Interactions between cat lateral geniculate neurons

Abstract

Action potentials of 31 pairs of cat LGN neurons were recorded on single electrodes. Cross-correlograms, response planes, and a new function, the logical response plane, were calculated. The cross-correlograms between these pairs revealed four interactive classes: 1) a class with a flat cross-correlogram, 2) a class with a peak in the center of the cross-correlogram seen both during spontaneous activity and during driven activity, 3) a class with an inhibitory dip in the center of the cross-correlogram seen only when the cell pairs were driven by a stimulus and predicted by the shift predictor, 4) finally, a class with an inhibitory dip in the center of the cross-correlogram seen both during driven activity and spontaneous activity and not predicted by the shift predictor. Response plane pairs calculated for the unit pairs with flat cross-correlograms showed no predictable relationship. The pairs with a dip in the center of the cross-correlograms always had response planes that were antagonistic (i.e., approximate negative images of each other). When one cell was excited, the second cell was inhibited, and vice versa. More detailed analysis, using the logical response plane, demonstrated that the majority of the antagonistic response planes had either excitatory or inhibitory overlap. That is, the cells were simultaneously excited and/or inhibited at specific spatiotemporal loci on the response plane. These data are consistent with a feed-forward inhibitory circuit in LGN. Furthermore, the data suggest that retinal centers (PE domains) produce LGN excitatory centers (PE domains) and inhibitory centers (PI domains). In turn, retinal excitatory surrounds (SE domains) produce LGN excitatory surrounds (SE domains) and inhibitory surrounds (SI domains).