The cells had to meet a specific criteria to be included in the analysis, such as well separated clusters, spikes with broad widths (peak-to-trough width > 300 μs), and presence of complex bursts with 2–7 spikes within 5–15 ms. To ensure that we recorded from the same place cell across sessions, we confirmed that the properties such as autocorrelation, waveform, firing rate and firing location were similar in both sessions. The inhibitory interneurons were easily identified by their high frequency of firing with narrow waveform width and place nonspecific firing. Position data of the mice, tracked by two colored LEDs, were collected at 50 Hz and sorted into 3 × 3 cm Paclitaxel in vitro bins. Each sorted place cell

was visualized by plotting its firing rate on top of an animal’s walking path, with heat map colors ranging from blue (little or no firing) to red (high firing rate). A normalized firing rate map was obtained by dividing the spiking activity with

the animal’s position at a particular place. Firing rate maps were smoothed with a filter such that 1 cm equaled 2 pixels. Place field size was measured as in previous studies (Muller et al., 1987). Briefly, we calculated the number of pixels inside the enclosure where place cells fired normalized with the number of pixels the mice visited. Only selleck kinase inhibitor the top 80% of the firing peak with at least 8 contiguous pixels was used and defined as the place field. The pixel area covered by the mice in the box or track enclosure was converted to the respective percentage (%) of total enclosure area for cross-comparison. Two separate measures were used for calculating place field stability. First, a peak-shift measure was used where the firing field peak of session 1 was compared with the firing peak of session 2. before A shift (in cm) in peak 1 to peak 2 was calculated by the formula (x1−x2)2+(y1−y2)2,where x1, x2 are the x coordinates and y1, y2 are the y coordinates

of peaks 1 and 2. Second, a cross-correlation measure was used. Prior to applying this measure the firing maps were normalized to a standard size (Figure 4C). From the place field rate map only the in-field firing map (top 80% of the place field peak) was extracted and scaled down to a standard size of about 20 cm using the centroid as the midpoint. This was done to eliminate cross-correlation bias; correlation of larger place fields would produce better stability scores as there are more bins available. Normalized maps from session 1 were compared with session 2 using Pearson’s product moment correlations, given by the formula: r=1n−1∑i=1n[(Xi−X¯σX)(Yi−Y¯σY)]where Xi−X¯/σX,X¯ and σx are the standard score, sample mean, and sample standard deviation of data X, respectively. Spatial coherence estimates smoothness of a place field. It was calculated by correlating the firing rate in each pixel with firing rates averaged with its neighboring 8 pixels.