Optical signals originate ventrolaterally at the onset of a spontaneous episode.

<p>Both intrinsic (A) and dye-related (B) optical signals originate over the motor column at the onset of a spontaneous episode. Each optical signal was spatially averaged from the diodes shown in the schematic of the cord above the traces and then normalized to its peak amplitude. The electrical activity was simultaneously recorded from the ipsilateral ventral root (VR). DC-unfiltered. AC-band pass filtered from 20-312Hz. The arrows delineate the initial slow rise of the depolarization and the onset of discharge (dotted gray line) in the ventral root. Data in A were obtained from an E9 embryo, while those in B were from an E10 embryo. C. Spread of dye-related activity at the beginning of a spontaneously occurring episode. The data were averaged from two E10 embryos and synchronized to the onset of the ventral root discharge (dotted gray line). The smoothed DC ventral root potential (VR DC) and the integrated ventral root discharge (VR INT-25ms integration time) are displayed together with the optical responses from three different cord regions (ventral/lateral motor column-red; intermediate-green; dorsal-blue). Each record was averaged from several adjacent diodes (shown in panel A of the montage illustrated in D) and normalized to its peak amplitude. Data were obtained at a sampling interval of 0.64ms. The gray lines over the traces in C, delineate the frames that were averaged to produce the pseudocolored montage. D. Montage of the pseudocolored diode array signals superimposed on the outline of the transverse face of the cord slice. The number in each panel corresponds to the numbered intervals over the electrical and optical traces. The first image (Anti) in the sequence is a pseudocolored image of the optical signals during antidromic stimulation of the ipsilateral ventral root to identify the location of the lateral motor column. The colored regions on the image identify the location of the diodes whose signals were averaged to produce the optical records in C. The second image (1, Gain×4) was obtained before the onset of discharge (vertical dotted gray line in C) and was averaged from 105 frames (67ms/frame) is displayed at 4×the gain of the remaining images. All remaining images (2–8) were averaged from 45 frames (29ms/frame). The arrow shows the earliest detectable activity occurs over the lateral motor column.