Visual-cortex GABA concentrations predict incidence of cognitive failures in daily life in healthy volunteers
Since the amount of information one receives in daily life by far exceeds the limited capacity of one’s processing resources, selecting relevant information and suppressing irrelevant information is a vital ability. The link between this cognitive ability, termed selective attention, and cognitive failures in daily life (e.g., failing to notice things, getting distracted) is well established. On the other hand, gamma-aminobutyric acid (GABA), the most common inhibitory neurotransmitter in the human brain, has been observed to contribute to visual cortex selectivity to stimuli, a function that is an integral part of selective attention. What has not been investigated before, however, is whether inter-individual variability in the amount of visual-cortical GABA is linked with the frequency of cognitive failures in daily life.
In their recent study, Sandberg et al. (2013) had 36 healthy participants fill out a cognitive failures questionnaire, where participants were asked to self-rate frequency with which they experience common cognitive failures in perception, memory, and motor function. They then underwent 3T whole-head structural magnetic resonance imaging and focal magnetic resonance spectroscopy measurement of GABA concentration was obtained with two voxels placed in 1) calcarine sulcus in occipital cortex and 2) in the anterior part of the superior parietal lobule. It was observed that GABA concentrations in the visual cortex correlated with the incidence of self-reported cognitive failures. In contrast, the authors failed to see any correlation between GABA concentrations in the parietal voxel and cognitive failures. The authors however observed that gray matter volume in left superior parietal lobule and occipital GABA concentration independently predicted cognitive failures.
These exciting results first of all demonstrate nicely that it is possible to predict inter-individual variability in cognitive failures that take place in daily life with inter-individual differences in local brain neurochemical properties. The results further add an important piece of evidence pointing to the role of GABA in cognitive processing by suggesting that visual-cortical GABA concentrations impact selective attention under ecologically valid conditions as estimated by the questionnaire items. Third, these results suggest that the role of GABA in modulating selective attention is specific to the sensory cortical areas, whereas gray matter volume in parietal cortex additionally contributes to frequency of cognitive failures in daily life.
Reference: Sandberg K, Blicher JU, Dong MY, Rees G, Near J, Kanai R. Occipital GABA correlates with cognitive failures in daily life. Neuroimage (2013) e-publication ahead of print. http://dx.doi.org/10.1016/j.neuroimage.2013.10.059