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Oxana Eschenko, Dr.
Research Scientist (Postdoctoral Fellow) |
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MPI for Biological Cybernetics
Dept. Logothetis
Spemannstraße 38
72076 Tübingen
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+49-7071-601-1679 |
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230 |
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oxana.eschenko@tuebingen.mpg.de |
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The scientific interest of my research group is to better understand the neurophysiological mechanisms of noradrenergic neuromodulation in the brain. The noradrenergic system mediates many cognitive processes such as attention, perception, learning and memory. Dysfunction in noradrenergic system often leads to various psychiatric disorders.
The core of the noradrenergic system is a small brainstem nucleus with blue (cerulean) appearance, because of which this nucleus was named Locus Coeruleus (LC), i.e. “blue spot”. It contains noradrenergic neurons, and projects extensively throughout the brain, innervating the spinal cord, the brain stem, hypothalamus, cerebellum, thalamic relay nuclei, amygdala, basal telencephalon, as well as the cortex. As opposed to direct synaptic neurotransmission (wired transmission), in which one presynaptic neuron directly influences its postsynaptic target, the axons of noradrenergic neurons commonly have characteristic varicosities by means of which noradrenalin is secreted and diffused through large volumes of tissue (volume transmission), thereby affecting simultaneously multiple and diverse population of neurons. The mechanisms underlying the specificity of neuromodulatory effects at different projection targets are poorly understood. A major methodological challenge is to monitor neuromodulatory effects at multiple brain regions simultaneously.
One project of my research group aims to distinguish anatomical and effective (functional) connectivity of LC in the rat brain. To do so, we use the functional magnetic resonance imaging (fMRI) technique in combination with intrabrain electrical microstimulation of the LC nucleus. The results of these experiments are “paired” with tract-tracing studies using conventional histochemical, as well as MRI-detectable neural tracers, so-called T1-agents as well as - in the near future - smart contrast agents. While such studies set the constraints for anatomical and functional connectivity, they do not permit the characterization of the detailed physiological mechanisms underlying the communication between LC and the rest of the brain. To address this question we also perform MRI-guided multi-site extracellular recordings in order to characterize various temporal interactions between LC and its cortical targets during sensory processing in anesthetized rats. Finally, we combine electrophysiological recording and behavioral testing of rats in various learning situations to study what aspects of neural coding, information processing and behavioral performance are affected by noradrenergic modulation.
My group largely relies on interdisciplinary methodology. While its core consists of neurophysiologists, a number of collaborators come from the research field of computer science, mathematics, or spin physics. The investigation of neuromodulation, and of wide spread neuronal networks in general, requires analysis methods that take into account both local, regional and global response patterns. Thus, interdisciplinary experimental methodology is combined with advances in quantitative analysis, modeling and theory.
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