RT Journal Article SR Electronic T1 A Map of LTP-Related Synaptic Changes in Dorsal Hippocampus Following Unsupervised Learning JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 3033 OP 3041 DO 10.1523/JNEUROSCI.4159-13.2014 VO 34 IS 8 A1 Conor D. Cox A1 Christopher S. Rex A1 Linda C. Palmer A1 Alex H. Babayan A1 Danielle T. Pham A1 Samantha D. Corwin A1 Brian H. Trieu A1 Christine M. Gall A1 Gary Lynch YR 2014 UL http://www.jneurosci.org/content/34/8/3033.abstract AB Recent work showed that unsupervised learning of a complex environment activates synaptic proteins essential for the stabilization of long-term potentiation (LTP). The present study used automated methods to construct maps of excitatory synapses associated with high concentrations of one of these LTP-related proteins [CaMKII phosphorylated at T286/287, (pCaMKII)]. Labeling patterns across 42 sampling zones covering entire cross sections through rostral hippocampus were assessed for two groups of rats that explored a novel two-room arena for 30 min, with or without a response contingency involving mildly aversive cues. The number of pCaMKII-immunopositive (+) synapses was highly correlated between the two groups for the 21 sampling zones covering the dentate gyrus, CA3c/hilus, and apical dendrites of field CA1, but not for the remainder of the cross section. The distribution of pCaMKII+ synapses in the large uncorrelated segment differed markedly between the groups. Subtracting home-cage values removed high scores (i.e., sampling zones with a high percentage of pCaMKII+ contacts) in the negative contingency group, but not in the free-exploration animals. Three sites in the latter had values that were markedly elevated above other fields. These mapping results suggest that encoding of a form of memory that is dependent upon rostral hippocampus reliably occurs at high levels in discrete anatomical zones, and that this regionally differentiated response is blocked when animals are inhibited from freely exploring the environment by the introduction of a mildly aversive stimulus.