The gut-brain axis: Impact of a probiotic intervention on neurocognitive measures of emotion and cognitive control

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The human gut-microbiome plays a key role in human well-being. Specifically, differences have been found between the gut-microbiome compositions of healthy individuals compared with patient groups suffering from affective psychiatric disorders. Research has indicated that probiotics can have beneficial effects on the gut-microbiome and its functioning. More recent findings suggest also effects on the brain. Thereby it might be a potential new treatment for affective psychiatric disorders. In the present study we investigated the effects of a multispecies probiotic on neurocognitive measurements of emotion and cognitive control by means of three robust MRI tasks. Specifically, we were interested in whether the effects of a probiotic intervention can extend beyond effects on affective measures and brain regions, now also including cognitive control (of emotion). We applied a double blind, randomized, placebo-controlled, between-subjects design including paradigms covering general emotion processing, emotion regulation and cognitive control in absence of emotion. These three processes have been found to be of importance in affective psychiatric disorders. We hypothesized to find effects of the probiotic on affective brain regions mainly involved in emotion processing, indicated by previous research, and to extend to prefrontal regions crucial for emotion regulation and general cognitive control processes. We expected affective brain regions, particularly amygdala activity, to decrease after the probiotic intervention indicating probiotic effects on emotion processing and/or regulation. Prefrontal cortex activity was expected to be enhanced, thereby reflecting increased cognitive control. Analyses were carried out on a first, small subset of participants (N =11) who were divided into a placebo (N = 5) and a probiotic group (N = 6). In this study all participants were healthy women (mean age = 23.3 years). The study consisted of two measurement points separated by a four week probiotic vs. placebo intervention. In this preliminary study we did not find significant effects of the probiotic intervention on the brain. However, on exploratory thresholds, findings indicated an effect of the probiotic intervention on the amygdala during emotion regulation as well as on lateral frontal regions during general cognitive control processes, in line with our hypotheses. From these preliminary results we can conclude that probiotic effects tend to extend beyond modulating affective processes also tending to affect prefrontal cortex and associated cognitive control processes.
Faculteit der Sociale Wetenschappen