Oscillatory activity in the slow and the fast network when they are unconnected or connected.

Abstract

<p>Shown are the Fourier transform (<b>a, d, g</b>), wavelet transform (<b>b, e, h</b>) and raster diagram of cell firing (<b>c, f, i</b>) of the excitatory population in either the slow or the fast network. Color in the wavelet transforms indicates power of oscillation. The raster diagrams depict the firing times (indicated by dots). <b>a–c.</b> Activity of the slow network in isolation. The Fourier transform shows peaks at the base frequency (20.4 Hz) and at the first and second harmonics. Owing to the highly synchronized activity (making the signal effectively a comb function), the Fourier transform produced peaks at the harmonics, but there were no cells that actually fired at these frequencies (see panel c). <b>d–f</b>. Activity of the fast network in isolation. The Fourier transform shows peaks at the base frequency (32.4 Hz) and the first harmonic. <b>g–i.</b> Activity of the fast network when the excitatory cells of the slow network projected to the excitatory cells of the fast network (eE connection) with conductance factor (see Methods). With this connection strength, the slow network managed to impose its rhythm onto the fast network, in which the base frequency (20.4 Hz) of the slow network and its first harmonic were strongly expressed. Since there were no connections from the fast to the slow network, the activity of the slow network was not different from that in the unconnected situation.</p