Stochastic resonance in the sensory systems and its applications in neural prosthetics.

Noise is generally considered to be detrimental. In the right conditions, however, noise can improve signal detection or information transmission. This counterintuitive phenomenon is called stochastic resonance (SR). SR has generated significant interdisciplinary interest, particularly in physics, engineering, and medical and environmental sciences. In this review, we discuss a growing empirical literature that suggests that noise at the right intensity may improve the detection and processing of auditory, sensorimotor, and visual stimuli. We focus particularly on applications of SR in sensory biology and investigate whether SR-based technologies present a pathway to improve outcomes for individuals living with sensory impairments. We conclude that there is considerable evidence supporting the application of SR in developing sensory prosthetics. However, the progression of SR-based technologies is variable across the sensory modalities. We suggest opportunities for further advancements in each modality, considering the best approaches to maximise benefits and capitalise on progress already made. Overall, SR can offer opportunities to improve existing technologies or to motivate innovations.

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.

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.

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.

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.

Individual differences in high-level biological motion tasks correlate with autistic traits.

Human actions are rich in social cues and play an essential role in interacting with the social environment. Hence, the perception of biological motion (i.e., movement elicited by humans and other animals) is considered to be an important gauge of a person's social cognition capacities. It has been well-documented that Autism Spectrum Disorder (ASD) is associated with difficulties in social interactions. In the present study, we examined whether individual differences in biological motion perception relate to the degree of autistic traits among people in the typically-developing population. We employed three tasks that require different degrees of involvement of global action processing: action discrimination in noise, action inversion effect in binocular rivalry, and inter-personal interaction recognition. We found that individuals with higher numbers of autistic traits showed similar action discrimination performance as individuals with fewer autistic traits but exhibited a reduced inversion effect in binocular rivalry, and a decreased ability to recognize meaningful human interactions. These findings provide converging evidence that global processing of biological motion is affected in people with a high degree of autistic traits.

Social Interactions Receive Priority to Conscious Perception.

Humans are social animals, constantly engaged with other people. The importance of social thought and action is hard to overstate. However, is social information so important that it actually determines which stimuli are promoted to conscious experience and which stimuli are suppressed as invisible? To address this question, we used a binocular rivalry paradigm, in which the two eyes receive different action stimuli. In two experiments we measured the conscious percept of rival actions and found that actions engaged in social interactions are granted preferential access to visual awareness over non-interactive actions. Lastly, an attentional task that presumably engaged the mentalizing system enhanced the priority assigned to social interactions in reaching conscious perception. We also found a positive correlation between human identification of interactive activity and the promotion of socially-relevant information to visual awareness. The present findings suggest that the visual system amplifies socially-relevant sensory information and actively promotes it to consciousness, thereby facilitating inferences about social interactions.

Neural adaptation in pSTS correlates with perceptual aftereffects to biological motion and with autistic traits.

The adaptive nature of biological motion perception has been documented in behavioral studies, with research showing that prolonged viewing of an action can bias judgments of subsequent actions towards the opposite of its attributes. However, the neural mechanisms underlying action adaptation aftereffects remain unknown. We examined adaptation-induced changes in brain responses to an ambiguous action after adapting to walking or running actions within two bilateral regions of interest: 1) human middle temporal area (hMT+), a lower-level motion-sensitive region of cortex, and 2) posterior superior temporal sulcus (pSTS), a higher-level action-selective area. We found a significant correlation between neural adaptation strength in right pSTS and perceptual aftereffects to biological motion measured behaviorally, but not in hMT+. The magnitude of neural adaptation in right pSTS was also strongly correlated with individual differences in the degree of autistic traits. Participants with more autistic traits exhibited less adaptation-induced modulations of brain responses in right pSTS and correspondingly weaker perceptual aftereffects. These results suggest a direct link between perceptual aftereffects and adaptation of neural populations in right pSTS after prolonged viewing of a biological motion stimulus, and highlight the potential importance of this brain region for understanding differences in social-cognitive processing along the autistic spectrum.

Reevaluating excess success in psychological science.

Francis (Psychonomic Bulletin Review, 21, 1180-1187, 2014) recently claimed that 82 % of articles with four or more experiments published in Psychological Science between 2009 and 2012 cannot be trusted. We critique Francis' analysis and point out the dependence of his approach on including the appropriate experiments and significance tests. We focus on one of the articles (van Boxtel & Koch, in Psychological Science, 23(4), 410-418, 2012) flagged by Francis and show that the inappropriate inclusion of experiments and tests have led Francis to mistakenly flag this article. We found that decisions about whether to include certain tests potentially affect 34 of the 44 articles analyzed by Francis. We further performed p-curve analyses on the articles discussed in Francis' analysis. We found that 9 of 44 studies showed significant evidential value, 11 studies showed insufficient evidential value, and 1 study showed evidence of p-hacking. Our reevaluation is important, because some researchers may have gained the false impression that none of the quoted articles in Psychological Science can be trusted (as stated by Francis). The analysis by Francis is most likely insufficient to warrant this conclusion for some articles and certainly is insufficient with respect to the study by van Boxtel and Koch (Psychological Science, 23, 410-418, 2012).

Intact recognition, but attenuated adaptation, for biological motion in youth with autism spectrum disorder.

Given the ecological importance of biological motion and its relevance to social cognition, considerable effort has been devoted over the past decade to studying biological motion perception in autism. However, previous studies have asked observers to detect or recognize briefly presented human actions placed in isolation, without spatial or temporal context. Research on typical populations has shown the influence of temporal context in biological motion perception: prolonged exposure to one action gives rise to an aftereffect that biases perception of a subsequently displayed action. Whether people with autism spectrum disorders (ASD) show such adaptation effects for biological motion stimuli remains unknown. To address this question, this study examined how well youth with ASD recognize ambiguous actions and adapt to recently-observed actions. Compared to typically-developing (TD) controls, youth with ASD showed no differences in perceptual boundaries between actions categories, indicating intact ability in recognizing actions. However, children with ASD showed weakened adaptation to biological motion. It is unlikely that the reduced action adaptability in autism was due to delayed developmental trajectory, as older children with ASD showed weaker adaptation to actions than younger children with ASD. Our results further suggest that high-level (i.e., action) processing weakens with age for children with ASD, but this change may be accompanied by a potentially compensatory mechanism based on more involvement of low-level (i.e., motion) processing. Autism Res 2016, 9: 1103-1113. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.