Simultaneous recording of lagged and nonlagged cells in the cat dorsal lateral geniculate nucleus.

It has been suggested that lagged and non-lagged cells in the cat dorsal lateral geniculate nucleus (LGN) represent state-dependent response modes of the same class of LGN cells. In two separate experiments with single-unit recording in the LGN of anaesthetized and paralysed adult cats, a lagged and a nonlagged X-cell were recorded simultaneously with the same microelectrode. For each pair of cells, the amplitude of the action potentials was sufficiently different to allow separate compilation of peri-stimulus-time-histograms. For all 4 cells, the visual response pattern to a stationary flashing light spot was typical of their respective cell class. These findings support the hypothesis that lagged and non-lagged cells are separate cell classes and indicate that the population of LGN cells do not appear as lagged during one state of modulatory input and as nonlagged during another.