butyrylcholinesterase specific imaging agents. Methods: A series of benzoate oxyand thioesters were synthesized containing the N-methylpiperidinyl moiety. The benzoate oxyesters were measured for hydrolysis using changes in UV absorption for the benzoate reactants and products and comparable thioesters were analyzed using the Ellman method. In addition, thioesters of several acetyl-, propionyland butyryl-containing oxyester cholinesterase imaging agents were synthesized and their kinetic parameters evaluated using the Ellman method. Several of the thioester compounds were used for histochemical staining of post-mortem human tissue to assess their distribution and specificity towards acetylcholinesterase or butyrylcholinesterase. Results:Nmethylpiperidinyl oxyand thioesters (Figure 1) were synthesized in analogous reaction procedures. Enzyme kinetic analyses indicated comparable interactions of oxyand thioesters with acetylcholinesterase and butyrylcholinesterase. Histochemical studies indicate a unique distribution of each thioester, dependent upon their specificity towards the cholinesterases. Conclusions: We have established a strategy for the development of cholinesterase ligands based on thioesters of N-methyl piperidinol. Molecules derived from this moiety can be rapidly evaluated in vitro for their potential as imaging agents. Imaging agents developed using this approach have the potential to detect cholinesterase levels associated with disease pathology, thus providing an approach for early diagnosis and treatment monitoring of AD. P4-066 RESTING STATE CONNECTIVITY IN POSTERIOR CINGULATE AND HYPPOCAMPUS IN MILD ALZHEIMER’S DISEASE AND MILD COGNITIVE IMPAIRMENT Patrizia Montella, Fabrizio Esposito, Manuela de Stefano, Daniela Buonanno, Angiola Maria Fasanaro, Mario Cirillo, Antonella Paccone, Gioacchino Tedeschi, Second University of Naples, Naples, Italy; University of Naples Federico II, Naples, Italy; Second University of Naples, Naples, Italy; Second University of Naples, Naples, Italy; Neurological Institute for Diagnosis and Care “Hermitage Capodimonte”, Naples, Italy.