Table 1.
MRS studies measuring GABA in aged individuals and/or patients with AD.
| Author first (Year) | Groups | Average Age (Range or ±SD) Sex (%) |
Brain areas | Cognitive Testing | Principal findings |
|---|---|---|---|---|---|
| Bai et al. (2014) [179] | 15 Controls 15 AD patients |
Controls: 66.3 (±4.6); ♀, 57.3% AD: 65.7 (±8.5); ♀, 60.0% |
mPLmFL | Global cognition: MMSE | AD patients presented lower GABA+ levels in the mPL No correlation between MMSE and GABA+ signal in the mPL or in the mFL |
| Hermansetal. (2018) [174] | 30 Young participants 29 Healthy older adults |
Young group: 23.2 (±4.3); ♀, 53.3% Elderly group: 67.5 (±3.9); ♀, 55.2% |
LSM PreSMA RIFC StriatumOL | Proactive and reactive inhibition: Stop signal task | GABA+ levels were on average lower in older adults Older adults with lower GABA in the preSMA were slower at stopping (worse inhibition function) |
| Huang et al. (2017) [176] | 17 Young adults 15 Healthy older adults 21 MCI 17 AD |
Young group: 24.4 (±2.6); ♀, 58.8% Elderly group: 61.9 (±6.3); ♀, 60.0% MCI: 64.6 (±7.7); ♀, 61.9% AD: 65.4 (±8.4); ♀, 52.9% |
ACCrH | N/A | Decreased GABA levels at the rH location for healthy older adults compared to younger adults No difference in GABA levels between healthy older adults and patients with MCI or AD |
| Jiménez-Balado et al. (2021) [277] [Under Review] | 20 Healthy older adults | 61 (±6.7); ♀,55.0% | rH | Episodic Memory: Directed Forgetting | Females with lower GABA levels presented a lower performance in episodic memory |
| Marenco et al. (2018) [178] | 229 Healthy volunteers | 30 (18-54); ♀, 55.5% | dACC |
Verbal memory Working memory: N-back task Visual memory Processing speed Executive function: Wisconsin Card Sorting Test (WCST) Digit span |
GABA+ was inversely correlated with age GABA levels mediated the relationship between age and WCST decline |
| Oeltzschner et al. (2019) [177] | 13 Controls 13 MCI |
Controls: 63.6 (±7.8); ♀, 53.8% MCI: 69.6 (±7.7); ♀, 23.1% |
ACCPCC |
Global cognition: MMSE Executive function: Fluency letter Memory: California verbal learning test; Brief visuoespatial memory test |
MCI subjects presented lower GABA levels in the ACC and PCC No association between GABA levels and cognitive performance in neuropsychological tests |
| Porges et al. (2017) [180] | 94 Healthy older adults | 73.1 (±9.9); ♀, 57.4% | mFLmPL | Global cognition: MOCA | GABA was inversely correlated with age at both mFC and mPC locations. Reduced frontal, but not posterior, GABA concentration was associated with lower MoCA scores |
| Riese et al. (2014) [181] | 21 Controls 15 Amnesic MCI |
Controls: 70.5 (±4.0); ♀, 33.3% MCI: 74.2 (±9.6); ♀, 26.6% |
PCC | CERAD-Plus test battery: MMSE; letter fluency; verbal learning, recall and recognition; figure copy and recall; Boston naming test; TMT A and B; category, and letter fluency; RAVLT; Visual Paired Associates test from the WMS-R; short version of the Stroop | GABA was not correlated with age GABA positively correlated with CERAD word learning score Amnesic MCI patients presented lower GABA levels in the PCC |
| Simmonite et al. (2019) [175] | 17 Young participants 18 Healthy older adults |
Young group: 20.7 (±1.4); ♀, 52.6% Elderly group: 76.5 (±8.7); ♀, 60.0% |
OL |
Perceptual processing: Contour detection; Digit-Symbol coding; Pattern comparison; Cambridge face perception test upright; Cambridge face perception test inverted; Dot speed and Dot coherence. Executive function:COWAT; TMT A and B. Memory: Cambridge Face memory test |
Older participants presented lower GABA+ levels in the OL Positive correlation between GABA performance in COWAT, trail making test B, Cambridge face perception test upright and dot coherence |
| Thielen et al. (2019) [272] | 14 Controls 17 Diabetic participants |
Controls:55.0(±8); ♀, 7.1% Diabetics: 55.1 (±6); ♀, 17.6% |
mPFCPrecuneus | Episodic memory: face profession encoding task (inside scanner) | Higher mPFC GABA levels in diabetic participants Negative correlation between GABA in mPFC and memory |
| Van Bussel et al. (2016) [273] | 21 Control high cognition 20 Diabetic high cognition 18 Controllow cognition Diabetic-low cognition |
High cognitive function: 62.7(±6.6); ♀, 43.9% Low cognitive function:61.1(±9.7); ♀, 43.6% |
OL |
Verbal memory: Verbal word learning Executive function: Stroop test Verbal fluency |
Higher GABA levels in diabetic participants Positive correlation between GABA and HbA1c Higher GABA in participants with increased HbA1c and lower cognition |
Notes: ACC, anterior cingulate cortex; AD, Alzheimer’s disease; COWAT, Controlled oral word association test; dACC, dorsal anterior cingulated cortex; HbA1c, Hemoglobin A1C; LSM, left sensorimotor cortex; MCI, mild cognitive impairment; mFL, medial frontal lobe; MMSE, Mini-Mental State Examination; MOCA, Montreal Cognitive Assessment; mPFC, medial prefrontal cortex; mPL, medial parietal lobe; OL, occipital lobe; PL, parietal lobe; PCC, posterior cingulate cortex; preSMA, bilateral pre supplementary area; rH, right hippocampus; RAVLT, Rey Auditory Verbal Learning Test; RIFC, right inferior frontal cortex; TMT, Trail Making Test; WCST, Wisconsin Card Sorting Test; WMS-R, Wechsler Memory Scale revised version.