Brain activations by umami and salty taste in humans

Abstract

OBJECTIVES: This study sought to investigate which part of human brain activates by a combined umami and salty taste stimuli on the tongue under standardized taste delivery conditions. METHODS: The study was carried out in 26 healthy volunteers: 12 females and 14 males (19 - 27 yrs). Taste solution contained an umami (10.68 mM monosodium L-glutamate, MSG) and salty (171.0 mM sodium chloride, NaCl) mixture at the set concentrations assumed to be present in noodle soup. Functional magnetic resonance image was performed and brain functional data was acquired while each participant was tasting solution. Each participant was delivered the MSG + NaCl solution for 6 s and distilled water for 15 s alternately on the tongue using original intraoral device and taste delivery system. Image pre-processing and data analysis were performed using the Statistical Parametric Mapping 8 (SPM8) software package (Wellcome Trust Centre for Neuroimaging, London, UK) implemented in MATLAB R2012a (The MathWorks Inc., Natick, MA, USA). We examined the effect of solution by one-sample t-test. We investigated the statistical parametric maps generated by solution at an initial threshold of uncorrected P < 0.005 and cluster size of > 10 voxels. Clusters that had a cluster P < 0.05 corrected for family-wise error (FWE) were defined as significant. RESULTS: Functional MRI showed that brain regions activated by taste solution in the insula, orbitofrontal cortex, and inferior frontal gyrus (z value = 3.9, 3.8, and 3.7, respectively; cluster PFWE < 0.003). CONCLUSIONS: The result demonstrated brain activatios both in the primary (taste identification and intensity) and seondary (reward and emotion) taste cortices while humans were tasting an umami and salty mixture. THIS ABSTRACT IS BASED ON RESEARCH THAT WAS FUNDED ENTIRELY OR PARTIALLY BY AN OUTSIDE SOURCE: General Research Fund grant from the Research Grants Council of Hong Kong [Code: HKU 766212M] and from Society for Research on Umami Taste, Japan.