The aftereffect of perceived duration is contingent on auditory frequency but not visual orientation

Neural correlates of aftereffects induced by adaptations to single and average durations

Duration perception can be heavily distorted owing to repetitive exposure to a relatively long or short sensory event, often causing a duration aftereffect. Here, we used a novel procedure to show that adaptations to both single and average durations produced the duration aftereffect. Participants completed a duration reproduction task (Experiment 1) or a duration category rating task (Experiment 2) after long-term adaptations to a stimulus of medium duration and to stimuli of averagely medium duration. We found that adaptations to both single and average durations resulted in duration aftereffects. The simultaneously recorded functional magnetic resonance imaging (fMRI) data revealed that the reduction in neural activity due to long-term adaptation to single duration was observed in the right supramarginal gyrus (SMG) of the parietal lobe, while adaptation to average duration resulted in fMRI adaptations in the left postcentral gyrus (PCG) and middle cingulate gyrus (MCG). At the individual level, the magnitude of the behavioral aftereffect was positively correlated with the magnitude of fMRI adaptation in the right SMG after adaptation to single duration, while there were no significantly positive correlations between the behavioral aftereffect and fMRI adaptations in the left PCG and MCG. These results suggest that there are different neural mechanisms for aftereffects caused by adaptations to single and average durations.

Modality-specific sensory and decisional carryover effects in duration perception

BACKGROUND

The brain uses recent history when forming perceptual decisions. This results in carryover effects in perception. Although separate sensory and decisional carryover effects have been shown in many perceptual tasks, their existence and nature in temporal processing are unclear. Here, we investigated whether and how previous stimuli and previous choices affect subsequent duration perception, in vision and audition.

RESULTS

In a series of three experiments, participants were asked to classify visual or auditory stimuli into "shorter" or "longer" duration categories. In experiment 1, visual and auditory stimuli were presented in separate blocks. Results showed that current duration estimates were repelled away from the previous trial's stimulus duration, but attracted towards the previous choice, in both vision and audition. In experiment 2, visual and auditory stimuli were pseudorandomly presented in one block. We found that sensory and decisional carryover effects occurred only when previous and current stimuli were from the same modality. Experiment 3 further investigated the stimulus dependence of carryover effects within each modality. In this experiment, visual stimuli with different shape topologies (or auditory stimuli with different audio frequencies) were pseudorandomly presented in one visual (or auditory) block. Results demonstrated sensory carryover (within each modality) despite task-irrelevant differences in visual shape topology or audio frequency. By contrast, decisional carryover was reduced (but still present) across different visual topologies and completely absent across different audio frequencies.

CONCLUSIONS

These results suggest that serial dependence in duration perception is modality-specific. Moreover, repulsive sensory carryover effects generalize within each modality, whereas attractive decisional carryover effects are contingent on contextual details.

Color Sensitivity of the Duration Aftereffect Depends on Sub- and Supra-second Durations

The perception of duration becomes biased after repetitive duration adaptation; this is known as the duration aftereffect. The duration aftereffect exists in both the sub-second and supra-second ranges. However, it is unknown whether the properties and mechanisms of the adaptation aftereffect differ between sub-second and supra-second durations. In the present study, we addressed this question by investigating the color sensitivity of the duration aftereffect in the sub-second (Experiment 1) and supra-second (Experiment 2) ranges separately. We found that the duration aftereffect in the sub-second range could only partly transfer across different visual colors, whereas the duration aftereffect in the supra-second range could completely transfer across different visual colors. That is, the color-sensitivity of the duration aftereffect in the sub-second duration was stronger than that in the supra-second duration. These results imply that the mechanisms underlying the adaptation aftereffects of the sub-second and supra-second ranges are distinct.

The rhythm aftereffect induced by adaptation to the decelerating rhythm

Rhythm perception can be distorted following prolonged exposure to an isochronous rhythm. It has been suggested that this might arise from the neural adaptation of temporal interval selective neurons. However, the rhythm in our daily life is not always isochronous, and the mechanism that rules the anisochronous rhythm is unclear. Here, we used a sensory adaptation paradigm to investigate whether rhythm perception can be affected by adaptation to the anisochronous rhythm. In Experiments 1 and 2, the direction of tempo change (accelerating vs. decelerating) judgment task and the rhythmic isochronism (isochronous vs. anisochronous) judgment task were used to evaluate participants' perception of rhythms, respectively. We found that after adaptation to a decelerating rhythm, participants tended to perceive the subsequent isochronous rhythm as accelerating. In Experiment 3, visual test rhythms followed the auditory adapting rhythm. In this situation, we did not find any adaptation effects on subsequent rhythm perception. Our results suggest that adaptation to the decelerating rhythm can induce a modality-specific rhythm aftereffect, which is consistent with the temporal order contingent duration aftereffect. It implies a unified timing mechanism for duration and rhythm perception.

Electrophysiological correlates of the somatotopically organized tactile duration aftereffect

Adaptation to sensory events of long or short duration leads to a negative aftereffect, in which a new target event (of median duration) following the adaptation will be perceived to be shorter or longer than is actually the case. This illusion has been observed in visual, auditory, and tactile modalities. This study used event-related potentials (ERPs) to examine the tactile duration aftereffect, using the contingent negative variation (CNV) and the late positive component (LPC) as a way to characterize the temporal processes. The tactile duration adaptation was found to induce a significant aftereffect within a somatotopic framework. Moreover, the CNV in the contralateral scalp and the LPC in the fronto-central scalp were both modulated by the tactile duration adaptation. Specifically, adaptation to a short tactile duration increased the CNV and LPC amplitudes, whereas adaptation to a long tactile duration decreased them. This modulation was contingent on the topographic distance between fingers, which was only observed when the adapting and test fingers were consistent or adjacent, but not homologous. In sum, these results reveal a coherent behavioral-electrophysiological link in the somatotopically organized tactile duration aftereffect.

Duration Selectivity in Right Parietal Cortex Reflects the Subjective Experience of Time

The perception of duration in the subsecond range has been hypothesized to be mediated by the population response of duration-sensitive units, each tuned to a preferred duration. One line of support for this hypothesis comes from neuroimaging studies showing that cortical regions, such as in parietal cortex exhibit duration tuning. It remains unclear whether this representation is based on the physical duration of the sensory input or the subjective duration, a question that is important given that our perception of the passage of time is often not veridical, but rather, biased by various contextual factors. Here we used fMRI to examine the neural correlates of subjective time perception in human participants. To manipulate perceived duration while holding physical duration constant, we used an adaptation method, in which, before judging the duration of a test stimulus, the participants were exposed to a train of adapting stimuli of a fixed duration. Behaviorally, this procedure produced a pronounced negative aftereffect: A short adaptor biased participants to judge stimuli as longer and a long adaptor-biased participants to judge stimuli as shorter. Duration tuning modulation, manifest as an attenuated BOLD response to stimuli similar in duration to the adaptor, was only observed in the right supramarginal gyrus (SMG) of the parietal lobe and middle occipital gyrus, bilaterally. Across individuals, the magnitude of the behavioral aftereffect was positively correlated with the magnitude of duration tuning modulation in SMG. These results indicate that duration-tuned neural populations in right SMG reflect the subjective experience of time.SIGNIFICANCE STATEMENT The subjective sense of time is a fundamental dimension of sensory experience. To investigate the neural basis of subjective time, we conducted an fMRI study, using an adaptation procedure that allowed us to manipulate perceived duration while holding physical duration constant. Regions within the occipital cortex and right parietal lobe showed duration tuning that was modulated when the test stimuli were similar in duration to the adaptor. Moreover, the magnitude of the distortion in perceived duration was correlated with the degree of duration tuning modulation in the parietal region. These results provide strong physiological evidence that the population coding of time in the right parietal cortex reflects our subjective experience of time.

The duration aftereffect does not reflect adaptation to perceived duration

Recent studies have provided evidence for a role of duration-tuned channels in the encoding of duration. Duration encoding in these channels is thought to reflect the time between responses to the onset and offset of an event. This notion is in apparent conflict with studies that demonstrate that the perceived duration of an event can vary independently from the time separating its perceived onset and offset. Instead, these studies suggest that duration encoding is sensitive to other temporal aspects of a sensory event. In the current study, we investigated whether duration-tuned channels encode duration based on the time between the on- and offset of an event (onset-offset duration), or if they encode a duration corresponding to the perceived duration of that event. We used a duration illusion to dissociate onset-offset duration and perceived duration and measured whether repeated exposure to illusion-inducing stimuli caused adaptation to the onset-offset duration or the perceived duration of these illusion-inducing stimuli. We report clear evidence for adaptation to the onset-offset duration of illusion-inducing stimuli. This finding supports the notion that duration-tuned mechanisms respond to the time between the onset and offset of an event, without necessarily reflecting the duration perceived, and eventually reported by the participant. Implications for the duration channel model and the mechanisms underlying duration illusions are discussed.

Adaptation reveals multi-stage coding of visual duration

In conflict with historically dominant models of time perception, recent evidence suggests that the encoding of our environment's temporal properties may not require a separate class of neurons whose raison d'être is the dedicated processing of temporal information. If true, it follows that temporal processing should be imbued with the known selectivity found within non-temporal neurons. In the current study, we tested this hypothesis for the processing of a poorly understood stimulus parameter: visual event duration. We used sensory adaptation techniques to generate duration aftereffects: bidirectional distortions of perceived duration. Presenting adapting and test durations to the same vs different eyes utilises the visual system's anatomical progression from monocular, pre-cortical neurons to their binocular, cortical counterparts. Duration aftereffects exhibited robust inter-ocular transfer alongside a small but significant contribution from monocular mechanisms. We then used novel stimuli which provided duration information that was invisible to monocular neurons. These stimuli generated robust duration aftereffects which showed partial selectivity for adapt-test changes in retinal disparity. Our findings reveal distinct duration encoding mechanisms at monocular, depth-selective and depth-invariant stages of the visual hierarchy.

Feature-based attentional selection affects the perceived duration of a stimulus having two superposed patterns

The perceived duration of a visual event is highly related to stimulus attributes. It is well known that a moving stimulus appears to last longer than a static one does. Previous studies have demonstrated that the time dilation in a moving stimulus can be influenced by perceived motion, rather than by mere physical motion, and that a faster motion appears to last longer than a slower one does. However, whether a top-down attentional set for the feature value can modulate the time dilation in a moving stimulus when two different visual patterns coexist within the same region of the visual field is still unknown. To test this, in Experiment 1, we presented a moving and a static random-dot pattern simultaneously within the same region, and instructed the observer to attend to one of these two patterns. The results demonstrate that perceived duration was longer when attention was directed to the moving, rather than static pattern, although both patterns physically coexisted at the same time and place and for the same duration. In Experiment 2, slow and/or fast moving patterns were presented at the same time and place, and again, feature-based attentional selection affected the perceived duration of the identical physical display. These results suggest that attention to a moving stimulus is an essential factor that determines the time dilation in a moving stimulus. This study revealed that feature-based attention, as opposed to location-based attention, plays an important role in motion-induced time dilation.

Attention Gates the Selective Encoding of Duration

The abundance of temporal information in our environment calls for the effective selection and utilization of temporal information that is relevant for our behavior. Here we investigated whether visual attention gates the selective encoding of relevant duration information when multiple sources of duration information are present. We probed the encoding of duration by using a duration-adaptation paradigm. Participants adapted to two concurrently presented streams of stimuli with different durations, while detecting oddballs in one of the streams. We measured the resulting duration after-effect (DAE) and found that the DAE reflects stronger relative adaptation to attended durations, compared to unattended durations. Additionally, we demonstrate that unattended durations do not contribute to the measured DAE. These results suggest that attention plays a crucial role in the selective encoding of duration: attended durations are encoded, while encoding of unattended durations is either weak or absent.

Rate after-effects fail to transfer cross-modally: Evidence for distributed sensory timing mechanisms

Accurate time perception is critical for a number of human behaviours, such as understanding speech and the appreciation of music. However, it remains unresolved whether sensory time perception is mediated by a central timing component regulating all senses, or by a set of distributed mechanisms, each dedicated to a single sensory modality and operating in a largely independent manner. To address this issue, we conducted a range of unimodal and cross-modal rate adaptation experiments, in order to establish the degree of specificity of classical after-effects of sensory adaptation. Adapting to a fast rate of sensory stimulation typically makes a moderate rate appear slower (repulsive after-effect), and vice versa. A central timing hypothesis predicts general transfer of adaptation effects across modalities, whilst distributed mechanisms predict a high degree of sensory selectivity. Rate perception was quantified by a method of temporal reproduction across all combinations of visual, auditory and tactile senses. Robust repulsive after-effects were observed in all unimodal rate conditions, but were not observed for any cross-modal pairings. Our results show that sensory timing abilities are adaptable but, crucially, that this change is modality-specific - an outcome that is consistent with a distributed sensory timing hypothesis.

Object size determines the spatial spread of visual time

A key question for temporal processing research is how the nervous system extracts event duration, despite a notable lack of neural structures dedicated to duration encoding. This is in stark contrast with the orderly arrangement of neurons tasked with spatial processing. In this study, we examine the linkage between the spatial and temporal domains. We use sensory adaptation techniques to generate after-effects where perceived duration is either compressed or expanded in the opposite direction to the adapting stimulus' duration. Our results indicate that these after-effects are broadly tuned, extending over an area approximately five times the size of the stimulus. This region is directly related to the size of the adapting stimulus-the larger the adapting stimulus the greater the spatial spread of the after-effect. We construct a simple model to test predictions based on overlapping adapted versus non-adapted neuronal populations and show that our effects cannot be explained by any single, fixed-scale neural filtering. Rather, our effects are best explained by a self-scaled mechanism underpinned by duration selective neurons that also pool spatial information across earlier stages of visual processing.

Duration Aftereffect Depends on the Duration of Adaptation

It has been widely demonstrated that a prolonged adaptation to a relatively long or short stimulus leads to a robust repulsive duration aftereffect. However, little is known about the rapid adaptation to stimulus duration. In this study, we investigated whether the duration aftereffect could also be induced by short-term adaptation to stimuli of both sub- and supra-second durations. To control for the internal reference for duration judgment, participants were adapted to a stimulus of medium duration, and then tested with both longer and shorter stimuli. We found that the duration aftereffect was only observed after long-term adaptation to stimuli of both sub- and supra-second durations, which suggests that the exposure time to the adaptor is a fundamental factor in determining the duration aftereffect. Our findings offer further evidence of the duration aftereffect, which in this study was dissociated from the anchor effect and high-level aftereffects.

Perceived Duration Increases with Contrast, but Only a Little

Recent adaptation studies provide evidence for early visual areas playing a role in duration perception. One explanation for the pronounced duration compression commonly found with adaptation is that it reflects adaptation-driven stimulus-specific reduction in neural activity in early visual areas. If this level of stimulus-associated neural activity does drive duration, then we would expect a strong effect of contrast on perceived duration as electrophysiological studies shows neural activity in early visual areas to be strongly related to contrast. We employed a spatially isotropic noise stimulus where the luminance of each noise element was independently sinusoidally modulated at 4 Hz. Participants matched the perceived duration of a high (0.9) or low (0.1) contrast stimulus to a previously presented standard stimulus (600 ms, contrast = 0.3). To achieve perceptually equivalent durations, the low contrast stimulus had to be presented for longer than the high contrast stimulus. This occurred when we controlled for stimulus size and when we adjusted for individual differences in perceived temporal frequency. Further, we show that the effect cannot be explained by shifts in perceived onset and offset and is not explained by a simple contrast-driven response bias. The direction of our results is clearly consistent with the idea that level of neural activity drives duration. However, the magnitude of the effect (~10% duration difference over a 0.9-0.1 contrast reduction) is in marked contrast to the larger duration distortions that can be found with repetition suppression and the oddball effect; particularly when these may be associated with smaller differences in neural activity than that expected from our contrast difference. Taken together, these results indicate that level of stimulus-related neural activity in early visual areas is unlikely to provide a general mechanism for explaining differences in perceived duration.

An investigation of the spatial selectivity of the duration after-effect

Adaptation to the duration of a visual stimulus causes the perceived duration of a subsequently presented stimulus with a slightly different duration to be skewed away from the adapted duration. This pattern of repulsion following adaptation is similar to that observed for other visual properties, such as orientation, and is considered evidence for the involvement of duration-selective mechanisms in duration encoding. Here, we investigated whether the encoding of duration - by duration-selective mechanisms - occurs early on in the visual processing hierarchy. To this end, we investigated the spatial specificity of the duration after-effect in two experiments. We measured the duration after-effect at adapter-test distances ranging between 0 and 15° of visual angle and for within- and between-hemifield presentations. We replicated the duration after-effect: the test stimulus was perceived to have a longer duration following adaptation to a shorter duration, and a shorter duration following adaptation to a longer duration. Importantly, this duration after-effect occurred at all measured distances, with no evidence for a decrease in the magnitude of the after-effect at larger distances or across hemifields. This shows that adaptation to duration does not result from adaptation occurring early on in the visual processing hierarchy. Instead, it seems likely that duration information is a high-level stimulus property that is encoded later on in the visual processing hierarchy.

Multiple channels of visual time perception

The proposal that the processing of visual time might rely on a network of distributed mechanisms that are vision-specific and timescale-specific stands in contrast to the classical view of time perception as the product of a single supramodal clock. Evidence showing that some of these mechanisms have a sensory component that can be locally adapted is at odds with another traditional assumption, namely that time is completely divorced from space. Recent evidence suggests that multiple timing mechanisms exist across and within sensory modalities and that they operate in various neural regions. The current review summarizes this evidence and frames it into the broader scope of models for time perception in the visual domain.

A single mechanism account of duration and rate processing via the pacemaker-accumulator and beat frequency models

Time is an essential dimension of our environment that allows us to extract meaningful information about speed of movement, speech, motor actions and fine motor control. Traditionally, models of time have tried to quantify how the brain might process the duration of an event. The most commonly cited are the pacemaker-accumulator model and the beat frequency model of interval timing, which explain how duration is perceived, represented and encoded. Here we posit such models as providing a powerful tool for simultaneously extracting, representing and encoding stimulus rate information. That is, any model that can process duration has all the information needed to code stimulus rate. We explore different processing strategies which would enable rate to be read off from both the pacemaker-accumulator and beat frequency model of interval timing. Finally we explore open questions that, when answered, will shed light upon potential mechanisms for duration and rate estimation.

Duration Adaptation Occurs Across the Sub- and Supra-Second Systems

After repetitive exposure to a stimulus of relatively short duration, a subsequent stimulus of long duration is perceived as being even longer, and after repetitive exposure to a stimulus of relatively long duration, a subsequent stimulus of short duration is perceived as being even shorter. This phenomenon is called duration adaptation, and has been reported only for sub-second durations. We examined whether duration adaptation also occurs for supra-second durations (Experiment 1) and whether duration adaptation occurs across sub- and supra-second durations (Experiment 2). Duration adaptation occurred not only for sub-second durations, but also for supra-second durations and across sub- and supra-second durations. These results suggest that duration adaptation involves an interval-independent system or two functionally related systems that are associated with both the sub- and supra-second durations.

Single-material solvent-sensitive actuator from poly(ionic liquid) inverse opals based on gradient dewetting

A novel and reversible single-material solvent-sensitive actuator was developed from poly(ionic liquid) inverse opals based on gradient wetting/dewetting process.

Visual duration aftereffect is position invariant

Adaptation to relatively long or short sensory events leads to a negative aftereffect, such that the durations of the subsequent events within a certain range appear to be contracted or expanded. The distortion in perceived duration is presumed to arise from the adaptation of duration detectors. Here, we focus on the positional sensitivity of those visual duration detectors by exploring whether the duration aftereffect may be constrained by the visual location of stimuli. We adopted two different paradigms, one that tests for transfer across visual hemifields, and the other that tests for simultaneous selectivity between visual hemifields. By employing these experimental designs, we show that the duration aftereffect strongly transfers across visual hemifields and is not contingent on them. The lack of position specificity suggests that duration detectors in the visual system may operate at a relatively later stage of sensory processing.