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. 2012 Mar 14;109(13):5086–5091. doi: 10.1073/pnas.1114415109

Fig. 2.

Fig. 2.

Comparison of mPFC and hippocampal ensemble representations and temporal context effects. (A) mPFC ensemble encoding of locations within a single environment on two different exposures. Upper: Animals were exposed to one environment on two occasions. Dots denote the location of the rat in the environment in 500-ms time bins. Black dots correspond to the time bins when the rat was in the NE corner during first exposure, and dark green dots correspond to the time bins when the rat was in the same corner of the same environment on the second exposure. Gray dots correspond to the time bins when the rat was in the SW corner during first exposure, and light green dots to those when the rat was in the same corner of the same environment on the second exposure. Red dots correspond to all other time bins for all other locations that were not considered in the present analysis. Lower: MSUA space representation for the ensemble of mPFC neurons recorded during the same session. Dots correspond to the state of the network in MSUA space in 500-ms bins and are colored according to the time bins in the location map above. (B) Hippocampal ensemble encoding of locations within a single environment on two different exposures. Upper: Dots denote the location of the rat in the environment in 500-ms time bins, based on the same color scheme as used in A. Lower: MSUA space for the ensemble of hippocampal neurons recorded during the same session. Dots correspond to the state of the network in MSUA space in 500-ms bins and are colored according to the time bins in the location map above, as in A. (C) Mean Mahalanobis distances in MSUA space comparing time bins when subjects were in the same location in the same environment on two different exposures (black bars) vs. different locations in the same environment on a single exposure (striped bars). Data for mPFC ensembles are shown at left, and data for hippocampal (HPC) ensembles at right (**P < 0.0001; error bars = SEM; n = 24 data points from 6 sessions from five animals). Note that mPFC population vectors differentiated more between the two exposures for the same location, whereas hippocampal ensembles differentiated more strongly between different locations during a single exposure.