Brain activation and affective judgements in response to personal dietary images: An fMRI preliminary study.

Emerging evidence from functional magnetic resonance imaging (fMRI) brain activation studies associated with dietary behavior reveals significant interaction of biological and behavioral mechanisms in response to visualized food stimuli. Because food intake is influenced by neurosensory stimulation and memory cues, personalized food images may be useful in prompting appropriate affective responses to food intake, which may subsequently lead to healthier eating behaviors. The current study used a cross-sectional mixed methods approach to explore neural responses and self-perceptions of eating behavior during review of personalized food images. A sample of college students (N = 16; 9 females; M age = 21.44) used cell-phone cameras and an online dietary tracking website to collect and report three days of diet. Within 2-3 weeks of completing dietary tracking activity, participants underwent an fMRI scan while reviewing recorded personal images and text descriptions of their diet. They also responded to three questions related to memory for the food items and future eating intentions. Post-scan interviews explored how participants felt after reviewing personal food images and the possible impact that such review might have on future food choices. Whole brain analyses suggested, compared to a written dietary record, that the visualization of personal images of diet evoked greater brain activation in memory regions (e.g., superior frontal gyrus) along with mediating emotion (e.g., thalamus, putamen, anterior cingulate cortex), imagery and executive functions (e.g., inferior orbitofrontal gyrus, fusiform, and parietal lobe). This study offers preliminary support for the use of personal food images to strengthen dietary monitoring.

l-Theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: a human functional magnetic resonance imaging study.

Oral intake of l-theanine and caffeine supplements is known to be associated with faster stimulus discrimination, possibly via improving attention to stimuli. We hypothesized that l-theanine and caffeine may be bringing about this beneficial effect by increasing attention-related neural resource allocation to target stimuli and decreasing deviation of neural resources to distractors. We used functional magnetic resonance imaging (fMRI) to test this hypothesis. Solutions of 200mg of l-theanine, 160mg of caffeine, their combination, or the vehicle (distilled water; placebo) were administered in a randomized 4-way crossover design to 9 healthy adult men. Sixty minutes after administration, a 20-minute fMRI scan was performed while the subjects performed a visual color stimulus discrimination task. l-Theanine and l-theanine-caffeine combination resulted in faster responses to targets compared with placebo (∆=27.8milliseconds, P=.018 and ∆=26.7milliseconds, P=.037, respectively). l-Theanine was associated with decreased fMRI responses to distractor stimuli in brain regions that regulate visual attention, suggesting that l-theanine may be decreasing neural resource allocation to process distractors, thus allowing to attend to targets more efficiently. l-Theanine-caffeine combination was associated with decreased fMRI responses to target stimuli as compared with distractors in several brain regions that typically show increased activation during mind wandering. Factorial analysis suggested that l-theanine and caffeine seem to have a synergistic action in decreasing mind wandering. Therefore, our hypothesis is that l-theanine and caffeine may be decreasing deviation of attention to distractors (including mind wandering); thus, enhancing attention to target stimuli was confirmed.

Acute effects of theanine, caffeine and theanine-caffeine combination on attention.

OBJECTIVE: l-theanine is a constituent of tea which is claimed to enhance cognitive functions. We aimed to determine whether theanine and theanine-caffeine combination have acute positive effects on cognitive and neurophysiological measures of attention, compared to caffeine (a positive control) and a placebo in healthy individuals. DESIGN: In a placebo-controlled, five-way crossover trial in 20 healthy male volunteers, we compared the effects of l-theanine (200 mg), caffeine (160 mg), their combination, black tea (one cup) and a placebo (distilled water) on cognitive (simple [SVRT] and recognition visual reaction time [RVRT]) and neurophysiological (event-related potentials [ERPs]) measures of attention. We also recorded visual (VEPs) and motor evoked potentials (MEPs) to examine any effects of treatments on peripheral visual and motor conduction, respectively. RESULTS: Mean RVRT was significantly improved by theanine (P = 0.019), caffeine (P = 0.043), and theanine-caffeine combination (P = 0.001), but not by tea (P = 0.429) or placebo (P = 0.822). VEP or MEP latencies or SVRT did not show significant inter-treatment differences. Theanine (P = 0.001) and caffeine (P = 0.001) elicited significantly larger mean peak-to-peak N2-P300 ERP amplitudes than the placebo, whereas theanine-caffeine combination elicited a significantly larger mean N2-P300 amplitude than placebo (P < 0.001), theanine (P = 0.029) or caffeine (P = 0.005). No significant theanine × caffeine interaction was observed for RVRT or N2-P300 amplitude. DISCUSSION: A dose of theanine equivalent of eight cups of back tea improves cognitive and neurophysiological measures of selective attention, to a degree that is comparable with that of caffeine. Theanine and caffeine seem to have additive effects on attention in high doses.