The Effect of Visual Stimulation on GABA and Macromolecules Levels in Human Brain in vivo
GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the brain and plays an important role in various types of synaptic plasticity and pathology. In present work, MEGA-PRESS pulse sequence is used for GABA measurement in the region of activated visual cortex. The results demonstrate that the GABA signal intensity was decreased significantly in the visual cortex during stimulation when measured with macromolecular suppression (-GABA), but in case of measurement without suppression (+GABA), the effect is not observed; this may demonstrate the effect-masking properties of macromolecular signal. The hypothesis of the macromolecular signal change in response to visual stimulation was tested. For this reason, inversion-recovery sequence for metabolite nulling and macromolecular signal acquisition was developed; macromolecular signal intensity remained constant during stimulation. Hence, there are two possible reasons for GABA decrease: inactivation of GABA synthesis or the increase in its consumption as a substrate in tricarboxylic acid cycle.