. If so, then perisaccadic mislocalization should also do so, which we confirmed.

neuroscience↗

bioRxiv2022

Sensory tuning in neuronal movement commands

Movement control is critical for successful interaction with our environment. However, movement does not occur in complete isolation of sensation, and this is particularly true of eye movements. Here we show that the neuronal eye movement commands emitted by the superior colliculus, a structure classically associated with oculomotor control, encompass a robust visual sensory representation of eye movement targets. Thus, similar saccades towards different images are associated with different saccade-related "motor" bursts. Such sensory tuning in superior colliculus saccade motor commands appeared for all image manipulations that we tested, from simple visual features to real-life object images, and it was also strongest in the most motor neurons in the deeper collicular layers. Visual-feature discrimination performance in the motor commands was also stronger than in visual responses. Comparing superior colliculus motor command feature discrimination performance to that in the primary visual cortex during steady gaze fixation revealed that collicular motor bursts possess a reliable peri-saccadic sensory representation of the peripheral saccade targets visual appearance, exactly when retinal input is most uncertain. Consistent with this, we found that peri-saccadic perception is altered as a function of saccade target visual features. Therefore, superior colliculus neuronal movement commands likely serve a fundamentally sensory function.

neuroscience↗