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Neuropsychologia May 2019Patient DF, who has bilateral damage in the ventral visual stream, is perhaps the best known individual with visual form agnosia in the world, and has been the focus of... (Review)
Review
Patient DF, who has bilateral damage in the ventral visual stream, is perhaps the best known individual with visual form agnosia in the world, and has been the focus of scores of research papers over the past twenty-five years. The remarkable dissociation she exhibits between a profound deficit in perceptual report and a preserved ability to generate relatively normal visuomotor behaviour was early on a cornerstone in Goodale and Milner's (1992) two visual systems hypothesis. In recent years, however, there has been a greater emphasis on the damage that is evident in the posterior regions of her parietal cortex in both hemispheres. Deficits in several aspects of visuomotor control in the visual periphery have been demonstrated, leading some researchers to conclude that the double dissociation between vision-for-perception and vision-for-action in DF and patients with classic optic ataxia can no longer be assumed to be strong evidence for the division of labour between the dorsal and ventral streams of visual processing. In this short review, we argue that this is not the case. Indeed, after evaluating DF's performance and the location of her brain lesions, a clear picture of a double dissociation between DF and patients with optic ataxia is revealed. More than quarter of a century after the initial presentation of DF's unique case, she continues to provide compelling evidence for the idea that the ventral stream is critical for the perception of the shape and orientation of objects but not the visual control of skilled actions directed at those objects.
Topics: Aged; Agnosia; Female; Humans; Motion Perception; Movement; Psychomotor Performance; Visual Fields; Visual Perception
PubMed: 28951167
DOI: 10.1016/j.neuropsychologia.2017.09.016 -
Attention, Perception & Psychophysics Feb 2024Visual scenes are too complex for one to immediately perceive all their details. As suggested by Gestalt psychologists, grouping similar scene elements and perceiving...
Visual scenes are too complex for one to immediately perceive all their details. As suggested by Gestalt psychologists, grouping similar scene elements and perceiving their summary statistics provides one shortcut for evaluating scene gist. Perceiving ensemble statistics overcomes processing, attention, and memory limits, facilitating higher-order scene understanding. Ensemble perception spans simple/complex dimensions (circle size, face emotion), including various statistics (mean, range), and inherently spans space and/or time, when sets are presented scattered across the visual scene, and/or sequentially in rapid series. Furthermore, ensemble perception occurs explicitly, when observers are asked to judge set mean, and also automatically/implicitly, when observers are engaged in an orthogonal task. We now study relationships among these ensemble-perception phenomena, testing explicit and implicit ensemble perception; for sets varying in circle size, line orientation, or disc brightness; and with spatial, temporal or spatio-temporal presentation. Following ensemble set presentation, observers were asked if a test image, or which of two test images, had been present in the set. Confirming previous results, responses reflected implicit mean perception, depending on test image distance from the mean, and on its being within or outside ensemble range. Subsequent experiments asked the same observers to explicitly judge whether test images were larger, more clockwise, or brighter than the set mean, or which of two test images was closer to the mean. Comparing implicit and explicit mean perception, we find that explicit ensemble averaging is more precise than implicit mean perception-for each ensemble variable and presentation mode. Implications are discussed regarding possible separate mechanisms for explicit versus implicit ensemble perception.
Topics: Humans; Attention; Emotions; Perception; Visual Perception
PubMed: 37821745
DOI: 10.3758/s13414-023-02784-4 -
Psychological Science Feb 2022Visual scene context is well-known to facilitate the recognition of scene-congruent objects. Interestingly, however, according to predictive-processing accounts of brain...
Visual scene context is well-known to facilitate the recognition of scene-congruent objects. Interestingly, however, according to predictive-processing accounts of brain function, scene congruency may lead to reduced (rather than enhanced) processing of congruent objects, compared with incongruent ones, because congruent objects elicit reduced prediction-error responses. We tested this counterintuitive hypothesis in two online behavioral experiments with human participants ( = 300). We found clear evidence for impaired perception of congruent objects, both in a change-detection task measuring response times and in a bias-free object-discrimination task measuring accuracy. Congruency costs were related to independent subjective congruency ratings. Finally, we show that the reported effects cannot be explained by low-level stimulus confounds, response biases, or top-down strategy. These results provide convincing evidence for perceptual congruency costs during scene viewing, in line with predictive-processing theory.
Topics: Humans; Pattern Recognition, Visual; Perception; Photic Stimulation; Reaction Time; Recognition, Psychology; Visual Perception
PubMed: 35020519
DOI: 10.1177/09567976211032676 -
Proceedings. Biological Sciences Jul 2020Perceiving the positions of objects is a prerequisite for most other visual and visuomotor functions, but human perception of object position varies from one individual...
Perceiving the positions of objects is a prerequisite for most other visual and visuomotor functions, but human perception of object position varies from one individual to the next. The source of these individual differences in perceived position and their perceptual consequences are unknown. Here, we tested whether idiosyncratic biases in the underlying representation of visual space propagate across different levels of visual processing. In Experiment 1, using a position matching task, we found stable, observer-specific compressions and expansions within local regions throughout the visual field. We then measured Vernier acuity (Experiment 2) and perceived size of objects (Experiment 3) across the visual field and found that individualized spatial distortions were closely associated with variations in both visual acuity and apparent object size. Our results reveal idiosyncratic biases in perceived position and size, originating from a heterogeneous spatial resolution that carries across the visual hierarchy.
Topics: Humans; Size Perception; Space Perception; Visual Acuity; Visual Fields; Visual Perception
PubMed: 32635869
DOI: 10.1098/rspb.2020.0825 -
Attention, Perception & Psychophysics Jul 2018Regularities like symmetry (mirror reflection) and repetition (translation) play an important role in both visual and haptic (active touch) shape perception. Altering...
Regularities like symmetry (mirror reflection) and repetition (translation) play an important role in both visual and haptic (active touch) shape perception. Altering figure-ground factors to change what is perceived as an object influences regularity detection. For vision, symmetry is usually easier to detect within one object, whereas repetition is easier to detect across two objects. For haptics, we have not found this interaction between regularity type and objectness (Cecchetto & Lawson, Journal of Experimental Psychology: Human Perception and Performance, 43, 103-125, 2017; Lawson, Ajvani, & Cecchetto, Experimental Psychology, 63, 197-214, 2016). However, our studies used repetition stimuli with mismatched concavities, convexities, and luminance, and so had mismatched contour polarities. Such stimuli may be processed differently to stimuli with matching contour polarities. We investigated this possibility. For haptics, speeded symmetry and repetition detection for novel, planar shapes was similar. Performance deteriorated strikingly if contour polarity mismatched (keeping objectness constant), whilst there was a modest disadvantage for between-2objects:facing-sides compared to within-1object:outer-sides comparisons (keeping contour polarity constant). For the same task for vision, symmetry detection was similar to haptics (strong costs for mismatched contour polarity, weaker costs for between-2objects:facing-sides comparisons), but repetition detection was very different (weak costs for mismatched contour polarity, strong benefits for between-2objects:facing-sides comparisons). Thus, objectness was less influential than contour polarity for both haptic and visual symmetry detection, and for haptic repetition detection. However, for visual repetition detection, objectness effects reversed direction (within-1object:outer-sides comparisons were harder) and were stronger than contour polarity effects. This pattern of results suggests that regularity detection reflects information extraction as well as regularity distributions in the physical world.
Topics: Adolescent; Adult; Female; Form Perception; Humans; Male; Pattern Recognition, Visual; Touch; Visual Perception; Young Adult
PubMed: 29549662
DOI: 10.3758/s13414-018-1499-6 -
The Journal of Neuroscience : the... Dec 2023During binocular rivalry, conflicting images are presented one to each eye and perception alternates stochastically between them. Despite stable percepts between...
During binocular rivalry, conflicting images are presented one to each eye and perception alternates stochastically between them. Despite stable percepts between alternations, modeling suggests that neural signals representing the two images change gradually, and that the duration of stable percepts are determined by the time required for these signals to reach a threshold that triggers an alternation. However, direct physiological evidence for such signals has been lacking. Here, we identify a neural signal in the human visual cortex that shows these predicted properties. We measured steady-state visual evoked potentials (SSVEPs) in 84 human participants (62 females, 22 males) who were presented with orthogonal gratings, one to each eye, flickering at different frequencies. Participants indicated their percept while EEG data were collected. The time courses of the SSVEP amplitudes at the two frequencies were then compared across different percept durations, within participants. For all durations, the amplitude of signals corresponding to the suppressed stimulus increased and the amplitude corresponding to the dominant stimulus decreased throughout the percept. Critically, longer percepts were characterized by more gradual increases in the suppressed signal and more gradual decreases of the dominant signal. Changes in signals were similar and rapid at the end of all percepts, presumably reflecting perceptual transitions. These features of the SSVEP time courses are well predicted by a model in which perceptual transitions are produced by the accumulation of noisy signals. Identification of this signal underlying binocular rivalry should allow strong tests of neural models of rivalry, bistable perception, and neural suppression. During binocular rivalry, two conflicting images are presented to the two eyes and perception alternates between them, with switches occurring at seemingly random times. Rivalry is an important and longstanding model system in neuroscience, used for understanding neural suppression, intrinsic neural dynamics, and even the neural correlates of consciousness. All models of rivalry propose that it depends on gradually changing neural activity that on reaching some threshold triggers the perceptual switches. This manuscript reports the first physiological measurement of neural signals with that set of properties in human participants. The signals, measured with EEG in human observers, closely match the predictions of recent models of rivalry, and should pave the way for much future work.
Topics: Male; Female; Humans; Visual Perception; Vision, Binocular; Evoked Potentials, Visual; Photic Stimulation; Visual Cortex; Vision Disparity
PubMed: 37907256
DOI: 10.1523/JNEUROSCI.1325-23.2023 -
Attention, Perception & Psychophysics Jul 2022Maintaining object correspondence among multiple moving objects is an essential task of the perceptual system in many everyday life activities. A substantial body of...
Maintaining object correspondence among multiple moving objects is an essential task of the perceptual system in many everyday life activities. A substantial body of research has confirmed that observers are able to track multiple target objects amongst identical distractors based only on their spatiotemporal information. However, naturalistic tasks typically involve the integration of information from more than one modality, and there is limited research investigating whether auditory and audio-visual cues improve tracking. In two experiments, we asked participants to track either five target objects or three versus five target objects amongst similarly indistinguishable distractor objects for 14 s. During the tracking interval, the target objects bounced occasionally against the boundary of a centralised orange circle. A visual cue, an auditory cue, neither or both coincided with these collisions. Following the motion interval, the participants were asked to indicate all target objects. Across both experiments and both set sizes, our results indicated that visual and auditory cues increased tracking accuracy although visual cues were more effective than auditory cues. Audio-visual cues, however, did not increase tracking performance beyond the level of purely visual cues for both high and low load conditions. We discuss the theoretical implications of our findings for multiple object tracking as well as for the principles of multisensory integration.
Topics: Attention; Auditory Perception; Cues; Humans; Motion; Motion Perception; Photic Stimulation; Visual Perception
PubMed: 35610410
DOI: 10.3758/s13414-022-02492-5 -
Developmental Psychobiology May 2022Most fundamental aspects of information processing in infancy have been primarily investigated using simplified images centrally presented on computer displays. This...
Most fundamental aspects of information processing in infancy have been primarily investigated using simplified images centrally presented on computer displays. This approach lacks ecological validity as in reality the majority of visual information is presented across the visual field, over a range of eccentricities. Limited studies are present, however, about the extent and the characteristics of infant peripheral vision after 7 months of age. The present work investigates the limits of infant (9-month-olds) and adult visual fields using a detection task. Gabor patches were presented at one of six eccentricities per hemifield, from 35° up to 60° in the left and right mid-peripheral visual fields. Detection rates at different eccentricities were measured from video recordings (infant sample) or key press responses (adult sample). Infant performance declined below chance level beyond 50°, whereas adults performed at ceiling level across all eccentricities. The performance of 9-month-olds was unequal even within 50°, suggesting regions of differential sensitivity to low-level visual information in the infant's periphery. These findings are key to understanding the limits of visual fields in the infant and, in turn, will inform the design of future infant studies.
Topics: Adult; Cognition; Humans; Infant; Visual Fields; Visual Perception
PubMed: 35452547
DOI: 10.1002/dev.22274 -
Multisensory Research 2015The role of the vestibular system in posture and eye movement control has been extensively described. By contrast, how vestibular signals contribute to bodily... (Review)
Review
The role of the vestibular system in posture and eye movement control has been extensively described. By contrast, how vestibular signals contribute to bodily perceptions is a more recent research area in the field of cognitive neuroscience. In the present review article, I will summarize recent findings showing that vestibular signals play a crucial role in making sense of the body. First, data will be presented showing that vestibular signals contribute to bodily perceptions ranging from low-level bodily perceptions, such as touch, pain, and the processing of the body's metric properties, to higher level bodily perceptions, such as the sense of owning a body, the sense of being located within this body (embodiment), and the anchoring of the visuo-spatial perspective to this body. In the second part of the review article, I will show that vestibular information seems to be crucially involved in the visual perception of biological motion and in the visual perception of human body structure. Reciprocally, observing human bodies in motion influences vestibular self-motion perception, presumably due to sensorimotor resonance between the self and others. I will argue that recent advances in the mapping of the human vestibular cortex afford neuroscientific models of the vestibular contributions to human bodily self-consciousness.
Topics: Body Image; Emotions; Humans; Motion Perception; Posture; Self Concept; Vestibule, Labyrinth; Visual Perception
PubMed: 26595955
DOI: 10.1163/22134808-00002490 -
Neuropsychologia Nov 2023We present a comprehensive review of the rare syndrome visual form agnosia (VFA). We begin by documenting its history, including the origins of the term, and the first... (Review)
Review
We present a comprehensive review of the rare syndrome visual form agnosia (VFA). We begin by documenting its history, including the origins of the term, and the first case study labelled as VFA. The defining characteristics of the syndrome, as others have previously defined it, are then described. The impairments, preserved aspects of visual perception, and areas of brain damage in 21 patients who meet these defining characteristics are described in detail, including which tests were used to verify the presence or absence of key symptoms. From this, we note important similarities along with notable areas of divergence between patients. Damage to the occipital lobe (20/21), an inability to recognise line drawings (19/21), preserved colour vision (14/21), and visual field defects (16/21) were areas of consistency across most cases. We found it useful to distinguish between shape and form as distinct constructs when examining perceptual abilities in VFA patients. Our observations suggest that these patients often exhibit difficulties in processing simplified versions of form. Deficits in processing orientation and size were uncommon. Motion perception and visual imagery were not widely tested for despite being typically cited as defining features of the syndrome - although in the sample described, motion perception was never found to be a deficit. Moreover, problems with vision (e.g., poor visual acuity and the presence of hemianopias/scotomas in the visual fields) are more common than we would have thought and may also contribute to perceptual impairments in patients with VFA. We conclude that VFA is a perceptual disorder where the visual system has a reduced ability to synthesise lines together for the purposes of making sense of what images represent holistically.
Topics: Humans; Pattern Recognition, Visual; Visual Perception; Vision, Ocular; Visual Fields; Vision Disorders; Agnosia
PubMed: 37634886
DOI: 10.1016/j.neuropsychologia.2023.108666