Diurnal stability of gamma-aminobutyric acid concentration in visual and sensorimotor cortex.
OBJECTIVE
To establish the diurnal stability of edited magnetic resonance spectroscopy measurements of gamma-aminobutyric acid (GABA) in visual and sensorimotor regions of the brain.


METHODS
GABA measurements were made in two regions of the brain (an occipital, "visual" region and a "sensorimotor" region centered on the precentral gyrus) using the MEGA-PRESS editing method, scanning eight healthy adults at five timepoints during a single day. GABA concentration was quantified from the ratio of the GABA integral to the unsuppressed water signal.


RESULTS
No significant effect of time on GABA concentration was seen (P = 0.35). GABA was shown to be significantly more concentrated in visual regions than in sensorimotor regions (1.10 i.u. and 1.03 i.u., respectively; P = 0.050). Coefficients of variability (CVs) across all subjects of 9.1% and 12% (visual and sensorimotor) were significantly higher than mean within-subjects CVs of 6.5% and 8.8.


CONCLUSIONS
This study demonstrates the excellent reproducibility of MEGA-PRESS detection of GABA, demonstrating that the method is sufficiently sensitive to detect inter-subject variability, and suggests that (within the sensitivity limits of current measurements) time of day can be ignored in the design of MRS studies of visual and sensorimotor regions.
Evans
Christopher John
CJ
CUBRIC, School of Psychology, Cardiff University, Cardiff, Wales, UK.
McGonigle
David John
DJ
Edden
Richard Anthony Edward
RA
D002648:Child; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D009044:Motor Cortex / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013003:Somatosensory Cortex / Q000378:metabolism*; D014793:Visual Cortex / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
D005680:gamma-Aminobutyric Acid