Role of midline thalamic inputs to neocortical layer 1 in coordinating sleep rhythms. An implication for memory consolidation? – SOLTI

In Europe, more than a third of individuals suffers from poor sleep quality and 30% of them suffers from severe sleep deprivation. Fundamental research on sleep mechanisms, especially deep sleep stages that are known to be essential for recovery and memory consolidation, is of primary importance to develop new strategies to improve citizen life quality.?
Deep sleep stages are characterised by coordinated oscillations across brain areas. The coordination of these oscillations is thought to support memory consolidation. This proposal aims at elucidating the mechanisms responsible for the coordination of sleep oscillations across distant brain areas. I propose that midline thalamic neurons, via their projection to neocortical layer 1 neurogliaform interneurons, promote this coordination, and thus is instrumental for memory consolidation.

This hypothesis is based on my previous results that show that the midline thalamus synchronises sleep slow oscillations across cortical areas by inducing Down states. Moreover, others have shown that Down states is pivotal in the sequence of sharp wave ripple-Down state-spindle that is necessary for memory consolidation. Last lesions of the midline thalamus impairs specifically the performance at hippocampus-dependent long term memory tasks.

Thus, in this project I will address the three following points: 1- do midline thalamic neurons coordinate sharp wave-ripples and spindles around Down states; 2- is cortical silencing that precedes a sharp wave-ripple promoted by layer 1 interneurons; 3- do midline thalamic neurons promote memory consolidation by coordinating sleep oscillations? To address these questions, I will use a variety of techniques allowing to record neuronal activity in naturally sleeping mice. These include: multi-site local field potential recordings, tetrode recording, Ca2+ imaging (miniscope) and optogenetic to silence or activate thalamic and cortical neurons.