Long-duration Stimuli Research Articles

Radiation of pain: Psychophysical evidence for a population coding mechanism in humans.

The spread of pain across body locations remains poorly understood but may provide important insights into the encoding of sensory features of noxious stimuli by populations of neurons. In this psychophysical experiment, we hypothesized that more intense noxious stimuli would lead to spread of pain, but more intense light stimuli would not produce perceptual radiation. Fifty healthy volunteers (27 females, 23 males, ages 14-44) participated in this study wherein noxious stimuli (43, 45, 47 and 49°C) were applied to glabrous (hand) and hairy skin (forearm) skin with 5s and 10s durations. Also, visual stimuli displayed on the target bodily area were utilized as a control. Participants provided pain (and light) spatial extent ratings as well as pain (and light) intensity ratings. In the extent rating procedure, participants adjusted the extent of the square displayed on the screen with the extent of pain (or light) which they experienced. Pain extent ratings showed statistically significant radiation of pain indicated by 12.42× greater spatial spread of pain (pain extent) than the area of the stimulation with 49°C (p<0.001), in contrast to visual ratings which closely approximated the size of the stimulus (1.22×). Pain radiation was more pronounced in hairy than glabrous skin (p<0.05) and was more pronounced with longer stimulus duration (p<0.001). Pain intensity explained only 14% of the pain radiation variability. The relative independence of the pain radiation from pain intensity indicates that distinct components of population coding mechanisms may be involved in the spatial representation of pain versus intensity coding.

The feasibility and technical aspects of trigemino-cervical reflex elicitation in humans under general anesthesia

ObjectiveTo analyze the feasibility, neurophysiological aspects, stimulation patterns, and topographic distribution of trigemino-cervical reflex (TCR) components in humans under general anesthesia. MethodsThis prospective observational study enrolled 20 participants who underwent posterior fossa surgery, surgical proceduresin thecraniovertebral junction,or spinal cord surgery. TCR responses were simultaneously recorded in the sternocleidomastoid (SCM) and trapezius muscles after electrical stimulation of the supraorbital and infraorbital nerves. TCR responses were recorded preoperatively and intraoperatively using single-pulse and multipulse (trains of 2–7 electrical stimuli) stimulation, respectively. Two stimulus duration patterns were evaluated: 0.2–0.5 ms and 0.5–1.0 ms. ResultsIntraoperatively, short- and long-latency TCR components were obtained in the SCM ipsilateral to the stimulation with variable recordability. Short-latency responses were the most commonly recorded components. A longer stimulus duration (0.5–1.0 ms) seems to favor the elicitation of TCR responses under general anesthesia. ConclusionsShort-latency components recorded in the SCM ipsilateral to the stimulation could be regularly elicited under general anesthesia when a larger stimulus duration (0.5–1.0 ms) was applied. SignificanceThis is the first study to demonstrate the elicitation of TCR components in humans under general anesthesia. This neurophysiological technique can potentially optimize intraoperative neurophysiological monitoring during brainstem surgery.

Auditory brainstem mechanisms likely compensate for self-imposed peripheral inhibition

Feedback networks in the brain regulate downstream auditory function as peripheral as the cochlea. However, the upstream neural consequences of this peripheral regulation are less understood. For instance, the medial olivocochlear reflex (MOCR) in the brainstem causes putative attenuation of responses generated in the cochlea and cortex, but those generated in the brainstem are perplexingly unaffected. Based on known neural circuitry, we hypothesized that the inhibition of peripheral input is compensated for by positive feedback in the brainstem over time. We predicted that the inhibition could be captured at the brainstem with shorter (1.5 s) than previously employed long duration (240 s) stimuli where this inhibition is likely compensated for. Results from 16 normal-hearing human listeners support our hypothesis in that when the MOCR is activated, there is a robust reduction of responses generated at the periphery, brainstem, and cortex for short-duration stimuli. Such inhibition at the brainstem, however, diminishes for long-duration stimuli suggesting some compensatory mechanisms at play. Our findings provide a novel non-invasive window into potential gain compensation mechanisms in the brainstem that may have implications for auditory disorders such as tinnitus. Our methodology will be useful in the evaluation of efferent function in individuals with hearing loss.

Temporal Dynamics of Neural Responses in Human Visual Cortex.

Neural responses to visual stimuli exhibit complex temporal dynamics, including subadditive temporal summation, response reduction with repeated or sustained stimuli (adaptation), and slower dynamics at low contrast. These phenomena are often studied independently. Here, we demonstrate these phenomena within the same experiment and model the underlying neural computations with a single computational model. We extracted time-varying responses from electrocorticographic recordings from patients presented with stimuli that varied in duration, interstimulus interval (ISI) and contrast. Aggregating data across patients from both sexes yielded 98 electrodes with robust visual responses, covering both earlier (V1-V3) and higher-order (V3a/b, LO, TO, IPS) retinotopic maps. In all regions, the temporal dynamics of neural responses exhibit several nonlinear features. Peak response amplitude saturates with high contrast and longer stimulus durations, the response to a second stimulus is suppressed for short ISIs and recovers for longer ISIs, and response latency decreases with increasing contrast. These features are accurately captured by a computational model composed of a small set of canonical neuronal operations, that is, linear filtering, rectification, exponentiation, and a delayed divisive normalization. We find that an increased normalization term captures both contrast- and adaptation-related response reductions, suggesting potentially shared underlying mechanisms. We additionally demonstrate both changes and invariance in temporal response dynamics between earlier and higher-order visual areas. Together, our results reveal the presence of a wide range of temporal and contrast-dependent neuronal dynamics in the human visual cortex and demonstrate that a simple model captures these dynamics at millisecond resolution.SIGNIFICANCE STATEMENT Sensory inputs and neural responses change continuously over time. It is especially challenging to understand a system that has both dynamic inputs and outputs. Here, we use a computational modeling approach that specifies computations to convert a time-varying input stimulus to a neural response time course, and we use this to predict neural activity measured in the human visual cortex. We show that this computational model predicts a wide variety of complex neural response shapes, which we induced experimentally by manipulating the duration, repetition, and contrast of visual stimuli. By comparing data and model predictions, we uncover systematic properties of temporal dynamics of neural signals, allowing us to better understand how the brain processes dynamic sensory information.

Lateral Inhibition: Are two hands better than one?

This study investigated the differences in amplitude discrimination capacity between two stimuli delivered to adjacent fingertips on the same hand (contralateral delivery) and stimuli delivered to two fingers on opposite hands (bilateral delivery). The measures were obtained in order to study the impact of lateral inhibition via interhemispheric connections on cortical centers on opposite sides of the somatosensory cortex in comparison to lateral inhibition occurring between adjacent cortical centers within the same hemisphere. Using the Cortical Metrics Brain Gauge™ device, amplitude discrimination capacity of 37 healthy subjects was assessed at several different durations, ranging from 40 to 500 msec, of vibrotactile stimulation delivered contralaterally and bilaterally. The results demonstrate a significant difference in amplitude discrimination capacity between the two conditions for stimulus duration of 200ms, with performance being better for the contralateral delivery of the stimuli than the bilateral condition for most tested durations. Task performance was roughly the same for the two conditions at the extremes of short (40ms) and long (500ms) stimulus durations. Amplitude discrimination capacity improved with longer stimulus durations in both bilateral and contralateral conditions. Though slight variation was observed at the level of each individual subject, overall, it is clear that local lateral inhibition plays a role in assessing the two stimuli delivered to the same hand that gives same-handed discrimination an advantage over two-handed discrimination. Additionally, the trends identified may be useful in guiding future experimentation that investigates clinical assessments of deficits in cortical processing that is mediated by callosal connections.

Can the stimulus processing assumptions of the sometimes-opponent-process (SOP) model explain instances of contextual learning?

One of the most persisting assertions in Allan Wagner's view of conditioning is that the environment or context in which significant events occur can develop an association with these events, more or less in the same way as conditioned and unconditioned stimuli become associated with each other. He was drawn to this idea by evidence of contextual fear conditioning, contingency effects, some instances of context-specificity of long-term habituation, and latent inhibition. From a theoretical point of view, however, homologizing contexts to conditioned stimuli is not as simple as it seems, especially when quantitative theories are involved, as is the case of Wagner's work. It might be, for instance, that contexts cannot be represented merely as long-duration conditioned stimuli, in which case, no net contextual learning can occur due to the context being less correlated with reinforcement than with nonreinforcement. In this article, we use Wagner's sometimes-opponent-process model of conditioning to comment on the quantitative nature of this challenge. Also, based on an idea sketched by Mazur and Wagner, we describe a set of quantitative strategies that might be usefully considered to solve this dilemma within the general framework of Wagner's theory. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Individual listener differences in azimuthal front-back reversals.

Thirty-two listeners participated in experiments involving five filtered noises when listeners kept their eyes open or closed, for stimuli of short or long duration, and for stimuli that were presented at random locations or in a largely rotational procession. Individual differences in the proportion of front-back reversals (FBRs) were measured. There were strong positive correlations between the proportion of FBRs for any one filtered noise, but not when FBRs were compared across different filtered-noise conditions. The results suggest that, for each individual listener, the rate of FBRs is stable for any one filtered noise, but not across filtered noises.

The impact of peripheral mechanisms on the precedence effect.

When two similar sounds are presented from different locations, with one (the lead) preceding the other (the lag) by a small delay, listeners typically report hearing one sound near the location of the lead sound source-this is called the precedence effect (PE). Several questions about the underlying mechanisms that produce the PE are asked. (1) How might listeners' relative weighting of cues at onset versus ongoing stimulus portions affect perceived lateral position of long-duration lead/lag noise stimuli? (2) What are the factors that influence this weighting? (3) Are the mechanisms invoked to explain the PE for transient stimuli applicable to long-duration stimuli? To answer these questions, lead/lag noise stimuli are presented with a range of durations, onset slopes, and lag-to-lead level ratios over headphones. Monaural, peripheral mechanisms, and binaural cue extraction are modeled to estimate the cues available for determination of perceived laterality. Results showed that all three stimulus manipulations affect the relative weighting of onset and ongoing cues and that mechanisms invoked to explain the PE for transient stimuli are also applicable to the PE, in terms of both onset and ongoing segments of long-duration, lead/lag stimuli.

Stepwise increasing sequential offsets cannot be used to deliver high thermal intensities with little or no perception of pain.

Offset analgesia (OA) is the disproportionate decrease in pain experience following a slight decrease in noxious heat stimulus intensity. We tested whether sequential offsets would allow noxious temperatures to be reached with little or no perception of pain. Forty-eight participants continuously rated their pain experience during trials containing trains of heat stimuli delivered by Peltier thermode. Stimuli were adjusted through either stepwise sequential increases of 2°C and decreases of 1°C or direct step increases of 1°C up to a maximum of 46°C. Step durations (1, 2, 3, or 6 s) varied by trial. Pain ratings generally followed presented temperature, regardless of step condition or duration. For 6-s steps, OA was observed after each decrease, but the overall pain trajectory was unchanged. We found no evidence that sequential offsets could allow for little pain perception during noxious temperature presentation.NEW & NOTEWORTHY Offset analgesia is the disproportionate decrease in pain experience following a slight decrease in noxious heat stimulus intensity. We tested whether sequential offsets would allow noxious temperatures to be reached with little or no perception of pain. We found little evidence of such overall analgesia. In contrast, we observed analgesic effects after each offset with long-duration stimuli, even with relatively low-temperature noxious stimuli.

Low-Frequency Repetitive Transcranial Magnetic Stimulation to Right Parietal Cortex Disrupts Perception of Briefly Presented Stimuli.

Right parietal cortex has recently been linked to the temporal resolution of attention. We therefore sought to investigate whether disruption to right parietal cortex would affect attention to visual stimuli presented for brief durations. Participants performed a visual discrimination task before and after 10 minutes repetitive transcranial magnetic stimulation (1 Hz) to right or central parietal cortex as well as 20 minutes after the second block of trials. Participants reported the spatial frequency of a masked Gabor patch presented for a brief duration of 60, 120, or 240 ms. We calculated error magnitudes by comparing accuracy to a guessing model. We then compared error magnitudes to blocks with no stimulation, producing a measure of baselined performance. Baselined performance was poorer at longer stimulus durations after right parietal than central parietal stimulation, suggesting that right parietal cortex is involved in attention to briefly presented stimuli, particularly in situations where rapid accumulation of visual evidence is needed.

Assessment of the H-reflex using two synchronized magnetic stimulators in order to increase stimulus durations: A comparison with electrical stimulation

Magnetic nerve stimulation (MNS) may be a less painful alternative to electrical nerve stimulation (ENS) for Hoffmann reflex (H-reflex) measurement, however standard MNS (sMNS) techniques utilize a short stimulus duration, thereby limiting its use for H-reflex assessment. This limitation may be partly overcome by coupling two magnetic stimulators to increase the pulse duration (coupled MNS: cMNS). The aim of this study was to test this assumption by comparing the H-reflex characteristics evoked by ENS, sMNS and cMNS.Thirteen healthy volunteers were tested with ENS and both MNS in the prone position. Maximal soleus H-reflex (Hmax) and M-wave (Mmax) amplitudes were measured to compute the Hmax/Mmax ratio. Hmax was evoked at rest and during both isometric submaximal (10%MVC) and maximal plantar-flexions (MVC).At rest, MNS techniques underestimated Hmax (ENS: 8.32 ± 2.73 mV; sMNS: 6.85 ± 2.29 mV; cMNS: 7.48 ± 2.23 mV; p < 0.05). In contrast, no difference was observed for Hmax/Mmax (ENS: 0.59 ± 0.17; sMNS: 0.45 ± 0.28; cMNS: 0.47 ± 0.29; p = 0.11). sMNS, cMNS and ENS similarly detected Hmax facilitation during MVC (ENS: +120 ± 248%; sMNS: +228 ± 350%; cMNS: +162 ± 180% of the rest value; p = 0.344).Owing to their shorter stimulus duration, both MNS techniques underestimated the Hmax compared to ENS. However, when the gold standard ENS technique cannot be used, coupled MNS may be recommended since it provides better H-reflex characteristic assessment than standard MNS due to its longer stimulus duration.

Pupillary Light Reflexes in Severe Photoreceptor Blindness Isolate the Melanopic Component of Intrinsically Photosensitive Retinal Ganglion Cells.

PurposePupillary light reflex (PLR) is driven by outer retinal photoreceptors and by melanopsin-expressing intrinsically photosensitive retinal ganglion cells of the inner retina. To isolate the melanopic component, we studied patients with severe vision loss due to Leber congenital amaurosis (LCA) caused by gene mutations acting on the outer retina.MethodsDirect PLR was recorded in LCA patients (n = 21) with known molecular causation and severe vision loss. Standard stimuli (2.5 log scot-cd.m−2; ∼13 log quanta.cm−2.s−1; achromatic full-field) with 0.1- or 5-second duration were used in all patients. Additional recordings were performed with higher luminance (3.9 log scot-cd.m−2) in a subset of patients.ResultsThe LCA patients showed no detectable PLR to the standard stimulus with short duration. With longer-duration stimuli, a PLR was detectable in the majority (18/21) of patients. The latency of the PLR was 2.8 ± 1.3 seconds, whereas normal latency was 0.19 ± 0.02 seconds. Peak contraction amplitude in patients was 1.1 ± 0.9 mm at 6.2 ± 2.3 seconds, considerably different from normal amplitude of 4.2 ± 0.4 mm at 3.0 ± 0.4 seconds. Recordings with higher luminance demonstrated that PLRs in severe LCA could also be evoked with short-duration stimuli.ConclusionsThe PLR in severe LCA patients likely represents the activation of the melanopic circuit in isolation from rod and cone input. Knowledge of the properties of the human melanopic PLR allows not only comparison to those in animal models but also serves to define the fidelity of postretinal transmission in clinical trials targeting patients with no outer retinal function.

Aging alters intraocular but not interocular foveal center surround contrast suppression.

Numerous previous studies have shown that healthy aging results in increased foveal center surround contrast suppression when the center and surround patterns are presented to both eyes. The mechanistic cause of this observation is not well established. Neurophysiological and psychophysical studies have shown that different mechanisms of parafoveal center surround suppression can be tapped by manipulating viewing conditions to present the center and surround to the same eye (intraocular viewing) or to different eyes (interocular viewing), or by manipulating stimulus parameters such as duration. Here, we tested intraocular and interocular foveal center surround contrast suppression for stimuli of 40 ms and 200 ms duration in 18 younger and 18 older adults. For both groups, foveal intraocular center surround contrast suppression decreased with longer stimulus duration whereas interocular surround suppression did not, confirming contributions from separate mechanisms to these forms of suppression. Intraocular center surround contrast suppression was increased in older adults compared to younger adults; however, interocular suppression was similar in both groups. Our results indicate that aging differentially affects distinct forms of suppression arising at various levels of the visual pathway.

How well do measures of the precedence effect based on clicks predict performance for long-duration stimuli?

Despite multiple reflections off nearby surfaces, listeners often localize sound sources based primarily upon the first arriving, direct sound. This is called the precedence effect. Much has been learned about the precedence effect using transient clicks, but the vast majority of everyday sounds are relatively long in duration. Recently, Pastore and Braasch (JASA, 2015) tested the effects of increased lag intensity on localization dominance for longer, 200-ms duration stimuli with 20-ms cosine-squared ramps. Assuming that interactions at the onset of lead-lag stimuli are primarily responsible for the precedence effect, it has been suggested that the binaural cues important to the precedence mechanism are the same for clicks and longer-duration noise stimuli. To test this hypothesis, we presented lead-lag stimuli composed of 1-ms, rectangular clicks, as well as 41-ms and the previously used 200-ms long noise bursts. Five, lead-lag delays between 1 and 5 ms were tested for lead/lag level differences of 0-, ...

Ocular vestibular evoked myogenic potentials elicited with vibration applied to the teeth

ObjectivesThis study investigated whether the method for eliciting vibration-induced oVEMPs could be improved by applying vibration directly to the teeth, and how vibration-induced oVEMP responses depend on the duration of the applied vibration. MethodsIn 10 participants, a hand-held shaker was used to present 100-Hz vibration tone pips to the teeth via a customised bite-bar or to other parts of the head. oVEMP potentials were recorded in response to vibration in three orthogonal directions and five stimulus durations (10–180ms). The oVEMP responses were analysed in terms of the peak latency onset, peak-to-peak amplitude, and the quality of the trace. ResultsVibration applied to the teeth via the bite-bar produced oVEMPs that were more consistent, of higher quality and of greater amplitude than those evoked by vibration applied to the head.Longer duration stimuli produced longer duration oVEMP responses.One cycle duration stimuli produced responses that were smaller in amplitude and lower quality than the longer stimulus durations. ConclusionsApplication of vibration via the teeth using a bite-bar is an effective means of producing oVEMPs.A 1-cycle stimulus is not optimal to evoke an oVEMP because it produces less robust responses than those of longer stimulus duration.A positive relationship between the duration of the stimulus and the response is consistent with the notion that the vibration-induced oVEMP is an oscillatory response to the motion of the head, rather than being a simple reflex response that occurs when the stimulus exceeds a threshold level of stimulation. SignificanceApplying acceleration to the teeth through a bite-bar elicits clearer oVEMP responses than direct application to other parts of the head and has potential to improve clinical measurements. A 100-Hz 1-cycle stimulus produces less robust oVEMP responses than longer 100-Hz stimuli.

Distortions of Time Perception during Critical Situations

Humans are good at estimating durations of time. The person's time perception is affected by emotion (Eiser, 2009). To allow for these predictions, an internal signal that provides the organism with a sense of time has to exist. An information-processing model of Scalar Expectancy Theory (SET) and its evolution into the neurobiologically plausible Striatal Beat-Frequency (SBF) theory, contemporaneously are the most accepted to explain this ability to perceive time (van Rijn, Gu & Meck, 2014). According to this theory initially developed by Gibbon et al, the “internal clock” is comprised of a pacemaker that emits pulses at a regular rate and a switch controls how many pulses enter into an accumulator, which stores the number of pulses during the event to be timed. With longer stimulus duration, more pulses are accumulated and consequently the higher the value of the time (Weber’s law) (Gibbon, 1977).

Crowding, grouping, timing

In crowding, target perception is deteriorated by flanking elements. For example, when a vernier is flanked by two lines of the same length, vernier offset discrimination strongly deteriorates. Interestingly, changing the color of the flankers can reduce crowding (uncrowding). Similarly, when the flanking lines are part of a cube, i.e., a good Gestalt, crowding is weak. Conversely, however, scrambling the lines of the cubes, i.e., a “bad” Gestalt, leads to strong crowding. We proposed that crowding is strong when target and flankers group (two-lines, scrambled cubes). Crowding is weak when the target ungroups from the flankers (two flanking lines with different color, cubes). Here, we show, first, that when target and flankers group (strong crowding), crowding is unaffected by stimulus duration. Two same-length flankers presented for 20 ms lead to similar performance as when presented for 150 ms. Second, in uncrowding with flankers of different color (and other basic feature differences), performance is again unaffected by stimulus duration. Third, in uncrowding with cubes, duration matters. For short durations (20 ms), crowding is strong and only for longer stimulus durations (from 120 ms on) does crowding decrease. We suggest that, for short durations, the brain cannot process the good Gestalt of the cubes. The representation of the cube’s lines is “unstructured”, as in the scrambled cubes, and hence crowding is strong. Interestingly, a short preview (20 ms duration) of only the cubes strongly reduces crowding, even when the preview is presented one second before the “crowded” stimulus. Our results suggest that uncrowding emerges in a slow, recurrent manner, with iconic memory playing an important role.

Stimulus duration and diversity do not reverse the advantage for superordinate‐level representations: the animal is seen before the bird

Basic-level categorization has long been thought to be the entry level for object representations. However, this view is now challenged. In particular, Macé et al. [M.J.-M. Macé et al. (2009) PLoS One, 4, e5927] showed that basic-level categorization (such as 'bird') requires a longer processing time than superordinate-level categorization (such as 'animal'). It has been argued that this result depends on the brief stimulus presentation times used in their study, which would degrade the visual information available. Here, we used a go/no-go paradigm to test whether the superordinate-level advantage could be observed with longer stimulus durations, and also investigated the impact of manipulating the target and distractor set heterogeneity. Our results clearly show that presentation time had no effect on categorization performance. Both target and distractor diversity influenced performance, but basic-level categories were never accessed faster or with higher accuracy than superordinate-level categories. These results argue in favor of coarse to fine visual processing to access perceptual representations.

Digoxin-Induced Reversible Dysfunction of the Cone Photoreceptors in Monkeys

To investigate functional alteration of the retina induced by digoxin in monkeys. Digoxin was intravenously administered to cynomolgus monkeys and standard full-field electroretinograms (ERGs) were serially recorded. In other digoxin-treated monkeys, the rod and cone a-waves to high-intensity flashes were obtained and analyzed by the a-wave fitting model (a-wave analysis). The following responses were also recorded: dark- and light-adapted responses to flashes of different intensities (dark- and light-adapted luminance responses), photopic ERG elicited by long-duration stimulus (ON-OFF response), and the photopic negative response (PhNR). Delayed b-wave was observed in all responses of the standard full-field ERGs; amplitude of the b-wave was increased in the rod response, but was decreased in the single-flash cone response and the 30-Hz flicker. These changes recovered gradually after elimination of digoxin from the blood. Digoxin enhanced and delayed the b-wave in the dark-adapted luminance-response analysis regardless of stimulus intensity. In the light-adapted luminance-response analysis, digoxin attenuated the a- and b-waves only at high and middle stimulus intensity, respectively. The a-wave analysis revealed selective decrease in the maximum response parameter (Rmax) in the cone a-wave. Both the b- and d-waves of the ON-OFF response were delayed. The selectively reduced Rmax in the cone a-wave indicated dysfunction of the cone photoreceptors in digoxin-treated monkeys. Meanwhile, the enhanced and delayed rod response suggested alteration of retinal components other than the cone photoreceptors. These results may contribute to the understanding of digoxin-induced visual disturbances in humans. It is suggested that the cone function is markedly, but not exclusively, affected in the retina of such patients.

Crowding and grouping: how much time is needed to process good Gestalt?

In crowding, perception of a target is deteriorated by flanking elements. Crowding is usually explained by pooling models where target and flanker signals are averaged. We show here that crowding is rather determined by grouping and good Gestalt. We determined offset discrimination thresholds for verniers with different flanker configurations. When the vernier was flanked by two vertical lines, thresholds increased. Surprisingly, when the two lines were part of two cubes, thresholds decreased. This finding cannot be explained by pooling models, which predict stronger crowding for the cubes because more irrelevant lines are pooled. We explain our results in terms of grouping. When the target groups with the flankers, performance deteriorates (two-lines condition). When the flankers are part of a good Gestalt, the target ungroups from the flankers and performance improves (cube condition). For short durations (20-80 ms), thresholds were similarly high for the lines and the cubes conditions. For longer stimulus durations (160, 320 and 640 ms), thresholds stayed high for the two-lines conditions but decreased for the cubes condition. Our results show that Good Gestalt in crowding emerges “slowly” within 160 ms.