The role of sleep for neuronal plasticity
Niels Niethard, PhD, University of Tuebingen
The idea that the main function of sleep is to maintain the organism’s homeostatic balance is at the center of my research into the dynamics of the sleeping brain and their functional significance. In 2012 at the University of Innsbruck, I obtained my diploma in Psychology and continued as a Neuroscience PhD student at the Institute of Medical Psychology and Behavioral Neurobiology at the University in Tuebingen. Since 2019, I am a post doc and I am expanding my research focus to investigate how sleep regulates metabolic functions by synaptic scaling within the hypothalamus.
Sleep concurrently contributes to homeostatic down-regulation and mnemonic synaptic up-regulation in cortical networks. We used two-photon imaging of calcium activity to examine how these seemingly opposing functions are established. We found that neuronal excitability on average decreases across sleep, whereas subsets of neurons increase firing rates across sleep. Studies of the excitation/inhibition balance in cortical circuits suggest that both processes are connected to a specific inhibitory regulation of cortical principal neurons, characterized by an enhanced perisomatic inhibition via parvalbumin positive (PV+) cells, together with a release from dendritic inhibition by somatostatin positive (SOM+) cells. Such shift towards increased perisomatic inhibition of principal cells appears to be a general motif which underlies the plastic synaptic changes observed during sleep, regardless of whether towards up or downregulation.