Fig. 8.

Coherence between signals recorded from CA1 str. radiatum (r) and dentate inner molecular (im) layers. A, Effect of partialization on the str. radium–inner molecular ordinary coherence using neighboring signals recorded 100 μm on either side of radiatum (left) or inner molecular (right) electrodes. Ordinary coherence between ch6 and ch11 was relatively low in the entire 0–30 Hz frequency range (top), including the theta band. Elimination of the locally shared components (with ch5 and ch7) from the r (ch6) recording increased radiatum–inner molecular pairwise theta coherence (see Results for more details). Similar enhancement of theta coherence was obtained after elimination of the local components with its neighbors (ch10 and ch12) from the inner molecular (ch11) recording. The largest increase in theta coherence occurred after partialization with ch7 or ch10. B, Coherence map after partialization with hippocampal fissure signal (ch 9). Grayscale indicates the magnitude of the coherence value at the theta frequency. The lowest ordinary coherence values (inset) were found between the inner molecular and the recordings from different locations in radiatum (pr, proximal radiatum; dr, distal radiatum; lm, str. lacunosum moleculare). These ordinary coherence functions did not have peaks at theta, whereas all the others exhibited strong theta coherence (Fig. 3A), which could be eliminated by partialization with the hippocampal fissure signal. On the other hand, partialization with signals close to inner molecular (including ch9 as shown here) eliminated a substantial part of the inner molecular signal (see relatively high ch9–ch11 ordinary coherence in the entire 0–30 Hz range in Fig. 3A), thereby uncovering a weak theta component unrelated to the hippocampal fissure signal. This “uncovered” theta was specifically localized to inner molecular and was coherent only with the radiatum recordings.