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1.
Figure 2

Figure 2. Recording locations. From: Perirhinal cortex represents nonspatial, but not spatial, information in rats foraging in the presence of objects: Comparison with lateral entorhinal cortex.

The distribution of recording locations in PRC, LEC and MEC are shown in cresyl violet stained sections from one of the rats used in this study. These sections are approximately 470 µm apart, assuming 15% shrinkage. Contours mark the range of locations from which single units were recorded in the three regions.

Sachin S. Deshmukh, et al. Hippocampus. ;22(10):10.1002/hipo.22046.
2.
Figure 4

Figure 4. Object-related activity in PRC and LEC, and place-related activity in LEC. From: Perirhinal cortex represents nonspatial, but not spatial, information in rats foraging in the presence of objects: Comparison with lateral entorhinal cortex.

Units 1–3 are from PRC, while units 4–6 are from deep LEC. See Deshmukh and Knierim (2011) for rate maps of neurons from superficial LEC. Units 1–5 show different types of object related activity, while unit 6 shows place cell-like activity. Blue corresponds to no firing while red corresponds to peak firing rate for the given neuron, indicated at the top of each rate map (pk). Spatial information score, in bits/spike for each session is also indicated at the top of each rate map (i).

Sachin S. Deshmukh, et al. Hippocampus. ;22(10):10.1002/hipo.22046.
3.
Figure 7

Figure 7. Cortical inputs to the hippocampus are segregated (Burwell, 2000; Witter and Amaral, 2004). From: Perirhinal cortex represents nonspatial, but not spatial, information in rats foraging in the presence of objects: Comparison with lateral entorhinal cortex.

Inputs from the cortical “where” pathway enter medial temporal lobe through postrhinal cortex and MEC, while inputs from the “what” pathway enter medial temporal lobe via PRC and LEC. Both these streams converge onto hippocampus, which may synthesize the conjunctive “object + place” representation that might be a critical component of episodic memory. Roles of different components of the pathway, as suggested by the present report, are shown under the components.

Sachin S. Deshmukh, et al. Hippocampus. ;22(10):10.1002/hipo.22046.
4.
Figure 5

Figure 5. Spatial information scores in PRC and LEC. From: Perirhinal cortex represents nonspatial, but not spatial, information in rats foraging in the presence of objects: Comparison with lateral entorhinal cortex.

(A) Distribution of spatial information scores in PRC and LEC are similar to each other, but PRC has a much smaller proportion of neurons with significant spatial information scores compared to LEC. Black bars correspond to neurons with statistically significant information scores. (B) A similar pattern is seen after subdividing spatial information scores by deep and superficial layers of PRC and LEC. (C) Area 35 has more spatial information than area 36, but the majority of neurons in both regions do not have statistically significant information scores.

Sachin S. Deshmukh, et al. Hippocampus. ;22(10):10.1002/hipo.22046.
5.
Figure 6

Figure 6. Similar proportions of PRC and LEC neurons are object responsive. From: Perirhinal cortex represents nonspatial, but not spatial, information in rats foraging in the presence of objects: Comparison with lateral entorhinal cortex.

Distributions of pmin(ORI) in PRC (top) and LEC (bottom) neurons in the four standard sessions are similar. Black bars indicate cells that showed statistically significant [pmin(ORI) < 0.05] object-related firing. Logarithmic scale is used for pmin(ORI). PRC and LEC showed similar proportions of neurons with object-related activity in the four standard sessions (session 1 PRC: 13/67, LEC: 28/127, χ2 = 0.059, p = 0.81; session 2 PRC: 13/68, LEC: 26/119, χ2 = 0.065, p = 0.8; session 4 PRC: 16/58, LEC: 20/106, χ2 = 1.19, p = 0.27; session 6 PRC: 7/48, LEC: 26/90, χ2 = 2.78, p = 0.095).

Sachin S. Deshmukh, et al. Hippocampus. ;22(10):10.1002/hipo.22046.
6.
Figure 3

Figure 3. Absence of high firing rate interneurons in PRC and LEC. From: Perirhinal cortex represents nonspatial, but not spatial, information in rats foraging in the presence of objects: Comparison with lateral entorhinal cortex.

(A) Scatter plots of spike width vs. mean firing rate show that MEC has putative interneurons with narrow (< 0.25 ms) spike widths and high (> 10 Hz) mean firing rates, which are missing in PRC and LEC. (B) Scatter plots with expanded × axis to show that PRC and LEC do not show two clusters [one with broad spikes and low firing rates and another with narrow spikes and high firing rates (lower than 10 Hz)], even at the expanded scale.

Sachin S. Deshmukh, et al. Hippocampus. ;22(10):10.1002/hipo.22046.
7.
Figure 1

Figure 1. Experimental protocol. From: Perirhinal cortex represents nonspatial, but not spatial, information in rats foraging in the presence of objects: Comparison with lateral entorhinal cortex.

A typical experimental protocol consisted of 6 consecutive 15 minute foraging sessions in the presence of objects. Sessions 1, 2, 4, and 6 were standard sessions where objects were in their standard configuration. Sessions 3 and 5 were object manipulation sessions, where either a novel object was introduced in the box or one (or occasionally two) familiar object was misplaced. The type of object manipulation was counterbalanced, such that if day n session 3 was a novel-object session while session 5 was a misplaced-object session, then day n + 1 session 3 was a misplaced-object session while session 5 was novel-object session. This was done to reduce the potential effects of ordering. Circles represent familiar objects in their standard locations, while stars represent either novel objects or familiar objects in misplaced locations. Magenta lines connect the standard and misplaced locations of familiar objects in misplaced object sessions.

Sachin S. Deshmukh, et al. Hippocampus. ;22(10):10.1002/hipo.22046.

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