Creatine (Cre) is a neuro-metabolite found in all human brain regions. Its concentration is considered evenly distributed among cortical areas and is believed to represent a "healthy neuronal state" uninfluenced by brief experimental manipulations. It therefore commonly serves as reference spectrum in magnetic resonance spectroscopy (MRS) studies.
Current report analyzed Cre concentrations in anterior/posterior and left/right insular subdivisions prior to and after electric right maxillary canine stimulation (baseline and relaxation periods). The null hypothesis postulated that no Cre concentration differences exist among analyzed brain regions within and between pre/post stimulation periods.
Method:
16 healthy males (mean age 33.1; 23-52) participated. Spectroscopy measurements were performed on a 3T Philips Achieva scanner in anterior and posterior insular subdivisions bilaterally with PRESS technique. By LC Model, data were exported and analyzed for the concentrations of metabolites choline, creatine (Cre), N-acetyl aspartate, glutamate, glutamine, glutamine/glutamate, myo-Inositol, alanine, lactate, aspartate and others (chemical shift range between 0.5 and 4.2 ppm). For this report, only Cre was analyzed using SPSS 20.0.0 by applying repeated measures ANOVA for baseline and relaxation phases (2 factors) as well as insular subdivisions (4 factors) as within-subjects factors.
Result:
Baseline measurements of Cre revealed a highly significant effect with higher concentrations in left and right posterior insular subdivisions (F = 8.724 / p < 0.001). This effect remained on a comparable level also during relaxation with F = 7.882 / p <0.001) so that no significant differences were found between baseline and relaxation periods.
Conclusion:
This MR spectroscopic analysis revealed unexpected stable differences of Cre concentrations among insular subdivisons during baseline and relaxation periods. Whether such topographic concentration differences are limited to the insular cortex or may be found in other brain regions requires clarification in future studies.