Synaesthesia is an unusual perceptual phenomenon in which events in one sensory modality induce vivid sensations in another. Individuals may 'taste' shapes, 'hear' colours, or 'feel' sounds. Synaesthesia was first described over a century ago, but little is known about its underlying causes or its effects on cognition. Most reports have been anecdotal or have focused on isolated unusual cases. Here we report an investigation of 15 individuals with colour-graphemic synaesthesia, each of whom experiences idiosyncratic but highly consistent colours for letters and digits. Using a colour-form interference paradigm, we show that induced synaesthetic experiences cannot be consciously suppressed even when detrimental to task performance. In contrast, if letters and digits are presented briefly and masked, so that they are processed but unavailable for overt report, the synaesthesia is eliminated. These results show that synaesthetic experiences can be prevented despite substantial processing of the sensory stimuli that otherwise trigger them. We conclude that automatic binding of colour and alphanumeric form in synaesthesia arises after initial processes of letter and digit recognition are complete.

Summary Background A low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet is effective in treating irritable bowel syndrome (IBS). Aim To compare the effects of gut‐directed hypnotherapy to the low FODMAP diet on gastrointestinal symptoms and psychological indices, and assess additive effects. Methods Irritable bowel syndrome patients were randomised (computer‐generated list), to receive hypnotherapy, diet or a combination. Primary end‐point: change in overall gastrointestinal symptoms across the three groups from baseline to week 6. Secondary end‐points: changes in psychological indices, and the durability of effects over 6 months. Results Of 74 participants, 25 received hypnotherapy, 24 diet and 25 combination. There were no demographic differences at baseline across groups. Improvements in overall symptoms were observed from baseline to week 6 for hypnotherapy [mean difference (95% CI): −33 (−41 to −25)], diet [−30 (−42 to −19)] and combination [−36 (−45 to −27)] with no difference across groups (P = 0.67). This represented ≥20 mm improvement on visual analogue scale in 72%, 71% and 72%, respectively. This improvement relative to baseline symptoms was maintained 6 months post‐treatment in 74%, 82% and 54%. Individual gastrointestinal symptoms similarly improved. Hypnotherapy resulted in superior improvements on psychological indices with mean change from baseline to 6 months in State Trait Personality Inventory trait anxiety of −4(95% CI −6 to −2) P < 0.0001; −1(−3 to 0.3) P = ns; and 0.3(−2 to 2) P = ns, and in trait depression of −3(−5 to −0.7) P = 0.011; −0.8(−2 to 0.2) P = ns; and 0.6(−2 to 3) P = ns, respectively. Groups improved similarly for QOL (all p ≤ 0.001). Conclusions Durable effects of gut‐directed hypnotherapy are similar to those of the low FODMAP diet for relief of gastrointestinal symptoms. Hypnotherapy has superior efficacy to the diet on psychological indices. No additive effects were observed.

BackgroundCows’ milk generally contains two types of β-casein, A1 and A2 types. Digestion of A1 type can yield the peptide β-casomorphin-7, which is implicated in adverse gastrointestinal effects of milk consumption, some of which resemble those in lactose intolerance. This study aimed to compare the effects of milk containing A1 β-casein with those of milk containing only A2 β-casein on inflammation, symptoms of post-dairy digestive discomfort (PD3), and cognitive processing in subjects with self-reported lactose intolerance.MethodsForty-five Han Chinese subjects participated in this double-blind, randomized, 2 × 2 crossover trial and consumed milk containing both β-casein types or milk containing only A2 β-casein. Each treatment period was 14 days with a 14-day washout period at baseline and between treatment periods. Outcomes included PD3, gastrointestinal function (measured by smart pill), Subtle Cognitive Impairment Test (SCIT), serum/fecal laboratory biomarkers, and adverse events.ResultsCompared with milk containing only A2 β-casein, the consumption of milk containing both β-casein types was associated with significantly greater PD3 symptoms; higher concentrations of inflammation-related biomarkers and β-casomorphin-7; longer gastrointestinal transit times and lower levels of short-chain fatty acids; and increased response time and error rate on the SCIT. Consumption of milk containing both β-casein types was associated with worsening of PD3 symptoms relative to baseline in lactose tolerant and lactose intolerant subjects. Consumption of milk containing only A2 β-casein did not aggravate PD3 symptoms relative to baseline (i.e., after washout of dairy products) in lactose tolerant and intolerant subjects.ConclusionsConsumption of milk containing A1 β-casein was associated with increased gastrointestinal inflammation, worsening of PD3 symptoms, delayed transit, and decreased cognitive processing speed and accuracy. Because elimination of A1 β-casein attenuated these effects, some symptoms of lactose intolerance may stem from inflammation it triggers, and can be avoided by consuming milk containing only the A2 type of beta casein.Trial registration ClinicalTrials.gov/NCT02406469 Electronic supplementary materialThe online version of this article (doi:10.1186/s12937-016-0147-z) contains supplementary material, which is available to authorized users.