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PubMed1992

Absence of smooth motion perception in color vision.

We have tested the behavioral evidence for a separation of the processing of color contrast from motion in the human visual system. Two different aspects of motion perception are examined; the identification of the direction of movement of a chromatic grating and the perception of smooth motion. The results show that color vision is at no great disadvantage in the identification of direction of movement, since this can be done at color contrasts quite close to detection threshold over a wide range of spatial and temporal frequencies. However, we find that subjects can identify direction without having the genuine perception of smooth motion. Smooth motion perception is revealed to be highly impaired since it is detected only at very high color contrasts and over a narrow range of spatial temporal conditions.

Color Perception↗

PubMed1996

Cyclopean motion perception produced by oscillations of size, disparity and location.

UNLABELLED: For cyclopean and monocularly-visible targets we measured psychophysical thresholds for perceptions produced by the following three stimuli: oscillations of disparity (DO), oscillations of size (SO) and oscillatory motion within the frontoparallel plane (FPO). RESULTS: thresholds for motion in depth perception produced by DO were similar for cyclopean and non-cyclopean targets over the entire 0.25-8 Hz frequency range investigated. Thresholds for perceiving motion in depth produced by SO were considerably (up to 2.5 times) higher for cyclopean targets than for monocularly-visible targets, as were thresholds for perceiving size oscillations. For both cyclopean and monocularly-visible target the perception of motion in depth could be canceled by pitting DO vs SO. Thresholds for perceiving FPO were similar to DO thresholds for the monocularly-visible target, but for the cyclopean targets FPO thresholds rose more steeply than DO thresholds for oscillation frequencies above 1 Hz. CONCLUSIONS: (1) for our subjects, the effective binocular stimulus for motion in depth perception is a rate of change of disparity; an interocular velocity difference is significant only to the extent that it produces a rate of change of disparity. (2) The sensations of motion in depth produced by DO and SO are qualitatively identical. (3) Neural signals produced by DO and SO converge onto a single neural mechanism that signals motion in depth.

Adaptation, Ocular↗

PubMed1996

Binocular eye movements caused by the perception of three-dimensional structure from motion.

We report that the perception of three-dimensional structure from monocular two-dimensional images changing over time--the kinetic depth effect (KDE)--can evoke binocular eye movements consistent with a three-dimensional percept. We used a monocular KDE stimulus that induced a vivid perception of a rigid three-dimensional sphere rotating in space. The gaze directions of both eyes were measured while observers pursued the motion of a patch on the surface of the perceived sphere as it went through a complete revolution. We found that the eyes converged when the patch was perceived on the front surface of the KDE sphere and diverged when the patch was perceived in the back. The pattern, magnitude and dynamics of binocular eye movements observed in the KDE experiment resembled those obtained when subjects viewed binocularly a light-emitting diode (LED) rotating in space and to the responses obtained with a dynamic stereogram simulating a rotating random dot sphere. Thus, the perception of three-dimensional structure from motion, stereopsis, or motion and stereopsis combined, were effective in guiding binocular eye movements.

Convergence, Ocular↗

PubMed2006

Measuring causal perception: connections to representational momentum?

In a collision between two objects, we can perceive not only low-level properties, such as color and motion, but also the seemingly high-level property of causality. It has proven difficult, however, to measure causal perception in a quantitatively rigorous way which goes beyond perceptual reports. Here we focus on the possibility of measuring perceived causality using the phenomenon of representational momentum (RM). Recent studies suggest a relationship between causal perception and RM, based on the fact that RM appears to be attenuated for causally 'launched' objects. This is explained by appeal to the visual expectation that a 'launched' object is inert and thus should eventually cease its movement after a collision, without a source of self-propulsion. We first replicated these demonstrations, and then evaluated this alleged connection by exploring RM for different types of displays, including the contrast between causal launching and non-causal 'passing'. These experiments suggest that the RM-attenuation effect is not a pure measure of causal perception, but rather may reflect lower-level spatiotemporal correlates of only some causal displays. We conclude by discussing the strengths and pitfalls of various methods of measuring causal perception.

Cognition↗

PubMedDate not supplied

Developmental deficits in social perception in autism: the role of the amygdala and fusiform face area.

Autism is a severe developmental disorder marked by a triad of deficits, including impairments in reciprocal social interaction, delays in early language and communication, and the presence of restrictive, repetitive and stereotyped behaviors. In this review, it is argued that the search for the neurobiological bases of the autism spectrum disorders should focus on the social deficits, as they alone are specific to autism and they are likely to be most informative with respect to modeling the pathophysiology of the disorder. Many recent studies have documented the difficulties persons with an autism spectrum disorder have accurately perceiving facial identity and facial expressions. This behavioral literature on face perception abnormalities in autism is reviewed and integrated with the functional magnetic resonance imaging (fMRI) literature in this area, and a heuristic model of the pathophysiology of autism is presented. This model posits an early developmental failure in autism involving the amygdala, with a cascading influence on the development of cortical areas that mediate social perception in the visual domain, specifically the fusiform "face area" of the ventral temporal lobe. Moreover, there are now some provocative data to suggest that visual perceptual areas of the ventral temporal pathway are also involved in important ways in representations of the semantic attributes of people, social knowledge and social cognition. Social perception and social cognition are postulated as normally linked during development such that growth in social perceptual skills during childhood provides important scaffolding for social skill development. It is argued that the development of face perception and social cognitive skills are supported by the amygdala-fusiform system, and that deficits in this network are instrumental in causing autism.

Amygdala↗

PubMed2005

Perception of opposite-moving dots in 3- to 5-month-old infants.

We conducted four experiments on the development of motion perception in a total of 109 3- to 5-month-old infants using motion stimuli consisting of opposite-moving dots. A psychophysical study showed that adult subjects perceived two global planes with opposite-moving dots, but this global perception collapsed when paired opposite-moving dots were located within 0.4 deg of one another (Qian, Andersen, & Adelson, 1994). We used this paired-dot stimulus as a non-target and the opponent motion stimulus as a target and examined target preference using methods based on forced-choice-preferential looking (Teller, 1979). In Experiment 1, we used 90 moving dots as stimuli. The results showed that 5-month-old infants had a significant preference for the targets but 4- and 3-month-olds did not. In Experiment 2, we used a small number of dots, and the results showed that 5-month-old infants did not prefer the target significantly. These results suggest that the preference for a target decreases according to the number of dots. In Experiment 3, we used opponent motion with long traveling length of the dots, and the results showed that all age groups, including 3-month-olds, had a preference for the moving targets. We showed that the preference observed in Experiment 3 was dependent not on local traveling length but on the global opponency. These results suggest that the perception of motion opponency based on a global motion cue emerges at 5 months of age (Experiments 1 and 2) and that the traveling length of the dots promote this perception (Experiments 3 and 4).

Child Development↗

PubMed2002

Haptic perception of parallelity in the midsagittal plane.

Previous studies [Perception 28 (1999) 1001; Perception 28 (1999) 781] on the haptic perception of parallelity on a horizontal plane showed that what subjects haptically perceive as being parallel deviates considerably from what is physically parallel. The deviations could be described with a subject-dependent orientation gradient in the left-right direction. The gradients found in the bimanual conditions were significantly larger (about 70%) than those in the unimanual conditions. The questions to be answered in the present study are the following: (1) Does the haptic perception of parallelity in the midsagittal plane also show systematic deviations from veridicality? (2) Are the unimanual and bimanual performances again quantitatively but not qualitatively different? The set-up consisted of a plate positioned in the midsagittal plane of the subject. The subject touched the right side of the plate with his/her right hand and the left side with the left hand. The results show again large systematic deviations. The major part of the deviations can be described by means of a subject-dependent orientation gradient in the vertical direction. The quantitative (but not qualitative) difference between the unimanual and the bimanual conditions is much larger in the midsagittal plane than in the horizontal plane.

Adolescent↗

PubMed2004

Acceleration perception and spatial distortion in a left unilateral neglect patient.

To explain relative leftward overextension in a line extension task by left unilateral neglect subjects, Bisiach et al. (1998) suggested that the representation of space is distorted--i.e., dilated towards the left side. If perception of the velocity of a moving stimulus is due to a calculation of the distance covered per unit time in representational space, then a stimulus with uniform linear motion should be perceived as decelerating when moving leftwards in the visual field of a subject with left unilateral neglect. We investigated the perception of acceleration in a patient with left unilateral neglect and spatial distortion (revealed as relative left overextension in a line extension task) using a task in which the stimuli were right and left moving targets with variable acceleration. The patient's ability to perceive acceleration was much lower (higher acceleration threshold) for leftward movements than rightward movements. Fourteen months later unilateral neglect had improved, and the relative left overextension and decreasing acceleration threshold for leftward movements were reduced. By contrast, alterations in the perception of acceleration for leftward movements were not found in a patient with left unilateral neglect and left underextension and in a patient with right brain damage and left hemianopia. These findings in one patient with left spatial unilateral neglect and a relative left overextension in a line extension task are consistent with the hypothesis that representational space is distorted, with a disproportionate leftward expansion, that affects perception of movement.

Aged↗

PubMed2000

Visual attention and metacontrast modify latency to perception in opposite directions.

In human observers, cue-induced visual attention ('bottom-up' transient focal attention) shortens the latency of perception. Metacontrast reduces the intensity of perception and can even obliterate it. We show that a close relationship exists between both, but that their effects are reversed: cue-induced visual attention not only shortens latency but also intensifies perception, and metacontrast not only lowers intensity of perception but also prolongs latency. A common neurophysiological mechanism for both is possible. Indirect evidence suggests that this could be a subthreshold modulation of neuronal thresholds by de- and hyperpolarization.

Adult↗

PubMed2003

Perception of dyadic relationship and emotional states in patients with affective disorder.

BACKGROUND: Previous research has shown that interpersonal processes play a significant role in the development and maintenance of affective disorders. In this study, this claim was further investigated by comparing the perception of the dyadic relationship and judgment of other's emotions in affective disorder patients. METHOD: The sample included 39 couples (n=39 couples) with one of the partners suffering from an affective disorder and currently either in an acute or remitted depressive state. All participants completed four instruments, measuring the perceived quality of the dyadic relationship and the perception of other's emotions as reflected by judgments of facial expressions line drawings. RESULTS: While the level of marital satisfaction was found to be lower in the acute than in the remitted group both for ill partners and their spouses, spouses in both the acute and remitted group tended to be more critical of their ill partners. Patients who were depressed judged facial expressions significantly less positively than did remitted patients. Judgments of negative emotions were highly correlated between partners in the acute group, but uncorrelated in the remitted group. Acutely depressed patients were less sensitive to invitation than remitted patients, while their spouses displayed the opposite pattern. CONCLUSION: The present results shed further light on the interpersonal dynamics between depressed patients and their spouses by underscoring differences between couples with a remitted vs. acutely depressed partner in their perception of the dyadic unit and their judgments of facial emotions. LIMITATIONS: Longitudinal research is needed, in which the same patients are tested during periods of remission and acute episodes, as well as research investigating the role of patient gender in the perception of facial expressions of emotions.

Adult↗

PubMed2003

Laterality and pattern persistence in bistable motion perception.

Bistable motion perception refers to two competing perceptions that can result when frames consisting of three elements are displaced laterally by one element. At short inter-frame intervals, the dominant percept is that the end elements in the display are moving; at long inter-frame intervals, perception is of all the elements moving coherently to the right or left. This research shows that coherent motion is more likely to be perceived when presentations are parafoveal than foveal and when they are to the right visual field than the left visual field. These results support the idea that visual pattern persistence is shorter in the parafovea than in the fovea, and shorter in the right than in the left visual field.

Adult↗

PubMed1998

Direction-specific impairment of motion perception and spatial orientation in downbeat and upbeat nystagmus in humans.

Downbeat and upbeat nystagmus can be classified as central vestibular syndromes in the vertical (pitch) plane of the vestibulo-ocular reflex (VOR) which are defined by ocular motor, perceptual, and postural manifestations. While the ocular motor syndrome was often studied investigations on the perceptual consequences for spatial orientation and motion perception are rare. Subjective visual straight ahead (SVA) and perception of object motion were measured in 11 patients with downbeat (n=6) and upbeat (n=5) nystagmus. Upward deviations of SVA (median +5.2 degrees) were found in downbeat nystagmus, and downward deviations (median -7.8 degrees) in upbeat nystagmus. SVA was deviated toward the slow phase of the vertical nystagmus in the pitch plane and associated with increased fore-aft body sway. Perception of object motion was more severely impaired for vertical (particularly for motion in the direction of slow nystagmus phases) than for horizontal directions in both downbeat and upbeat nystagmus. Impairment of motion perception in the vertical pitch plane of the VOR is beneficial to the extent that it alleviates disturbing oscillopsia due to the involuntary retinal slip. Thus, our findings confirm the hypothesis that downbeat and upbeat nystagmus reflect a central tone imbalance of the VOR in the vertical pitch plane with ocular motor, postural, and perceptual manifestations.

Adult↗

PubMed1999

A two-process theory of facial perception of emotions.

A two-process probabilistic theory of emotion perception based on a non-linear combination of facial features is presented. Assuming that the upper and the lower part of the face function as the building blocks at the basis of emotion perception, an empirical test is provided with fear and happiness as target emotions. Subjects were presented with prototypical fearful and happy faces and with computer-generated chimerical expressions that were a combination of happy and fearful. Subjects were asked to indicate the emotions they perceive using an extensive list of emotions. We show that some emotions require a conjunction of the two halves of a face to be perceived, whereas for some other emotions only one half is sufficient. We demonstrate that chimerical faces give rise to the perception of genuine emotions. The findings provide evidence that different combinations of the two halves of a fearful and a happy face, either congruent or not, do generate the perception of emotions other than fear and happiness.

Association Learning↗

PubMed1997

The influence of established and new antiepileptic drugs on visual perception. 1. A placebo-controlled, double-blind, single-dose study in healthy volunteers.

The influence of single oral dosages of carbamazepine (CBZ), valproic acid, vigabatrin (VGB), lamotrigine (LTG), gabapentin (GBP), and losigamone (LSG) on visual perception was investigated in ten healthy volunteers according to a double-blind, placebo-controlled, cross-over study design. The test battery comprised visual acuity, the Lanthony-D-15-désaturé colour perception test, increment, postadaptation and transient tritanopia threshold measurements, perception threshold assessment for monochromatic and chromatic gaussian dots, monochromatic gratings and gratings of differing spatial frequency, and critical flicker fusion tests with various stimuli. The only consistent and partly significant effects were seen after VGB and GBP. After VGB, increment, postadaptation and transient tritanopia thresholds and the critical flicker fusion increased, whereas GBP led to a somewhat converse profile. The other tests were not influenced consistently by any antiepileptic drug (AED). We conclude that: (i) gamma-amino-butyric acid-(GABA)-related properties as under the prototype drug VGB result in specific alterations of the transient tritanopia phenomenon which is consistent with the physiological hypothesis for this retinal paradigm based on extracellular recordings in primates. The possible mechanisms why VGB improved critical flicker fusion as the only AED in this trial are discussed. The profile of GBP indicates a unique mechanism of action. We have not observed specific influences on visual perception under AEDs which act mainly via alterations of ion membrane conductance. The transient tritanopia and flicker fusion paradigms we used appear to be promising to investigate antiepileptic drugs with hitherto unknown modes of actions in human noninvasively.

Adaptation, Ocular↗

PubMed2003

Social perception and early visual processing in schizophrenia.

Persons with schizophrenia experience deficits in social cognition-the cognitive processes involved in how people perceive and interpret information about themselves, others, and social situations. These deficits may be related to the neurocognitive impairments often experienced by persons with schizophrenia. Our primary objective was to examine associations between social perception and early visual processing in schizophrenia. Our secondary objective was to examine whether outpatients with schizophrenia and healthy persons differ in social perception. Forty outpatients with schizophrenia and 30 healthy persons completed a measure of social perception (the Half-Profile of Nonverbal Sensitivity), visual masking procedures, and ratings of positive and negative symptoms. Within patients, performance on visual masking procedures was related to performance on the Half-Profile of Nonverbal Sensitivity. Patients with schizophrenia and the healthy persons differed significantly in their performance on the Half-Profile of Nonverbal Sensitivity, but this difference became nonsignificant when education was a covariate. These findings suggest that social perception in schizophrenia is related to very early aspects of visual processing.

Adult↗

PubMed1996

Egocentric perception through interaction among many sensory systems.

We perceive the egocentric position and velocity of ourselves by many senses, such as vision, proprioception and vestibular sense. Normally the information by these senses is in harmony. However, there are situations in which the information is inharmonious. When we watch a wide-screen monitor or we ride in an accelerating or turning vehicle, visual information conflicts with proprioceptive and vestibular information. Since human egocentric perception has been studied for each separate sense in the previous research, it is not clear how the integration among these senses contributes to perception of human orientation. In Experiment 1, we investigated the contribution of visual, proprioceptive and vestibular information in isolation and in combination to perception of direction of forward self-motion. An observer rode in small vehicle (vestibular information) or walked (proprioceptive information) through a narrow corridor. Many vertical bars were hung from a ceiling of the corridor. When the observer moved forward, she/he viewed expanding optic flow of the bars (visual information) through video cameras and a helmet-mounted stereoscopic display. By fastening the observer and/or the cameras at different angles, consistent or conflicting information about forward direction was given through each sense. It was found that when there was conflicting information about the direction of forward motion (a) vestibular information was more dominant than visual cute, (b) visual and proprioceptive information was linearly added with weighting, and (c) visual information was dominant for backward motion. In Experiment 2, we investigated sensory integration when we moved forward with linear acceleration. Direction of the acceleration was either forward or sideways, namely corresponding to a ride in an accelerating or turning vehicle. We developed a new method to measure sensation or self-motion more objectively by using the three-dimensional position-sensor system. Positions of observer's head, shoulder, waist and ankle were measured to find body tilt accompanied by sensation of self-motion. It was found that the body tilted towards the opposite direction of the self-acceleration and the angle of body tilt was in good agreement with the subjective amount of the accelerating sensation. The body tilt was even induced by solely visual information. This implied that visual information contributed to perception of self-acceleration as well as self-motion.

Evoked Potentials, Somatosensory↗

PubMed2002

Two visual systems and two theories of perception: An attempt to reconcile the constructivist and ecological approaches.

The two contrasting theoretical approaches to visual perception, the constructivist and the ecological, are briefly presented and illustrated through their analyses of space and size perception. Earlier calls for their reconciliation and unification are reviewed. Neurophysiological, neuropsychological, and psychophysical evidence for the existence of two quite distinct visual systems, the ventral and the dorsal, is presented. These two perceptual systems differ in their functions; the ventral system's central function is that of identification, while the dorsal system is mainly engaged in the visual control of motor behavior. The strong parallels between the ecological approach and the functioning of the dorsal system, and between the constructivist approach and the functioning of the ventral system are noted. It is also shown that the experimental paradigms used by the proponents of these two approaches match the functions of the respective visual systems. A dual-process approach to visual perception emerges from this analysis, with the ecological-dorsal process transpiring mainly without conscious awareness, while the constructivist-ventral process is normally conscious. Some implications of this dual-process approach to visual-perceptual phenomena are presented, with emphasis on space perception.

Animals↗

PubMed1975

Aging faces as viscal-elastic events: implications for a theory of nonrigid shape perception.

A theory for the perception of events is proposed using the concepts of transformational and structural invariants. This approach involves the application of a method of spatial coordinate transformation to characterize the remodeling of faces by growth. By construing growing faces to the viscal-elastic events, the perception of the relative age level faces in made amenable to the proposed event perception analysis. Shear and strain transformation are compared as alternative formulations of growth-produced changes in the shape of human profiles. Thes studies indicate that profiles transformed by strain elicit more reliable rank-order age judgments than those transformed by shear, although shear had a small significant effect. It is also shown that subjects are highly sensitive to small changes in strain, and that perceived identity of a shape is preserved under the strain transformation. The explanatory adequacy of the event perception theory of age information is compared to that of more traditional feature analytic theories.

Aging↗