Effect of SNc lesion and impact of STN HFS on the spontaneous activity of cortico-STN cells and on the electrocorticogram (ECoG) of the orofacial motor cortex.

<p>The spontaneous activity of a cortico-STN neuron was extracellularly recorded simultaneously with the ECoG signal of the orofacial cortex in control rats (<b><i>A</i></b>), and in SNc-lesioned animals, before (<b><i>B</i></b>) and during STN HFS (<b><i>C</i></b>). Note that the SNc lesion induces an increased firing rate of the cortico-STN neuron (<b><i>B1</i></b>) that is accompanied by an increased number of bursts and by the appearance of an excessive synchronization in beta frequency band in the ECoG (<b><i>B2, inset</i></b>) compared to control situation (<b><i>A1, A2, inset</i></b>). These SNc lesions-induced changes were abolished during STN HFS (<b><i>C</i></b>). In panels <b><i>A1</i></b><b>, </b><b><i>B1</i></b>, and <b><i>C1</i></b>, the different traces correspond, from the top to the bottom, to the ECoG signal, the simultaneous extracellular recording of the cortico-STN cell, the bursting discharge detected by Poisson Surprise analysis (<i>S</i>≤2) and the discharge of the cell represented as a sequence of spikes. In panels <b><i>A2</i></b><b>, </b><b><i>B2</i></b>, and <b><i>C2</i></b>, histograms display the corresponding interspike intervals and insets show the power spectrum (FFT) of the corresponding ECoGs. In <b><i>C1</i></b>, arrows indicate the stimulation artifacts and the asterisk an action potential. Abbreviation: ECoG: electrocorticogram; FFT: Fast Fourier Transform; HFS: high-frequency stimulation; ISI: interspike interval; SNc: substantia nigra pars compacta; STN: subthalamic nucleus.