Figure 12. Schematic circuit for the interplay between bottom-up and top-down signaling characterized by differential frequency-band synchrony.

In a reciprocally connected loop between a sensory-type area and a cognitive-type area, neural circuits in the superficial layers are endowed with strong intrinsic synaptic connections and generate stochastic oscillations in the gamma frequency range, whereas the deep layers have a propensity to display slower oscillations in the lower beta or alpha frequency range. Top-down projections originate in the deep layers and innervate pyramidal cells (brown), as well as dendrite-targeting (purple) and perisoma-targeting (blue) inhibitory interneurons. In this scenario, low beta/alpha oscillations are directly involved in top-down signaling, which interacts with locally generated gamma oscillations. Adopted with permission from Wang (Wang, 2010).