Cross-correlation analysis of connectivities among cat lumbosacral dorsal horn cells.

1. Eighty-three cell pairs were recorded in dorsal horns of 19 cats. Cross-correlograms were flat in 65 cell pairs; of the remaining 18 pairs, cross-correlograms had broad peaks or troughs suggestive of nonmonosynaptic causal relations in their discharges; one cell pair had a biphasic deviation from base line. 2. No cross-correlograms indicative of monosynaptic interactions were observed. 3. All cell pairs with nonflat cross-correlograms had overlapping receptive fields. 4. It is concluded that monosynaptically connected cell pairs are rare at the interelectrode distances used in this experiment because such cell pairs must lie close together on the somatotopic map or because our recording methods bias against monosynaptically linked cell pairs.