Abstract
RationaleIt 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.ObjectivesThis 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 methodsUsing 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.ResultsGreen 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.ConclusionsOur 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.
Highlights
Recent research indicates that green tea extract or its main ingredients has a beneficial impact on cognitive functioning in humans
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
Differences in local brain activity between the different treatment conditions have previously been reported (Borgwardt et al 2012); here, we extended this study by conducting an effective connectivity analysis using dynamic causal modeling (DCM) (Friston et al 2003), which was restricted to the bilateral superior parietal lobule (SPL) and middle frontal gyrus (MFG)
Summary
Recent research indicates that green tea extract or its main ingredients has a beneficial impact on cognitive functioning in humans. A study used functional magnetic resonance imaging (fMRI) to investigate whether this beneficial impact of green tea on cognition could be related to altered brain activity in regions crucially engaged during higher-order cognitive functioning (Borgwardt et al 2012). They demonstrated relatively increased brain activation in fronto-parietal regions, most pronounced in the right frontal cortex after the administration of green tea extract during working memory (WM) processing as assessed by the N-back task (Borgwardt et al 2012). It is conceivable that the increased frontal activity during WM processing after green tea administration (Borgwardt et al 2012) may have resulted from a change in functional coupling connectivity from the parietal to the frontal cortex
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