Center–surround inhibition deepens binocular rivalry suppression

AbstractWhen dissimilar stimuli are presented to each eye, perception alternates between both images—a phenomenon known as binocular rivalry. It has been shown that stimuli presented in proximity of rival targets modulate the time each target is perceptually dominant. For example, presenting motion to the region surrounding the rival targets decreases the predominance of the same-direction target. Here, using a stationary concentric grating rivaling with a drifting grating, we show that a drifting surround grating also increases the depth of binocular rivalry suppression, as measured by sensitivity to a speed discrimination probe on the rival grating. This was especially so when the surround moved in the same direction as the grating, and was slightly weaker for opposed directions. Suppression in both cases was deeper than a no-surround control condition. We hypothesize that surround suppression often observed in area MT (V5)—a visual area implicated in visual motion perception—is responsible for this increase in suppression. In support of this hypothesis, monocular and binocular surrounds were both effective in increasing suppression depth, as were surrounds contralateral to the probed eye. Static and orthogonal motion surrounds failed to add to the depth of rivalry suppression. These results implicate a higher-level, fully binocular area whose surround inhibition provides an additional source of suppression which sums with rivalry suppression to effectively deepen suppression of an unseen rival target

Mountains of memory in a sea of uncertainty: Sampling the external world despite useful information in visual working memory

A large part of research on visual working memory (VWM) has traditionally focused on estimating its maximum capacity. Yet, humans rarely need to load up their VWM maximally during natural behavior, since visual information often remains accessible in the external world. Recent work, using paradigms that take into account the accessibility of information in the outside world, has indeed shown that observers utilize only one or two items in VWM before sampling from the external world again. One straightforward interpretation of this finding is that, in daily behavior, much fewer items are memorized than the typically reported capacity limits. Here, we first investigate whether this lower reliance on VWM when information is externally accessible might instead reflect resampling before VWM is actually depleted. To this aim we devised an online task, in which participants copied a model (six items in a 4x4 grid; always accessible) in an adjacent empty 4x4 grid. A key aspect of our paradigm is that we (unpredictably) interrupted participants just before inspection of the model with a 2-alternative-forced-choice (2-AFC) question, probing their VWM content. Critically, we observed above-chance performance on probes appearing just before model inspection. This finding shows that the external world was resampled, despite VWM still containing relevant information. We then asked whether increasing the cost of sampling causes participants to load up more information in VWM or, alternatively, to squeeze out more information from VWM (at the cost of making more errors). To manipulate the cost of resampling, we made it more difficult (specifically, more time-consuming) to access the model. We show that with increased cost of accessing the model (which lead to fewer, but longer model inspections), participants could place more items correctly immediately after sampling, and they kept attempting to place items for longer after their first error. These findings demonstrate that participants both encoded more information in VWM and made attempts to squeeze out more information from VWM when sampling became more costly. We argue that human observers constantly evaluate how certain they are of their VWM contents, and only use that VWM content of which their certainty exceeds a context-dependent “action threshold”. This threshold, in turn, depends on the trade-off between the cost of resampling and the benefits of making an action. We argue that considering the interplay between the available VWM contents and a context-dependent action threshold, is key for reconciling the traditional VWM literature with VWM use in our day-to-day behavior

Cortical depth dependent population receptive field attraction by spatial attention in human V1

Visual spatial attention concentrates neural resources at the attended location. Recently, we demonstrated that voluntary spatial attention attracts population receptive fields (pRFs) toward its location throughout the visual hierarchy. Theoretically, both a feed forward or feedback mechanism could underlie pRF attraction in a given cortical area. Here, we use sub-millimeter ultra-high field functional MRI to measure pRF attraction across cortical depth and assess the contribution of feed forward and feedback signals to pRF attraction. In line with previous findings, we find consistent attraction of pRFs with voluntary spatial attention in V1. When assessed as a function of cortical depth, we find pRF attraction in every cortical portion (deep, center and superficial), although the attraction is strongest in deep cortical portions (near the gray-white matter boundary). Following the organization of feed forward and feedback processing across V1, we speculate that a mixture of feed forward and feedback processing underlies pRF attraction in V1. Specifically, we propose that feedback processing contributes to the pRF attraction in deep cortical portions

Colour-grapheme synaesthesia affects binocular vision

In colour-grapheme synaesthesia, non-coloured graphemes are perceived as being inherently coloured. In recent years, it has become evident that synaesthesia-inducing graphemes can affect visual processing in a manner comparable to real, physical colours. Here, we exploit the phenomenon of binocular rivalry in which incompatible images presented dichoptically compete for conscious expression. Importantly, the competition only arises if the two images are sufficiently different; if the difference between the images is small, the images will fuse into a single mixed percept. We show that achromatic graphemes that induce synaesthetic colour percepts evoke binocular rivalry, while without the synaesthetic percept, they do not. That is, compared to achromatically perceived graphemes, synaesthesia-inducing graphemes increase the predominance of binocular rivalry over binocular fusion. This finding shows that the synaesthetic colour experience can provide the conditions for evoking binocular rivalry, much like stimulus features that induce rivalry in normal vision

Classbeacons: enhancing reflection-inaction of teachers through spatially distributed ambient information

Reflection-in-action (RiA) refers to teachers' reflections on their teaching performance during busy classroom routines. RiA is a demanding competence for teachers, but little has been known about how HCI systems could support teachers' RiA during their busy and intensive teaching. To bridge this gap, we design and evaluate an ambient information system named ClassBeacons. ClassBeacons aims to help teachers intuitively reflect-in-action on how to divide time and attention over pupils throughout a lesson. ClassBeacons subtly depicts teachers' division of time and attention over pupils through multiple light-objects distributed over students' desks. Each light-object indicates how long the teacher has been cumulatively around it (helping an adjacent student) by shifting color. A field evaluation with eleven teachers proved that ClassBeacons enhanced teachers' RiA by supporting their sensemaking of ongoing performance and modification of upcoming actions. Furthermore, ClassBeacons was experienced to unobtrusively fit into teachers' routines without overburdening teaching in progress

Unobtrusively enhancing reflection-in-action of teachers through spatially distributed ambient information

Reflecting on their performance during classroom-teaching is an important competence for teachers. Such reflection-inaction (RiA) enables them to optimize teaching on the spot. But RiA is also challenging, demanding extra thinking in teachers’ already intensive routines. Little is known on how HCI systems can facilitate teachers’ RiA during classroom-teaching. To fill in this gap, we evaluate ClassBeacons, a system that uses spatially distributed lamps to depict teachers’ ongoing performance on how they have divided their time and attention over students in the classroom. Empirical qualitative data from eleven teachers in 22 class periods show that this ambient information facilitated teachers’ RiA without burdening teaching in progress. Based on our theoretical grounding and field evaluation, we contribute empirical knowledge about how an HCI system enhanced teachers’ process of RiA as well as a set of design principles for unobtrusively supporting RiA.</p

Prospectively reinstated memory drives conscious access of matching visual input

Maintaining information in visual working memory (VWM) biases attentional selection of concurrent visual input, by favoring VWM-matching over VWM-mismatching visual input. Recently, it was shown that this bias disappears when the same item is memorized on consecutive occasions (as memoranda presumably transit from VWM to long-term memory), but reemerges when observers anticipate to memorize a novel item on a subsequent trial. Here, we aimed to conceptually replicate and extend this intriguing finding, by investigating whether prospectively reinstated memory drives conscious access of memory-matching visual input. We measured the time it took for participants to detect interocularly suppressed target stimuli, which were either from the same color category as a concurrently memorized color or not. Our results showed that the advantage of memory-matching targets in overcoming suppression progresses non-monotonically across consecutive memorizations of the same color (‘repetitions’): the advantage for memory-matching visual input initially declined to asymptote, before being fully revived on the last repetition. This revival was not observed in a control experiment in which targets were not interocularly suppressed. The results suggest that, as observers anticipate to memorize a novel item imminently, VWM usage is prospectively reinstated, causing memory-matching visual input to gain accelerated access to consciousness again

Prioritization of emotional faces is not driven by emotional content

Emotional faces have prioritized access to visual awareness. However, studies concerned with what expressions are prioritized most are inconsistent and the source of prioritization remains elusive. Here we tested the predictive value of spatial frequency-based image-features and emotional content, the sub-part of the image content that signals the emotional expression of the actor in the image as opposed to the image content irrelevant for the emotional expression, for prioritization for awareness. Participants reported which of two faces (displaying a combination of angry, happy, and neutral expressions), that were temporarily suppressed from awareness, was perceived first. Even though the results show that happy expressions were prioritized for awareness, this prioritization was driven by the contrast energy of the images. In fact, emotional content could not predict prioritization at all. Our findings show that the source of prioritization for awareness is not the information carrying the emotional content. We argue that the methods used here, or similar approaches, should become standard practice to break the chain of inconsistent findings regarding emotional superiority effects that have been part of the field for decades

Cortical depth dependent population receptive field attraction by spatial attention in human V1

Visual spatial attention concentrates neural resources at the attended location. Recently, we demonstrated that voluntary spatial attention attracts population receptive fields (pRFs) toward its location throughout the visual hierarchy. Theoretically, both a feed forward or feedback mechanism could underlie pRF attraction in a given cortical area. Here, we use sub-millimeter ultra-high field functional MRI to measure pRF attraction across cortical depth and assess the contribution of feed forward and feedback signals to pRF attraction. In line with previous findings, we find consistent attraction of pRFs with voluntary spatial attention in V1. When assessed as a function of cortical depth, we find pRF attraction in every cortical portion (deep, center and superficial), although the attraction is strongest in deep cortical portions (near the gray-white matter boundary). Following the organization of feed forward and feedback processing across V1, we speculate that a mixture of feed forward and feedback processing underlies pRF attraction in V1. Specifically, we propose that feedback processing contributes to the pRF attraction in deep cortical portions

Cortical depth dependent population receptive field attraction by spatial attention in human V1

Visual spatial attention concentrates neural resources at the attended location. Recently, we demonstrated that voluntary spatial attention attracts population receptive fields (pRFs) toward its location throughout the visual hierarchy. Theoretically, both a feed forward or feedback mechanism could underlie pRF attraction in a given cortical area. Here, we use sub-millimeter ultra-high field functional MRI to measure pRF attraction across cortical depth and assess the contribution of feed forward and feedback signals to pRF attraction. In line with previous findings, we find consistent attraction of pRFs with voluntary spatial attention in V1. When assessed as a function of cortical depth, we find pRF attraction in every cortical portion (deep, center and superficial), although the attraction is strongest in deep cortical portions (near the gray-white matter boundary). Following the organization of feed forward and feedback processing across V1, we speculate that a mixture of feed forward and feedback processing underlies pRF attraction in V1. Specifically, we propose that feedback processing contributes to the pRF attraction in deep cortical portions