Biology subjects

Sumser, A.

Publications and source records attributed to Sumser, A..

5 recordsLinked to original sources

bioRxiv2026

Intrinsic Population Dynamics are a Neuronal Substrate for Visual Attention

Perception results from a dynamic interplay between the feedforward processing of sensory stimuli and intrinsic neural activity 1, which is often dismissed as noise 2. To tailor perceptual processes to the organisms current needs on a continuous, moment-to-moment basis, intrinsic dynamics - rather than just being noise - have been suggested to reflect prior expectations 3,4, task demands 5, and attentional focus 6. Here, we identify a novel signature of attentive state in which intrinsic, collective neural activity modulates visuospatial attention by dynamically interacting with sensory input within the superior colliculus (SC), a midbrain hub that integrates bottom-up visual input with top-down signals 7. We show that these intrinsic dynamics organize cell activity into structured, blob-like features that are temporally and topographically localized and that rival sensory-evoked responses in strength. These features emerge as animals learn to engage in the visual detection task, and predict behavioral outcomes on a trial-by-trial basis. Although independent of sensory input or overt behavior, the features can be recruited to enhance visual responses four-fold in the attentive state, generating a "dynamic saliency map" that aligns with reaction times and behavioral outcomes. A computational model indicates that tunable blob-like features can arise from local excitatory-inhibitory interactions within the SC, and enhance sensory-evoked responses in line with observations. Together, our results identify state-dependent intrinsic population activity that interacts with sensory input to give rise to a saliency-map-like representation linked to flexible, goal-directed behavior.

neuroscience↗

bioRxiv2026

The functional organization of retinal input to the mouse superior colliculus

The superior colliculus integrates retinal input to drive rapid, adaptive visual behavior, yet how the functional diversity of retinal ganglion cell types is represented in superior colliculus remains poorly understood. Using chronic two-photon calcium imaging of retinal ganglion cell axonal boutons in awake mice, we recorded over 200,000 boutons across superficial superior colliculus layers -- a scale that enabled systematic comparison with large-scale ex vivo retinal datasets. This revealed that the superior colliculus receives a near-complete sampling of retinal ganglion cell functional diversity. Functionally distinct response types were organized in systematic laminar gradients: not only response properties such as direction selectivity and contrast suppression, but retinal response types themselves varied systematically with depth. To probe how this organized input encodes natural scenes, we trained a "digital twin" deep network model on natural movie responses and validated its generalization to parametric stimuli, including cell type identification. Leveraging this model to generate predicted responses to looming stimuli, we identify a discrete subset of retinal response types tuned for collision detection at low angular thresholds -- a specialization embedded within a broader, non-specialized retinal population. The digital twin is made publicly available as a community resource. Together, these findings provide a comprehensive functional map of retinal drive to the superior colliculus and an in silico platform for linking retinal cell types to behaviorally relevant superior colliculus computations.

neuroscience↗

bioRxiv2024

Differential representation of active and passive touch in mouse somatosensory thalamus

Active and passive sensing strategies are integral to an animals behavioral repertoire. Nevertheless, there is a lack of information regarding the neuronal circuitry that underpins these strategies, particularly at the thalamus level. We evaluated how active versus passive whisker deflections are represented in single neurons of the ventral posterior thalamus (VPM) and the posterior medial thalamus (POm) in awake mice. These are the first-and higher-order thalamic nuclei of the whisker system, respectively. VPM neurons robustly responded to both active and passive whisker deflections, while POm neurons showed a preference for passive deflections and responded poorly to active touches. This response disparity could not be explained by the animals voluntary whisking state or stimulus kinetics. In contrast, cortical activity significantly influenced POms responses to passive touch. Inhibition of the barrel cortex strongly attenuated whisker responses in POm and simultaneously increased the whisking phase coding. This suggests that POm receives touch information from the cortex and phase information from the brainstem. Together, these findings suggest two thalamic relay streams, where VPM robustly relays both active and passive deflection, while POms sensitivity requires top-down cortical involvement to signal salient events such as unexpected passive deflections.

neuroscience↗

bioRxiv2023

A thalamic hub of action cues coordinates early visual processing and perception

Distinguishing between sensory experiences elicited by external stimuli and an animals own actions is critical for accurate perception and motor control. However, the diversity of behaviors and their complex influences on the senses make this distinction challenging. Here, we uncover an action cue hub that coordinates both visual processing in the brains first visual relay and motor commands. We show that the ventral lateral geniculate nucleus (vLGN) acts as a corollary discharge (CD) center, integrating visual translational optic flow signals and motor copies from saccades, locomotion, and pupil dynamics. The vLGN relays these signals to correct action-specific visual distortions and refine perception, as shown for the superior colliculus and a depth estimation task. Simultaneously, brain-wide vLGN projections drive corrective actions necessary for accurate visuomotor control. Our results reveal an extended CD architecture that refines early visual transformations and coordinates actions via a distributed hub-and-spoke network enabling visual perception during action.

neuroscience↗

bioRxiv2021

An extended toolkit for production and use of RVdG-CVS-N2c rabies viral vectors uncovers hidden hippocampal connections

To understand the function of neuronal circuits it is crucial to disentangle the connectivity patterns within the network. However, most tools currently used to explore connectivity have low-throughput, low-selectivity, or limited accessibility. Here, we report the development of an improved packaging system for the production of the highly neurotrophic RVdGenvA-CVS-N2c rabies viral vectors, yielding titers orders of magnitude higher with no background contamination, at a fraction of the production time, while preserving the efficiency of transsynaptic labeling. Along with the production pipeline, we developed suites of "starter" AAV and bicistronic RVdG-CVS-N2c vectors, enabling retrograde labeling from a wide range of neuronal populations, tailored for diverse experimental requirements. We demonstrate the power and flexibility of the new system by uncovering hidden local and distal inhibitory connections in the hippocampal formation and by imaging the functional properties of a cortical microcircuit across weeks. Our novel production pipeline provides a convenient approach to generate new rabies vectors, while our toolkit flexibly and efficiently expands the current capacity to label, manipulate and image the neuronal activity of interconnected neuronal circuits in vitro and in vivo.

neuroscience↗