Converging lines of evidence from postmortem studies provide strong evidence that brain muscarinic M1 receptor deficit is present in a subset of schizophrenia (SZ) patients. M1 receptors are an important target for cognitive deficits in SZ. However, until now, it has not been possible to examine the heterogeneity of SZ with respect to M1 receptor availability in vivo. The development of a novel positron emission tomography (PET) ligand, [11C]EMO, at Yale PET Center provides a unique opportunity to, for the first time, examine in vivo brain muscarinic M1 receptor availability in SZ and, concurrently, elucidate the relationship of M1 receptors to cognitive deficits in SZ.~The investigators will compare M1 receptor availability in SZ patients and age-, gender-matched healthy controls using [11C]EMO and the High Resolution Research Tomograph (HRRT), a PET scanner with high sensitivity and resolution available for human brain imaging. This study will explore the relationship between: hippocampal [11C]EMO binding (as a measure of hippocampal M1 AChR availability), encoding-related γ power during a verbal memory task, verbal memory, gender, and serum acetylcholine level. This exploratory study will provide the necessary pilot data to conduct a larger study to fully investigate the heterogeneity of SZ with respect to M1 receptor availability.
This exploratory study seeks to examine M1 receptor availability in SZ patients and to relate M1 receptor availability to proximal and distal measures of cognitive performance, namely evoked ɣ oscillations in the EEG and verbal memory. Furthermore, the relationship between hippocampal [11C]EMO availability (BPND), evoked ɣ oscillations, verbal memory, and measures of illness severity will be explored.