it is driven by neurons taking part in two assemblies, two separate phase precession cycles are clearly revealed in ‘phase-space’ (arrows in Figure 9C). Using the spike phase information, two distinct place-related firing patterns of the same interneuron can be readily segregated, each with a monotonic phase dynamic (Figure 9C), an indication that its firing is under the control of two distinct cell assemblies. In addition, Figure 9D shows that some interneurons are not only driven specifically by assemblies but they also actively contribute to the segregation of competing assemblies. In this example, two spatially overlapping place cells were simultaneously recorded with a putative basket interneuron (Geisler et al., 2007). The gamma time-scale positive correlation between one place cell (P1) and the interneuron suggests that both cells belonged to the same cell assembly. In contrast, the spiking activity and phase-precession of the second place cell (P2) was anti-correlated with the discharge of the interneuron (Figure 9D), indicating an enabling mechanism of the interneuron at times when P2 and its assembly peers were active.
