Abstract
Central nervous systems receive and process information from the internal and external environment to maintain homeostasis. This includes interoceptive awareness of the organism’s nutritional state. Whenever food supply is required, feelings of hunger initiate the search for and the consumption of appropriate amounts of nutrients. How this is physiologically regulated in humans has been subjected to research into interoceptive awareness of body states during fasting and food consumption. However, there is no research on the distinct effects of carbohydrate or protein intake on interoception. Therefore, we aimed to investigate the impact of fasting and consumption of standardized carbohydrate and protein shakes on interoception in a repeated-measures cross-over design in a sample of 37 healthy, normal weight males. As a physiological correlate of interoception, we measured heartbeat-evoked potentials (HEPs), which are suggested to reflect the cortical representation of cardiac signals, during eight-minutes resting state EEG-recordings. After a 16-hour fasting period, the HEP amplitudes were lower over right central and parietal electrodes and increased after ingestion of the nutritional shake. Exploratory analyses indicated that the difference between fasting and satiety was more prominent at carbohydrate compared protein testing days. Correlation analyses with heart rate variability (HRV) suggested that high cardiac sympathetic activity is related to lower HEP amplitudes. Furthermore, cardiac sympathetic activity and stress indices decreased from before to after the intervention, whereas HRV increased. Together, this study shows for the first time that fasting and the intake of a nutritional shake affects cardiac measures of autonomic nervous system functioning and the neural correlates of cardiac interoception. These findings could be relevant for diets and psychosomatic disorders, including eating disorders.
Highlights
Central nervous systems receive and process information from the internal and external environment to maintain homeostasis
Non-invasive method for the study of the physiology of interoception is the analysis of heartbeat-evoked potentials (HEPs), which are suggested to be a measure of neural cortical activation reflecting cardiac signal perception (Schandry et al, 1986; Schandry and Montoya, 1996)
The analysis of HEP amplitudes by repeated-measures ANOVA with the factors nutrition, time point, eyes, frontal–parietal position, and hemisphere showed a main effect of frontal–parietal position [F(1.3, 41.8) = 21.34, p < 0.001; partial η2 = 0.400] and a main effect of hemisphere [F(1.9, 60.6) = 5.94, p = 0.005; partial η2 = 0.157]
Summary
Central nervous systems receive and process information from the internal and external environment to maintain homeostasis. This includes interoceptive awareness of the organism’s nutritional state. Interoception refers to the awareness of internal states, in terms of visceral sensations, including cardiovascular and gastrointestinal signals, hunger and thirst, and tactile aspects comprising pain, pressure, and temperature perception (Craig, 2002; Herbert and Pollatos, 2012; Quadt et al, 2018). Non-invasive method for the study of the physiology of interoception is the analysis of heartbeat-evoked potentials (HEPs), which are suggested to be a measure of neural cortical activation reflecting cardiac signal perception (Schandry et al, 1986; Schandry and Montoya, 1996). HEP seem to be a reliable neurophysiological measure of interoception
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