Example VSD recordings of transient, spontaneous epileptiform discharges at three sites along the hippocampal—neocortical axis.

A. Cartoon illustrating the 3 sites the example fluorescence changes illustrated were taken from: 1—stratum radiatum of area CA1 of the hippocampus, 2—layer 5/6 of medial entorhinal cortex (mEC), 3—layer 5/6 of auditory cortex (Au1). Box shows the coverage of the CCD chip used to record the data. Scale bar 1 mm. B/C. Examples of the 4 subtypes of spatiotemporal, interictal activity seen, each example is 2 x 2 pixel binned and temporally filtered (see methods). Bi. Non-propagating events originating in hippocampus. Bii. Non-propagating events originating in Au1 (note amplitude-degraded event visible in mEC but not hippocampus). Ci. Propagating, reverberating events originating in hippocampus, projecting to neocortex and returning to hippocampus. Cii. Propagating, non-reverberating events originating inhippocampus. Scale bars B/C 0.1% Δf, 2 sec.