Visual Masking

Hauch

Atten Percept Psychophys

2015

Rapid motor responses to visual stimuli can involve both the activation and inhibition of motor responses. Here, we trace the early processing dynamics of response generation, examining whether activation and inhibition events form a strict sequence when elicited by sequential stimuli, as we would expect if motor events are driven by fast, stimulustriggered feedforward sweeps. We employed identical stimuli in two complementary paradigms. In response priming, responses to a target stimulus are speeded or slowed by a masked prime triggering the same or an alternative response, respectively. By prolonging the prime-target interval, the response-priming effect can reverse to form the negative compatibility effect (NCE), especially when the mask contains response-relevant features. We report two experiments in which primed pointing movements going in ten possible directions were measured with response-relevant, response-irrelevant, or no masks interleaved between the primes and targets, while selective visual attention was varied. We showed that in response priming, initial responses are controlled exclusively by the prime. In the NCE, however, even the earliest movement phase is controlled jointly by the prime, mask, and target information, and a massive force in counterdirection to the primed response reverses the priming effects specifically for slow responses. We conclude that response priming reflects a strict sequence of feedforward response activations, whereas the activation/inhibition events in the NCE are not strictly serial, but integrate information from the different stimuli over time. Even though the mask features and visual attention modulate the NCE, its major source is a mask-induced, direction-specific thrust reversal of the initial response.

Section: Motor Activation In Response Primingmentioning

confidence: 99%

Mask-triggered thrust reversal in the negative compatibility effect

Hauch

Atten Percept Psychophys

2015

Proc. Natl. Acad. Sci. U.S.A.

“…This goal has often been approached by comparing the effects of a stimulus on the brain when subjects are aware vs. unaware of the stimulus. A number of elegant paradigms have been designed for this purpose, with the aim of making the stimulus as similar as possible in the two conditions (1,2), such that any neural differences that emerge are more reasonably attributed to a difference in awareness than to a difference in the stimuli themselves. Using this approach, studies have pointed to a frontoparietal network, including the dorsolateral prefrontal cortex, the middle and inferior frontal gyri, the intraparietal sulcus, the superior parietal lobule, and a number of regions within the temporoparietal junction (TPJ) (3)(4)(5)(6)(7)(8)(9), although some questions remain regarding the specific role of each of these regions (9)(10)(11).…”

mentioning

confidence: 99%

“…We used a Posner cueing paradigm, a standard way to measure bottom-up spatial attention drawn to a visual cue (27). The cue was masked with metacontrast masking, a commonly used method to manipulate visual awareness (2). In one condition, the timing of the mask rendered the cue perceptually visible to the participants (aware trials), and in another condition, the timing of the mask rendered the cue perceptually invisible (unaware trials).…”

mentioning

confidence: 99%

Cortical networks involved in visual awareness independent of visual attention

Webb

Igelström

Schurger

et al. 2016

It is now well established that visual attention, as measured with standard spatial attention tasks, and visual awareness, as measured by report, can be dissociated. It is possible to attend to a stimulus with no reported awareness of the stimulus. We used a behavioral paradigm in which people were aware of a stimulus in one condition and unaware of it in another condition, but the stimulus drew a similar amount of spatial attention in both conditions. The paradigm allowed us to test for brain regions active in association with awareness independent of level of attention. Participants performed the task in an MRI scanner. We looked for brain regions that were more active in the aware than the unaware trials. The largest cluster of activity was obtained in the temporoparietal junction (TPJ) bilaterally. Local independent component analysis (ICA) revealed that this activity contained three distinct, but overlapping, components: a bilateral, anterior component; a left dorsal component; and a right dorsal component. These components had brain-wide functional connectivity that partially overlapped the ventral attention network and the frontoparietal control network. In contrast, no significant activity in association with awareness was found in the banks of the intraparietal sulcus, a region connected to the dorsal attention network and traditionally associated with attention control. These results show the importance of separating awareness and attention when testing for cortical substrates. They are also consistent with a recent proposal that awareness is associated with ventral attention areas, especially in the TPJ.A major goal of the scientific study of consciousness is to understand which brain regions form the substrate of subjective awareness. This goal has often been approached by comparing the effects of a stimulus on the brain when subjects are aware vs. unaware of the stimulus. A number of elegant paradigms have been designed for this purpose, with the aim of making the stimulus as similar as possible in the two conditions (1, 2), such that any neural differences that emerge are more reasonably attributed to a difference in awareness than to a difference in the stimuli themselves. Using this approach, studies have pointed to a frontoparietal network, including the dorsolateral prefrontal cortex, the middle and inferior frontal gyri, the intraparietal sulcus, the superior parietal lobule, and a number of regions within the temporoparietal junction (TPJ) (3-9), although some questions remain regarding the specific role of each of these regions (9-11).One potential concern is the conflation of attention and awareness. During the last 15 y, it has become well established that awareness and attention can be separated. It is possible for people to attend to a visual stimulus, as measured by standard attention tasks such as the spatial Posner cuing task, while reporting no subjective awareness of the stimulus (12-15). Attention and awareness are, however, closely linked. They covary under normal conditions (16-1...

Atten Percept Psychophys

“…Indeed, a major limitation for most studies measuring unconscious processing is that they use visual stimuli that are impoverished in many different ways. For example, studies often manipulate stimulus duration or the delay between the onset of a stimulus and the onset of a mask (Breitmeyer & Öğmen, 2006), curtailing the amount of stimulus exposure time. Other studies, such as the one by Harris et al (2011), use CFS, which presents a stimulus to one eye and a mask to the other, thereby limiting processing to early visual areas where monocular neurons are most abundant.…”

mentioning

confidence: 99%

Perceptual overloading reveals illusory contour perception without awareness of the inducers

Persuh

Emmanouil

2016

Unconscious perception is frequently examined by restricting visual input (e.g., using short stimulus durations followed by masking) to prevent that information from entering visual awareness. Failures to demonstrate perception without awareness may thus be a consequence of this restricted input rather than of limitations in unconscious perception. Here, we demonstrate a novel method that circumvents these significant drawbacks inherent in other methods. Using this new perceptual overloading technique (POT), in which stimuli are repeatedly presented in alternation with a stream of variable masks, we demonstrate illusory contour perception and modal completion even when subjects are completely unaware of the inducing elements. In addition to demonstrating a powerful new method to study consciousness by effectively gating robust visual input from visual awareness, we show that more complex contextual effects, previously considered to be a privilege only of conscious vision, can occur without awareness.