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. 2014 Oct;231(19):3879-88.
doi: 10.1007/s00213-014-3526-1. Epub 2014 Mar 19.

Green Tea Extract Enhances Parieto-Frontal Connectivity During Working Memory Processing

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Free PMC article

Green Tea Extract Enhances Parieto-Frontal Connectivity During Working Memory Processing

André Schmidt et al. Psychopharmacology (Berl). .
Free PMC article

Abstract

Rationale: It has been proposed that green tea extract may have a beneficial impact on cognitive functioning, suggesting promising clinical implications. However, the neural mechanisms underlying this putative cognitive enhancing effect of green tea extract still remain unknown.

Objectives: This study investigates whether the intake of green tea extract modulates effective brain connectivity during working memory processing and whether connectivity parameters are related to task performance.

Material and methods: Using a double-blind, counterbalanced, within-subject design, 12 healthy volunteers received a milk whey-based soft drink containing 27.5 g of green tea extract or a milk whey-based soft drink without green tea as control substance while undergoing functional magnetic resonance imaging. Working memory effect on effective connectivity between frontal and parietal brain regions was evaluated using dynamic causal modeling.

Results: Green tea extract increased the working memory induced modulation of connectivity from the right superior parietal lobule to the middle frontal gyrus. Notably, the magnitude of green tea induced increase in parieto-frontal connectivity positively correlated with improvement in task performance.

Conclusions: Our findings provide first evidence for the putative beneficial effect of green tea on cognitive functioning, in particular, on working memory processing at the neural system level by suggesting changes in short-term plasticity of parieto-frontal brain connections. Modeling effective connectivity among frontal and parietal brain regions during working memory processing might help to assess the efficacy of green tea for the treatment of cognitive impairments in psychiatric disorders such as dementia.

Figures

Fig. 1
Fig. 1
a Local maxima with the bilateral superior parietal lobule and middle frontal gyri induced by the main effect of task (2-back >0-back contrast) after the administration of green extract or the of the control substance (FWE cluster level corrected at p < 0.05). b Model space tested in this study. 1 right SPL, 2 left SPL, 3 right MFG, and 4 left MFG. In particular, we contrasted models in which the 2-back WM condition was allowed to modulate, within both hemispheres: (F1) the parieto-frontal connections, (F2) the fronto-parietal connections, or (F3) both. These three intrahemispheric options were crossed with four possibilities which interhemispheric connections might be modulated by the 2-back WM condition, i.e., (a) none (first column of Fig. 1b), (b) the interhemispheric connections between parietal areas (second column of Fig. 1b), (c) the interhemispheric connections between frontal areas (third column of Fig. 1b), or (d) both (fourth column of Fig. 1b). As a result, our model space consisted of 12 alternative models, each of which was fitted to the data from each individual subject
Fig. 2
Fig. 2
Mean of sensitivity indexes (d′) ± SE during working memory processing for both treatment conditions. (Asterisk) indicates a between-treatment difference at p = 0.066
Fig. 3
Fig. 3
Bayesian model selection (BMS) results on family level (upper column) and single model level (lower column) over both treatment conditions separately. BMS results are reported in terms of exceedance probabilities
Fig. 4
Fig. 4
The modulatory effect of the 2-back WM condition on the connection from the right SPL to the right MFG in the sham condition and after the administration of green tea extract. The y axis denotes the average over all subjects and all 12 DCMs (using BMA) with regard to the posterior mean (1/s) of the modulatory effect; this encodes changes in connection strength induced by the 2-back WM condition. Significant between-treatment differences at (asterisk) p < 0.05. Error bars represent standard deviations derived from Bayesian parameter averages
Fig. 5
Fig. 5
Significant positive correlation between the effect of green tea on task performance and SPL→MFG connectivity (green tea minus control substance; r = 0.64, p < 0.05). That is, the stronger the increase in SPL→MFG connectivity induced by green tea, the higher the improvement in the task performance compared with the control drink

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