The relation of phase noise and luminance contrast to overt attention in complex visual stimuli

W. Einhauser; U. Rutishauser; E. P. Frady; S. Nadler; P. Konig; C. Koch

doi:10.1167/6.11.1

Luminance and color effects on localization of briefly flashed visual stimuli

Visual Neuroscience ◽

10.1017/s0952523800008245 ◽

1996 ◽

Vol 13 (3) ◽

pp. 567-573 ◽

Cited By ~ 4

Author(s):

Roger E. Graves

Keyword(s):

Visual Stimuli ◽

High Sensitivity ◽

Luminance Contrast ◽

Stimulus Size ◽

Color Contrast ◽

Visual Localization ◽

Magnocellular Pathway ◽

Localization Task ◽

Parvocellular System ◽

Green Background

AbstractVisual localization was studied by flashing small stimuli on a green background and requiring observers to press keys to indicate whether the stimulus appeared to the left or right of fixation. The results suggest that, for small (0.25 deg) briefly flashed (17 ms) stimuli at an eccentric location (10 deg), color contrast is not useable and localization presumably must rely on the magnocellular pathway. When stimulus size and duration were increased at 10-deg eccentricity, isochromatic stimuli could be localized at less than 10% luminance contrast (again suggesting use of the magnocellular high sensitivity luminance-contrast system), but isoluminant color-contrast stimuli could also be localized (suggesting use of the color-contrast sensitive parvocellular system). Thus, the results indicate that, dependent on stimulus conditions, both magnocellular and parvocellular pathways were utilized by normal observers in this localization task.

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Spatial arrangement drastically changes the neural representation of multiple visual stimuli that compete in more than one feature domain

10.1101/692541 ◽

2019 ◽

Author(s):

Steven Wiesner ◽

Ian W. Baumgart ◽

Xin Huang

Keyword(s):

Visual Cortex ◽

Visual Stimuli ◽

Spatial Arrangement ◽

Luminance Contrast ◽

Neural Representation ◽

High Contrast ◽

Stimulus Component ◽

Mt Neurons ◽

Area Of Interest ◽

The Impact

ABSTRACTNatural scenes often contain multiple objects and surfaces. However, how neurons in the visual cortex represent multiple visual stimuli is not well understood. Previous studies have shown that, when multiple stimuli compete in one feature domain, the evoked neuronal response is biased toward the stimulus that has a stronger signal strength. Here we investigate how neurons in the middle temporal (MT) cortex of macaques represent multiple stimuli that compete in more than one feature domain. Visual stimuli were two random-dot patches moving in different directions. One stimulus had low luminance contrast and moved with high coherence, whereas the other had high contrast and moved with low coherence. We found that how MT neurons represent multiple stimuli depended on the spatial arrangement of the stimuli. When two stimuli were overlapping, MT responses were dominated by the stimulus component that had high contrast. When two stimuli were spatially separated within the receptive fields, the contrast dominance was abolished. We found the same results when using contrast to compete with motion speed. Our neural data and computer simulations using a V1-MT model suggest that the contrast dominance found with overlapping stimuli is due to normalization occurring at an input stage fed to MT, and MT neurons cannot overturn this bias based on their own feature selectivity. The interaction between spatially separated stimuli can largely be explained by normalization within MT. Our results revealed new rules on stimulus competition and highlighted the impact of hierarchical processing on representing multiple stimuli in the visual cortex.SIGNIFICANCE STATEMENTPrevious studies have shown that the neural representation of multiple visual stimuli can be accounted for by a divisive normalization model. By using multiple stimuli that compete in more than one feature domain, we found that luminance contrast has a dominant effect in determining competition between multiple stimuli when they were overlapping but not spatially separated. Our results revealed that neuronal responses to multiple stimuli in a given cortical area cannot be simply predicted by the population neural responses elicited in that area by the individual stimulus components. To understand the neural representation of multiple stimuli, rather than considering response normalization only within the area of interest, one must consider the computations including normalization occurring along the hierarchical visual pathway.

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Entrainment of visual steady-state responses is modulated by global spatial statistics

Journal of Neurophysiology ◽

10.1152/jn.00129.2017 ◽

2017 ◽

Vol 118 (1) ◽

pp. 344-352 ◽

Cited By ~ 2

Author(s):

Thomas Nguyen ◽

Karl Kuntzelman ◽

Vladimir Miskovic

Keyword(s):

Steady State ◽

Spatial Statistics ◽

Visual Stimuli ◽

Luminance Contrast ◽

Broadband Noise ◽

Visual Noise ◽

Natural Scenes ◽

Brain Oscillations ◽

Global Properties ◽

Phase Alignment

The rhythmic delivery of visual stimuli evokes large-scale neuronal entrainment in the form of steady-state oscillatory field potentials. The spatiotemporal properties of stimulus drive appear to constrain the relative degrees of neuronal entrainment. Specific frequency ranges, for example, are uniquely suited for enhancing the strength of stimulus-driven brain oscillations. When it comes to the nature of the visual stimulus itself, studies have used a plethora of inputs ranging from spatially unstructured empty fields to simple contrast patterns (checkerboards, gratings, stripes) and complex arrays (human faces, houses, natural scenes). At present, little is known about how the global spatial statistics of the input stimulus influence entrainment of scalp-recorded electrophysiological signals. In this study, we used rhythmic entrainment source separation of scalp EEG to compare stimulus-driven phase alignment for distinct classes of visual inputs, including broadband spatial noise ensembles with varying second-order statistics, natural scenes, and narrowband sine-wave gratings delivered at a constant flicker frequency. The relative magnitude of visual entrainment was modulated by the global properties of the driving stimulus. Entrainment was strongest for pseudo-naturalistic broadband visual noise patterns in which luminance contrast is greatest at low spatial frequencies (a power spectrum slope characterized by 1/ƒ−2). NEW & NOTEWORTHY Rhythmically modulated visual stimuli entrain the activity of neuronal populations, but the effect of global stimulus statistics on this entrainment is unknown. We assessed entrainment evoked by 1) visual noise ensembles with different spectral slopes, 2) complex natural scenes, and 3) narrowband sinusoidal gratings. Entrainment was most effective for broadband noise with naturalistic luminance contrast. This reveals some global properties shaping stimulus-driven brain oscillations in the human visual system.

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Neural responses to natural visual motion are spatially selective across the visual field, with selectivity differing across brain areas and task

10.1101/2021.03.05.434148 ◽

2021 ◽

Author(s):

Jason J Ki ◽

Jacek P Dmochowski ◽

Jonathan Touryan ◽

Lucas C Parra

Keyword(s):

Visual Field ◽

Video Game ◽

Visual Motion ◽

Visual Stimuli ◽

Visual Space ◽

Neural Responses ◽

Brain Areas ◽

Spatial Selectivity ◽

Overt Attention ◽

Visual Cueing

AbstractIt is well established that neural responses to visual stimuli are enhanced at select locations in the visual field. While spatial selectivity and the effects of spatial attention are well-understood for discrete tasks (e.g., visual cueing paradigms), little is known about neural response during a naturalistic visual experience that involves complex dynamic visual stimuli, for instance, driving. In this study, we assess the strength of neural responses across the visual space during a kart race video game. Specifically, we measure the correlation strength of scalp evoked potentials with optical flow magnitude at individual locations on the screen. We find the strongest neural responses for task-relevant locations in visual space, selectively extending to areas beyond the focus of overt attention: while the driver’s gaze is directed upon the heading direction at the center of the screen, we observe robust neural evoked responses also to peripheral areas such as the road and surrounding buildings. Importantly, this spatial selectivity of neural responses differs across scalp locations. Moreover, during active gameplay, the strength of the spatially-selective neural responses are enhanced compared to passive viewing. Spatially selective neural gains have previously been interpreted as an attentional gain mechanism. In this view, the present data suggest that different brain areas focus attention on different task-relevant portions of the visual field, reaching beyond the focus of overt attention.

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