This study investigates the roles of hippocampal N-methyl-D-aspartate (NMDA) glutamate receptors and CaMKII (calcium/calmodulin-dependent protein kinase II) in amphetamine-produced conditioned place preference (AMPH-CPP) in rats. An earlier report showed that AMPH-CPP resulted in the enhancement of hippocampal CaMKII activity. In this study, AMPH-CPP significantly increased hippocampal GluR1 receptors, though AMPH-CPP was impaired by either blockade of NMDA receptors (AP5) or inhibition of CaMKII (KN-93) during conditioning. These treatments also impaired CPP if administered before testing, but CPP recovered during the next testing session. Therefore, these treatments had no effect on the extinction of CPP. If the conditioned rats were, however, reexposed to AMPH-CPP after a hippocampal-infusion of AP5 or KN-93, the extinction of the original CPP was greater than that seen in the controls. The hippocampal-infusion of D-cycloserine before CPP testing enhanced the extinction of CPP. These results, taken together, indicate that NMDA receptor activation and CaMKII activity are essential for the AMPH-CPP. AMPH-CPP reexposure is similar to the memory reconsolidation process, being disrupted by either a blockade of the NMDA receptor or an inhibition of CaMKII. Furthermore, the extinction of CPP resembles new learning, which is an active process and is facilitated by a partial NMDA agonist.
Similarities of language-independent form symbolism were tested across different geographical regions. In Experiment 1, word-form matching between 10 abstract words and 16 computer-generated nonsense forms was performed by between 61 and 107 undergraduate or volunteer participants in nine geographic regions of the world. Participants were native speakers of one of eight different languages: Japanese, Chinese, Korean, English, Italian, German, Serbian and Slovakian. The results demonstrated similar trends across languages and geographic regions. The small but significant differences between Eastern and Western groups found in Experiment 1 could be attributed to differences between them in the affective meanings of words rather than forms, as suggested by the results of Experiment 2. Experiment 2 involved participants (49 to 116 undergraduates from Japan, Taiwan, the US and Serbia) performing the 11-scale Semantic Differential technique on 10 words and eight of the 16 forms used in Experiment 1. It was concluded that the cross-regional similarity of form symbolism is based on the similarity of affective meanings of forms across different regions and languages.
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