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Effect of Locus Coeruleus Activation on State-Dependent Whisker-Evoked Responses in Barrel Field: Insights from Current Source Density Analysis

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Neves,  RM
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Logothetis,  NK
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Eschenko,  O
Max Planck Institute for Biological Cybernetics, Max Planck Society;
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Neves, R., Logothetis, N., & Eschenko, O. (2011). Effect of Locus Coeruleus Activation on State-Dependent Whisker-Evoked Responses in Barrel Field: Insights from Current Source Density Analysis. Poster presented at 43rd Meeting of the European Brain and Behavior Society (EBBS 2011), Sevilla, Spain.


Cite as: http://hdl.handle.net/21.11116/0000-0002-45D4-1
Abstract
Cortical evoked response can markedly vary across presentation of identical sensory stimuli. Spontaneous subthreshold fluctuations of the membrane potential of cortical neurons are thought to underline this variability. During sleep or under anesthesia the activity of cortical neurons is highly synchronized. Their membrane potential fluctuates between de- and hyperpolarized levels, also known as UP/DOWN states. Previous studies have shown that such intracellular states can be predicted by the local field potential (LFP) and multi unity activity (MUA). This study examined the effect of LC electrical microstimulation on whisker-evoked responses in barrel cortex of urethane anesthetized rats by analyzing sensory response during predicted UP or DOWN states. LFP signal was recorded from 32-channel microelectrode array with 50 microns interchannel distance and Current Source- Density (CSD) profiles were derived. After deflection on and offset of principle whisker (2 mm, 200 ms) current sinks we generated in layer IV of the corresponding barrel field, reflecting thalamic input. The dynamic of current flow markedly differed between UP and DOWN states. Deflection onset produced high amplitude (0.19 ± 0.1 mV/ mm2) and long lasting current sink during DOWN state, while during UP state current sink was significant smaller (0.07 + 0.2 mV/mm2) and followed by a long lasting reversion of polarity (100-120 ms). LC stimulation resulted in a systematic shift of cortical LFPs from a synchronized to a desynchronized state. We used trains of biphasic square pulses 0.5 ms, 100 mA, 5 pulses at 100 Hz. The desynchronization was transient and relatively short-lasting. 3 trains (250 ms inter-train interval) produced ~1 sec desynchronization. CSD analysis showed that the cortical response profile followed by a priming LC stimulation was similar to such during UP state. Our results demonstrate that LC electrical stimulation alters the dynamics of cortical network as reflected in LFP signal. Moreover, LC discharge and accompanying noradrenaline (NE) release from the terminal fields of LC-NE neurons may shift the membrane potential of somatosensory neurons toward threshold level. This is consistent with previous observations that LC activation facilitates phasic response of sensory neurons in primary somatosensory cortex. We conclude that the smaller amplitude of current sink during UP state and after LC activation is result of a smaller driving force of the network at the moment of sensory input, and it is not due reduction of synaptic input to the somatosensory network.