Search

Background: Recent evidence in systems neuroscience suggests that lighting conditions affect the whole chain of brain processing, from retina to high-level cortical networks, for perceptual and cognitive function. Here, visual adaptation levels to three different environmental lighting conditions, (1) darkness, (2) daylight, and (3) prolonged exposure to very bright light akin to sunlight, were simulated in lab to investigate the effects of light adaptation levels on classic cases of subjective contrast, assimilation, and contrast-induced relative depth in achromatic, i.e., ON–OFF pathway mediated visual configurations. Methods: After adaptation/exposure to a given lighting condition, configurations were shown in grouped and ungrouped conditions in random order to healthy young humans in computer-controlled two-alternative forced-choice procedures that consisted of deciding, as quickly as possible, which of two background patterns in a given configuration of achromatic contrast appeared lighter, or which of two foreground patterns appeared to stand out in front, as if it were nearer to the observer. Results: We found a statistically significant effect of the adaptation levels on the consciously perceived subjective contrast (F(2,23) = 20.73; p < 0.001) and the relative depth (F(2,23) = 12.67; p < 0.001), a statistically significant interaction between the adaptation levels and the grouping factor (F(2,23) = 4.73; p < 0.05) on subjective contrast, and a statistically significant effect of the grouping factor on the relative depth (F(2,23) = 13.71; p < 0.01). Conclusions: Visual adaption to different lighting conditions significantly alters the conscious perception of contrast and assimilation, classically linked to non-linear functional synergies between ON and OFF processing channels in the visual brain, and modulates the repeatedly demonstrated effectiveness of luminance contrast as a depth cue; the physically brighter pattern regions in the configurations are no longer consistently perceived as nearer to a conscious observer under daylight and extreme bright light adapted (rod-saturated) conditions. [ABSTRACT FROM AUTHOR]

When information about an event is perceptually occluded, individuals might recognize that the event might be present but that they cannot detect it because of the occluder. In such situations, an individual should continue to believe that the prevailing contingencies have not changed. This is in stark contrast to conditions where an expected event is explicitly absent, which should lead the individual to update their contingency knowledge. In an autoshaping procedure, we tested whether pigeons can discriminate conditions of perceptual ambiguity from perceptual certainty. Pigeons first learned to peck at two Pavlovian visual cues, followed by extinction of one of the cues. During extinction, the feeder was occluded by a metal shield for pigeons in Group Occluded, while the metal shield was placed next to but not covering the feeder for pigeons in Group Un-Occluded. On a final test with the metal shield removed, pigeons in Group Un-occluded pecked less at the extinguished cue than at the un-extinguished cue; while pigeons in Group Occluded pecked at an equally high rate to both cues. These results replicate in pigeons similar results reported in rats by Waldmann et al. (2012), and show that pigeons are able to discriminate conditions of certainty from conditions of ambiguity.

Spontaneous eye blinks are modulated around perceptual events. Our previous study, using a visual ambiguous stimulus, indicated that blink probability decreases before a reported perceptual switch. In the current study, we tested our hypothesis that an absence of blinks marks a time in which perceptual switches are facilitated in‐ and outside the visual domain. In three experiments, presenting either a visual motion quartet in light or darkness or a bistable auditory streaming stimulus, we found a co‐occurrence of blink rate reduction with increased perceptual switch probability. In the visual domain, perceptual switches induced by a short interruption of visual input (blank) allowed an estimate of the timing of the perceptual event with respect to the motor response. This provided the first evidence that the blink reduction was not a consequence of the perceptual switch. Importantly, by showing that the time between switches and the previous blink was significantly longer than the inter‐blink interval, our studies allowed to conclude that perceptual switches did not happen at random but followed a prolonged period of nonblinking. Correspondingly, blink rate and switch rate showed an inverse relationship. Our study supports the idea that the absence or presence of blinks maps perceptual processes independent of the sensory modality. [ABSTRACT FROM AUTHOR]

In biological motion perception, movements of several point lights can evoke a vivid impression of living animals, including humans. Recent studies have reported that male point-light walkers tend to be perceived as facing toward the viewer more than female walkers, and have hypothesized that the gender-based facing bias arises from motion signals. The purpose of this study was to test this hypothesis under experimental conditions where binocular disparity was added to biological motion stimuli. In the two experiments reported here, participants were presented with disparity-defined female and male point-light figures facing toward or away from the viewer. In Experiment 1, we measured "facing-the-viewer" responses in upright and inverted walker configurations. It was found that the facing bias was greater for the male walker than for the female walker in most disparity magnitudes, regardless of walker inversion. In Experiment 2, the walker stimuli were replaced by static snapshots of the walkers. The results showed that the facing bias did not differ between the female and male static figures. These results suggest that motion signals play an important role in producing the gender-based facing bias, even when binocular disparity is added to biological motion stimuli. [ABSTRACT FROM AUTHOR]

In the cognitive neuroscience of consciousness, participants have commonly been instructed to report their conscious content. This, it was claimed, risks confounding the neural correlates of consciousness (NCC) with their preconditions, i.e., allocation of attention, and consequences, i.e., metacognitive reflection. Recently, the field has therefore been shifting towards no-report paradigms. No-report paradigms draw their validity from a direct comparison with no-report conditions. We analyze several examples of such comparisons and identify alternative interpretations of their results and/or methodological issues in all cases. These go beyond the previous criticism that just removing the report is insufficient, because it does not prevent metacognitive reflection. The conscious mind is fickle. Without having much to do, it will turn inward and switch, or timeshare, between the stimuli on display and daydreaming or mind-wandering. Thus, rather than the NCC, no-report paradigms might be addressing the neural correlates of conscious disengagement. This observation reaffirms the conclusion that no-report paradigms are no less problematic than report paradigms. [ABSTRACT FROM AUTHOR]

Stimulus statistics can induce expectations that in turn can influence multisensory perception. In three experiments, we manipulate perceptual history by biasing stimulus statistics and examined the effect of implicit expectations on the perceptual resolution of a bistable visual stimulus that is modulated by sound. First, we found a general effect of expectation such that responses were biased in line with the biased statistics and interpret this as a bias towards an implicitly expected outcome. Second, expectation did not influence the perception of all types of stimuli. In both Experiment 1 and Experiment 2, integrated audio-visual stimuli were affected by expectation but visual-only and unintegrated audio-visual stimuli were not. In Experiment 3 we examined the sensory versus interpretational effects of expectation and found that contrary to our predictions, an expectation of audio-visually integrated stimuli was associated with impaired multisensory integration compared to visual-only or unintegrated audio-visual stimuli. Our findings suggest that perceptual experience implicitly creates expectations that influence multisensory perception, which appear to be about perceptual outcomes rather than sensory stimuli. Finally, in the case of resolving perceptual ambiguity, the expectation effect is an effect on cognitive rather than sensory processes. [ABSTRACT FROM AUTHOR]

Introduction: Auditory verbal hallucinations (AVH) are a cardinal symptom of schizophrenia but are also reported in the general population without need for psychiatric care. Previous evidence suggests that AVH may reflect an imbalance of prior expectation and sensory information, and that altered salience processing is characteristic of both psychotic and non-clinical voice hearers. However, it remains to be shown how such an imbalance affects the categorisation of vocal emotions in perceptual ambiguity. Methods: Neutral and emotional nonverbal vocalisations were morphed along two continua differing in valence (anger; pleasure), each including 11 morphing steps at intervals of 10%. College students (N = 234) differing in AVH proneness (measured with the Launay-Slade Hallucination Scale) evaluated the emotional quality of the vocalisations. Results: Increased AVH proneness was associated with more frequent categorisation of ambiguous vocalisations as 'neutral', irrespective of valence. Similarly, the perceptual boundary for emotional classification was shifted by AVH proneness: participants needed more emotional information to categorise a voice as emotional. Conclusions: These findings suggest that emotional salience in vocalisations is dampened as a function of increased AVH proneness. This could be related to changes in the acoustic representations of emotions or reflect top-down expectations of less salient information in the social environment. [ABSTRACT FROM AUTHOR]

In the cognitive neuroscience of consciousness, participants have commonly been instructed to report their conscious content. This, it was claimed, risks confounding the neural correlates of consciousness (NCC) with their preconditions, i.e., allocation of attention, and consequences, i.e., metacognitive reflection. Recently, the field has therefore been shifting towards no-report paradigms. No-report paradigms draw their validity from a direct comparison with no-report conditions. We analyze several examples of such comparisons and identify alternative interpretations of their results and/or methodological issues in all cases. These go beyond the previous criticism that just removing the report is insufficient, because it does not prevent metacognitive reflection. The conscious mind is fickle. Without having much to do, it will turn inward and switch, or timeshare, between the stimuli on display and daydreaming or mind-wandering. Thus, rather than the NCC, no-report paradigms might be addressing the neural correlates of conscious disengagement. This observation reaffirms the conclusion that no-report paradigms are no less problematic than report paradigms.

Musical syntax has been studied mainly in terms of “syntactic irregularity” in harmonic/melodic sequences. However, “perceptual ambiguity” referring to the uncertainty of judgment/classification of presented stimuli can in addition be involved in our musical stimuli using three different chord sequences. The present study addresses how “syntactic irregularity” and “perceptual ambiguity” on musical syntax are dissociated, in terms of effective connectivity between the bilateral inferior frontal gyrus (IFGs) and superior temporal gyrus (STGs) by linearized time-delayed mutual information (LTDMI). Three conditions were of five-chord sequences with endings of dominant to tonic, dominant to submediant, and dominant to supertonic. The dominant to supertonic is most irregular, compared with the regular dominant to tonic. The dominant to submediant of the less irregular condition is the most ambiguous condition. In the LTDMI results, connectivity from the right to the left IFG (IFG-LTDMI) was enhanced for the most irregular condition, whereas that from the right to the left STG (STG-LTDMI) was enhanced for the most ambiguous condition (p = 0.024 in IFG-LTDMI, p < 0.001 in STG-LTDMI, false discovery rate (FDR) corrected). Correct rate was negatively correlated with STG-LTDMI, further reflecting perceptual ambiguity (p = 0.026). We found for the first time that syntactic irregularity and perceptual ambiguity coexist in chord stimulus testing musical syntax and that the two processes are dissociated in interhemispheric connectivities in the IFG and STG, respectively.

Musical syntax has been studied mainly in terms of "syntactic irregularity" in harmonic/melodic sequences. However, "perceptual ambiguity" referring to the uncertainty of judgment/classification of presented stimuli can in addition be involved in our musical stimuli using three different chord sequences. The present study addresses how "syntactic irregularity" and "perceptual ambiguity" on musical syntax are dissociated, in terms of effective connectivity between the bilateral inferior frontal gyrus (IFGs) and superior temporal gyrus (STGs) by linearized time-delayed mutual information (LTDMI). Three conditions were of five-chord sequences with endings of dominant to tonic, dominant to submediant, and dominant to supertonic. The dominant to supertonic is most irregular, compared with the regular dominant to tonic. The dominant to submediant of the less irregular condition is the most ambiguous condition. In the LTDMI results, connectivity from the right to the left IFG (IFG-LTDMI) was enhanced for the most irregular condition, whereas that from the right to the left STG (STG-LTDMI) was enhanced for the most ambiguous condition (p = 0.024 in IFG-LTDMI, p < 0.001 in STG-LTDMI, false discovery rate (FDR) corrected). Correct rate was negatively correlated with STG-LTDMI, further reflecting perceptual ambiguity (p = 0.026). We found for the first time that syntactic irregularity and perceptual ambiguity coexist in chord stimulus testing musical syntax and that the two processes are dissociated in interhemispheric connectivities in the IFG and STG, respectively. [ABSTRACT FROM AUTHOR]

Esthetic experience is the result of the coordination of different cognitive processes. It has been widely reported that top-down processes of orienting of attention interact with bottom-up perceptual facilitation occurring during esthetic experience of artworks. Here we use whole-part ambiguity as a tool to test the effect of global and local prime on esthetic appreciation of complex visual artworks. To this aim 139 healthy young individuals completed an esthetic judgment of Arcimboldo's ambiguous artworks, which were preceded by a local or global prime. Their perceptual style was also assessed using a Navon task. We found that local prime significantly enhanced esthetic appreciation of ambiguous portraits. Also, we found that prime level interacted with individual's perceptual style: participants showing local perceptual style liked less ambiguous portraits when they were preceded by global prime. Overall, the present findings shed some light on the processes involved in esthetic experience, pointing towards a pivotal role of re-direction of attention towards perceptual features of the artworks and its interaction with individual factors, such as perceptual style. [ABSTRACT FROM AUTHOR]

When recognizing objects in our environments, we rely on both what we see and what we know. While older adults often display increased sensitivity to top-down influences of contextual information during object recognition, the locus of this increased sensitivity remains unresolved. To examine the effects of aging on the neural dynamics of bottom-up and top-down visual processing during rapid object recognition, we probed the differential effects of object perceptual ambiguity and scene context congruity on specific EEG event-related potential components indexing dissociable processes along the visual processing stream. Older adults displayed larger behavioral scene congruity effects than young adults. Older adults' larger visual P2 amplitudes to object perceptual ambiguity (as opposed to the scene congruity P2 effects in young adults) suggest continued resolution of perceptual ambiguity that interfered with scene congruity processing, while post-perceptual semantic integration (as indexed by N400) remained largely intact. These findings suggest that compromised bottom-up perceptual processing in healthy aging leads to an increased involvement of top-down processes to resolve greater perceptual ambiguity during object recognition. • Older adults display increased scene congruity effects during object recognition. • Young adults display increased visual P2 amplitudes to scene context incongruity. • Older adults display increased visual P2 amplitudes to object perceptual ambiguity. • Older adults may display increased top-down attention to perceptual ambiguity. [ABSTRACT FROM AUTHOR]

Background: Aesthetic experience begins through an intentional shift from automatic visual perceptual processing to an aesthetic state of mind that is evidently directed towards sensory experience. In the present study, we investigated whether portrait descriptions affect the aesthetic pleasure of both ambiguous (i.e., Arcimboldo’s portraits) and unambiguous portraits (i.e., Renaissance portraits). Method: A total sample of 86 participants were recruited and completed both a baseline and a retest session. In the retest session, we implemented a sample audio description for each portrait. The portraits were described by three types of treatment, namely global, local, and historical descriptions. Results: During the retest session, aesthetic pleasure was higher than the baseline. Both the local and the historical treatments improved the aesthetic appreciation of ambiguous portraits; instead, the global and the historical treatment improved aesthetic appreciation of Renaissance portraits during the retest session. Additionally, we found that the response times were slower in the retest session. Conclusion: taken together, these findings suggest that aesthetic preference was affected by the description of an artwork, likely due to a better knowledge of the painting, which prompts a more accurate (and slower) reading of the artwork.

People often make decisions in the face of ambiguous information, but it remains unclear how ambiguity is represented in the brain. We used three types of ambiguous stimuli and combined EEG and fMRI to examine the neural representation of perceptual decisions under ambiguity. We identified a late positive potential, the LPP, which differentiated levels of ambiguity, and which was specifically associated with behavioral judgments about choices that were ambiguous, rather than passive perception of ambiguous stimuli. Mediation analyses together with two further control experiments confirmed that the LPP was generated only when decisions are made (not during mere perception of ambiguous stimuli), and only when those decisions involved choices on a dimension that is ambiguous. A further control experiment showed that a stronger LPP arose in the presence of ambiguous stimuli compared to when only unambiguous stimuli were present. Source modeling suggested that the LPP originated from multiple loci in cingulate cortex, a finding we further confirmed using fMRI and fMRI-guided ERP source prediction. Taken together, our findings argue for a role of an LPP originating from cingulate cortex in encoding decisions based on task-relevant perceptual ambiguity, a process that may in turn influence confidence judgment, response conflict, and error correction.

When two eyes view dissimilar images, an observer typically reports ambiguous perception called binocular rivalry where the subjective perception fluctuates between the two inputs. This perceptual instability is often comprised of exclusive dominance of each image and a transition state called piecemeal state where the two images are intermingled in patchwork manner. Herein, we investigated the effects of multimodal association of sensory congruent pair, arbitrary pair, and reverse pair on piecemeal state in order to see how each level of association affects the ambiguous perception during binocular rivalry. To induce the multisensory associations, we designed a matching task with audiovisual feedback where subjects were required to respond according to given pairing rules. We found that explicit audiovisual associations can substantially affect the piecemeal state during binocular rivalry and that this congruency effect that reduces the amount of visual ambiguity originates primarily from explicit audiovisual association training rather than common sensory features. Furthermore, when one information is associated with multiple information, recent and preexisting associations work collectively to influence the perceptual ambiguity during rivalry. Our findings show that learned multimodal association directly affects the temporal dynamics of ambiguous perception during binocular rivalry by modulating not only the exclusive dominance but also the piecemeal state in a systematic manner. [ABSTRACT FROM AUTHOR]

A mobile robot equipped with 2D or 3D range sensors can move without changing its range readings if the perceived environment is poor in features. This is an ambiguous situation because a single perception can be associated with several robot poses. In consequence, robot localization capability is reduced. The problem we address is the quantification of this perceptual ambiguity as a property inherent to the system composed of the sensor and the static environment. Perceptual ambiguity is different from uncertainty of robot localization, although it is a cause of it. We propose an ambiguity model independent of the robot navigation system. It includes a probabilistic model of the indistinguishability of range readings, a generic range sensor model that supports laser and sonar sensors, and a generic range scanner model that supports any 2D or 3D range perception platform. Ambiguity is expressed in colour floor maps, which may be available before navigation starts, and where “bad localization” zones are easily detected. Experiments with virtual and real environments perceived from 2D laser and sonar scanners are presented, including the validation of the model with a real scans dataset. Results show how ambiguous zones are precisely determined, how to determine the optimum scanner orientation and aperture, and how to reduce the number of readings per scan for improving the robot's computational load and navigation speed. [ABSTRACT FROM AUTHOR]

The effects of age on the ability to resolve perceptual ambiguity are unknown, though it depends on frontoparietal attentional networks known to change with age. We presented the bistable Necker cube to 24 middle-aged and OAs (older adults; 56–78 years) and 20 YAs (younger adults; 18–24 years) under passive-viewing and volitional control conditions:Holdone cube percept andSwitchbetween cube percepts. During passive viewing, OAs had longer dominance durations (time spent on each percept) than YAs. In theHoldcondition, OAs were less able than YAs to increase dominance durations. In theSwitchcondition, OAs and YAs did not differ in performance. Dominance durations in either condition correlated with performance on tests of executive function mediated by the frontal lobes. Eye movements (fixation deviations) did not differ between groups. These results suggest that OAs’ reduced ability to hold a percept may arise from reduced selective attention. The lack of correlation of performance betweenHoldand executive-function measures suggests at least a partial segregation of underlying mechanisms. [ABSTRACT FROM PUBLISHER]

Relations between perceiving and knowing are well-worn problems that become visceral encounters with doubt and ambiguity in 'mixed-reality' environments. Locative narrative situates participants within stories where existent places function as the setting. Experiential confusion, between what is talked of as real and as imagined, is an often-reported phenomenon. Classical pragmatisms, and more broadly the writings of William James, understand the functioning of the body to be for the production of action, from which flows a naturalistic epistemology. for James, a thought's reference to an object occurs in the medium of an 'experienceable environment' and is a condition of it being known; what something is known-as is how it functions in a particular context and the consequences that follow. Contemporary pragmatists express varying positions on the function of representation in perception at different levels of cognitive awareness, and the extent to which intentionality is derivative of linguistic norms. In the locative narrative iOS application The Lost Index No.1 - Landscape with Figures strategies of directing participant attention, movement, cognitive tasks and propositional content are used to guide the interpretation of events. The complex environment that is created plays with the multi-stability of perception and the 'multi-stability meaning' between terms, resulting in ambiguity and an enhanced flexibility of interpretation. [ABSTRACT FROM AUTHOR]

Ambiguous figures attract observers because perception alternates between different interpretations while the sensory information stays unchanged. Understanding the underlying processes is difficult because the precise time instant of this endogenous reversal event needs to be known but is difficult to measure. Presenting ambiguous figures discontinuously and using stimulus onset as estimation of the reversal event increased temporal resolution and provided a series of well-confirmed EEG signatures. In the current EEG study we used this 'onset paradigm' for the first time with Boring's old/young woman stimulus. We found an early occipital event-related potential (ERP) correlate of reversals between the perception of the old woman and the perception of the young woman that fits well with previous ERP findings. This component was not followed by the often-reported occipito-parietal Reversal Negativity at 260 ms, but instead by an occipito-temporal N170, that is typically reported with face stimuli. We interpret our results as follows: ambiguity conflicts take place during processing of stimulus elements in early visual areas roughly 130 ms after stimulus onset. The disambiguation of these elements and their assembly to object 'gestalts' result from an interplay between early visual and object-specific brain areas in a temporal window between 130 and 260 ms after stimulus onset. In the particular case of Boring's old/young woman the processes of element disambiguation and gestalt construction are already finished at 170 ms and, thus, 90 ms earlier than in the case of ambiguous geometric figures (eg Necker cube or Schroeder staircase) or of binocular rivalrous gratings. [ABSTRACT FROM AUTHOR]

Are pictorial spaces evoked by intentionally ambiguous pictures internally coherent? If so, then we expect these to be idiosyncratic. We addressed this issue empirically. Three sheets from the second edition of Piranesi's Carceri d'Inventione were selected for the experiment. These were compared with a conventional landscape drawing (after a Capriccio by Guardi) as a base line. The pictorial spaces were probed by way of pairwise depth-order judgments. In each image about fifty landmarks were selected, thus yielding over a thousand binary depth-order judgments per image. From such a full set of pairwise comparisons one obtains a linear depth order. This linear order again yields postdictions for the individual pairwise judgments. Actual judgments differ from these postdictions, thereby yielding a convenient handle on the coherence of the pictorial space. Since the Piranesi Carceri are generally considered to be 'difficult', 'ambiguous' or 'labyrinthine', whereas a conven-tional landscape as the Guardi is designed for its well-defined depth structure, it is expected that they will give rise to very distinct degrees of coherence. This is indeed what we find. We studied the variation of coherence over observers and images in detail. The pictorial locations that are heavily involved in incoherent responses were identified, and the reason for their ambiguous nature traced in the structure of the depth cues provided by the artist (Piranesi). We speculate that the Carceri manage to strike just the right level of ambiguity (between total chaos and obvious structure) so as to render them visually attractive. [ABSTRACT FROM AUTHOR]

Abstract: A previous study has shown that diverting attention from binocular rivalry to a visual distractor task results in a slowing of rivalry alternation rate between simple orthogonal orientations. Here, we investigate whether the slowing of visual perceptual alternations will occur when attention is diverted to an auditory distractor task, and we extend the investigation by testing this for two kinds of binocular rivalry stimuli and for the Necker cube. Our results show that doing the auditory attention task does indeed slow visual perceptual alternations, that the slowing effect is a graded function of attentional load, and that the attentional slowing effect is less pronounced for grating rivalry than for house/face rivalry and for the Necker cube. These results are explained in terms of supramodal attentional resources modulating a high-level interpretative process in perceptual ambiguity, together with a role for feedback to early visual processes in the case of binocular rivalry. [Copyright &y& Elsevier]

Abstract: Binocular rivalry occurs when different images are presented one to each eye: the images are visible only alternately. Monocular rivalry occurs when different images are presented both to the same eye: the clarity of the images fluctuates alternately. Could both sorts of rivalry reflect the operation of a general visual mechanism for dealing with perceptual ambiguity? We report four experiments showing similarities between the two phenomena. First, we show that monocular rivalry can occur with complex images, as with binocular rivalry, and that the two phenomena are affected similarly by the size (Experiment 1) and colour (Experiment 2) of the images. Second, we show that the distribution of dominance periods during monocular rivalry has a gamma shape and is stochastic (Experiment 3). Third, we show that during periods of monocular-rivalry suppression, the threshold to detect a probe (a contrast pulse to the suppressed stimulus) is raised compared with during periods of dominance (Experiment 4). The threshold elevation is much weaker than during binocular rivalry, consistent with monocular rivalry’s weak appearance. We discuss other similarities between monocular and binocular rivalry, and also some differences, concluding that part of the processing underlying both phenomena is a general visual mechanism for dealing with perceptual ambiguity. [Copyright &y& Elsevier]

Reactive agents are generally believed to be incapable of coping with perceptual ambiguity (i.e., identical sensory states that require different responses). However, a recent finding suggests that reactive agents can cope with perceptual ambiguity in a simple model (Nolfi, 2002). This paper investigates to what extent reactive and nonreactive agents can cope with perception ambiguity, and which strategies are employed when doing so. A model of active categorical perception (called Acp) is introduced. In Acp, situated agents with different types of neurocontrollers are optimized to categorize objects by adaptively coordinating action and perception. Our experiments show that both nonreactive and reactive agents can cope with perceptual ambiguity. An analysis of the behavior reveals that nonreactive agents use their internal memory to cope with perceptual ambiguity, while reactive agents use the environment as an external memory to compensate for their lack of internal memory. We conclude that reactive agents can cope with perceptual ambiguity in the context of active categorical perception, and that they can organize their behavior according to stimuli that are no longer present, especially when they incorporate a nonlinear sensorimotor mapping. Moreover, we may conclude that sensory state-transition diagrams provide insight into the strategies employed by reactive agents to deal with perceptual ambiguity, and their use of the environment as an external memory. [ABSTRACT FROM AUTHOR]

Abstract: How can our percept spontaneously change while the observed object stays unchanged? This happens with ambiguous figures, like the Necker cube. Explanations favor either bottom–up factors in early visual processing, or top–down factors near awareness. The EEG has a high temporal resolution, so event related potentials (ERPs) may help to throw light on these alternative explanations. However, the precise point in time of neural correlates of perceptual reversal is difficult to estimate. We developed a paradigm that overcomes this problem and found an early (120ms) occipital ERP signal correlated with endogenous perceptual reversal. Parallels of ambiguous-figure-reversal to binocular-rivalry-reversals are explored. [Copyright &y& Elsevier]

Normally we experience the visual world as stable. Ambiguous figures provide a fascinating exception: On prolonged inspection, the “Necker cube” undergoes a sudden, unavoidable reversal of its perceived front-back orientation. What happens in the brain when spontaneously switching between these equally likely interpretations? Does neural processing differ between an endogenously perceived reversal of a physically unchanged ambiguous stimulus and an exogenously caused reversal of an unambiguous stimulus? A refined EEG paradigm to measure such endogenous events uncovered an early electrophysiological correlate of this spontaneous reversal, a negativity beginning at 160 ms. Comparing across nine electrode locations suggests that this component originates in early visual areas. An EEG component of similar shape and scalp distribution, but 50 ms earlier, was evoked by an external reversal of unambiguous figures. Perceptual disambiguation seems to be accomplished by the same structures that represent objects per se, and to occur early in the visual stream. This suggests that low-level mechanisms play a crucial role in resolving perceptual ambiguity. [ABSTRACT FROM AUTHOR]

Both self-motion and objects moving in our visual field generate visual motion by displacing images on the retina. Resolving this ambiguity may seem effortless but large-field visual-motion stimuli can yield perceptual rivalry between the real percept of object-motion and the illusory percept of self-motion (vection). We used functional magnetic resonance imaging to record brain activity in human observers exposed to constant-velocity roll-motion. This stimulus induced responses in areas reaching from calcarine to parieto-occipital and to ventral and lateral temporo-occipital cortex and the anterior insula. During vection, early motion-sensitive visual areas and vestibular parieto-insular cortex deactivated, whereas higher-order parieto- and temporo-occipital areas known to respond to optical flow retained identical activity levels. Within this sustained response, these latter areas displayed transient activations in response to each perceptual switch as identified in event-related analyses. Our results thus show that these areas are responsive to the type of visual motion stimulus and highly sensitive to its perceptual bistability. The only region to be more active during perceived self-motion was in, or close to, the cerebellar nodulus. This activation may correspond to the gain increase of torsional optokinetic nystagmus during vection and/or to changes in sensory processing related to the rotational percept. In conclusion, we identified neural correlates of perceiving self-motion from vision alone, i.e., in the absence of confirmatory vestibular or proprioceptive input. These functional properties preserve the organism''s ability to move accurately in its environment by relying on visual cues under conditions when the other spatial senses fail to provide such information. [Copyright &y& Elsevier]

Perceptual ambiguity is a state of thinking that disturbs the either-or mode of knowledge. It causes one to face with the condition of two possible correct knowledges. This state of thinking, however, might be advantageous and contributive positively. Robert Venturi's dictum both-and is just one example of taking the advantageous of this perceptual ambiguity. Taking one Jawanese corpus titled Serat Balewarna, this study tries to present the practice of either-or mode of knowledge in Jawa around the 1920-s. A critical examination upon its content shows that the rational-universal knowledge had only becomes one lethal weapon against the Jawanese architectural knowledge. Toward thee end of the examination, this paper proposes to locate the jawanese architecture in a state of perceptual ambiguity. This re-location will open the way to allow the Jawanese architectural knowledge enter the world of discourse of knowledge in architecture. Abstract in Bahasa Indonesia : Ambiguitas perseptual adalah sebuah keadaan berpikir yang memusingkan pengetahuan ini-itu (either-or), mengingat keadaan itu memaksa seseorang untuk memilih satu dari dua kebenaran pengetahuan. Dari sisi lain, ambiguitas perseptual ternyata dapat menjadi keadaan yang menguntungkan dan memberi sumbangan yang positif. Diktum Robert Venturi "yang ini - dan - yang itu" adalah salah satu contoh dari penggunaan keadaan itu dari segi keuntungan dan sumbangan positif bagi pengetahuan. Dengan mengambil salah satu naskah Jawa tentang bangunan yang berjudul Serat Balewarna, kajian ini mencoba untuk memperlhatkan praktek pengetahuan 'ini-atau-itu' di Jawa dalam kurun waktu 1920-an. Pemeriksaan kritis atas naskah tersebut menunjukkan bahwa pengetahuan rasional-universal ternyata menjadi senjata yang ampuh dalam mematikan pengetahuan arsitektur Jawa. Menjelang akhir kajian ini, dicoba pula untuk ditunjukkan bahwa keadaan "yang ini-atau-yang itu" dapat dimanfaatkan untuk mendapatkan keuntungan dan sumbangan pengetahuan yang tersendiri. Re-lokasi keadaan, dari merugikan menjadi menguntungkan ini, ternyata dapat digunakan untuk menempatkan pengetahuan arsitektur Jawa di lingkungan wacana pengetahuan arsitektur seumumnya. Kata kunci: Ambiguitas perseptual, pengetahuan arsitektur Jawa, wacana pengetahuan arsitektur.

Background: Aesthetic experience begins through an intentional shift from automatic visual perceptual processing to an aesthetic state of mind that is evidently directed towards sensory experience. In the present study, we investigated whether portrait descriptions affect the aesthetic pleasure of both ambiguous (i.e., Arcimboldo's portraits) and unambiguous portraits (i.e., Renaissance portraits). Method: A total sample of 86 participants were recruited and completed both a baseline and a retest session. In the retest session, we implemented a sample audio description for each portrait. The portraits were described by three types of treatment, namely global, local, and historical descriptions. Results: During the retest session, aesthetic pleasure was higher than the baseline. Both the local and the historical treatments improved the aesthetic appreciation of ambiguous portraits; instead, the global and the historical treatment improved aesthetic appreciation of Renaissance portraits during the retest session. Additionally, we found that the response times were slower in the retest session. Conclusion: taken together, these findings suggest that aesthetic preference was affected by the description of an artwork, likely due to a better knowledge of the painting, which prompts a more accurate (and slower) reading of the artwork. [ABSTRACT FROM AUTHOR]