Brain activity associated with taste stimulation: A mechanism for neuroplastic change?

Abstract

Purpose Neuroplasticity may be enhanced by increasing brain activation and bloodflow in neural regions relevant to the target behavior. We administered precisely formulated and dosed taste stimuli to determine whether the associated brain activity patterns included areas that underlie swallowing control. Methods Five taste stimuli (unflavored, sour, sweet‐sour, lemon, and orange suspensions) were administered in timing‐regulated and temperature‐controlled 3 mL doses via a customized pump/tubing system to 21 healthy adults during functional magnetic resonance imaging (fMRI). Whole‐brain analyses of fMRI data assessed main effects of taste stimulation as well as differential effects of taste profile. Results Differences in brain activity associated with taste stimulation overall as well as specific stimulus type were observed in key taste and swallowing regions including the orbitofrontal cortex, insula, cingulate, and pre‐ and postcentral gyri. Overall, taste stimulation elicited increased activation in swallowing‐related brain regions compared to unflavored trials. Different patterns of blood oxygen level‐dependent (BOLD) signal were noted by taste profile. For most areas, sweet‐sour and sour trials elicited increases in BOLD compared to unflavored trials within that region, whereas lemon and orange trials yielded reductions in BOLD. This was despite identical concentrations of citric acid and sweetener in the lemon, orange, and sweet‐sour solutions. Conclusions These results suggest that neural activity in swallowing‐relevant regions can be amplified with taste stimuli and may be differentially affected by specific properties within very similar taste profiles. These findings provide critical foundational information for interpreting disparities in previous studies of taste effects on brain activity and swallowing function, defining optimal stimuli to increase brain activity in swallowing‐relevant regions, and harnessing taste to enhance neuroplasticity and recovery for persons with swallowing disorders.

Comparing Taste Perception Across Modalities in Healthy Adults: Liquids Versus Dissolvable Taste Strips

“…The liquid profiles used in this study, which the taste strips were deliberately designed to match, have also been used to investigate taste’s effect on neural activity using functional magnetic resonance imaging. Compared to a neutral stimulus (i.e., water), tastants led to significant blood-oxygen-level-dependent changes in the pre- and post-central gyri, insula, anterior cingulate cortex, and secondary/associative sensorimotor areas in healthy young participants [ 17 ]. These neural areas are primary cortical and sub-cortical regions active in swallowing [ 18 ].…”

“…Neural underpinnings of sensorimotor behaviors that are inactive for long durations are susceptible to weakened sensory processing and motor control from disuse or deconditioning effects [ 15 ], an effect commonly known as the neuroplasticity principle of “use it or lose it” [ 16 ]. A sensation that could be of potential benefit to incorporate in swallowing rehabilitation is taste, as it involves numerous overlapping neural pathways and substrates with swallowing [ 17 , 18 ].…”

“…The aims of the current study were to compare taste-related ratings of intensity and palatability between liquid and taste strip modalities of flavored stimuli, and to assess any perceptual differences in intensity and palatability ratings across flavor profiles. The taste strips made in this study were designed to specifically match the flavor profiles of the liquid tastants that have been used in other studies investigating swallowing biomechanics and neural hemodynamics in response to taste stimuli [ 17 , 35 ]. It was hypothesized that intensity and palatability ratings would be similar for liquid tastants and taste strips across flavor profiles (H1), and intensity and hedonic ratings would differ from one flavor profile to another within liquid and taste strip modalities (H2).…”