PhD Scientific Days 2024

Poster Session I - Neurosciences 2.

Complex synaptic mechanisms between superior colliculus and thalamus during multisensory processes

Text of the abstract

In a dynamic, multisensory environment the brain plays an important role by recognizing and integrating the relevant incoming stimuli and developing an appropriate behavioral response. As these processes are essential for the survival, the underlying network must be fast and precise. An early stage in the processing of affective stimuli is the superior colliculus (SC), a known site of multisensory signal integration, but in recent years the structure has also been associated with higher cognitive processes, such as the elicitation of fear learning.
Our recent findings have revealed that during fear conditioning, the association of the conditioned (CS) and the unconditioned stimuli (US) could occur even before the conventionally accepted brain area - the lateral amygdala (LA) - at the level of the LA-projecting calretinin-expressing lateral thalamic (LTCR) cells that receive strong SC input (Barsy, Kocsis et al. 2020). However, the type of the transferred signal as well as the SC-LTCR circuit’s contribution in the fear processes are largely unknown.
To answer these questions, we anatomically dissected the SC-LTCR route and found that not only the glutamatergic, but also the GABAergic SC cells, were able to form synaptic contact with LTCR neurons, or even with the same cell. Then, using optogenetic and electrophysiological approaches we investigated the response properties of the LT-projecting SC cells evoked by uni- and multimodal signals in vGAT- and vGluT2-Cre mice. We found that multisensory signals rather than the single sensory cues were able to alter the activity pattern of both vGAT+ and vGluT2+ SC cells, which, in turn, affected the LTCR cells with short latency. These latencies were comparable to the time window of the CS-US association measured in the LT and the LA. Further examinations are in progress to clarify exact electrophysiological features and roles of these fast SC-LTCR transmissions in associative fear learning. Collectively, complex synaptic transmissions by SC-LTCR routes can contribute to the fast and plastic signal integration during affective processes and promote the survival of the animal.

This work was supported by the Hungarian Scientific Research Fund NKFIH-FK 135285(SB), FK144583(SB), K138836(FM) and KKP126998(FM), by ÚNKP-22-2-III-ELTE-539(AVB), by ELKH SA-48/2021(FM) and by the Cooperative Doctoral Programme KD2020(AM).