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Nature Communications Apr 2024Brightness illusions are a powerful tool in studying vision, yet their neural correlates are poorly understood. Based on a human paradigm, we presented illusory drifting...
Brightness illusions are a powerful tool in studying vision, yet their neural correlates are poorly understood. Based on a human paradigm, we presented illusory drifting gratings to mice. Primary visual cortex (V1) neurons responded to illusory gratings, matching their direction selectivity for real gratings, and they tracked the spatial phase offset between illusory and real gratings. Illusion responses were delayed compared to real gratings, in line with the theory that processing illusions requires feedback from higher visual areas (HVAs). We provide support for this theory by showing a reduced V1 response to illusions, but not real gratings, following HVAs optogenetic inhibition. Finally, we used the pupil response (PR) as an indirect perceptual report and showed that the mouse PR matches the human PR to perceived luminance changes. Our findings resolve debates over whether V1 neurons are involved in processing illusions and highlight the involvement of feedback from HVAs.
Topics: Animals; Neurons; Primary Visual Cortex; Mice; Photic Stimulation; Male; Humans; Optogenetics; Female; Visual Perception; Illusions; Optical Illusions; Mice, Inbred C57BL; Pupil; Visual Cortex
PubMed: 38653975
DOI: 10.1038/s41467-024-46885-6 -
Heliyon Nov 2023According to research, it has been suggested that individuals who are affected by depression could potentially engage in the creation and experience emotional advantages...
UNLABELLED
According to research, it has been suggested that individuals who are affected by depression could potentially engage in the creation and experience emotional advantages relating to positive events directed towards the past or future, with the condition that they are provided with suitable mental imagery techniques. The main aim of this study was to assess the impact of utilizing positive imagery, specifically through the utilization of photographs featuring loved ones, on mood states and suicidal ideation among individuals diagnosed with depression and exhibiting suicidal tendencies. This randomized, double-blind, controlled crossover trial was conducted among 78 hospitalized depressive patients at three psychiatric services between April and August 2019. The patients participated in four individual picture-viewing sessions on four consecutive days. The four categories of pictures were included: loved ones, neutral faces of strangers, natural landscapes, and optical illusions. Directly prior to and immediately following the observation of the visual stimuli (photographs), the Brunel Mood Scale (BRUMS) and the Beck Scale for Suicide Ideation (BSSI) were completed by the patients. Repeated measures ANOVAs conducted in this study revealed a significant main effect of time on ratings of tension, depression, fatigue, vigor, calmness, and happiness (P values < 0.001). Additionally, statistically significant interactions were identified between picture category and time in relation to the variables of tension, depression, fatigue, vigor, calmness, and happiness (P values < 0.001). The analysis did not reveal a significant main effect of time on ratings of anger, confusion, and suicidal ideation (P values > 0.05). Likewise, the interaction between picture category and time did not yield significant results for the variables of anger, confusion, and suicidal ideation (P values > 0.05). The positive imagery procedure using the presentation of loved ones' photos showed beneficial effects on the mood states of depressed patients. The findings of this study suggest that incorporating a greater emphasis on positive imagery within the context of clinical depression may offer potential advantages. This highlights the potential for novel opportunities in the treatment of depression.
TRIAL REGISTRATION
The study has been registered in the Iranian Registry of Clinical Trials (registration number: IRCT20180808040744N1; first registration date: December 22, 2018; website: https://en.irct.ir/trial/33186).
PubMed: 38058624
DOI: 10.1016/j.heliyon.2023.e22312 -
Quarterly Journal of Experimental... Jun 2024Although it is known that the availability of visual feedback modulates grasping kinematics, it is unclear whether this extends to both the early and late stages of the...
Although it is known that the availability of visual feedback modulates grasping kinematics, it is unclear whether this extends to both the early and late stages of the movement. We tackled this issue by exposing participants to the Uznadze illusion (a medium stimulus appears larger or smaller after exposure to smaller or larger inducers). After seeing smaller or larger discs, participants grasped a medium disc with (closed-loop [CL]) or without (open-loop [OL]) visual feedback. Our main aim was to assess whether the time course of the illusion from the movement onset up to the grasp differed between OL and CL. Moreover, we compared OL and CL illusory effects on maximum grip aperture (MGA) and tested whether preparation time, movement time, and time to MGA predicted illusion magnitude. Results revealed that CL illusory effects decreased over movement time, whereas OL ones remained constant. At the time of MGA, OL, and CL effects were, however, of similar size. Although OL grasps were longer to prepare and showed earlier and larger MGAs, such differences had little impact on modulating the illusion. These results suggest that the early stage of grasping is sensitive to the Uznadze illusion both under CL and OL conditions, whereas the late phase is sensitive to it only under OL conditions. We discuss these findings within the framework of theoretical models on the functional properties of the dorsal stream for visually guided actions.
Topics: Humans; Male; Female; Adult; Young Adult; Psychomotor Performance; Hand Strength; Feedback, Sensory; Time Factors; Illusions; Photic Stimulation; Biomechanical Phenomena; Optical Illusions; Visual Perception; Size Perception
PubMed: 37784227
DOI: 10.1177/17470218231206907 -
Animal Cognition May 2024Optical illusions have long been used in behavioural studies to investigate the perceptual mechanisms underlying vision in animals. So far, three studies have focused on...
Optical illusions have long been used in behavioural studies to investigate the perceptual mechanisms underlying vision in animals. So far, three studies have focused on ungulates, providing evidence that they may be susceptible to some optical illusions, in a way similar to humans. Here, we used two food-choice tasks to study susceptibility to the Müller-Lyer and Delboeuf illusions in 17 captive individuals belonging to four ungulate species (Lama guanicoe, Lama glama, Ovis aries, Capra hircus). At the group level, there was a significant preference for the longer/larger food over the shorter/smaller one in control trials. Additionally, the whole group significantly preferred the food stick between two inward arrowheads over an identical one between two outward arrowheads in experimental trials of the Müller-Lyer task, and also preferred the food on the smaller circle over an identical one on the larger circle in the experimental trials of the Delboeuf task. Group-level analyses further showed no significant differences across species, although at the individual level we found significant variation in performance. Our findings suggest that, in line with our predictions, ungulates are overall susceptible to the Müller-Lyer and the Delboeuf illusions, and indicate that the perceptual mechanisms underlying size estimation in artiodactyls might be similar to those of other species, including humans.
Topics: Animals; Camelids, New World; Optical Illusions; Female; Male; Goats; Size Perception; Sheep
PubMed: 38789595
DOI: 10.1007/s10071-024-01878-2 -
Scientific Reports Mar 2024Perceptual grouping is impaired following mild traumatic brain injury (mTBI). This may affect visual size perception, a process influenced by perceptual grouping...
Perceptual grouping is impaired following mild traumatic brain injury (mTBI). This may affect visual size perception, a process influenced by perceptual grouping abilities. We conducted two experiments to evaluate visual size perception in people with self-reported history of mTBI, using two different size-contrast illusions: the Ebbinghaus Illusion (Experiment 1) and the Müller-Lyer illusion (Experiment 2). In Experiment 1, individuals with mTBI and healthy controls were asked to compare the size of two target circles that were either the same size or different sizes. The target circles appeared by themselves (no-context condition), or were surrounded by smaller or larger circles (context condition). Similar levels of accuracy were evident between the groups in the no-context condition. However, size judgements by mTBI participants were more accurate in the context condition, suggesting that they processed the target circles separately from the surrounding circles. In Experiment 2, individuals with mTBI and healthy controls judged the length of parallel lines that appeared with arrowheads (context condition) or without arrowheads (no context condition). Consistent with Experiment 1, size judgements by mTBI participants were more accurate than size judgements by control participants in the context condition. These findings suggest that mTBI influences size perception by impairing perceptual grouping of visual stimuli in near proximity.
Topics: Humans; Illusions; Optical Illusions; Brain Concussion; Visual Perception; Size Perception; Judgment
PubMed: 38499578
DOI: 10.1038/s41598-024-56713-y -
Perception May 2024Vittorio Benussi (1878-1927) is known for numerous studies on optical illusions, visual and haptic perception, spatial and time perception. In Padova, he had a brilliant...
Vittorio Benussi (1878-1927) is known for numerous studies on optical illusions, visual and haptic perception, spatial and time perception. In Padova, he had a brilliant student who carefully worked on the topic of how people estimate numerosity, Silvia De Marchi (1897-1936). Her writings have never been translated into English before. Here we comment on her work and life, characterized also by the challenges faced by women in academia. The studies on perception of numerosity from her thesis were published as an article in 1929. We provide a translation from Italian, a redrawing of its 23 illustrations and of the graphs. It shows an original experimental approach and an anticipation of what later became known as magnitude estimation.
Topics: Humans; History, 20th Century; Italy; History, 19th Century; Mathematical Concepts; Mathematics
PubMed: 38620014
DOI: 10.1177/03010066241234612 -
Journal of Vision Jun 2024The watercolor effect (WCE) is a striking visual illusion elicited by a bichromatic double contour, such as a light orange and a dark purple, hugging each other on a... (Review)
Review
The watercolor effect (WCE) is a striking visual illusion elicited by a bichromatic double contour, such as a light orange and a dark purple, hugging each other on a white background. Color assimilation, emanating from the lighter contour, spreads onto the enclosed surface area, thereby tinting it with a chromatic veil, not unlike a weak but real color. Map makers in the 17th century utilized the WCE to better demarcate the shape of adjoining states, while 20th-century artist Bridget Riley created illusory watercolor as part of her op-art. Today's visual scientists study the WCE for its filling-in properties and strong figure-ground segregation. This review emphasizes the superior strength of the WCE for grouping and figure-ground organization vis-à-vis the classical Gestalt factors of Max Wertheimer (1923), thereby inspiring a notion of form from induced color. It also demonstrates that a thin chromatic line, flanking the inside of a black Mondrian-type pattern, induces the WCE across a large white surface area. Phenomenological, psychophysical, and neurophysiological approaches are reviewed.
Topics: Humans; Color Perception; History, 20th Century; Optical Illusions; Form Perception; History, 17th Century; History, 19th Century; History, 18th Century
PubMed: 38913017
DOI: 10.1167/jov.24.6.15