Segregation of gustatory cortex in response to salt and umami taste studied through event-related potentials Preet Bano Singh a,b , Emilia Iannilli a and Thomas Hummel a In this study, we report gustatory event-related potentials in response to stimulation with monosodium glutamate (MSG) and salt (NaCl). We investigated differences in event-related potential related to stimulus quality, stimulus concentration, cortical topography, and participants’ sex. Our results showed that amplitudes P1N1 and N1P2 were significantly larger in response to stimulation with NaCl compared with stimulation with MSG and the topographical distribution of amplitudes varied significantly for the two stimuli. In addition, responses were significantly larger in the right hemisphere compared with the left hemisphere for both stimuli, suggesting right hemispheric dominance for gustatory processing. In conclusion, this study shows significant differences in cerebral processing of MSG and NaCl in the human brain. NeuroReport 22:299–303  c 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins. NeuroReport 2011, 22:299–303 Keywords: chemosensory, electrophysiology, evoked potentials, salt, taste, umami a Smell and Taste Clinic, Department of Otorhinolaryngology, University of Dresden Medical School, Dresden, Germany and b Department of Oral Biology, Faculty of Dentistry, Oslo, Norway Correspondence to Dr Preet Bano Singh, DDS, Department of Oral Biology, Faculty of Dentistry, Sognsvannsveien 10, Oslo 0372, Norway Tel: + 47 22840341; fax: + 47 22840302; e-mail: p.b.singh@odont.uio.no Received 15 February 2011 accepted 20 February 2011 Introduction Taste perception plays an important role in maintaining nutritional balance in mammals. By providing important information regarding the nutritional value and toxicity of food, sense of taste indicates whether the foodstuff should be ingested or rejected [1,2]. Noninvasive brain imaging techniques like functional magnetic resonance imaging (fMRI), positron emission tomography, magne- toencephalography (MEG), and electroencephalography (EEG) allow us to measure the gustatory cerebral activity in humans. Thus, anterior insula, frontal operculum, and parietal cortex have been identified as primary and secondary taste areas using positron emission tomography [3], fMRI [4], and MEG [5]. These areas have been shown to be activated also by umami taste [6]. An fMRI study showing representation of salty and sweet taste in the human brain suggests that both sweet and salty tastes are represented in the middle insula and activation in amygdala is modulated only by saltiness [7]. Further, segregation of neural representation in human brain was found with respect to the intensity and affective value of sweet and bitter taste [8]. Umami has been known as a specific taste for more than 100 years. Nevertheless, relatively little is known about the central nervous processing of this taste as compared with other tastes, like that of salt. Umami and salt taste are mediated through different types of taste receptors. The umami taste is mediated through G-protein-coupled receptors, whereas salt taste is mediated through channel-type receptors. Moreover, psychophysical studies show that salt and umami taste are perceived very differently; umami represents a characteristic taste often described as intense, lingers on the tongue, and there is a delay of approximately 2 s before participants perceive the taste compared with salt. Hence, the aim of this study was to record gustatory event-related potential (ERP) for umami and salt taste in order to investigate the manner in which human gustatory cortex encodes the two stimuli. Materials and methods Participants The study was conducted according to the Declaration of Helsinki. Its design was approved by the Ethics Commit- tee of the University of Dresden Medical School, Dresden, Germany. Informed written consent was obtain- ed from the participants before the study. A total of 17 healthy, right-handed individuals participated in the study (seven women, 10 men, age range, 21–46 years, mean age 30 years). Health status and olfactory and gustatory functions were ascertained with a detailed med- ical history, the Sniffin Sticks Screening Odor Identifica- tion test [9] and regional gustatory testing using taste strips [10]. Stimuli The liquid stimuli monosodium glutamate (MSG) and sodium chloride (NaCl) were applied in two different concentrations (weak and strong: 200 and 400 mM, respectively). The participants were made familiar with the two tastants before the experiment and they went through a psychophysical test [11] to establish that they could discriminate these concentrations. In addition, the participants were thoroughly acquainted with the experi- mental setup: the delivery of the tastants through the gustometer, ERP recordings with electrodes, intensity rating, and tracking task. Behavioral, integrative and clinical neuroscience 299 0959-4965  c 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/WNR.0b013e32834601e8