Prandial States Modify the Reactivity of the Gustatory Cortex Using Gustatory Evoked Potentials in Humans

Abstract

Previous functional Magnetic Resonance Imaging studies evaluated the role of satiety on cortical taste area activity and highlighted decreased activation in the orbito-frontal cortex when food was eaten until satiation. The modulation of orbito-frontal neurons (secondary taste area) by ad libitum food intake has been associated with the pleasantness of the food's flavor. The insula and frontal operculum (primary taste area) are also involved in reward processing. The aim was to compare human gustatory evoked potentials (GEP) recorded in the primary and secondary gustatory cortices in a fasted state with those after food intake. Fifteen healthy volunteers were enrolled in this observational study. In each of two sessions, two GEP recordings were performed (at 11:00 am and 1:30 pm) in response to sucrose gustatory stimulation, and a sucrose-gustatory threshold was determined. During one session, a standard lunch was provided between the two GEP recordings. During the other session, subjects had nothing to eat. Hunger sensation, wanting, liking, and the perception of the solution's intensity were evaluated with visual analog scales. GEP latencies measured in the Pz (p < 0.001), Cz (p < 0.01), Fz (p < 0.001) recordings (primary taste area) were longer after lunch than in the pre-prandial condition. Fp1 and Fp2 latencies (secondary taste area) tended to be longer after lunch, but the difference was not significant. No difference was observed for the sucrose-gustatory threshold regardless of the session and time. Modifications in the primary taste area activity during the post-prandial period occurred regardless of the nature of the food eaten and could represent the activity of the frontal operculum and insula, which was recently shown to be modulated by gut signals (GLP-1, CCK, ghrelin, or insulin) through vagal afferent neurons or metabolic changes of the internal milieu after nutrient absorption. This trial was registered at clinicalstrials.gov as NCT02472444.

Cerebral gustatory activation in response to free fatty acids using gustatory evoked potentials in humans

“…Healthy men were enrolled in this study. The mean age and BMI were 22 ± 2 years old (range: [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]) and 23 ± 3 kg/m 2 (range: [19][20][21][22][23][24][25][26][27][28][29], respectively. All of the subjects were nonsmokers or mild smokers who had not smoked during the day before GEP recordings.…”

“…Eighteen healthy men were enrolled in this second experiment. The mean age and BMI were 25 ± 6 years old (range: [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]) and 22 ± 2 kg/m 2 (range: 19-26), respectively. Age and BMI of the subjects were comparable in the two experiments (P > 0.05 for both).…”

“…The taste-delivery system has been described in detail in previous studies (29,30). Briefly, control and taste solutions were driven through the system by compressed air.…”

“…Moreover, averaging decreased  wave contamination. GEP was defined by three peaks, as described in previous studies (29,30): P1 the first positive peak, N1 the higher negative peak, and P2 the second positive peak. P1 latency (in milliseconds), N1 latency (in milliseconds), and P1N1 amplitude (in microvolts) of the GEPs were registered for each recorded electrode.…”

“…We recently reported a noninvasive method with high time resolution to study the gustatory pathway: gustatory evoked potentials (GEPs) (26,27). GEPs have already been obtained in response to primary taste (salty, sweet, sour, bitter, and umami) solutions (29)(30)(31).…”