FIGURE 4.

Experimental recurrent febrile seizures (eRFSs) decrease the efficacy of signal propagation along the somatodendritic axis. (A) Phase coherence (referenced to stratum lacunosum moleculare [SLM]) for control (CTL) and eRFS rats plotted as a function of depth (μm) for theta (4–12 Hz, left), slow gamma (30–50 Hz, middle), and medium gamma (70–90 Hz, right) bandwidths. Filled circles = CTL; empty circles = eRFS. Phase coherence exhibits a distinctive pattern along the CA1 somatodendritic axis. The coherence peak was at the reference region and the trough was at stratum pyramidale (SP) for both groups across all bandwidths. (B, C) Phase coherence plotted by frequency (step size = ~1 Hz) for SP (B; probe depth = 100–180 μm) and stratum radiatum (SR; C; probe depth = 280–400 μm) referenced to SLM. Filled circles = CTL; white circles = eRFS. (D) Voltage correlation analysis of lag time, indicating when the reference local field potential (LFP) channel (SLM) was leading or following the target LFP channel (all other depths) for the theta bandwidth. Theta exhibits a dynamic time lag by depth that is corrected at SP, whereas eRFS remains largely stable throughout. (E) Voltage correlation measurements plotted by depth for theta (left), slow gamma (middle), and medium gamma (right). Filled circles = CTL; empty circles = eRFS. For all plots, relative CA1 location corresponding to depth is superimposed in colors: blue = stratum oriens (SO), yellow = SP, pink = SR, green = SLM. White = dentate gyrus molecular layer (MOL), dentate gyrus cell layer (DEN), hilus (HIL). Filled circles = CTL, empty circles = eRFS. All statistical analyses were performed using generalized linear models. CTL, n = 5; eRFS, n = 6. In CA1, inputs propagate more effectively along the somatodendritic axis than eRFSs as measured by coherence and voltage correlation. *p < .05