Characterising modulatory effects of high-intensity high frequency transcranial random noise stimulation using the perceptual template model.

Neural noise is an inherent property of all nervous systems. However, our understanding of the mechanisms by which noise influences perception is still limited. To elucidate this relationship, we require techniques that can safely modulate noise in humans. Transcranial random noise stimulation (tRNS) has been proposed to induce noise into cortical processing areas according to the principles of stochastic resonance (SR). Specifically, it has been demonstrated that small to moderate intensities of noise improve performance. To date, however, high intensity tRNS effects on neural noise levels have not been directly quantified, nor have the detrimental effects proposed by SR been demonstrated in early visual function. Here, we applied 3 mA high-frequency tRNS to primary visual cortex during an orientation-discrimination task across increasing external noise levels and used the Perceptual Template Model to quantify the mechanisms by which noise changes perceptual performance in healthy observers. Results show that, at a group level, high-intensity tRNS worsened perceptual performance. Our computational analysis reveals that this change in performance was underpinned by an increased amount of additive noise and a reduced ability to filter external noise compared to sham stimulation. Interestingly, while most observers experienced detrimental effects, a subset of participants demonstrated improved performance. Preliminary evidence suggests that differences in baseline internal noise levels might account for these individual differences. Together, these results refine our understanding of the mechanisms underlying the influence of neural noise on perception and have important implications for the application of tRNS as a research tool.

Drive in the Moment: An evaluation of a web-based tool designed to reduce smartphone use among young drivers.

OBJECTIVE: Young drivers are overrepresented in road traffic crashes and fatalities. Distracted driving, including use of a smartphone while driving (SWD), is a major risk factor for crashes for this age group. We evaluated a web-based tool (Drive in the Moment or DITM) designed to reduce SWD among young drivers. METHODS: A pretest-posttest experimental design with a follow-up was used to assess the efficacy of the DITM intervention on SWD intentions and behaviors, and perceived risk (of having a crash and of being apprehended by the police) associated with SWD. One hundred and eighty young drivers (aged 17-25 years old) were randomly assigned to either the DITM intervention or a control group where participants completed an unrelated activity. Self-reported measures of SWD and perceptions of risk were obtained pre-intervention, immediately post-intervention and at a follow-up 25 days after the intervention. RESULTS: Participants who engaged with the DITM showed a significant reduction in the number of times they used their SWD at follow-up compared to their pre-intervention scores. Future intentions to SWD were also reduced from pre-intervention to post-intervention and follow-up. There was also an increase in the perceived risk of SWD following the intervention. CONCLUSIONS: Our evaluation of DITM suggests that the intervention had an impact on reducing SWD among young drivers. Further research is needed to establish which particular elements of the DITM are associated with reductions in SWD and whether similar findings would be identified in other age groups.

Does stochastic resonance improve performance for individuals with higher autism-spectrum quotient?

While noise is generally believed to impair performance, the detection of weak stimuli can sometimes be enhanced by introducing optimum noise levels. This phenomenon is termed 'Stochastic Resonance' (SR). Past evidence suggests that autistic individuals exhibit higher neural noise than neurotypical individuals. It has been proposed that the enhanced performance in Autism Spectrum Disorder (ASD) on some tasks could be due to SR. Here we present a computational model, lab-based, and online visual identification experiments to find corroborating evidence for this hypothesis in individuals without a formal ASD diagnosis. Our modeling predicts that artificially increasing noise results in SR for individuals with low internal noise (e.g., neurotypical), however not for those with higher internal noise (e.g., autistic, or neurotypical individuals with higher autistic traits). It also predicts that at low stimulus noise, individuals with higher internal noise outperform those with lower internal noise. We tested these predictions using visual identification tasks among participants from the general population with autistic traits measured by the Autism-Spectrum Quotient (AQ). While all participants showed SR in the lab-based experiment, this did not support our model strongly. In the online experiment, significant SR was not found, however participants with higher AQ scores outperformed those with lower AQ scores at low stimulus noise levels, which is consistent with our modeling. In conclusion, our study is the first to investigate the link between SR and superior performance by those with ASD-related traits, and reports limited evidence to support the high neural noise/SR hypothesis.

Internal noise measures in coarse and fine motion direction discrimination tasks and the correlation with autism traits.

Motion perception is essential for visual guidance of behavior and is known to be limited by both internal additive noise (i.e., a constant level of random fluctuations in neural activity independent of the stimulus) and motion pooling (global integration of local motion signals across space). People with autism spectrum disorder (ASD) display abnormalities in motion processing, which have been linked to both elevated noise and abnormal pooling. However, to date, the impact of a third limit-induced internal noise (internal noise that scales up with increases in external stimulus noise)-has not been investigated in motion perception of any group. Here, we describe an extension on the double-pass paradigm to quantify additive noise and induced noise in a motion paradigm. We also introduce a new way to experimentally estimate motion pooling. We measured the impact of induced noise on direction discrimination, which we ascribe to fluctuations in decision-related variables. Our results are suggestive of higher internal noise in individuals with high ASD traits only on coarse but not fine motion direction discrimination tasks. However, we report no significant correlations between autism traits and additive noise, induced noise, or motion pooling in either task. We conclude that, under some conditions, the internal noise may be higher in individuals with pronounced ASD traits and that the assessment of induced internal noise is a useful way of exploring decision-related limits on motion perception, irrespective of ASD traits.

Seeing faces where there are none: Pareidolia correlates with age but not autism traits.

Previous research has found that individuals with autism spectrum disorder experience difficulties when visually processing face stimuli compared to developmentally typical individuals. Whether, in the typically-developing population, face detection depends on autism-like traits (ALTs) is less clear. In this report, we aimed to develop an experimental design that is more sensitive to any individual differences in face detection than previous reports. We employed pareidolia, that is, cases where non-face stimuli are perceived to be faces, assuming this is more difficult than detection of 'real' faces, decreasing changes of ceiling performance. We also show multiple faces per trial, allowing for a more graded assessment of face detection ability. Participants were 263 individuals aged between 18 and 82 years of age. Pareidolia was investigated in two online experiments, with different types of stimuli: objects that could be perceived as faces (i.e., embedded faces task) and Mooney faces (Mooney face task). In the latter condition, we also investigated the face inversion effect. We found that neither detection ability or the inversion effect depended on ALTs. We did find a dependence of age for both measures, and a complex dependence on gender for Mooney faces. Our data suggest that face detection (and specifically pareidolia) does not depend on ALTs, but does depend on the age of the observer. The dependence on age appears to be different between the two experiments, suggesting that the underlying mechanisms necessary for face detection in our two experiments mature and decline at different rates.

The SSVEP tracks attention, not consciousness, during perceptual filling-in.

Research on the neural basis of conscious perception has almost exclusively shown that becoming aware of a stimulus leads to increased neural responses. By designing a novel form of perceptual filling-in (PFI) overlaid with a dynamic texture display, we frequency-tagged multiple disappearing targets as well as their surroundings. We show that in a PFI paradigm, the disappearance of a stimulus and subjective invisibility is associated with increases in neural activity, as measured with steady-state visually evoked potentials (SSVEPs), in electroencephalography (EEG). We also find that this increase correlates with alpha-band activity, a well-established neural measure of attention. These findings cast doubt on the direct relationship previously reported between the strength of neural activity and conscious perception, at least when measured with current tools, such as the SSVEP. Instead, we conclude that SSVEP strength more closely measures changes in attention.

A multiple-response frequency-tagging paradigm measures graded changes in consciousness during perceptual filling-in.

Perceptual filling-in (PFI) occurs when a physically present visual target disappears from conscious perception, with its location filled-in by the surrounding visual background. These perceptual changes are complete, near instantaneous, and can occur for multiple separate locations simultaneously. Here, we show that contrasting neural activity during the presence or absence of multi-target PFI can complement other findings from multistable phenomena to reveal the neural correlates of consciousness (NCC). We presented four peripheral targets over a background dynamically updating at 20 Hz. While participants reported on target disappearances/reappearances via button press/release, we tracked neural activity entrained by the background during PFI using steady-state visually evoked potentials (SSVEPs) recorded in the electroencephalogram. We found background SSVEPs closely correlated with subjective report, and increased with an increasing amount of PFI. Unexpectedly, we found that as the number of filled-in targets increased, the duration of target disappearances also increased, suggesting that facilitatory interactions exist between targets in separate visual quadrants. We also found distinct spatiotemporal correlates for the background SSVEP harmonics. Prior to genuine PFI, the response at the second harmonic (40 Hz) increased before the first (20 Hz), which we tentatively link to an attentional effect, while no such difference between harmonics was observed for physically removed stimuli. These results demonstrate that PFI can be used to study multi-object perceptual suppression when frequency-tagging the background of a visual display, and because there are distinct neural correlates for endogenously and exogenously induced changes in consciousness, that it is ideally suited to study the NCC.

Motion-induced blindness as a tool to measure attentional biases and the link to attention-deficit/hyperactivity traits.

Typically, individuals have an attentional bias toward the left visual field. This is often absent in individuals with attention-deficit/hyperactivity (ADH) disorder (ADHD). We used a motion-induced blindness task with targets in 4 quadrants to assess left/right as well as upper/lower spatial biases in perceptual disappearances and also measured changes in the disappearances with time-on-task. Fifty-eight university students (41 female) completed the Conners Adult ADHD self-report short-form to assess the number of ADH traits, and 48 trials of a 1-min motion-induced blindness (MIB) task. Through a hybrid hypothesis-driven and data-driven analysis approach, we found that the MIB illusion increased with more ADH traits, decreased with time-on-task, and was stronger for left and lower quadrants. The time-on-task likely contributed to the strength of the illusion through changes in arousal, as pupil size decreased with time-on-trial in a subset of participants (n = 11) for whom we measure eye movements. In addition, although participants were biased toward the lower left visual field, this was, unexpectedly, most prominent with those with higher ADH traits. This novel result suggests an additive effect of left/right and upper/lower spatial biases. Taken together, this study supports an association between spatial attention, arousal and ADH traits in MIB. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Modeling stochastic resonance in humans: The influence of lapse rate.

Adding noise to sensory signals generally decreases human performance. However, noise can improve performance too, through a process called stochastic resonance (SR). This paradoxical effect may be exploited in psychophysical experiments to provide insights into how the sensory system processes noise. Here, I develop an extension on signal detection theory to model stochastic resonance. I show that the inclusion of lapse rate allows for the occurrence of stochastic resonance in terms of the performance metric d', when the criterion is set suboptimally. High levels of lapse rate, however, cause stochastic resonance to disappear. It is also shown that noise generated in the brain (i.e., internal noise) may obscure any effect of stochastic resonance in experimental settings. I further relate the model to a standard equivalent noise model, the linear amplifier model, and show that lapse rate scales the threshold versus noise (TvN) curve, similar to the efficiency parameter in equivalent noise (EN) models. Therefore, lapse rate provides a psychophysical explanation for reduced efficiency in EN paradigms. Furthermore, I note that ignoring lapse rate may lead to an overestimation of internal noise in EN paradigms. Overall, describing stochastic resonance in terms of signal detection theory, with the inclusion of lapse rate, may provide valuable new insights into how human performance depends on internal and external noise. It may have applications in improving human performance in situations where the criterion is set suboptimally, and it may provide additional insight into internal noise hypotheses related to autism spectrum disorder.

Motor difficulties are associated with impaired perception of interactive human movement in autism spectrum disorder: A pilot study.

Introduction: The ability to accurately perceive human movement is fundamental to social functioning and known to be influenced by one's own motor skills. In Autism Spectrum Disorder (ASD), there is ongoing debate about whether human movement perception is impaired. Given that motor skills vary considerably among these individuals, it may be that human movement perception is differentially affected as a function of motor proficiency. The aim of the current study was, thus, to explore whether individuals with ASD with and without motor difficulties differ in the way they visually attend to and perceive human movement. Method: Three groups of children aged 6 to 14 completed the study: an ASD group with motor difficulties (ASDMD), an ASD group without motor difficulties (ASDNMD), and a typically-developing control group (TD). All participants (N = 31) underwent eye-tracking while they viewed communicative interactions performed by two point-light actors. Primary analyses considered group differences in perceptual accuracy and gaze patterns. Results: Results revealed poorer perceptual accuracy in the ASDMD group compared to the ASDNMD and TD groups. Both ASD groups also exhibited gaze anomalies. Unlike the ASDNMD and TD groups who preferentially allocated their gaze to the actor initiating the interaction, the ASDMD group gazed at both actors equally. In contrast, the ASDNMD group shifted their gaze between the actors more frequently than the other groups. Conclusions: These preliminary findings suggest that individuals with ASD and co-occurring motor difficulties employ an atypical attentional style that may hinder accurate human movement perception, whereas those without motor difficulties may employ a compensatory attentional style that facilitates typical perception. Improving our understanding of how attention and perception are affected across the ASD spectrum has the potential to provide insight into the mechanisms that underlie the core social deficits that define this disorder.

From intermodulation components to visual perception and cognition-a review.

Perception results from complex interactions among sensory and cognitive processes across hierarchical levels in the brain. Intermodulation (IM) components, used in frequency tagging neuroimaging designs, have emerged as a promising direct measure of such neural interactions. IMs have initially been used in electroencephalography (EEG) to investigate low-level visual processing. In a more recent trend, IMs in EEG and other neuroimaging methods are being used to shed light on mechanisms of mid- and high-level perceptual processes, including the involvement of cognitive functions such as attention and expectation. Here, we provide an account of various mechanisms that may give rise to IMs in neuroimaging data, and what these IMs may look like. We discuss methodologies that can be implemented for different uses of IMs and we demonstrate how IMs can provide insights into the existence, the degree and the type of neural integration mechanisms at hand. We then review a range of recent studies exploiting IMs in visual perception research, placing an emphasis on high-level vision and the influence of awareness and cognition on visual processing. We conclude by suggesting future directions that can enhance the benefits of IM-methodology in perception research.

Does It Matter Whether You or Your Brain Did It? An Empirical Investigation of the Influence of the Double Subject Fallacy on Moral Responsibility Judgments.

Despite progress in cognitive neuroscience, we are still far from understanding the relations between the brain and the conscious self. We previously suggested that some neuroscientific texts that attempt to clarify these relations may in fact make them more difficult to understand. Such texts-ranging from popular science to high-impact scientific publications-position the brain and the conscious self as two independent, interacting subjects, capable of possessing opposite psychological states. We termed such writing 'Double Subject Fallacy' (DSF). We further suggested that such DSF language, besides being conceptually confusing and reflecting dualistic intuitions, might affect people's conceptions of moral responsibility, lessening the perception of guilt over actions. Here, we empirically investigated this proposition with a series of three experiments (pilot and two preregistered replications). Subjects were presented with moral scenarios where the defendant was either (1) clearly guilty, (2) ambiguous, or (3) clearly innocent while the accompanying neuroscientific evidence about the defendant was presented using DSF or non-DSF language. Subjects were instructed to rate the defendant's guilt in all experiments. Subjects rated the defendant in the clearly guilty scenario as guiltier than in the two other scenarios and the defendant in the ambiguously described scenario as guiltier than in the innocent scenario, as expected. In Experiment 1 (N = 609), an effect was further found for DSF language in the expected direction: subjects rated the defendant less guilty when the neuroscientific evidence was described using DSF language, across all levels of culpability. However, this effect did not replicate in Experiment 2 (N = 1794), which focused on different moral scenario, nor in Experiment 3 (N = 1810), which was an exact replication of Experiment 1. Bayesian analyses yielded strong evidence against the existence of an effect of DSF language on the perception of guilt. Our results thus challenge the claim that DSF language affects subjects' moral judgments. They further demonstrate the importance of good scientific practice, including preregistration and-most critically-replication, to avoid reaching erroneous conclusions based on false-positive results.

Sustained conscious access to incidental memories in RSVP.

In visual search of natural scenes, differentiation of briefly fixated but task-irrelevant distractor items from incidental memory is often comparable to explicit memorization. However, many characteristics of incidental memory remain unclear, including the capacity for its conscious retrieval. Here, we examined incidental memory for faces in either upright or inverted orientation using Rapid Serial Visual Presentation (RSVP). Subjects were instructed to detect a target face in a sequence of 8-15 faces cropped from natural scene photographs (Experiment 1). If the target face was identified within a brief time window, the subject proceeded to an incidental memory task. Here, subjects used incidental memory to discriminate between a probe face (a distractor in the RSVP stream) and a novel, foil face. In Experiment 2 we reduced scene-related semantic coherency by intermixing faces from multiple scenes and contrasted incidental memory with explicit memory, a condition where subjects actively memorized each face from the sequence without searching for a target. In both experiments, we measured objective performance (Type 1 AUC) and metacognitive accuracy (Type 2 AUC), revealing sustained and consciously accessible incidental memory for upright and inverted faces. In novel analyses of face categories, we examined whether accuracy or metacognitive judgments are affected by shared semantic features (i.e., similarity in gender, race, age). Similarity enhanced the accuracy of incidental memory discriminations but did not influence metacognition. We conclude that incidental memory is sustained and consciously accessible, is not reliant on scene contexts, and is not enhanced by explicit memorization.

Attention periodically samples competing stimuli during binocular rivalry.

The attentional sampling hypothesis suggests that attention rhythmically enhances sensory processing when attending to a single (~8 Hz), or multiple (~4 Hz) objects. Here, we investigated whether attention samples sensory representations that are not part of the conscious percept during binocular rivalry. When crossmodally cued toward a conscious image, subsequent changes in consciousness occurred at ~8 Hz, consistent with the rates of undivided attentional sampling. However, when attention was cued toward the suppressed image, changes in consciousness slowed to ~3.5 Hz, indicating the division of attention away from the conscious visual image. In the electroencephalogram, we found that at attentional sampling frequencies, the strength of inter-trial phase-coherence over fronto-temporal and parieto-occipital regions correlated with changes in perception. When cues were not task-relevant, these effects disappeared, confirming that perceptual changes were dependent upon the allocation of attention, and that attention can flexibly sample away from a conscious image in a task-dependent manner.

Conscious access in the near absence of attention: critical extensions on the dual-task paradigm.

Whether conscious perception requires attention remains a topic of intense debate. While certain complex stimuli such as faces and animals can be discriminated outside the focus of spatial attention, many simpler stimuli cannot. Because such evidence was obtained in dual-task paradigms involving no measure of subjective insight, it remains unclear whether accurate discrimination of unattended complex stimuli is the product of automatic, unconscious processing, as in blindsight, or is accessible to consciousness. Furthermore, these paradigms typically require extensive training over many hours, bringing into question whether this phenomenon can be achieved in naive subjects. We developed a novel dual-task paradigm incorporating confidence ratings to calculate metacognition and adaptive staircase procedures to reduce training. With minimal training, subjects were able to discriminate face-gender in the near absence of top-down attentional amplification, while also displaying above-chance metacognitive accuracy. By contrast, the discrimination of simple coloured discs was significantly impaired and metacognitive accuracy dropped to chance-level, even in a partial-report condition. In a final experiment, we used blended face/disc stimuli and confirmed that face-gender but not colour orientation can be discriminated in the dual task. Our results show direct evidence for metacognitive conscious access in the near absence of attention for complex, but not simple, stimuli.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

The role of transparency cues in afterimage color perception.

Recent evidence has shown that afterimage perception and completion are amenable to contextual information. It has previously been shown that placing an outline around part of the afterimage can induce colors in areas that were uncolored. A thorough explanation of this effect is lacking, although this color completion was thought to be due to a diffusion-like filling-in of the uncolored patch with colors of the surrounding areas. Here, we show that an important step in visual completion is the decomposition of the visual scene into different depth layers, i.e. scission, which, we show, is guided by transparency cues in the van Lier et al. STUDY: In three experiments, we show that when decomposition is prevented, color completion does not occur. We also show that this decomposition can induce color completion in real images. These results demonstrate that transparency information plays an important role in determining visual color completion processes.

Simulated forward and backward self motion, based on realistic parameters, causes motion induced blindness.

Motion Induced Blindness (MIB) is a well-established visual phenomenon whereby highly salient targets disappear when viewed against a moving background mask. No research has yet explored whether contracting and expanding optic flow can also trigger target disappearance. We explored MIB using mask speeds corresponding to driving at 35, 50, 65 and 80 km/h in simulated forward (expansion) and backward (contraction) motion as well as 2-D radial movement, random, and static mask motion types. Participants (n = 18) viewed MIB targets against masks with different movement types, speed, and target locations. To understand the relationship between saccades, pupil response and perceptual disappearance, we ran two additional eye-tracking experiments (n = 19). Target disappearance increased significantly with faster mask speeds and upper visual field target presentation. Simulated optic flow and 2-D radial movement caused comparable disappearance, and all moving masks caused significantly more disappearance than a static mask. Saccades could not entirely account for differences between conditions, suggesting that self-motion optic flow does cause MIB in an artificial setting. Pupil analyses implied that MIB disappearance induced by optic flow is not subjectively salient, potentially explaining why MIB is not noticed during driving. Potential implications of MIB for driving safety and Head-Up-Display (HUD) technologies are discussed.

Different Signal Enhancement Pathways of Attention and Consciousness Underlie Perception in Humans.

It is not yet known whether attention and consciousness operate through similar or largely different mechanisms. Visual processing mechanisms are routinely characterized by measuring contrast response functions (CRFs). In this report, behavioral CRFs were obtained in humans (both males and females) by measuring afterimage durations over the entire range of inducer stimulus contrasts to reveal visual mechanisms behind attention and consciousness. Deviations relative to the standard CRF, i.e., gain functions, describe the strength of signal enhancement, which were assessed for both changes due to attentional task and conscious perception. It was found that attention displayed a response-gain function, whereas consciousness displayed a contrast-gain function. Through model comparisons, which only included contrast-gain modulations, both contrast-gain and response-gain effects can be explained with a two-level normalization model, in which consciousness affects only the first level and attention affects only the second level. These results demonstrate that attention and consciousness can effectively show different gain functions because they operate through different signal enhancement mechanisms.SIGNIFICANCE STATEMENT The relationship between attention and consciousness is still debated. Mapping contrast response functions (CRFs) has allowed (neuro)scientists to gain important insights into the mechanistic underpinnings of visual processing. Here, the influence of both attention and consciousness on these functions were measured and they displayed a strong dissociation. First, attention lowered CRFs, whereas consciousness raised them. Second, attention manifests itself as a response-gain function, whereas consciousness manifests itself as a contrast-gain function. Extensive model comparisons show that these results are best explained in a two-level normalization model in which consciousness affects only the first level, whereas attention affects only the second level. These findings show dissociations between both the computational mechanisms behind attention and consciousness and the perceptual consequences that they induce.