Figure 19. Schematic circuit for the interplay between beta- and gamma-band oscillations in top-down signaling.

Shown is a reciprocally connected loop between a sensory-type area and a cognitive-type area. In each area, the superficial layers are endowed with strong intrinsic synaptic connections and generate synchronous oscillations in the gamma frequency range, whereas the deep layers has a propensity to display oscillations in the beta frequency range. Top-down projections originate in the deep layers and predominantly target the superficial layers, where they innervate pyramidal cells (red), as well as dendrite-targeting (purple) and perisoma-targeting (blue) inhibitory interneurons. In this scenario, beta oscillations are directly involved in top-down signaling, which interacts with locally generated gamma oscillations.