Biology subjects

Skromne Carrasco, S.

Publications and source records attributed to Skromne Carrasco, S..

3 recordsLinked to original sources

bioRxiv2025

Coherent dynamics of thalamic head-direction neurons irrespective of input

The generation of the head-direction (HD) signal, a cornerstone of the brains navigation system, is classically attributed to the lateral mammillary nucleus (LMN) and associated brainstem structures, where attractor-like dynamics are thought to maintain population coherence. Here, using multi-site recordings and optogenetic perturbations along the mammillary-thalamic-cortical pathway, we demonstrate that HD neurons in the anterodorsal nucleus of the thalamus (ADN) maintain coherent population dynamics even when their LMN inputs become decorrelated during non-REM sleep. These findings reveal that thalamic coherence does not strictly depend on structured input from the LMN; instead, it can emerge from local thalamic processes involving shared inhibition and non-linear responses. Together, our findings reveal a previously unrecognized, state-dependent shift in the circuit organizing the HD signal, establishing the thalamus as an active substrate capable of independently sustaining internal representations across brain states.

neuroscience↗

bioRxiv2024

Visual objects refine head direction coding

Animals use visual objects to guide navigation-related behaviors, from hunting prey, to escaping predators, to exploring the world. However, little is known about where visual objects are encoded in the mouse brain or how they impact processing in the spatial navigation system. Using functional ultrasound imaging in mice, we conducted a brain-wide screen and identified brain areas that were preferentially activated by images of objects compared to scrambled versions of the same images. While visual cortical areas did not show a significant preference, regions associated with spatial navigation were preferentially activated by visual objects. Electrophysiological recordings in postsubiculum, the primary cortical area of the head direction (HD) system, further confirmed a preference for visual objects, which was present in both HD cells and fast-spiking interneurons. Finally, we found that visual objects dynamically modulated HD cells, selectively increasing firing rates of HD cells aligned with a visual landmarks direction, while decreasing activity in HD cells coding for other directions. These results reveal that visual objects refine population-level coding of head direction.

neuroscience↗

bioRxiv2022

Reciprocal representation of encoded features by cortical excitatory and inhibitory neuronal populations.

In the cortex, the interplay between excitation and inhibition determines the fidelity of neuronal representations. However, while the receptive fields of excitatory neurons are often fine-tuned to the encoded features, the principles governing the tuning of inhibitory neurons are still elusive. We addressed this problem by recording populations of neurons in the postsubiculum (PoSub), a cortical area where the receptive fields of most excitatory neurons correspond to a specific head-direction (HD). In contrast to PoSub-HD cells, the tuning of fast-spiking (FS) cells, the largest class of cortical inhibitory neurons, was broad and heterogeneous. However, we found that PoSub-FS cell tuning curves were often fine-tuned in the spatial frequency domain, which resulted in various radial symmetries in their HD tuning. In addition, recordings and specific optogenetic manipulations of the upstream thalamic populations as well as computational models suggest that this population co-tuning in the frequency domain has a local origin. Together, these findings provide evidence that the resolution of neuronal tuning is an intrinsic property of local cortical networks, shared by both excitatory and inhibitory cell populations.

neuroscience↗