Fig. 6.

Responses of two simultaneously recorded place cells during light inactivation. Pairs of trials are shown to illustrate the spatially selective activity that occurred during the con-to-con and con-to-inact spatial correlation. A, In this case the cell showed a preferred field on the western maze arm during trials 1 and 2 and during trials 4 and 5 (con-to-con trials). During retrosplenial cortex inactivation, the location of the field changed to firing on two arms and then began to fire on the northwestern maze arm in the subsequent trials. The preferred location for the cell did not return until the subsequent test day.B, This cell showed a similar consistent field during control light trials; during inactivation the field changed locations and then began to fire on the southeastern maze arm. Interestingly, the simultaneously recorded cells both rotated their preferred fields during inactivation but by different amounts. In both cases, the preferred field did not return until the next test day. All of the spatial plots omit cellular activity that is <20% of the maximum rate of the cell during the trials. The maximum rate is shown as dark areas, and shaded areas correspond to intermediate rates. This form of presentation is the same for Figures 7, 8, and 10. It should be noted that the small sample size for the spatial plots reduces the variability in the firing of the place cell (the animal only passes through the place field a total of four times, and if the field is directional the cell only has two opportunities to be active for a given plot). Accordingly, the firing-rate distribution is reduced substantially because of the small sample size.