How does the thalamus mediate brain-wide memory consolidation during sleep?

• Applicant: Dr. Jens Klinzing
• Subject Area: Cognitive, Systems and Behavioural Neurobiology ; Human Cognitive and Systems Neuroscience
• Term: from 2019 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 430174808

Memories are stored across distributed networks in the brain. In the case of autobiographical memories, these include regions in the neocortex and hippocampus, each hosting different aspects of a given experience. When memories are formed in our brain, they start out fragile and only few will endure. For an event to become part of our long-term memory, involved brain areas need to repeatedly reactive their respective piece of the experience during sleep. If the reactivation occurs frequently and synchronously, it will result in long-lasting synaptic changes in the entire network and a strengthening of the associated memory. The mechanisms coordinating this precise interplay between brain regions is not well understood. A subcortical region that flexibly connects other brain areas during wakefulness, the thalamus, appears to also organize neuronal activity during sleep. Nevertheless, its functional role in the strengthening of memories is largely unknown. Because the thalamus is a deep structure, it is invisible to non-invasive measures of brain activity. The proposed project thus aims at shining light at how memories are stabilized in the brain by conducting neuronal recordings in non-human primates. Macaque monkeys will be trained on a learning task. We will record neuronal firing and oscillations simultaneously from areas of a well-described distributed neuronal network. This network, which includes the thalamus, is known to be engaged by the task and the formation of new memories. We will track how neurons interact across brain areas to represent new information learned during the task. We will continue the recordings while the animal engages in a nap. By doing so, we aim at assessing how prior learning affects the recorded network during sleep. Based on a series of previous studies, we predict that during sleep, thalamic neurons provide temporal structure to activity in other brain areas that were involved in prior learning. We expect this thalamic control during sleep to be tightly linked to the animal’s subsequent memory performance. The proposed project is designed to provide new insights into how neuronal networks interact in the sleeping brain to form stable long-term memories. By relating our findings to neocortical oscillations, which in contrast to thalamic activity can be measured non-invasively, the project is specifically designed to inform future human research.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Dr. Sabine Kastner