1. Neuroscience

Perception: In sync with the heart

People actively adjust how they acquire sensory information, such as tactile cues, based on how their bodily functions alter their senses.
https://doi.org/10.7554/eLife.84298
Share this article
Cite this article
  1. Aleksandra M Herman
(2022)
Perception: In sync with the heart
eLife 11:e84298.
https://doi.org/10.7554/eLife.84298
  2. Download BibTeX
  3. Download .RIS
  1. Aleksandra M Herman  Is a corresponding author
  1. Laboratory of Brain Imaging, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Poland

Sit back and relax. Close your eyes. Can you feel your heart beating in your chest? What you are experiencing is your heart working in a cyclic manner. During the systolic phase, the heart contracts, ejecting blood into the vessels that lead out of it, and increasing the activity of pressure sensors called baroreceptors. During the diastolic phase, the heart expands, allowing blood to flow into it, while the baroreceptors remain quiescent.

Even though the whole cycle usually takes just under a second, a lot is happening during that time. With every heartbeat, the brain receives input about the strength and precise timing of each cardiac contraction – information that needs to be promptly processed and acted upon if necessary. In recent years, a lot of studies have focused on the internal state of our body and the way we process its subtle signals; and in how physiological fluctuations in our bodies (such as the cardiac cycle) can impact our cognition and behaviour.

Certain behaviours have been shown to occur in sync with internal bodily oscillations (Kunzendorf et al., 2019; Ohl et al., 2016). For example, when we look for something, we fixate our eyes more (i.e., sample new information) during diastole, and move our eyes more (to search new areas) during systole (Galvez-Pol et al., 2020). Moreover, the sensitivity of touch also varies between the two phases: people are less perceptive to touch during systole than during diastole (Al et al., 2020; Motyka et al., 2019). So far, it was unclear what behavioural benefits such synchronicity brings (Herman and Tsakiris, 2021). Now, in eLife, Alejandro Galvez-Pol, Pavandeep Virdee, Javier Villacampa and James Kilner of University College London and the University of the Balearic Islands report new insights on this matter (Galvez-Pol et al., 2022).

In a cleverly designed experiment, Galvez-Pol et al. used electrocardiography to record the cardiac activity of participants while they performed a simple tactile discrimination task. Without looking, the participants had to figure out whether the objects they touched had vertical or horizontal grooves. They found that touches initiated during systole were held for longer than touches initiated during diastole (Figure 1). This was particularly pronounced when it was difficult to discriminate the objects, indicating that people use prolonged touch to compensate for the reduced sensitivity during systole.

Figure 1
Download asset Open asset
Schematic representation of the interplay between cardiac cycles and perception.

The heart beats in a cyclic manner. It contracts to actively push blood around the body (systolic phase, red, top centre) and relaxes to refill again (diastolic phase, blue, bottom centre). Using a tactile discrimination task, Galvez-Pol et al. show that the sensitivity of touch decreases during systole: therefore, to compensate, people hold their fingers longer over an object (red clock), especially when the task was more difficult. Conversely, people will hold their fingers on an object for a shorter time if they start touching it during diastole (blue clock).

Moreover, Galvez-Pol et al. found that the timing of touch also affected the duration of a cardiac cycle. When touch was initiated during systole, it increased the proportion of the cycle in diastole, which had previously been associated with the greatest tactile sensitivity. Thus, people adapt their behaviour in line with their perceptual needs; but their internal bodily cycles also adjust according to external demands to ensure a stable perception of the world around us.

Our bodies work in a rhythmic fashion – a fact that we typically pay little attention to in our daily lives. However, these internal rhythms have a much greater influence on our cognition than previously thought and can modulate how we perceive the environment around us. But there is still a lot to discover. Bodily signals may impact our perception in a relatively simple tactile discrimination task, but do they also affect more complex cognitive processes, such as decision-making? And are individuals, who are more attuned to subtle changes in their physiology, better able to adjust their behaviours to overcome cardiac-related effects? Answering these questions will allow us to better understand the complex interplay between the brain and the rest of the body and, ultimately, better understand ourselves.

References

Article and author information

Author details

  1. Aleksandra M Herman

    Aleksandra M Herman is in the Laboratory of Brain Imaging, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
    For correspondence
    a.herman@nencki.edu.pl
    Competing interests
    No competing interests declared
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-3338-0543

Publication history

  1. Version of Record published: November 17, 2022 (version 1)

Copyright

© 2022, Herman

This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 756
    views
  • 75
    downloads
  • 1
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Aleksandra M Herman
(2022)
Perception: In sync with the heart
eLife 11:e84298.
https://doi.org/10.7554/eLife.84298

Categories and tags

Research organism

    1. Related to

    Active tactile discrimination is coupled with and modulated by the cardiac cycle

    Alejandro Galvez-Pol, Pavandeep Virdee ... James Kilner
  2. Further reading

Further reading

    1. Neuroscience

    Active tactile discrimination is coupled with and modulated by the cardiac cycle

    Alejandro Galvez-Pol, Pavandeep Virdee ... James Kilner
    Research Article Updated

    Perception and cognition are modulated by the phase of the cardiac signal in which the stimuli are presented. This has been shown by locking the presentation of stimuli to distinct cardiac phases. However, in everyday life sensory information is not presented in this passive and phase-locked manner, instead we actively move and control our sensors to perceive the world. Whether active sensing is coupled and modulated with the cardiac cycle remains largely unknown. Here, we recorded the electrocardiograms of human participants while they actively performed a tactile grating orientation task. We show that the duration of subjects’ touch varied as a function of the cardiac phase in which they initiated it. Touches initiated in the systole phase were held for longer periods of time than touches initiated in the diastole phase. This effect was most pronounced when elongating the duration of the touches to sense the most difficult gratings. Conversely, while touches in the control condition were coupled to the cardiac cycle, their length did not vary as a function of the phase in which these were initiated. Our results reveal that we actively spend more time sensing during systole periods, the cardiac phase associated with lower perceptual sensitivity (vs. diastole). In line with interoceptive inference accounts, these results indicate that we actively adjust the acquisition of sense data to our internal bodily cycles.

    1. Neuroscience

    Emergence of brain-like mirror-symmetric viewpoint tuning in convolutional neural networks

    Amirhossein Farzmahdi, Wilbert Zarco ... Tal Golan
    Research Article Updated

    Primates can recognize objects despite 3D geometric variations such as in-depth rotations. The computational mechanisms that give rise to such invariances are yet to be fully understood. A curious case of partial invariance occurs in the macaque face-patch AL and in fully connected layers of deep convolutional networks in which neurons respond similarly to mirror-symmetric views (e.g. left and right profiles). Why does this tuning develop? Here, we propose a simple learning-driven explanation for mirror-symmetric viewpoint tuning. We show that mirror-symmetric viewpoint tuning for faces emerges in the fully connected layers of convolutional deep neural networks trained on object recognition tasks, even when the training dataset does not include faces. First, using 3D objects rendered from multiple views as test stimuli, we demonstrate that mirror-symmetric viewpoint tuning in convolutional neural network models is not unique to faces: it emerges for multiple object categories with bilateral symmetry. Second, we show why this invariance emerges in the models. Learning to discriminate among bilaterally symmetric object categories induces reflection-equivariant intermediate representations. AL-like mirror-symmetric tuning is achieved when such equivariant responses are spatially pooled by downstream units with sufficiently large receptive fields. These results explain how mirror-symmetric viewpoint tuning can emerge in neural networks, providing a theory of how they might emerge in the primate brain. Our theory predicts that mirror-symmetric viewpoint tuning can emerge as a consequence of exposure to bilaterally symmetric objects beyond the category of faces, and that it can generalize beyond previously experienced object categories.

    1. Neuroscience

    Genetically defined nucleus incertus neurons differ in connectivity and function

    Emma D Spikol, Ji Cheng ... Marnie E Halpern
    Research Article

    The nucleus incertus (NI), a conserved hindbrain structure implicated in the stress response, arousal, and memory, is a major site for production of the neuropeptide relaxin-3. On the basis of goosecoid homeobox 2 (gsc2) expression, we identified a neuronal cluster that lies adjacent to relaxin 3a (rln3a) neurons in the zebrafish analogue of the NI. To delineate the characteristics of the gsc2 and rln3a NI neurons, we used CRISPR/Cas9 targeted integration to drive gene expression specifically in each neuronal group, and found that they differ in their efferent and afferent connectivity, spontaneous activity, and functional properties. gsc2 and rln3a NI neurons have widely divergent projection patterns and innervate distinct subregions of the midbrain interpeduncular nucleus (IPN). Whereas gsc2 neurons are activated more robustly by electric shock, rln3a neurons exhibit spontaneous fluctuations in calcium signaling and regulate locomotor activity. Our findings define heterogeneous neurons in the NI and provide new tools to probe its diverse functions.