Perception of passing time can be distorted.Emotional experiences, particularly arousal, can contract or expand experienced duration via their interactions with attentional and sensory processing mechanisms.Current models suggest that perceived duration can be encoded from accumulation processesand from temporally evolving neural dynamics.Yet all neural dynamics and information processing ensue at the backdrop of continuous interoceptive signals originating from within the body. Indeed, phasic fluctuations within the cardiac cycle impact neural and information processing.Here, we show that these momentary cardiac fluctuations distort experienced time and that their effect interacts with subjectively experienced arousal. In a temporal bisection task, durations (200–400 ms) of an emotionally neutral visual shape or auditory tone (experiment 1) or of an image displaying happy or fearful facial expressions (experiment 2) were categorized as short or long.Across both experiments, stimulus presentation was time-locked to systole, when the heart contracts and baroreceptors fire signals to the brain, and to diastole, when the heart relaxes, and baroreceptors are quiescent. When participants judged the duration of emotionally neural stimuli (experiment 1), systole led to temporal contraction, whereas diastole led to temporal expansion. Such cardiac-led distortions were further modulated by the arousal ratings of the perceived facial expressions (experiment 2). At low arousal, systole contracted while diastole expanded time, but as arousal increased, this cardiac-led time distortion disappeared, shifting duration perception toward contraction. Thus, experienced time contracts and expands within each heartbeat—a balance that is disrupted under heightened arousal.
From the inside out: interoceptive feedback facilitates the integration of visceral signals for efficient sensory processing.
The insula mediates access to awareness of visual stimuli presented synchronously to the heartbeat.
Neural sequences as an optimal dynamical regime for the readout of time.
Second, we considered the arousal ratings given to each presented face ( Figure 1 A) because such ratings can capture the variance in people’s affective response to the stimuli and consequently in the arousal-led effects on time perception.For that reason, we included arousal ratings for each stimulus, independently of its valence, into the LMM model and controlled for the heart deceleration like in experiment 1 ( STAR Methods ). PSE values were significantly affected by an interaction between cardiac phase and arousal ratings (beta = −5.2, SE = 2.3, χ= 5.3, p = 0.02). The main effect of arousal ratings was not significant (beta = 0.9, SE = 1.7, χ= 0.3, p = 0.59), but the cardiac phase retained its statistical significance (beta = 9.2, SE = 2.3, χ= 16.1, p < 0.001). A significant cardiac phase by arousal interaction was followed up with simple slopes analysis ( Figure 3 ), which showed that the opposing effects of systole and diastole on time perception were present for low and average arousal ratings (beta = 14.4, SE = 3.2, t = 4.5, p < 0.001 and beta = 9.2, SE = 2.3, t = 4.1, p < 0.001, respectively) but disappeared when arousal ratings increased (beta = 4.1, SE = 3.2, t = 1.3, p = 0.21). For JND values, none of the predictors and their interactions made a statistically significant contribution. The main effect of the cardiac phase was no longer significant (beta = 2.8, SE = 2.1, χ= 1.8, p = 0.18).
A linear mixed model was run on the PSE values modeling the effects of the cardiac phase (systole, diastole), subjective arousal, and changes in heart rate. The cardiac effect on PSEs was concentrated at low and mean levels of arousal but disappeared at high arousal levels. Arousal ratings were mean-centered. The lines represent the slopes and the shading represents the 95% confidence band. n.s., non-significant; ∗∗ p < 0.001; ∗ p < 0.05.
Simple slopes analysis breaking down the cardiac phase by subjective arousal interaction on PSE values in experiment 2
Figure 3 Simple slopes analysis breaking down the cardiac phase by subjective arousal interaction on PSE values in experiment 2
First, experiment 2 ( Figure 2 D) was analyzed like experiment 1, with a repeated-measures ANOVA coding for the cardiac phase (diastole, systole) and the emotional valence of the presented face (happy, fearful). There was a significant main effect of cardiac phase on PSE values (F(1,38) = 20.9, p < 0.001, η2p = 0.35), with stimuli presented at diastole judged, on average, 9 ms longer (M = 305, SD = 25) than those at systole (M = 314, SD = 26). The effect of valence was not statistically significant (F(1,38) = 1.3, p = 0.27, η2p = 0.03) and neither was the cardiac phase by valence interaction (F(1,38) = 1.3, p = 0.26, η2p = 0.03; Figure 2 E). In contrast to experiment 1, the cardiac phase extended a small but statistically significant influence on JND values (F(1,38) = 4.5, p = 0.04, η2p = 0.14) with sensitivity being higher during the diastolic (M = 42, SD = 17) than during the systolic phase (M = 45, SD = 17). There was no interaction (F(1,38) < 0.001, p = 1.0, η2p < 0.001) and no main effect of valence (F(1,38) = 0.58, p = 0.45, η2p = 0.001; Figure 2 F).
Because we observed heart rate changes over the course of the trial, in particular, heart deceleration before and during the stimulus presentation, we tested whether the cardiac phase effect was independent from the effects arising from the heart rate changes. For that reason, we ran a mixed linear model (MLL) on PSE and JND values with predictors coding for cardiac phase and modality while controlling for heart deceleration just before and during the stimulus presentation ( STAR Methods ). The magnitude of heart deceleration did not affect PSE values (beta = −0.1, SE = 2.2, χ= 0.0, p = 0.96). Cardiac phase retained its effect when heart deceleration was added into the model (beta = 6.8, SE = 2.4, χ= 7.7, p = 0.006) and so did the effect of modality (beta = 12.7, SE = 5.3, χ= 5.3, p = 0.02). The interaction between cardiac phase and modality remained statistically not significant (beta = 6.6, SE = 4.8, χ= 1.9, p = 0.17). Heart deceleration did not affect JND values either (beta = 0.6, SE = 1.5, χ= 0.2, p = 0.66). When heart deceleration was added into the model, cardiac phase effect remained statistically not significant (beta = 1.9, SE = 1.9, χ= 1.0, p = 0.31) as well as its interaction with modality (beta = −0.3, SE = 3.8, χ= 0.0, p = 0.93). Modality retained its statistically significant effect (beta = 24.1, SE = 2.4, χ= 48.7, p < 0.001). Thus, the effect of the cardiac phase on duration perception was independent from heart rate changes.
Participants’ performance on the duration bisection task was modeled with psychometric functions, where the point of subjective equality (PSE) reflects the stimulus duration at which the participant is equally likely to respond “short” or “long.” Thus, shifts in PSE indicate relative under- or overestimation of stimulus durations ( Figures 2 A and 2B ). In experiment 1, repeated-measures ANOVA with factors modality (auditory, visual) and cardiac phase (diastole, systole) on PSE values yielded a significant main effect of cardiac phase (F(1,27) = 8.1, p = 0.01, η2p = 0.23), with stimuli presented at diastole judged, on average, 7 ms longer (M = 290, SD = 23) than those presented at systole (M = 297, SD = 26). The main effect of modality was also significant (F(1,27) = 5.7, p = 0.02, η2p = 0.17) with tones judged, on average, 13 ms longer (M = 287, SD = 15) than visual stimuli (M = 300, SD = 30). The interaction between modality and cardiac phase was not statistically significant (F(1,27) = 1.9, p = 0.18, η2p = 0.06), suggesting that the same temporal distortions occurred in both visual and auditory modalities. In addition to PSE, just noticeable difference (JND) reflects temporal sensitivity, where smaller values indicate better discriminability of changes in stimulus durations ( Figure 2 C). In experiment 1, the cardiac phase did not have a significant effect (F(1,27) = 1.5, p = 0.24, η2p = 0.05), but JND values were significantly affected by modality (F(1,27) = 100.0, p < 0.001, η2p = 0.79) with higher sensitivity for tone durations (M = 22, SD = 8) as compared with visual durations (M = 46, SD = 17). That auditory stimuli are perceived to last longer and result in more precise duration representation than visual stimuli is a common finding.The interaction between cardiac phase and modality was not statistically significant (F(1,27) = 0.001, p = 0.94, η2p < 0.001).
(F) Same for the JND values. The cardiac phase influenced JNDs without interaction by emotion. Participants were more sensitive to duration differences at diastole compared with systole. n.s., non-significant; ∗∗ p < 0.001; ∗ p < 0.05.
(E) PSE values in experiment 2 from systolic (red) and diastolic (blue) conditions, across emotion conditions. Labels in gray indicate the main effects and interactions of the repeated-measures ANOVA, n = 39. The cardiac phase influenced the PSEs in the same way as in experiment 1 without an interaction by emotion.
(D) Fitted individual (gray) and group-level (black) cumulative Gaussian functions showing the proportion of long responses as a function of test durations across emotion (happy, fearful) by cardiac (systole, diastole) conditions in experiment 2.
(B) PSE values in experiment 1 from systolic (red) and diastolic (blue) conditions, across modality conditions. Labels in gray indicate the main effects and interactions of the repeated-measures ANOVA, n = 28. The cardiac phase influenced PSEs without interaction by modality. Systolic durations were underestimated, whereas diastolic durations overestimation. The dots represent individual data while the boxplots reprsent group-level data (median and quartiles). Distribution plots were created with “raincloud” R package.
(A) Fitted individual (gray) and group-level (black) cumulative Gaussian functions showing the proportion of long responses as a function of test durations across modality (auditory, visual) by cardiac (systole, diastole) conditions in experiment 1. The vertical lines show the average PSE.
PSE and JND values estimated from the psychometric functions as a function of cardiac phase, modality (experiment 1), or emotion (experiment 2)
Figure 2 PSE and JND values estimated from the psychometric functions as a function of cardiac phase, modality (experiment 1), or emotion (experiment 2)
Across two experiments, participants first learned to discriminate a short (200 ms) from a long (400 ms) reference duration and were then asked to judge whether intermediate test durations (200, 250, 300, 350, and 400 ms) were more like the short or the long reference Figure 1 A; STAR Methods ). Across both experiments, stimulus presentation was time-locked to either the systolic (R + 100 ms) or the diastolic (R + 500 ms) cardiac phase ( Figure 1 B). In experiment 1, participants (n = 28) performed the task for visual and auditory stimuli in separate blocks, judging the duration of emotionally neutral visual images or auditory tones. In experiment 2, a new group of participants (n = 39) judged the duration of images depicting happy or fearful facial expressions presented in a random order. In experiment 2, after the temporal bisection task, participants were presented with each face again for 300 ms and were asked to rate how aroused it made them feel on an adapted 5-point self-assessment mannequin (SAM) scale from calm (1) to aroused (5). The averaged arousal ratings are shown in Figure 1 A.
(B) Schematic task design. Stimulus onset was time-locked to distinct cardiac phases: systole (red) and diastole (blue). The figure shows how the most ambiguous duration (300 ms) did not overlap across the phases. The black bars represent stimulus durations. Participants first learned to discriminate between the short (200 ms) and the long (400 ms) reference, and during bisection, they were presented with additional intermediate test durations.
(A) Schematic trial structure. A stimulus was presented on the screen, and participants judged whether the presented stimulus was long or short. In experiment 1, we manipulated the stimulus modality (auditory or visual), whereas in experiment 2, the emotional valence of the stimulus (happy or fearful face). At the end of experiment 2, participants rated the level of arousal they experienced in response to each presented face on a scale from 1 to 5. The plot shows individual and group-level ratings (mean and SEM).
Discussion
Experiment 1 showed that when timing emotionally neutral auditory and visual stimuli, cardiac systole contracted the experienced duration, while diastole expanded it. Experiment 2 replicated the observed cardiac-led temporal distortion and showed that it was further modulated by the subjectively experienced arousal in response to the presented facial expressions. As the experienced arousal increased, the relative cardiac-led temporal contraction-expansion was disrupted, biasing duration perception toward contraction.
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Sedlmeier P. The heart beat does not make us tick: the impacts of heart rate and arousal on time perception. There has been a growing interest in the idea of embodied time, according to which experienced time is influenced by physiological, interoceptive, signals from the body.For example, past studies have examined interoceptive attention effects,the cortical processing of cardiac signals,and heart rate changes.Specifically, asking participants to focus on bodily sensations exaggerates the emotional distortions of time so that negative experiences seem to last even longer and positive ones seem to pass even quicker compared with when participants focus externally.In addition, the strength of cortical processing of afferent cardiac signals indexed by heart-evoked potential (HEP) is modulated by the over- and underestimation of elapsed time so that lower amplitude in HEPs accompany duration overestimation.Furthermore, when performing daily activities participants tend to report quicker passage of time during periods of heightened heart rate(but not all studies have found significant influence of heart rate on temporal judgments).
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Stella G. Afferent impulses in the carotid sinus nerve I. The relation of the discharge from single end organs to arterial blood pressure. Although these findings correlate interoceptive processes in time perception, these studies demonstrated in a more mechanistic way how common time distortions—the contraction and the expansion of time—arise from the phasic modulations within each heartbeat. Ascending cardiac signals from the baroreceptors provide the brain with continuous information about the heart rate and blood pressure changes. However, baroreceptor activity is maximal during the systolic period of the cardiac cycle, and although some baroceptor activity may still be present during the diastolic period, it is reduced or ceased relative to the systolic period.Thus, the method of time-locking stimulus presentation to specific cardiac phases, while not necessarily reflecting real life perception, can be used to approximate the causal role of ascending cardiac signals in shaping temporal perception, as the only factor that varies across the two conditions is the timing of identical stimuli relative to the ECG R-wave.
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Rothwell J.C. Illusory perceptions of space and time preserve cross-saccadic perceptual continuity. A fundamental question pertains to how temporal distortions can arise from the ascending cardiac signals. One potential explanation stems from the observation that non-affective sensory processing is generally attenuated during the systole due to the neural noise produced by the baroreceptor output.According to the coding efficiency accounts of temporal processingmore efficient or enhanced sensory processing predicts temporal dilation, whereas suppressed sensory processing predicts temporal contraction. On this view, experienced time is encoded from the evolving neural networks during perception.Accordingly, temporal contraction during the systole may have resulted from a periodic sensory attenuation. The relative temporal expansion during the diastole may then act as a compensating mechanism that counteracts the systolic time contraction, similar to how time dilates post-saccade to compensate for the contraction caused by the saccade.
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Forschack N.
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Grund M.
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Villringer A. Heart–brain interactions shape somatosensory perception and evoked potentials. , 10 Al E.
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van Rijn H. Temporal context actively shapes EEG signatures of time perception. However, beyond this sensory modulation account, it is also possible that cardiac signals directly affect the temporal accumulation processesvia the physiological arousal they convey. Classical pacemaker-accumulation models conceptualize timing as an accumulation of internally produced ticks.To highlight the embodied nature of such temporal accumulation, the insular cortex, considered the main interoceptive hub in the brain,has been found to be consistently engaged during duration perception tasksand is argued to underpin the accumulation of “how do I feel” moments across time, essentially defining the subjective passage of time.Importantly, the rate of such accumulation can be influenced by arousal.It is often assumed that the systolic phase of the cardiac cycle represents a state of simulated heightened arousal, in contrast to the diastole.On that account, the neural encoding of cardiac signals could directly affect temporal accumulation processes, as the encoding of arousing physiological states at the systole would lead to temporal contraction, followed by a temporal elongation during the diastolic phase. This is consistent with the finding that a reduction in sympathetic tone induced by clonidine injection resulted in a subjective slowing of time.Combining the present paradigm with electroencephalography (EEG) methods could distinguish between these two accounts. Specifically, sensory modulation accounts would predict that cardiac signals attenuate the amplitude of sensory event-related potentials (ERPs),whereas temporal accumulation accounts would predict that cardiac signals either attenuate the amplitude of the contingent negative variation (CNV)or enhance the ERP response at the offset of the stimulus.While the two accounts are not mutually exclusive, meaning that cardiac signals likely affect a range of components, it would be important to examine which of these modulations (sensory ERP, CNV, or offset ERP) is ultimately predictive of the subjective contraction of the stimulus duration.
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Robinson O.J. Anxiety makes time pass quicker while fear has no effect. Interestingly, the opposing temporal distortions—contraction and expansion—within each heartbeat imply that over multiple heartbeats, such distortions would average out to produce a duration estimate that is close to the veridical duration of the stimulus. We show that the opposing effect of systole and diastole on duration perception breaks down, however, as the subjectively experienced arousal increased, skewing the duration representation toward contraction. Although arousal has been associated with temporal dilation,some studies find that if arousal arises due to anxiety or uncertainty it can lead to temporal contraction.Notably, we did not observe a main effect of arousal or valence on perceived stimulus durations in experiment 2. Rather, we show that subjectively felt arousal modulated how the cardiac effects shaped perceived stimulus durations, biasing temporal representation at the diastolic phase toward contraction. Static facial stimuli do not always induce temporal distortions,thus future studies could use more arousal-inducing paradigms involving, for example, unexpected painful stimulation.
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Friston K.J. In the body’s eye: the computational anatomy of interoceptive inference. This study demonstrated how fluctuations within the cardiac phases together with the subjectively experienced arousal affect perceptual temporal performance. Yet unexpected arousal can also reduce the metacognitive confidence in perceptual decisions.A recent computational model of phasic cardiac influences on perception suggests that systole reduces the confidence in exteroceptive sensory channels.However, direct evidence as to whether the ascending cardiac signals directly impact metacognitive processing is still lacking. Incorporating confidence judgements within the current paradigm would thus be a fruitful avenue for future studies to help disentangle the cardiac-driven temporal perceptual distortions from distortions in metacognition.