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. 2017 Dec 26;115(3):607–612. doi: 10.1073/pnas.1713530115

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Copyright © 2018 the Author(s). Published by PNAS.

This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

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Fig. 1. — Removal of PNNs in lateral secondary visual cortex disrupts recall of a remote fear memory. (A, Left) Coronal section of a rat brain, PNNs detected by Wisteria floribunda agglutinin (WFA; green) and neuronal cell bodies detected by Nissl staining (red). Au1, primary auditory cortex; V1, primary visual cortex; V2L, lateral secondary visual cortex; V2M, medial secondary visual cortex. (A, Right) Neuron expressing parvalbumin (Pvalb; red) enwrapped in a PNN (WFA; green). (B) Coronal section from a rat injected with chABC in V2L 1 wk before perfusion. PNNs detected by WFA staining (green). Activity by chABC causes reduced WFA staining (green) restricted to V2L. RSp, retrosplenial cortex; V1b, binocular V1; V1m, monocular V1. (C) Experimental timeline for remote fear conditioning (FC). (D) The extent of chABC digestion in gray superimposed on illustrations of brain sections (40) five different distances (mm) from bregma, red squares indicates V2L (Left), or V1 and V2L (Right). (E) Bilateral chABC injection in V2L (n = 7 rats) reduced freezing to light CS compared with sham controls (n = 12 rats). Each dot represents one animal, bars indicate population mean. Two-way ANOVA, treatment (aCSF or chABC) × condition (baseline or light CS) followed by post hoc Sidak test revealed that chABC treatment disrupted CS memory retrieval (***P < 0.0001). (F) Bilateral chABC injection in V1 (n = 9 rats) did not influence freezing to light CS compared with sham controls (n = 13 rats). (G) The extent of chABC activity confined to V2L (mean from both hemispheres) was correlated with the amount of freezing during light cues; r = −0.67, P = 0.003, n = 17 rats. (H) Experimental timeline for recent FC. (I) Recent memory testing 1 wk after FC. Bilateral ChABC injections in V2L (n = 8 rats) did not influence freezing to light CS compared with sham controls (n = 8 rats). (J) Recent memory testing 1 wk after FC. Bilateral ChABC injections in V1 (n = 4 rats) did not influence freezing to light CS compared with sham controls (n = 8 rats). Detailed statistics are shown in Fig. S1.