Perhaps the most versatile class of reader-integrator mechanisms of neuronal assemblies is oscillations. Neuronal oscillators belong to the family of relaxation oscillators, with separable input (charging or receiving) and output (discharging, transmitting or duty cycle) phases (Buzsáki, 2006; Pikovsky et al., 2001). This asymmetry is due mainly to the within-cycle offset of inhibition and excitation (Buzsáki et al., 1983; Csicsvari et al., 1999). The charging or accrual phase of the oscillator is a typical time integrator (‘reader’) mechanism of upstream activity. Oscillators are also natural parsing and chunking mechanisms of neuronal activity because they have well-defined onsets and offsets with characteristic maximum and minimum spiking activity of the information-transmitting principal cells (Masquelier et al., 2009). This stop-start parsing function of neuronal oscillators can determine the length of an information unit (‘neural word’ or assembly sequence), and multiple cycles can combine word sequences into ‘neural sentences’. Since oscillator readers are a collective product of neuronal cooperation, their occurrence is reflected in the LFP. Therefore, along with other intermittent population events, such as K-complexes, ponto-geniculo-occipital (PGO) spikes and hippocampal sharp waves, LFP
