Figure 8.

Beta 1 rhythm emerges from concatenation of gamma cycles and beta 2 cycles. Left – circuit diagrams portraying relevant connectivity between superficial FS interneurons, LTS interneurons, regular‐spiking pyramidal neurons (E), and deep‐layer IB neurons. Right – dynamics of each population over time, vertically aligned and color‐coded by cell type. Population spikes are portrayed as vertical lines. The time courses of synaptic and intrinsic currents are color‐coded by current type. (A) Under heavy kainate drive, a column of the cortex generates coexisting gamma and beta 2 rhythms in the superficial layers and deep layers, respectively. Gamma rhythms are paced by the rhythmic production of FS IPSPs, and beta 2 rhythms are paced by the rise and decay of the M‐current in IB neurons. (B) Under less drive and after plasticity, a column of the cortex generates a beta 1 rhythm that is coherent between superficial and deep layers. Owing to low drive, the H‐current builds up in the E and IB populations during IPSPs. When each IPSP wears off, the excitation provided by the H‐current triggers E or IB spikes, which, in turn, trigger LTS or FS spikes, respectively. FS and LTS create IPSPs in alternation, and beta 1 rhythms are paced by the concatenation of the gamma and beta 2 cycles.