M65. Assessing Visual Plasticity Response in Adults With Schizophrenia and Healthy Controls Using fMRI and MRS

• Published in: Schizophrenia bulletin 2017-03, Vol.43 (suppl_1), p.S233-S234
• Main Authors: Wijtenburg, Andrea, West, Jef
• Format: Article
• Language: English
• Subjects: Abstracts
• ISSN: 0586-7614; 1745-1701
• DOI: 10.1093/schbul/sbx022.060

Background: Long-term potentiation (LTP) is a basic cellular mechanism underlying learning and memory and thought to be impaired in schizophrenia (SZ). LTP-like visual plasticity can be induced by high frequency visual stimulation in rodents and humans. Since glutamate plays a fundamental role in LTP, this study investigated differences in visual plasticity in SZ and healthy controls, and if visual cortical glutamate (Glu) and glutamine (Gln) levels predict the amount of visual plasticity. Methods: Seventeen adults with schizophrenia and 18 healthy controls were scanned on a Siemens TIM TRIO 3-T MRI system. Visual plasticity was assessed using a modified visual plasticity fMRI task with 2 runs of low frequency stimulation (via a flashing checkerboard during the “on” condition and a crosshair during the “off” condition), one run of high frequency stimulation (HFS), followed by 2 more runs of low frequency stimulation applied. The fMRI data were processed using SPM. MRS data was acquired using a very short TE phase rotation STEAM sequence, and LCModel was used to quantify Glu and Gln. Symptom ratings were performed only in the SZ group, and cognitive measures of memory and level of functioning were conducted in both groups. Visual plasticity was tested by a one sample t test contrasting post-HFS vs pre-HFS for the “on” minus “off” conditions. A mask of the spectroscopic voxel was applied to assess activations that occurred only within the spectroscopic voxel. A double subtraction analysis examining the effects of post-HFS “on” and “off” from pre-HFS “on” and “off” was performed, and a Bonferonni-corrected correlation analysis was conducted between activations and metabolites. Results: In healthy controls, the one-sample t test contrasting showed significant activation post vs pre-HFS in the visual cortex, suggesting a visual plasticity effect. Three regions in the dorsal V2 and V3 were significant ( k > 130, T > 4.16, uncorrected P < .001). There was a significant correlation between Gln and the dorsal V3 ( r  = .64, P  = .004) such that higher Gln levels were associated with higher activation. In the adults with SZ as a group, there was no significant activation within the spectroscopic voxel ( P > .05); however, the data were heterogeneous and some did show a plasticity effect. ROI analyses showed significant relationships between Glu and Gln in both groups. BPRS total score and SANS were negatively correlated with Glu levels in SZ, and there were no corre