Task-dependent neuronal oscillations are often found in mammalian cortical networks, and investigating their origin and function is an open area of research. In this work we analyze LFPs and MUAs data from the barrel cortex of urethane anesthetized rats, and we find long-lasting collective oscillations in the 6-10 Hz band after stimulation of the rat whisker. In LFPs, they coexist with δ band oscillations, which dominate the resting state period and modulate the 6-10 Hz band, through Phase Amplitude Coupling. We also simultaneously record data from the thalamus, which is known to be part of the sensory path . Oscillations in the δ band always dominate the LFPs of the thalamus, which displays a weaker response to the stimulation. Yet, we can show that its response anticipates the one of the barrel cortex, suggesting the preferential direction of the propagation of the signal. To study the origin of these oscillations, we build a mesoscopic model, based on a two-nodes (thalamus and barrel) directed chain. Each node behaves as a damped oscillator of the Stochastic Wilson Cowan type , whose oscillations are amplified by the finite size noise. At rest, we assume that the two nodes are weakly coupled and oscillate at 3 Hz. We then increase the coupling between the two nodes, mimicking the facilitation of their synapses thanks to the whisker stimulation. Notably, if we consider just a coupling with the inhibitory subpopulation of the first node (thalamus), and not with the excitatory, automatically a second frequency around 6 Hz, analytically predicted, appears in the power spectrum of the second node (cortex), which coexists with the frequency at 3 Hz. Thus, our data analysis shows that evoked collective oscillations, modulated by slow oscillations, are present in the barrel after whisker stimulation, whose response propagates from thalamus to cortex. Our modeling framework highlights a particular effective coupling for the birth of the higher frequency, that in the barrel coexists with the δ band frequency.
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