Fig. 4.

Analysis of individual place field widths. (A) Example rate maps and phase precession plots before and after high-concentration muscimol infusion to dorsal MEC. (B) A color-coded example of the phase-by-position plot from which the experimenter manually selected place field boundaries. The gray boxes indicate track bins around the reward wells excluded due to low occupancy after velocity thresholding. The experimenter selected boundaries around the red and blue fields. The blue field was excluded from the analysis due to overlap with the middle gray box. The small phase-precessing field on the far left was not selected by the observer because it overlapped with another small field (to its left), which did not appear to be showing phase precession (both fields overlap the reward area, so they would have been automatically excluded on those grounds had boundaries been selected). The y axis is duplicated and spikes plotted twice to produce a contiguous cycle of phase procession for display purposes in both A and B. (C) Representative example of heat maps generated from spikes fired within the manually selected fields. The example uses all spikes fired by all CA1 neurons recorded through hyperdrive bundle 1 from all high-concentration dorsal site inactivation sessions. This plot shows that field boundaries were selected consistently and that fields were not artificially expanded (i.e., no large blank areas at either end of the population field) or shrunk (i.e., the population field is not truncated at either end). (D) Place field width data for all treatment subgroups recorded in CA3 (Top) or CA1 (Bottom) presented as mean ± SEM. L/H indicates low/high muscimol concentration. Vehicle or site of inactivation listed along the Bottom. The single asterisk (*) indicates significant difference between baseline and postinfusion within a treatment or treatment subgroup with a P < 0.05; the double asterisk (**) indicates P < 0.001.