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12 Jun 2018
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Hippocampal GABA helps suppress unwanted thoughts

10 Nov 2017
Depression has become the leading cause of morbidity and disability in the world.

Inhibition of hippocampal retrieval processes through gamma-aminobutyric acid (GABA) enables the suppression of intrusive thoughts, a recent study shows.

Thirty right-handed participants (mean age 24.7±4.3 years; males n=7) were subjected to two behavioural tasks. The first was a stop signal (SS) task, where participants were made to press a specific button in response to a coloured circle stimulus flashed on-screen. If the stimulus came with a beeping sound, participants were asked to prevent their response.

The second was a Think/No-Think (TNT) task, where they were shown reminders of unwanted thoughts and instructed to suppress retrieval. Functional magnetic resonance imaging (fMRI) was performed during each task and 1H magnetic resonance spectroscopy (1H-MRS) was used to measure GABA.

The researchers found that No-Think trial elicited significantly reduced activity both in right (p=0.003) and left (p=0.001) hippocampus. Retrieval suppression also resulted in impaired memory of the items, with No-Think items being recalled significantly less in a postscan recall test than the Think items (59±3 vs 65±3 percent; p=0.04).

Moreover, hippocampal GABA showed a significantly negative correlation with hippocampal blood-oxygen level-dependent activity signals during Think and No-Think (p<0.05 for both) conditions but not during Go or Stop conditions.

Finally, those with higher hippocampal GABA also showed stronger negative coupling between the hippocampus and dorsolateral prefrontal cortex, while those with lower hippocampal GABA did not show this negative coupling during retrieval suppression. The difference in connectivity between the two groups reached statistical significance (p=0.03).

“The present findings raise the possibility that GABAergic disinhibition in the hippocampus contributes to reduced fronto-hippocampal connectivity, hippocampal hyperactivity and intrusive symptomatology,” researchers said.

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Most Read Articles
12 Jun 2018
Percutaneous coronary intervention (PCI) is a safe procedure to perform on obese and morbidly obese patients, a recent study has shown.
Roshini Claire Anthony, 11 Jun 2018

Patients who received a combination of ticagrelor plus aspirin within 24 hours of undergoing coronary artery bypass grafting (CABG) had significantly improved saphenous vein graft patency rates 1 year post-procedure compared with those who only received aspirin, according to findings of the DACAB* trial.

4 days ago
Higher activity of plasma xanthine oxidase appears to be linked to insulin resistance and liver dysfunction among type 2 diabetes mellitus (T2DM) patients with metabolic syndrome (MetS), according to a recent Japan study.
4 days ago
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