I studied network dynamics related to sleep’s contribution to memory consolidation. Using in vivo, single unit recordings I assessed changes in the strength of functional connectivity relationships between individual neurons in the mouse hippocampus- a technique that I will develop in the suprachiasmatic nucleus (SCN) to assess changes in our central circadian clock. The SCN shows desynchronized neuronal activity in aged mice, thought to result from a change in the balance between excitation and inhibition (E/I balance), which is an important determining factor in the function of neuronal networks in the brain. The main objective of my current work is to determine the link between E/I balance in SCN and synchrony and show light-influence of E/I balance in the SCN and other brain areas. I aim to answer two questions: 1) What is the link between light induced changes in E/I balance and network status (synchrony) in the aging SCN, as well as in other brain areas (cortex, hippocampus) and 2) Predict interactions of cell networks using network rhythm data.
I obtained my PhD in March 2017 at the University of Michigan with Dr. Sara Aton where I worked of network dynamics related to changes in the hippocampus which accompany sleep-dependent consolidation of contextual fear memory (CFM). I did a short postdoc in Michigan where I continued my work aimed at investigating the causal role hippocampal interneurons play in memory consolidation. I found that PV+ interneurons: 1) are necessary during NREM sleep, but not REM sleep or wakefulness, immediately following CFC to establish fear memory and 2) stimulation at theta frequency following CFC is sufficient to rescue network oscillatory and memory deficits due to sleep deprivation. Additionally, through collaboration with the Zochowski lab in the Department of Physics at the University of Michigan, we developed a novel metric for assessment of functional network connectivity and found that it is sleep-dependent. In January 2018 I joined the Neurofysiologie group working for Stephan Michel to determine the link between E/I balance in the SCN and global network dynamics. For example, is the brain more stable at night in nocturnal animals, and how does aging and light affect this. I received a Marie-Curie cofund LEaDing Fellowship to begin this work in January 2019.
Hippocampal network oscillations rescue memory consolidation deficits caused by sleep loss.
Ognjanovski N, Broussard C, Zochowski M, Aton SJ.
Cerebral Cortex doi: 10.1093/cercor/bhy174
Parvalbumin-expressing interneurons promote memory consolidation by driving hippocampal network oscillations and stabilizing neuronal ensembles.
Ognjanovski N, Schaeffer S, Wu J, Mofakham S, Maruyama D, Zochowski M, Aton SJ.
Nature Communications doi:10.1038/ncomms15039
CA1 hippocampal network activity changes during sleep-dependent memory consolidation.
Ognjanovski N, Maruyama D, Lashner N, Zochowski M, Aton SJ.
Front Syst Neurosci; 8: 61. doi:10.3389/fnsys.2014.00061