Transformational Apparent Motion Research Articles

Endogenous attention biases transformational apparent motion based on high-level shape representations.

When two pre-existing, separated squares are connected by the sudden onset of a bar between them, viewers do not perceive the bar to appear all at once. Instead, they see an illusory morphing of the original squares over time. The direction of this transformational apparent motion (TAM) can be influenced by endogenous attention deployed before the appearance of the connecting bar. Here, we investigated whether the influence of endogenous attention on TAM results from operations over high-level feature-independent shape representations, or instead over lower level shape representations defined by specific visual features. To do so, we tested the influence of endogenous attention on TAM in first- and second-order displays, which shared common shapes but had different shape-defining attributes (luminance and texture contrast, respectively). In terms of both the magnitude of directional bias and timing, we found that endogenous attention exerted a similar influence on both first- and second-order objects. These results imply that endogenous attention biases the perceived direction of TAM by operating on high-level shape representations that are invariant to the low-level visual features that define them. Our results support a four-stage model of TAM, where a feature encoding stage passes a features-specific layout to a parsing stage that forms discrete, high-level meta-featural shapes, which are then matched and visually interpolated over time.

First- and second-order transformational apparent motion rely on common shape representations

When one figure is replaced with another that overlaps its spatial location, observers perceive an illusory, continuous shape change of the original object, a phenomenon known as transformational apparent motion (TAM). The current study investigated the extent to which TAM depends on a common, high-level shape representation that is independent of the shape-defining attribute. Specifically, we tested whether TAM is perceived similarly for both first- and second-order objects, defined by luminance and texture contrast, respectively. A compelling motion percept was observed in second-order TAM displays that was comparable to that seen in first-order TAM displays. Importantly, TAM for both stimulus classes showed the same pattern over a range of stimulus onset asynchronies. These results support the high-level shape account, indicating that TAM is driven by segmentation mechanisms that rely on high-level shape information rather than low-level visual characteristics.

Comparisons of flashILM, transformational apparent motion, and polarized gamma motion indicate these are three independent and separable illusions

Illusory line motion (ILM) refers to perceived motion in a bar when it is presented all at once. Explanations for ILM include low-level visual accounts, visual attention, and object tracking. These explanations tend to arise from studies using different protocols to induce ILM, based on the assumption that the same illusion is being generated. Using real motion in the same and in the opposite direction as the ILM quantifies the illusions from all protocols as the area between response curves for the left- and right-side inducers. This common measure enables testing of the assumption that two display configurations result in the same illusion. If there is a common underlying cause, an individual who shows a strong illusion in one situation should show a strong illusion in the other, but illusions that arise through different systems should not correlate. This approach has differentiated ILM induced by a flash (flashILM) from ILM induced by matching the bar to an attribute of the inducing stimuli (transformational apparent motion, TAM). The former is thought to reflect attention, while the latter is thought to reflect object processing. Low-level visual explanations are often offered based on ILM that occurs when the bar is adjacent to only a single inducer (polarized gamma motion, PGM) rather than between two stimuli (flashILM and TAM). The present study replicates the independence of flashILM and TAM and shows that neither is related to PGM, suggesting that all three explanations for ILM are warranted and that the debates in the literature are conflating at least three different illusions.

Flash-induced forward and reverse illusory line motion in offset bars.

Illusory line motion (ILM) refers to perception of motion in a bar that onsets or offsets all at once. When the bar onsets or offsets between two boxes after one of the boxes flashes, the bar appears to shoot out of the flashed box (flashILM). If the bar offsets during the flash, it appears to contract into the flashed box (reverse ILM; rILM). Onset bars do not show rILM. Moreover, rILM and flashILM are not correlated, indicating they are two different illusions. To date, rILM has only been studied using a 50-ms flash where the bar offsets 16.7 ms after flash onset. It is not clear if rILM is due to the 16.7-ms flash-bar-removal stimulus onset asynchrony (SOA) or due to the flash offsetting after the bar. The current studies explore these parameters to better understand the conditions that lead to rILM. The results suggest that flashILM is sensitive to the temporal interval between flash onset and bar offset, while rILM appears to arise when the flash offsets after the bar has been removed regardless of the temporal interval between flash onset and bar removal. These results are consistent with flashILM reflecting visual exogenous attention while rILM may reflect the low-level spreading of subthreshold activation radiating from the flashed box. The findings are incorporated into the recent work that suggests that the literature concerning ILM is possibly conflating a number of different illusions of line motion, including polarized gamma motion (PGM), transformational apparent motion (TAM), and exogenous attention induced motion (flashILM).

Transformational Apparent Motion is Driven by Figural Parsing, Not Low-Level Motion Signals

Transformational Apparent Motion is Driven by Figural Parsing, Not Low-Level Motion Signals

First and second order transformational apparent motion have similar temporal dynamics

First and second order transformational apparent motion have similar temporal dynamics

The Perception of History

The perception of shape, it has been argued, also often entails the perception of time. A cookie missing a bite, for example, is seen as a whole cookie that was subsequently bitten. It has never been clear, however, whether such observations truly reflect visual processing. To explore this possibility, we tested whether the perception of history in static shapes could actually induce illusory motion perception. Observers watched a square change to a truncated form, with a “piece” of it missing, and they reported whether this change was sudden or gradual. When the contours of the missing piece suggested a type of historical “intrusion” (as when one pokes a finger into a lump of clay), observers actually saw that intrusion occur: The change appeared to be gradual even when it was actually sudden, in a type of transformational apparent motion. This provides striking phenomenological evidence that vision involves reconstructing causal history from static shapes.

Extrastriate Visual Areas Integrate Form Features over Space and Time to Construct Representations of Stationary and Rigidly Rotating Objects.

When an object moves behind a bush, for example, its visible fragments are revealed at different times and locations across the visual field. Nonetheless, a whole moving object is perceived. Unlike traditional modal and amodal completion mechanisms known to support spatial form integration when all parts of a stimulus are simultaneously visible, relatively little is known about the neural substrates of the spatiotemporal form integration (STFI) processes involved in generating coherent object representations from a succession visible fragments. We used fMRI to identify brain regions involved in two mechanisms supporting the representation of stationary and rigidly rotating objects whose form features are shown in succession: STFI and position updating. STFI allows past and present form cues to be integrated over space and time into a coherent object even when the object is not visible in any given frame. STFI can occur whether or not the object is moving. Position updating allows us to perceive a moving object, whether rigidly rotating or translating, even when its form features are revealed at different times and locations in space. Our results suggest that STFI is mediated by visual regions beyond V1 and V2. Moreover, although widespread cortical activation has been observed for other motion percepts derived solely from form-based analyses [Tse, P. U. Neural correlates of transformational apparent motion. Neuroimage, 31, 766-773, 2006; Krekelberg, B., Vatakis, A., & Kourtzi, Z. Implied motion from form in the human visual cortex. Journal of Neurophysiology, 94, 4373-4386, 2005], increased responses for the position updating that lead to rigidly rotating object representations were only observed in visual areas KO and possibly hMT+, indicating that this is a distinct and highly specialized type of processing.

The shape of motion perception: Global pooling of transformational apparent motion

Transformational apparent motion (TAM) is a visual phenomenon highlighting the utility of form information in motion processing. In TAM, smooth apparent motion is perceived when shapes in certain spatiotemporal arrangements change. It has been argued that TAM relies on a separate high-level form-motion system. Few studies have, however, systematically examined how TAM relates to conventional low-level motion-energy systems. To this end, we report a series of experiments showing that, like conventional motion stimuli, multiple TAM signals can combine into a global motion percept. We show that, contrary to previous claims, TAM does not require selective attention, and instead, multiple TAM signals can be simultaneously combined with coherence thresholds reflecting integration across the entire stimulus area. This system is relatively weak, less tolerant to noise, and easily overridden when motion energy cues are sufficiently strong. We conclude that TAM arises from high-level form-motion information that enters the motion system by, at least, the stage of global motion pooling.

Global Pooling of Transformational Apparent Motion

Transformational apparent motion (TAM) is a relatively recently described visual phenomena highlighting the utility of form information in motion processing. In TAM, smooth apparent motion is perceived when shapes in certain spatiotemporal arrangements change. It has been argued that TAM relies on a separate high-level formmotion system, as certain spatial arrangements of TAM violate low-level motion energy models of vision. As yet, however, few studies have examined how TAM relates to the previously described motion system. We report a series of experiments showing that like, conventional motion stimuli, multiple TAM signals can combine into a global motion percept. After controlling for motion energy, we show that TAM appears to pool using a separate motion system than the motion energy system, that has less tolerance to noise. This system is relatively weak and is easily overridden when motion energy cues are sufficiently strong, but is not limited by attentional capacities. We conclude the ability to holistically integrate multiple TAM signals demonstrates this high-level form-motion information enters the motion system preceding the stage of global motion pooling.

Illusory line motion and transformational apparent motion during continuous flash suppression1

AbstractA static bar is perceived to dynamically extend from a peripheral cue (illusory line motion (ILM)) or from a part of another figure presented in the previous frame (transformational apparent motion (TAM)). We examined whether visibility for the cue stimuli affected these transformational motions. Continuous flash suppression, one kind of dynamic interocular masking, was used to reduce the visibility for the cue stimuli. Both ILM and TAM significantly occurred when the d' for cue stimuli was zero (Experiment 1) and when the cue stimuli were presented at subthreshold levels (Experiment 2). We discuss that higher‐order motion processing underlying TAM and ILM can be weakly but significantly activated by invisible visual information.

An intracranial event-related potential study on transformational apparent motion. Does its neural processing differ from real motion?

How the brain processes visual stimuli has been extensively studied using scalp surface electrodes and magnetic resonance imaging. Using these and other methods, complex gratings have been shown to activate the ventral visual stream, whereas moving stimuli preferentially activate the dorsal stream. In the current study, a first experiment assessed brain activations evoked by complex gratings using intracranial electroencephalography in 10 epileptic patients implanted with subdural electrodes. These stimuli of intermediate levels of complexity were presented in such a way that transformational apparent motion (TAM) was perceived. Responses from both the ventral and the dorsal pathways were obtained. The response characteristics of visual area 4 and the fusiform cortex were of similar amplitudes, suggesting that both ventral areas are recruited for the processing of complex gratings. On the other hand, TAM-induced responses of dorsal pathway areas were relatively noisier and of lower amplitudes, suggesting that TAM does not activate motion-specific structures to the same extent as does real motion. To test this hypothesis, we examined the activity evoked by TAM in comparison to the one produced by real motion in a patient implanted with the same subdural electrodes. Findings demonstrated that neural response to real motion was much stronger than that evoked by TAM, in both the primary visual cortex (V1) and other motion-sensitive areas within the dorsal pathway. These results support the conclusion that apparent motion, even if perceptually similar to real motion, is not processed in a similar manner.

Continuous perception of motion and shape across saccadic eye movements

Although our naïve experience of visual perception is that it is smooth and coherent, the actual input from the retina involves brief and discrete fixations separated by saccadic eye movements. This raises the question of whether our impression of stable and continuous vision is merely an illusion. To test this, we examined whether motion perception can "bridge" a saccade in a two-frame apparent motion display in which the two frames were separated by a saccade. We found that transformational apparent motion, in which an object is seen to change shape and even move in three dimensions during the motion trajectory, continues across saccades. Moreover, participants preferred an interpretation of motion in spatial, rather than retinal, coordinates. The strength of the motion percept depended on the temporal delay between the two motion frames and was sufficient to give rise to a motion-from-shape aftereffect, even when the motion was defined by a second-order shape cue ("phantom transformational apparent motion"). These findings suggest that motion and shape information are integrated across saccades into a single, coherent percept of a moving object.

FMRI reveals the neuronal substrate underlying form and motion processing in transformational apparent motion

fMRI reveals the neuronal substrate underlying form and motion processing in transformational apparent motion

Neural Correlates of Transformational Apparent Motion

Transformational apparent motion (TAM) arises when a shape that is abruptly flashed on and off next to a static shape of similar color or texture appears as a protrusion that extends and retracts smoothly from the static object. Here we report that the strength of the TAM percept can be predicted from the waveform of visual evoked potentials (VEPs) measured while observers rated their percepts. The VEPs at pattern onset and offset are maximally symmetric when the static inducer and the flashing patches of the display are of the same contrast. VEP symmetry is affected by how the two patches can be matched as a single surface and may reflect the relative contribution of different motion and object detection systems in visual cortex.

Neural correlates of transformational apparent motion

When a figure discretely and instantaneously changes its shape, observers typically do not perceive the abrupt transition between shapes that in fact occurs. Rather, a continuous shape change is perceived. Although this illusory “transformational apparent motion” (TAM) is a faulty construction of the visual system, it is not arbitrary. From the many possible shape changes that could have been inferred, usually just one is perceived because only one is consistent with the shape-based rules that the visual system uses to (1) segment figures from one another within a scene and (2) match figures to themselves across successive scenes. TAM requires an interaction between neuronal circuits that process form relationships with circuits that compute motion trajectories. In particular, this form–motion interaction must happen before TAM is perceived because the direction of perceived motion is dictated by form relationships among figures in successive images. The present fMRI study ( n = 19) provides the first evidence that both form (LOC, posterior fusiform gyrus) and motion (hMT+) processing areas are more active when TAM is perceived than in a control stimulus where it is not. Retinotopic areas ( n = 10), hMT+ ( n = 7), and LOC ( n = 7) were mapped in a subset of subjects. Results: There is greater BOLD response to TAM than to the control condition in V1 and all subsequent retinotopic areas, as well as in hMT+ and the LOC, suggesting that areas that process form interact with hMT+ to construct the perception of moving figures.

The evolution of the electroencephalographic response evoked by transformational apparent motion with age

The evolution of the electroencephalographic response evoked by transformational apparent motion with age

Do "Chinese and American see opposite apparent motions in a Chinese character"? Tse and Cavanagh (2000) replicated and revised

In a paper entitled “Chinese and Americans see opposite apparent motions in a Chinese character”, Tse and Cavanagh (2000) showed that when a Chinese character was presented stroke by stroke and the participants were asked to judge the motion direction of the last stroke (a horizontal line), the American participants perceived the direction predicted by transformational apparent motion, while the Chinese participants saw the opposite, writing direction. We demonstrate that Chinese readers do not always perceive the direction of writing; only when there are writing clues (such as a handwritten script presented in a writing sequence for a long enough duration) is the writing direction perceived. The top-down factors that make Chinese readers see the writing direction are the script and the stroke sequence, which are derived from writing experiences.

The duration of 3-d form analysis in transformational apparent motion.

Transformational apparent motion (TAM) occurs when a figure changes discretely from one configuration to another overlapping configuration. Rather than an abrupt shape change, the initial shape is perceived to transform smoothly into the final shape as if animated by a series of intermediate shapes. We find that TAM follows an analysis of form that takes 80-140 msec. Form analysis can function both at and away from equiluminance and can occur over contours defined by uniform regions as well as outlines. Moreover, the forms analyzed can be 3-D, resulting in motion paths that appear to smoothly project out from or into the stimulus plane. The perceived transformation is generally the one that involves the least change in the shape or location of the initial figure in a 3-D sense. We conclude that perception of TAM follows an analysis of 3-D form that takes approximately 100 msec. This stage of form analysis may be common to both TAM and second-order motion.

A neural model of high-level motion processing: Line motion and formotion dynamics

The percepts known variously as the line motion illusion, motion induction, and transformational apparent motion have attracted a great deal of experimental interest, since they sensitively probe interactions between preattentive and attentive vision processes. The present article develops a neural model that qualitatively explains essentially all the data reported thus far, and quantitatively simulates key illustrative percepts. The model suggests how these data arise from neural mechanisms of preattentive boundary and surface formation, long-range apparent motion, formotion interactions, and spatial attention. The boundary and surface formation processes model aspects of the interblob V1-->interstripe V2-->V4 and blob V1-->thin stripe V2-->V4 cortical processing streams, respectively. The long-range apparent motion process models aspects of the V1-->MT-->MST processing stream. An interstream V2-->MT form-motion interaction is proposed to allow the motion processing stream to track transient properties of emergent boundaries and filled-in surface colors from the form processing stream. It does so by generating motion waves using the long-range apparent motion process. This interstream interaction controls the formation of form-motion percepts, which are herein called formotion percepts. Other transients directly cause motion waves within the motion processing stream. All the data are attributed to properties of such motion waves. It is also suggested how bottom-up motion mechanisms can engage top-down attention as part of the motion capture process that solves the aperture problem. This interaction is proposed to occur between areas MT and MST. The model hereby explains how attention can be engaged even in percepts whose explanation can be derived from preattentive mechanisms.