Cognitive interference is associated with neuronal marker N-acetyl aspartate in the anterior cingulate cortex: an in vivo H-1-MRS study of the StroopColor-Word task

The neurobiology of cognitive interference is unknown. Previous brain imagi ng studies using the Stroop Color-Word (SCW) task indicate involvement of t he cingulate cortex cognitive division. The present study examines interrel ationships between regional brain N-Acetyl aspartate (NAA) levels (as ident ified by in vivo proton magnetic resonance spectroscopy in the right and le ft anterior cingulate cortex (ACC), dorsolateral prefrontal cortex, orbitof rontal cortex and thalamus) and cognitive interference (as measured by the SCW task) in 15 normal subjects. The results show that brain chemistry depe nds on cognitive interference levels (high vs low). Reduction of NAA levels was demonstrated in the right ACC (ie, cognitive midsupracallosal division ) of high interference subjects, as compared to the low interference group (P < 0.01, two-tailed t-test). Chemical-cognitive relationships were analyz ed by calculating correlations between regional NAA levels and the SCW task scores. Cognitive interference was highly correlated with the right anteri or cingulate NAA (r = 0.76, P < 0.001), and was unrelated to other studied regional NAA, including the left ACC (P < 0.025; comparing the difference b etween r values in the right and left ACC). The interrelationships between NAA across brain regions were examined using correlation analysis (square m atrix correlation maps), which detected different connectivity patterns bet ween the two groups. These findings provide evidence of ACC involvement in cognitive interference suggesting a possibility of neuronal reorganization in the physiological mechanism of interference (most likely due to genetica lly predetermined control of the number of neurons, dendrites and receptors , and their function). We conclude that spectroscopic brain mapping of NAA, the marker of neuronal density and function, to the SCW task measures diff erentiates between high and low interference in normal subjects. This neuro imaging/cognitive tool may be useful for documentation of interference in s tudying cognitive control mechanisms, and in diagnosis of neuropsychiatric disorders where dysfunction of cingulate cortex is expected.