Learning by heart: cardiac cycle reveals an effective time window for learning

Abstract

Cardiac cycle phase is known to modulate processing of simple sensory information. This effect of the heartbeat on brain function is likely exerted via baroreceptors, the neurons sensitive for changes in blood pressure. From baroreceptors, the signal is conveyed all the way to the forebrain and the medial prefrontal cortex. In the two experiments reported, we examined whether learning, as a more complex form of cognition, can be modulated by the cardiac cycle phase. Human participants ( experiment 1) and rabbits ( experiment 2) were trained in trace eyeblink conditioning while neural activity was recorded. The conditioned stimulus was presented contingently with either the systolic or diastolic phase of the cycle. The tone used as the conditioned stimulus evoked amplified responses in both humans (electroencephalogram from "vertex," Cz) and rabbits (hippocampal CA1 local field potential) when its onset was timed at systole. In humans, the cardiac cycle phase did not affect learning, but rabbits trained at diastole learned significantly better than those trained at a random phase of the cardiac cycle. In summary, our results suggest that neural processing of external stimuli and also learning can be affected by targeting stimuli on the basis of cardiac cycle phase. These findings might be useful in applications aimed at maximizing or minimizing the effects of external stimulation. NEW & NOTEWORTHY It has been shown that rapid changes in bodily states modulate neural processing of external stimulus in brain. In this study, we show that modulation of neural processing of external stimulus and learning about it depends on the phase of the cardiac cycle. This is a novel finding that can be applied to optimize associative learning.

Breathe out and learn: Expiration‐contingent stimulus presentation facilitates associative learning in trace eyeblink conditioning

“…Our current results add to findings from our previous study in which TEBC was enhanced when the conditioned stimulus was timed to the diastolic phase of the cardiac cycle (Waselius et al, ). Our previous results (Waselius et al, ) suggest that the brain processes information differently during the diastolic and systolic phases. In short, responses to external stimuli are attenuated during the diastolic phase and amplified during the systolic phase.…”

“…This cardiorespiratory regulation is driven by the pons of the brainstem via baroreceptors located on the walls of major blood vessels (Farmer, Dutschmann, Paton, Pickering, & McAllen, ). It is known that the phase of the cardiac cycle alone affects neural processing of external stimuli in humans (Gray et al, ; Martins, McIntyre, & Ring, ; Park, Correia, Ducorps, & Tallon‐Baudry, ; Waselius, Wikgren, Halkola, Penttonen, & Nokia, ). For example, negative pictures are judged to be more intense when presented during systole (Gray et al, ).…”

“…For example, negative pictures are judged to be more intense when presented during systole (Gray et al, ). In addition, in rabbits, learning trace eyeblink conditioning (TEBC), a hippocampus‐dependent variant of classical Pavlovian conditioning (Holland & Bouton, ; Solomon, Vander Schaaf, Thompson, & Weisz, ), is most effective if the conditioned stimulus is timed to the diastolic phase of the cardiac cycle (Waselius et al, ). Thus, rhythmic variation in bodily functions seems to have an impact on the encoding of external information in the brain.…”

Most hippocampal CA1 pyramidal cells in rabbits increase firing during awake sharp-wave ripples and some do so in response to external stimulation and theta

“…Further, SPW-R probability is increased during nasal expiration in mice (Liu et al 2017). There also seems to be an association between bodily rhythms and learning TEBC (Waselius et al 2018(Waselius et al , 2019:…”

In vivo Modelling of Toxicity of Eight Commercial Artificial Sweeteners in Daphnia Neonates and Zebrafish Embryos through Cardiac Performance Assessments

“…The cardiac cycle is divided into two phases: systole and diastole [45]. Increases in heart rate affect diastole by decreasing the time that it takes for blood to fill the ventricles.…”