ANTERIOR CINGULATE CORTEX EXHIBITS AGE-RELATED METABOLIC CHANGES: CORRELATION WITH BEHAVIORAL PERFORMANCE IN ATTENTION TASK

Abstract

The anterior cingulate cortex(ACC) has become a focus for aging research because of its implicated role in cognition. Furthermore, a prior fMRI study in older adults had demonstrated an increase in blood oxygen level-dependent(BOLD) signal in the ACC compared to young adults during Stroop task, suggesting compensation. In this study, we investigated the metabolic changes during aging in the dorsal ACC of a local Chinese cohort using quantitative proton magnetic resonance spectroscopy(1H-MRS). In addition, relationship between metabolite concentrations and performance from an attention task (numerical Stroop) will be assessed. 36 cognitively normal (Mini-mental State Examination≥28; Montreal Cognitive Assessment≥26) subjects (mean=49.3±17.5years, age range 24–84years) underwent MR scan using 3.0T Philips scanner. A PRESS(TR/TE=2000/39 ms) single voxel of 2x2x2cm3 was placed in the dorsal ACC. Choline(Cho),creatine (Cr),N-acetyl aspartate(NAA), myo-inositol(mI), and summation of glutamate and glutamine complex(Glx), were measured and quantified using internal water as reference by QUEST in jMRUI 4.0(Figure 1). Cerebrospinal fluid(CSF) normalization, water content correction for grey matter, white matter and CSF, and correction factors for T1 and T2 relaxations were implemented. Also, the subjects took part in a numerical Stroop task (Figure 2) inside the scanner(fMRI data was currently undergoing analysis). Pearson correlation coefficient(r) was calculated to assess any correlation between 1) absolute metabolite concentrations ([met]abs) and age in the ACC, and 2) [met]abs and behavioral performance. SPSS version 20.0 was used for statistical analysis and level of significance was set at 0.05. Mean [met]abs and behavioral performance were shown in Tables 1 and 2, respectively. In the ACC, both [Cr]abs(r = 0.336; p = 0.045) and [NAA]abs(r = 0.354; p = 0.034) showed significant positive correlation with age. Only [Cho]abs showed significant positive correlation with both Stroop effect (incongruent-congruent)(r = 0.378; p = 0.023) and Stroop interference (incongruent-neutral)(r = 0.549, p = 0.001) after age-effect adjustment (Figure 3). Age-related increase in [Cr]abs might imply altered energy metabolism[1], while increase in [NAA]abs with age might indicate compensation activity[2]. For the positive correlation between [Cho]abs with Stroop effect, and Stroop interference, higher [Cho]abs could signify glial proliferation which might in turn lead to deficits on executive function[3]. [1]Charlton et al., 2007,[2]Milham et al., 2000,[3]Russell et al., 2006. (a) Position of voxel placed in the anterior cingulatecortex, (b) Simulated spectrum using QUEST in jMRUI, and (c) Simulated spectrum (blue) fitted on spectrum from subject (red). Trial conditions shown in numerical Stroop Task. Scatter plots of [Cho]abs with behavioral performance of (a) Stroop effect, and (b) Stroop Interference.