Three-dimensional trajectories of the hippocampal rhythmic slow activity in the behaving rat

Movement-concurrent rhythmic slow activity (RSA) was recorded by means of 3 pairs of bipolar electrodes which were arranged so that they orthogonally encompassed the dorsal hippocampus in the freely moving rat. The 3-channel data were combined by synchronously plotting them on independent voltage axes and the resultant 3-channel Lissajous' trajectory (3-CLT) was depicted in 3-dimensional microcomputer processing. A type of 3-CLT which traversed the surface of an ellipsoid with the long axis nearly perpendicular to the medial CA1 pyramidal layer, appeared most abundantly during walking. A 3-CLT depicting curves on a spherical surface was frequently produced during sitting. A linear 3-CLT of short duration was occasionally produced during rearing. These findings suggest that alteration of voltage axis specific to a behavior is possibly generated associating with the hippocampal RSA.