Abstract:
Experimental manipulations have implicated dopamine and NMDA glutamate receptor activation as playing integral roles in the learning and memory process, but no research appears to have examined individual variability in the natural expression of dopamine and NMDA glutamate receptor levels. In this study, the naturally occurring variability of dopamine (D1, D2, D3) and glutamate NMDA NR2A receptor expression in the prefrontal cortex and nucleus accumbens, measured by in situ hybridization, in relation to individual differences in performance of spatial reference memory and spatial working memory tasks were examined. Spatial reference memory testing was conducted in the Morris water maze (MWM), utilizing the submersible Atlantis-style platform paradigm. Spatial working memory testing was conducted utilizing the MWM moving platform task. Significant correlations between mRNA values and behavioral values implicate the mRNA studies here in several aspects of learning. Dopamine D2 and D3, and NMDA NR2A in the nucleus accumbens is associated with memory consolidation in spatial reference memory. Dopamine D1 in the nucleus accumbens core is involved in the
acquisition and maintenance of a new strategy, whereas, D1 in the nucleus accumbens shell is involved in the consolidation process of spatial location in working memory task. The findings in this study are consistent with the substantial research using experimental manipulations that have identified dopamine and NMDA receptor activation as playing an integral role in the learning and memory process. Individual differences in both spatial reference and spatial working memory were correlated with individual differences in mRNA levels, suggesting that individual differences in mRNA expression are a determinant of individual performance differences in these aspects of behavior.
