Regional difference in GABA levels between medial prefrontal and occipital cortices.

Purpose: To avoid the confounding effects of variations in tissue composition this study measured regional GABA differences using two voxels with the same tissue composition.

Materials And Methods: Eighteen healthy adult volunteers were scanned using a 3 Tesla GE clinical scanner with a J-coupling based editing sequence. Spectroscopy voxels were placed in the medial prefrontal (MPFC) and occipital cortex (OCC) with essentially the same gray and white matter fractions.

Results: A 16% (P = 0.0001) significantly higher GABA to creatine ratio was found in the OCC (0.1103 ± 0.0050) compared with the MPFC (0.0953 ± 0.0041). When normalized to tissue water, GABA concentrations in the OCC were 14% higher than in the MPFC.

Conclusion: A difference in GABA concentration was found between the OCC and MPFC voxels in healthy subjects which is attributable to differences other than tissue composition.