4.3 Functional Magnetic Resonance Spectroscopy in Patients With Schizophrenia

Abstract

Background: There has been considerable interest in the role of glutamater-gic neurotransmission in schizophrenia, with elevations in medial prefron-tal glutamine being reported in the early phase of the illness. In contrast, in patients with chronic schizophrenia, reduced levels of glutamine and glutamate have been reported. These reductions may represent reductions in glutamatergic neurotransmission or loss of neuronal density or synaptic connectivity. Although standard magnetic resonance specrtoscopy allows estimation of brain glutamate and glutamine levels, there has been some controversy as to whether these are derived from metabolic or neurotrans-mitter pools. Functional MRS (fMRS) allows the measurement of dynamic changes in brain glutamate and glutamine levels during brain activity and may give a closer estimate of glutamatergic neurotransmission. Methods: Fifteen patients with schizophrenia (11 males, mean age (SD) = 40 (10)) and 13 healthy volunteers (7 males, mean age (SD) 31 (8.6)) underwent a 15-minute n-back task in a 48s block design during fMRS acquisition (TE = 105 ms, TR = 2000 ms, NEX = 8). Data from the frst second and third 16-second group of 8 spectra for each block were processed using TARQUIN. Changes in glutamate and Glx (glutamate + glutamine) between the 0-back and 2-back tasks were measured in controls and patients, and the differences between the 2 groups were compared. Results: There was a signifcant increase in Glx (P