Neural processing of basic tastes in healthy young and older adults - an fMRI study

AbstractAgeing affects taste perception as shown in psychophysical studies, however, underlying structural and functional mechanisms of these changes are still largely unknown. To investigate the neurobiology of age-related differences associated with processing of basic tastes, we measured brain activation (i.e. fMRI-BOLD activity) during tasting of four increasing concentrations of sweet, sour, salty, and bitter tastes in young (average 23years of age) and older (average 65years of age) adults. The current study highlighted age-related differences in taste perception at the different higher order brain areas of the taste pathway. We found that the taste information delivered to the brain in young and older adults was not different, as illustrated by the absence of age effects in NTS and VPM activity. Our results indicate that multisensory integration changes with age; older adults showed less brain activation to integrate both taste and somatosensory information. Furthermore, older adults directed less attention to the taste stimulus; therefore attention had to be reallocated by the older individuals in order to perceive the tastes. In addition, we considered that the observed age-related differences in brain activation between taste concentrations in the amygdala reflect its involvement in processing both concentration and pleasantness of taste. Finally, we state the importance of homeostatic mechanisms in understanding the taste quality specificity in age related differences in taste perception

Brain Potentials Highlight Stronger Implicit Food Memory for Taste than Health and Context Associations

Increasingly consumption of healthy foods is advised to improve population health. Reasons people give for choosing one food over another suggest that non-sensory features like health aspects are appreciated as of lower importance than taste. However, many food choices are made in the absence of the actual perception of a food's sensory properties, and therefore highly rely on previous experiences of similar consumptions stored in memory. In this study we assessed the differential strength of food associations implicitly stored in memory, using an associative priming paradigm. Participants (N = 30) were exposed to a forced-choice picture-categorization task, in which the food or non-food target images were primed with either non-sensory or sensory related words. We observed a smaller N400 amplitude at the parietal electrodes when categorizing food as compared to non-food images. While this effect was enhanced by the presentation of a food-related word prime during food trials, the primes had no effect in the non-food trials. More specifically, we found that sensory associations are stronger implicitly represented in memory as compared to non-sensory associations. Thus, this study highlights the neuronal mechanisms underlying previous observations that sensory associations are important features of food memory, and therefore a primary motive in food choice.</p

Physiological measurements:EEG and fMRI. EEG and FMRI

Neuroimaging techniques allow us to investigate neuronal mechanisms underlying information processing, thereby providing an indispensable tool to gain more insight and understanding of how behavior is associated with sensation and perception. Multiple imaging techniques are available. In consumer science, the most commonly used neuroimaging techniques are functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). In this chapter we will start by giving a short introduction on neuroimaging in consumer research and the neurobiology of taste processing. Subsequently, we will introduce how the techniques fMRI and EEG work, what questions they typically answer, and what their limitations are in the context of consumer science. Furthermore, we will describe how fMRI and EEG experiments are typically set up, what types of data are generated, and how these data are analyzed. We will end the chapter with final remarks about data quality and a short overview of the main differences between fMRI and EEG.</p

Physiological measurements: EEG and fMRI. EEG and FMRI

Neuroimaging techniques allow us to investigate neuronal mechanisms underlying information processing, thereby providing an indispensable tool to gain more insight and understanding of how behavior is associated with sensation and perception. Multiple imaging techniques are available. In consumer science, the most commonly used neuroimaging techniques are functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). In this chapter we will start by giving a short introduction on neuroimaging in consumer research and the neurobiology of taste processing. Subsequently, we will introduce how the techniques fMRI and EEG work, what questions they typically answer, and what their limitations are in the context of consumer science. Furthermore, we will describe how fMRI and EEG experiments are typically set up, what types of data are generated, and how these data are analyzed. We will end the chapter with final remarks about data quality and a short overview of the main differences between fMRI and EEG

Brain potentials highlight stronger implicit food memory for taste than context associations

Increasingly consumption of healthy foods is advised to improve population health. Reasons people give for choosing one food over another suggest that non-sensory features like health aspects are appreciated as of lower importance than taste. However, many food choices are made in the absence of the actual perception of a food’s sensory properties, and therefore highly rely on previous experiences of similar consumptions stored in memory. In this study we assessed the differential strength of food associations implicitly stored in memory, using an associative priming paradigm. Participants (N=30) were exposed to a forced-choice picture-categorization task, in which the food or non-food target images were primed with either non-sensory or sensory related words. We observed a smaller N400 amplitude at the parietal electrodes when categorizing food as compared to non-food images. While this effect was enhanced by the presentation of a food-related word prime during food categorization, the primes had no effect in the non-food trials. More specifically, we found that sensory associations are stronger implicitly represented in memory as compared to non-sensory associations. Thus, this study highlights the neuronal mechanisms underlying previous observations that sensory associations are important features of food memory, and therefore a primary motive in food choice

Brain Potentials Highlight Stronger Implicit Food Memory for Taste than Health and Context Associations.

Increasingly consumption of healthy foods is advised to improve population health. Reasons people give for choosing one food over another suggest that non-sensory features like health aspects are appreciated as of lower importance than taste. However, many food choices are made in the absence of the actual perception of a food's sensory properties, and therefore highly rely on previous experiences of similar consumptions stored in memory. In this study we assessed the differential strength of food associations implicitly stored in memory, using an associative priming paradigm. Participants (N = 30) were exposed to a forced-choice picture-categorization task, in which the food or non-food target images were primed with either non-sensory or sensory related words. We observed a smaller N400 amplitude at the parietal electrodes when categorizing food as compared to non-food images. While this effect was enhanced by the presentation of a food-related word prime during food trials, the primes had no effect in the non-food trials. More specifically, we found that sensory associations are stronger implicitly represented in memory as compared to non-sensory associations. Thus, this study highlights the neuronal mechanisms underlying previous observations that sensory associations are important features of food memory, and therefore a primary motive in food choice

Functional specialization of the male insula during taste perception

AbstractThe primary gustatory area is located in the insular cortex. Although the insular cortex has been the topic of multiple parcellation studies, its functional specialization regarding taste processing received relatively little attention. Studies investigating the brain response to taste suggested that the insular cortex is involved in processing multiple characteristics of a taste stimulus, such as its quality, intensity, and pleasantness. In the current functional magnetic resonance study, younger and older adult male subjects were exposed to four basic tastes in five increasing concentrations. We applied a data-driven analysis to obtain insular response maps, which showed that the insular cortex processes the presence of taste, its corresponding pleasantness, as well as its concentration. More specifically, the left and right insular cortices are differentially engaged in processing the aforementioned taste characteristics: representations of the presence of a taste stimulus as well as its corresponding pleasantness dominate in the left insular cortex, whereas taste concentration processing dominates in the right insular cortex. These results were similar across both age groups. Our results fit well within previous cytoarchitectural studies and show insular lateralization in processing different aspects of taste stimuli in men

Scalp topographies and ERP: congruence effect.

<p>The scalp topographies of the congruence effect (B) indicate the mean difference between congruent food-related prime and food target pairs as compared to incongruent pairs on the frontal FP2 electrode. The ERPs on the frontal electrode (A) show a larger negative amplitude elicited by congruent food-related prime and food target pairs (red) as compared to incongruent pairs (blue) between 130 and 500 ms after target onset. The difference wave is represented in black.</p

ERP amplitudes: priming effect.

<p>The mean and standard error of the mean ERP amplitudes in response to food target images averaged between 350 and 450 ms and combined into a parietal cluster (i.e. P3, P4, P7, P8, Pz). The bar graph shows 1) no differences between taste (green), time of consumption (purple), and health (orange) primes and 2) no interaction between congruence (congruent and incongruent respectively light and dark colored) and prime. The left (pink) bar represents the ERP amplitude following a neutral prime followed by a food target (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0154128#pone.0154128.g003" target="_blank">Fig 3c</a>).</p