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We examined whether food identity information presented as name labels would influence perception of basic tastes. To test this hypothesis, we used 10 aqueous taste solutions consisting of 2-3 of the 5 basic tastes in different ratios and presented them with one of these food names: "lemon," "coffee jelly," "caramel candy," and "consomme soup." Forty-six participants tasted samples presented with either food-name labels or random number labels. We found that participants who tasted samples with food-name labels rated tastes with significantly higher liking and familiarity scores than those presented with random numbers, especially when the names and tastes were perceived as being congruent. Though an effect on perceived intensity was not as prominent, we observed cases in which intensity ratings significantly changed. Effects of identity information have been shown in olfaction and flavors. This study demonstrates the first experimental evidence that identity information given as names also influence the perception of unimodal basic tastes.

The act of tasting is the product of inseparable integrative behavior consisting of multi-sensory processing and orolingual motor coordination. Often tasting-induced brain activity is looked at in a reductionist manner as a set of isolated components. However, brain activity as a whole during tasting may not simply be the sum of isolated brain responses; therefore, attempting to look at the cortical activation in a more holistic manner is important. Using functional near-infrared spectroscopy (fNIRS), we assessed cortical responses during tasting, contrasting observed neuronal activation of the lateral prefrontal cortex (LPFC), of 19 healthy participants before and during tasting of 8ml of sweet-based solutions. To examine the activated brain structure, we estimated the anatomical regions of the measured location in standard brain space. We also included simple tongue tapping movement (TT) and word fluency (WF) tasks as comparative functional markers. Significant activity was found in channels (CHs) estimated to be in the bilateral oral motor areas during the TT task, and those in the LPFC, primarily in the left hemisphere, during the WF task. During the tasting task, significant activation was observed in CHs estimated to lie in the ventral part of pre- and post-central gyri as well as in the ventro-LPFC (VLPFC). The activated regions partly overlapped with those detected during TT or WF tasks, but extended more anteriorly and ventrally. Our study suggests that, in addition to tongue motor areas, the VLPFC is involved in the act of tasting.

Humans use various higher cognitive processes for taste, including memorization, recollection, and imagination, in our dietary lives, as well as in more specialized situations, such as sensory evaluation used in the food industry. So far, the cognitive aspects of taste processing have been studied mainly with psychological approaches, and their neural bases are not yet well understood. Conventional neuroimaging techniques are being used to converge psychological findings with human brain functions. However, these techniques require subjects to be in a supine position and strictly restrict head movements, narrowing the range of experimental paradigms that can be performed. This is especially true for taste studies; it is difficult to taste samples and perform cognitive tasks on them under conventional neuroimaging conditions. Therefore, we have attempted to use functional near infrared spectroscopy (fNIRS), an emerging noninvasive neuroimaging technique, to study human cortical taste cognitive processing. fNIRS, utilizing light to measure cortical hemoglobin concentration changes associated with neural activities, is more tolerant of subject body movement, thus allowing a wider range of experimental tasks for taste. However, it has some shortcomings that needed to be addressed. In this review, we will show how these technical obstacles have been overcome, how fNIRS contributes to the mapping of taste-related brain functions, and further promote the understanding of human taste processing. We propose fNIRS as a potential mediator between psychology and neuroscience.

Sensory evaluation (SE) of food attributes involves various levels of cognitive functions, yet not much has been studied about its neural basis. Using multi-channel functional near-infrared spectroscopy (fNIRS), we examined the activation of the anterior portion of the lateral prefrontal cortex (LPFC) of 12 healthy volunteers during the SE of tea samples. The experimental task used corresponded to the early phase of the same-different test, and required subjects to attentively taste tea samples and memorize their flavors. To isolate activation associated with the cognitive functions involved in the task, we contrasted the results with those achieved by a control (Ctl) task during which subjects held familiar tea samples in their mouths without actively evaluating their flavor. We probabilistically registered the fNIRS data to the Montreal Neurological Institute standard brain space to examine the results as they correspond with other published neuroimaging studies. We found significant activation in the left LPFC and in the right inferior frontal gyrus. The activation pattern was consistent with earlier studies on encoding of other sensory stimuli, with cortical regions supposed to be involved in semantic and perceptual processing. This research makes a start on characterizing the cognitive process employed during SE from the neuroimaging perspective.

To elucidate the function of the lateral prefrontal cortex (LPFC) in taste encoding, it is worth applying to taste, the psychological paradigms of intentional memorization that have been used with other extensively studied senses, and thus updating current models for LPFC functions to include a taste modality. Using multichannel functional near-infrared spectroscopy (fNIRS), we examined the LPFC's of healthy volunteers (N = 18) during the intentional memorization of a basic taste. In order to minimize the confounding effects of verbal processes that are known to employ the left LPFC, we used quaternary taste mixtures that were difficult to verbalize, and confined analysis to those who did not use a verbal strategy during memorization (N = 10). In order to examine the results in association with data in the literature, the location of activity was probabilistically estimated and anatomically labeled in the Montreal Neurological Institute (MNI) standard brain space. By contrasting the cortical activation under encoding conditions with that under control conditions without memory requirement, we found activation in the bilateral ventro-LPFC and the right posterior portion of the LPFC. The activation pattern was consistent with previous studies on the encoding of nonverbal materials using other senses. This suggests that models for LPFC functions that derive from previous studies can be generalized to intentional encoding processes of taste information, at least at a macro-structural level. The current study also demonstrates that, by using fNIRS, LPFC functions on taste can be examined with experimental paradigms relevant to those used for other senses.

Recent anecdotal and scientific reports have provided evidence of a link between COVID-19 and chemosensory impairments, such as anosmia. However, these reports have downplayed or failed to distinguish potential effects on taste, ignored chemesthesis, and generally lacked quantitative measurements. Here, we report the development, implementation, and initial results of a multilingual, international questionnaire to assess self-reported quantity and quality of perception in 3 distinct chemosensory modalities (smell, taste, and chemesthesis) before and during COVID-19. In the first 11 days after questionnaire launch, 4039 participants (2913 women, 1118 men, and 8 others, aged 19-79) reported a COVID-19 diagnosis either via laboratory tests or clinical assessment. Importantly, smell, taste, and chemesthetic function were each significantly reduced compared to their status before the disease. Difference scores (maximum possible change ±100) revealed a mean reduction of smell (-79.7 ± 28.7, mean ± standard deviation), taste (-69.0 ± 32.6), and chemesthetic (-37.3 ± 36.2) function during COVID-19. Qualitative changes in olfactory ability (parosmia and phantosmia) were relatively rare and correlated with smell loss. Importantly, perceived nasal obstruction did not account for smell loss. Furthermore, chemosensory impairments were similar between participants in the laboratory test and clinical assessment groups. These results show that COVID-19-associated chemosensory impairment is not limited to smell but also affects taste and chemesthesis. The multimodal impact of COVID-19 and the lack of perceived nasal obstruction suggest that severe acute respiratory syndrome coronavirus strain 2 (SARS-CoV-2) infection may disrupt sensory-neural mechanisms.

Abstract: The neural basis of memory subprocesses, encoding and retrieval, have been extensively examined in functional neuroimaging studies. However, the cortical substrates of taste memory, which form an important part of our episodic memory, have rarely been explored in humans. Previously, we have used functional near-infrared spectroscopy (fNIRS) and found activation of the lateral prefrontal cortex (LPFC) related to taste encoding. The method used in the current study allowed brain monitoring while participants tasted liquid taste-stimuli in upright positions. Here, using the same system, we examined the LPFC activity of 28 healthy volunteers during both the encoding and the retrieval of taste memory. The contrast between the retrieval and eyes-closed-resting conditions revealed activation in the bilateral LPFC. This activation was significantly larger than that for encoding in the bilateral frontopolar and right dorso-LPFC regions, particularly in the right hemisphere (N=28, P<0.05, FDR corrected), exhibiting right hemispheric dominance. Our findings are in line with the hemispheric encoding/retrieval asymmetry (HERA) model, which proposes a process-specific prefrontal contribution to memory function. [ABSTRACT FROM AUTHOR]

Abstract: Most food packages contain images as well as textual information. While the influence of textual information on flavor evaluation has been well studied, the influence of images remains unexplored. Thus, this study investigated how the valence and congruency of images on juice packages influence flavor evaluations. There were 85 participants divided between four experimental conditions: (1) pleasant/congruent, with pleasant orange pictures; (2) unpleasant/congruent, with unpleasant orange pictures; (3) pleasant/incongruent, with pictures of pleasant non-food objects; and (4) unpleasant/incongruent, with pictures of unpleasant non-food objects. In each condition, pictures were attached to cups filled with juice. The participants rated the palatability, goodness of aroma, sweetness, bitterness, sourness, richness, freshness, and artificiality of 6 samples of the same juice. Juices presented with pleasant images were rated as more palatable and fresh. Juices presented with congruent images were rated with better aromas. This data shows that images on juice packages influence flavor evaluation. [Copyright &y& Elsevier]