scholarly journals Neural, functional, and aesthetic impacts of spatially heterogeneous flicker: A potential role of natural flicker

2019 ◽  
Author(s):  
Melisa Menceloglu ◽  
Marcia Grabowecky ◽  
Satoru Suzuki
Keyword(s):  
Visual System ◽  
Visual Processing ◽  
Top Down ◽  
Aesthetic Responses ◽  
Beta Power ◽  
Neural Interactions ◽  
The Aesthetic ◽  
Sensory Activation ◽  
Motion Detectors

AbstractSpatially heterogeneous flicker, characterized by probabilistic and locally independent luminance modulations, abounds in nature. It is generated by flames, water surfaces, rustling leaves, and so on, and it is pleasant to the senses. It affords spatiotemporal multistability that allows sensory activation conforming to the biases of the visual system, thereby generating the perception of spontaneous motion and likely facilitating the calibration of motion detectors. One may thus hypothesize that spatially heterogeneous flicker might potentially provide restoring stimuli to the visual system that engage fluent (requiring minimal top-down control) and self-calibrating processes. Here, we present some converging behavioral and electrophysiological evidence consistent with this idea. Spatially heterogeneous (multistable) flicker (relative to controls matched in temporal statistics) reduced posterior EEG (electroencephalography) beta power implicated in long-range neural interactions that impose top-down influences on sensory processing. Further, the degree of spatiotemporal multistability, the amount of posterior beta-power reduction, and the aesthetic responses to flicker were closely associated. These results are consistent with the idea that the pleasantness of natural flicker may derive from its spatiotemporal multistability that affords fluent and self-calibrating visual processing.

Top-Down Processing and Visual Reorientation Illusions in a Virtual Reality Environment

2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman
Keyword(s):  
Virtual Reality ◽  
Visual Processing ◽  
Line Length ◽  
Perceptual Cues ◽  
Virtual Reality Environment ◽  
Top Down ◽  
Test Conditions ◽  
The Subject ◽  
Processing Mechanisms

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.

scholarly journals Grass and Gravel: Investigating Visual Properties Preschool Children and Adults Use When Distinguishing Naturalistic Images

2020 ◽  
Author(s):  
Karola Schlegelmilch ◽  
Annie E. Wertz
Keyword(s):  
Visual System ◽  
Natural Environment ◽  
Visual Processing ◽  
Visual Information ◽  
Relative Sensitivity ◽  
Visual Similarity ◽  
Overall Performance ◽  
Perceptual Abilities ◽  
Visual Properties

Visual processing of a natural environment occurs quickly and effortlessly. Yet, little is known about how young children are able to visually categorize naturalistic structures, since their perceptual abilities are still developing. We addressed this question by asking 76 children (age: 4.1-6.1 years) and 72 adults (age: 18-50 years) to first sort cards with greyscale images depicting vegetation, manmade artifacts, and non-living natural elements (e.g., stones) into groups according to visual similarity. Then, they were asked to choose the images' superordinate categories. We analyzed the relevance of different visual properties to the decisions of the participant groups. Children were very well able to interpret complex visual structures. However, children relied on fewer visual properties and, in general, were less likely to include properties which afforded the analysis of detailed visual information in their categorization decisions than adults, suggesting that immaturities of the still-developing visual system affected categorization. Moreover, when sorting according to visual similarity, both groups attended to the images' assumed superordinate categories—in particular to vegetation—in addition to visual properties. Children had a higher relative sensitivity for vegetation than adults did in the classification task when controlling for overall performance differences. Taken together, these findings add to the sparse literature on the role of developing perceptual abilities in processing naturalistic visual input.

scholarly journals Νευροχημική και νευροβιολογική μελέτη της επίδρασης του εμπλουτισμένου περιβάλλοντος στη φυσιολογία της όρασης των επιμύων

2013 ◽  
Author(s):  
Δημήτριος Μπεσίνης
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Visual Processing ◽  
Environmental Enrichment ◽  
Optic Chiasm ◽  
Enriched Environment ◽  
Female Rats ◽  
Male And Female ◽  
Serotonergic Activity

Environmental enrichment refers to the changes that happen in the centralnervous system of an animal which lives in bigger cages than typical labcages, with tunnels, running wheels and two floors. The purpose of this studywas to investigate the effects of environmental enrichment in the physiology ofthe visual system as well as in regions which contribute to the elaboration ofthe visual information. Sex differences were also taken into consideration. Ourgoal was achieved with the observation of developmental clues and the studyof behavioral and neurochemical parameters in male and female Wistar rats.The results of our study show that environmental enrichment accelerates theeye-opening procedure. Early enrichment decreases mobility duringprepuberty, without affecting it during adult life. On the contrary introducingenvironmental enrichment during adulthood increases mobility in both sexes.Early and late environmental enrichment also increases attention of maleadult animals. At the same time increased environmental stimuli give theability to male and female rats to identify more easily a newly presentedobject. It seems that enriched environment affects visual processing mostly infemale animals.For the first time in the present study we identified the involvement ofhistamine in the development and adaptation of the visual system. Histaminelevels in the optic chiasm but not the visual cortex are decreased in bothsexes through lifespan development. Histamine levels are also double in theoptic chiasm of males compared to females at all ages studied. Similar sexdifference was observed only during prepuberty in the visual cortex. Earlyenrichment decreased histamine levels in the optic chiasm of both sexesduring prepuberty, maintaining the sex difference observed in the basal levels.Histamine levels were comparable from prepuberty to adulthood upon rearing in richer environment. In contrast, introducing the enriched environment modelin adult animals increased histamine levels in the optic chiasm of female rats,indicating a sex difference in the adaptation of the central histaminergicsystem which interacts with the visual system.Neurochemical changes were also noted in the dopaminergic system of theretina and the visual cortex. Early enrichment does not affect dopaminergicactivity of the retina during development. On the contrary it inducedneurochemical changes in the adult female retina underlying adaptation inhigh illumination conditions, whereas late enrichment induced the sameneurochemical alterations in the retina of both male and female rats.Moreover the present study provides evidence that dopamine in not involvedin the development of the visual cortex, but is implicated in the function of thevisual cortex as well as visual processing.Enriched environment also ineracts with the serotonergic system of the retina.Serotonergic activity is increased by enhanced environmental stimuli possiblyleading to increased endogenous neuroprotection of the photosensitive layerof the eye. The present study also clarifies the interplay of plasticity andserotonergic activity in the visual cortex. Serotonergic activity is decreasedfrom prepuberty to adulthood. It seems that there is a range of serotonergicactivity within which it promotes plasticity. If serotonergic activity is increasedor decreased out of this range then plasticity is inhibited. It is also importantthat apart from the increase in neurotrophins levels observed in the visualcortex after environmental enrichment, plasticity is also facilitated throughserotonergic activity.Another important finding is that enriched environment alters neurochemistryin the prefrontal cortex which is important for stress response. For the firsttime in the present study we provide evidence that enriched environment(either from birth or during adulthood), leads to sex dependent activation ofstress mechanisms. The changes observed in the serotonergic activity of theprefrontal cortex are also sex dependent. It is possible that early environmental enrichment reduces the vulnerability to depression in adultfemale rats through increased serotonergic activity in the prefrontal cortex.Serotonergic activity of the hippocampus is also influenced by environmentalstimuli. Environmental enrichment either from birth or during adulthood affectsserotonergic activity of the hippocampus only in female animals. Thesechanges are capable of either to increase vulnerability to depression orattribute therapeutical advantages against this disease.In the present study the neurochemical profile of visual tissues in differentperiods of lifespan development and the neurochemical changesaccompanying the beneficial effects of environmental enrichment wereidentified. The results of the present raise the question of the role of histaminereceptors in visual perception and visual processing. The above resultsemphasize how crucial it is to map all the regions of the brain which interactwith the visual system and are involved in the function of vision. In additionthe present study shows how important it is to elucidate the role of enrichedenvironment in learning-memory and in the regulation of the sentiments.

scholarly journals Characterizing the effects of feature salience and top-down attention in the early visual system

2017 ◽  
Vol 118 (1) ◽  
pp. 564-573 ◽  
Author(s):  
Sonia Poltoratski ◽  
Sam Ling ◽  
Devin McCormack ◽  
Frank Tong
Keyword(s):  
Visual System ◽  
Spatial Attention ◽  
Visual Processing ◽  
Visual Pathway ◽  
Additive Effects ◽  
Voluntary Attention ◽  
Top Down ◽  
Motion Direction ◽  
Bottom Up ◽  
Visual Areas

The visual system employs a sophisticated balance of attentional mechanisms: salient stimuli are prioritized for visual processing, yet observers can also ignore such stimuli when their goals require directing attention elsewhere. A powerful determinant of visual salience is local feature contrast: if a local region differs from its immediate surround along one or more feature dimensions, it will appear more salient. We used high-resolution functional MRI (fMRI) at 7T to characterize the modulatory effects of bottom-up salience and top-down voluntary attention within multiple sites along the early visual pathway, including visual areas V1–V4 and the lateral geniculate nucleus (LGN). Observers viewed arrays of spatially distributed gratings, where one of the gratings immediately to the left or right of fixation differed from all other items in orientation or motion direction, making it salient. To investigate the effects of directed attention, observers were cued to attend to the grating to the left or right of fixation, which was either salient or nonsalient. Results revealed reliable additive effects of top-down attention and stimulus-driven salience throughout visual areas V1–hV4. In comparison, the LGN exhibited significant attentional enhancement but was not reliably modulated by orientation- or motion-defined salience. Our findings indicate that top-down effects of spatial attention can influence visual processing at the earliest possible site along the visual pathway, including the LGN, whereas the processing of orientation- and motion-driven salience primarily involves feature-selective interactions that take place in early cortical visual areas. NEW & NOTEWORTHY While spatial attention allows for specific, goal-driven enhancement of stimuli, salient items outside of the current focus of attention must also be prioritized. We used 7T fMRI to compare salience and spatial attentional enhancement along the early visual hierarchy. We report additive effects of attention and bottom-up salience in early visual areas, suggesting that salience enhancement is not contingent on the observer’s attentional state.

scholarly journals Estimating null and potent modes of feedforward communication in a computational model of cortical activity

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Jean-Philippe Thivierge ◽  
Artem Pilzak
Keyword(s):  
Visual Processing ◽  
Null Space ◽  
Motor Processes ◽  
Cortical Areas ◽  
Pairwise Correlations ◽  
Neural Interactions ◽  
Modes Of Interaction ◽  
Systematic Control ◽  
The Brain

AbstractCommunication across anatomical areas of the brain is key to both sensory and motor processes. Dimensionality reduction approaches have shown that the covariation of activity across cortical areas follows well-delimited patterns. Some of these patterns fall within the "potent space" of neural interactions and generate downstream responses; other patterns fall within the "null space" and prevent the feedforward propagation of synaptic inputs. Despite growing evidence for the role of null space activity in visual processing as well as preparatory motor control, a mechanistic understanding of its neural origins is lacking. Here, we developed a mean-rate model that allowed for the systematic control of feedforward propagation by potent and null modes of interaction. In this model, altering the number of null modes led to no systematic changes in firing rates, pairwise correlations, or mean synaptic strengths across areas, making it difficult to characterize feedforward communication with common measures of functional connectivity. A novel measure termed the null ratio captured the proportion of null modes relayed from one area to another. Applied to simultaneous recordings of primate cortical areas V1 and V2 during image viewing, the null ratio revealed that feedforward interactions have a broad null space that may reflect properties of visual stimuli.

scholarly journals Wholes and subparts in visual processing of human agency

2008 ◽  
Vol 276 (1658) ◽  
pp. 861-869 ◽  
Author(s):  
Peter Neri
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Visual Processing ◽  
Conclusive Evidence ◽  
Stage Model ◽  
Local Motion ◽  
Top Down ◽  
Two Stage ◽  
One Stage ◽  
The Relationship

The human visual system is remarkably sensitive to stimuli conveying actions, for example the fighting action between two agents. A central unresolved question is whether each agent is processed as a whole in one stage, or as subparts (e.g. limbs) that are assembled into an agent at a later stage. We measured the perceptual impact of perturbing an agent either by scrambling individual limbs while leaving the relationship between limbs unaffected or conversely by scrambling the relationship between limbs while leaving individual limbs unaffected. Our measurements differed for the two conditions, providing conclusive evidence against a one-stage model. The results were instead consistent with a two-stage processing pathway: an early bottom-up stage where local motion signals are integrated to reconstruct individual limbs (arms and legs), and a subsequent top-down stage where limbs are combined to represent whole agents.

The Power of Paint

2017 ◽  
Author(s):  
Jennifer Van Horn
Keyword(s):  
Social Connections ◽  
Young Student ◽  
New Model ◽  
British Art ◽  
Aesthetic Responses ◽  
Benjamin West ◽  
Art Community ◽  
The Aesthetic ◽  
The City

Chapter 2 focuses on mid-century Philadelphia’s burgeoning art community through the figure of travelling English portrait painter John Wollaston, who visited the city in 1752 and 1758/9. Wollaston’s presence encouraged the young student Francis Hopkinson to write a poem about the artist in the new periodical the American Magazine. By tracing the aesthetic responses that Hopkinson and the fellow students in his circle (including Benjamin West) had to Wollaston’s portraits the chapter charts Philadelphians’ engagement with the aesthetic debates raging in London over the role of the artist and the power of the portrait to civilize. Hopkinson embraced the new model of connoisseurship being popularized in the British art capital of London but recast it to argue that the portrait could civilize the sitter. Reading Wollaston’s portraits through the model of physiognomy reveals how viewers understood his paintings to improve sitters’ civility and how his paintings forged social connections between sitters.

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