Temporal Alignment but not Complexity of Audiovisual Stimuli Influences Crossmodal Duration Percepts

Reliable duration perception is an integral aspect of daily life that impacts everyday perception, motor coordination, and subjective passage of time. The Scalar Expectancy Theory (SET) is a common model that explains how an internal pacemaker, gated by an external stimulus-driven switch, accumulates pulses during sensory events and compares these accumulated pulses to a reference memory duration for subsequent duration estimation. Second-order mechanisms, such as multisensory integration (MSI) and attention, can influence this model and affect duration perception. For instance, diverting attention away from temporal features could delay the switch closure or temporarily open the accumulator, altering pulse accumulation and distorting duration perception. In crossmodal duration perception, auditory signals of unequal duration can induce perceptual compression and expansion of durations of visual stimuli, presumably via auditory influence on the visual clock. The current project aimed to investigate the role of temporal (stimulus alignment) and nontemporal (stimulus complexity) features on crossmodal, specifically auditory over visual, duration perception. While temporal alignment revealed a larger impact on the strength of crossmodal duration percepts compared to stimulus complexity, both features showcase auditory dominance in processing visual duration.

Working memory performance is tied to stimulus complexity

1.SummaryWorking memory is the cognitive capability to maintain and process information over short periods. Recent behavioral and computational studies have shown that increased visual information of the presented stimulus material is associated with enhanced working memory performance. However, the underlying neural correlates of this association are unknown. To identify how stimuli of different visual information levels affect working memory performance, we conducted behavioral experiments and single unit recordings in the avian analog of the prefrontal cortex, the nidopallium caudolaterale (NCL). On the behavioral level, we confirmed that feature-rich complex stimuli demonstrated higher working memory performance compared to feature-poor simple stimuli. This difference was reflected by distinct neural coding patterns at the single unit level. For complex stimuli, we found a highly multiplexed neuronal code. During the sample presentation, NCL neurons initially reflected both visual and value-related features of the presented stimuli that switched to a representation of the upcoming choice during a delay period. When processing simple stimuli, NCL neurons did not multiplex and represented the upcoming choice already during stimulus presentation and throughout the delay period. It is conceivable that the maintenance of the upcoming choice in working memory was prolonged for simple stimuli due to the early choice representation. This possibly resulted in increased decay of the working memory trace ultimately leading to a decrease in performance. In conclusion, we found that increases in stimulus complexity are associated with increased neuronal multiplexing of the working memory representation. This could possibly allow for a facilitated read-out of the neural code resulting in further enhancements of working memory performance.

The nationality benefit: Long-term memory associations enhance visual working memory for color-shape conjunctions

Visual working memory (VWM) is typically found to be severely limited in capacity, but this limitation may be ameliorated by providing familiar objects that are associated with knowledge stored in long-term memory. However, comparing meaningful and meaningless stimuli usually entails a confound, because different types of objects also tend to vary in terms of their inherent perceptual complexity. The current study therefore aimed to dissociate stimulus complexity from object meaning in VWM. To this end, identical stimuli – namely, simple color-shape conjunctions – were presented, which either resembled meaningful configurations (“real” European flags), or which were rearranged to form perceptually identical but meaningless (“fake”) flags. The results revealed complexity estimates for “real” and “fake” flags to be higher than for unicolor baseline stimuli. However, VWM capacity for real flags was comparable to the unicolor baseline stimuli (and substantially higher than for fake flags). This shows that relatively complex, yet meaningful “real” flags reveal a VWM capacity that is comparable to rather simple, unicolored memory items. Moreover, this “nationality” benefit was related to individual flag recognition performance, thus showing that VWM depends on object knowledge.

Perceptual Load and Sex-Specific Personality Traits

The impact of sex-specific personality traits has often been investigated for visuospatial tasks such as mental rotation, but less is known about the influence of personality traits on visual search. We investigated whether the Big Five personality traits Extroversion (E), Openness (O), Agreeableness (A), Conscientiousness (C), and Neuroticism (N) and the Autism Quotient (AQ) influence visual search in a sample of N = 65 men and women. In three experiments, we varied stimulus complexity and predictability. As expected, latencies were longer when the target was absent. Pop-out search was faster than conjunction search. A large number of distracters slowed down reaction times (RTs). When stimulus complexity was not predictable in Experiment 3, this reduced search accuracy by about half. As could be predicted based on previous research on long RT tails, conjunction search in target absent trials revealed the impact of personality traits. The RT effect in visual search of the accelerating “less social” AQ score was specific to men, while the effects of the “more social” decelerating Big Five Inventory factors agreeableness and conscientiousness were specific to women. Thus, sex-specific personality traits could explain decision-making thresholds, while visual stimulus complexity yielded an impact of the classic personality traits neuroticism and extroversion.

What is the Effect of Stimulus Complexity on Attention to Repeating and Changing Information in Autism?

Slower habituation to repeating stimuli characterises Autism, but it is not known whether this is driven by difficulties with information processing or an attentional bias towards sameness. We conducted eye-tracking and presented looming geometrical shapes, clocks with moving arms and smiling faces, as two separate streams of stimuli (one repeating and one changing), to 7–15 years old children and adolescents (n = 103) with Autism, ADHD or co-occurring Autism+ADHD, and neurotypical children (Study-1); and to neurotypical children (n = 64) with varying levels of autistic traits (Study-2). Across both studies, autistic features were associated with longer looks to the repeating stimulus, and shorter looks to the changing stimulus, but only for more complex stimuli, indicating greater difficulty in processing complex or unpredictable information.

How Are Audiovisual Simultaneity Judgments Affected by Multisensory Complexity and Speech Specificity?

While stimulus complexity is known to affect the width of the temporal integration window (TIW), a quantitative evaluation of ecologically highly valid stimuli has not been conducted. We assumed that the degree of complexity is determined by the obviousness of the correspondence between the auditory onset and visual movement, and we evaluated the audiovisual complexity using video clips of a piano, a shakuhachi flute and human speech. In Experiment 1, a simultaneity judgment task was conducted using these three types of stimuli. The results showed that the width of TIW was wider for speech, compared with the shakuhachi and piano. Regression analysis revealed that the width of the TIW depended on the degree of complexity. In the second experiment, we investigated whether or not speech-specific factors affected the temporal integration. We used stimuli that either contained natural-speech sounds or white noise. The results revealed that the width of the TIW was wider for natural sentences, compared with white noise. Taken together, the width of the TIW might be affected by both the complexity and speech specificity.

What is the effect of stimulus complexity on attention to repeating and changing information in Autism?

Background Previous research has suggested that atypical attention in autism might be driven by a preference for sameness over novelty. There is also evidence of slower habituation to a repeating stimulus in autism. It is not known whether slower habituation is driven by atypically slower processing of repeating information or whether it is a manifestation of an attentional bias away from novelty towards sameness. Methods We adapted an existing eye-tracking task and measured eye movements to two streams of stimuli presented simultaneously, one each in the left and right sides of the screen. One stimulus repeated while the second stimulus changed across trials. We manipulated the complexity of the stimuli between three conditions: a simple shapes condition, a social (smiling faces) condition and a complex non-social condition (clocks with moving parts). Using the slope of change in the longest look duration to each stimulus over trials, we measured whether autistic features were associated with slower habituation (to the repeating stimulus) and/or reduced attention to novelty (changing stimulus) over trials, and whether these effects were more pronounced in conditions with higher stimulus complexity (social and non-social complex conditions) compared with low complexity (simple shapes condition). We presented the task to two independent samples of children: 7-15 years old children and adolescents (n=103) diagnosed with Autism, ADHD or co-occurring Autism and ADHD and neurotypical children (Study 1); neurotypical children (n=64) with varying levels of subclinical traits of Autism (Study 2). Results Across the two studies, autistic features were associated with positive slopes of change in look durations (longer looks over time) to the repeating stimulus and negative slopes (shorter looks over time) to the changing stimulus, only in conditions with higher stimulus complexity. Negative slopes to the changing stimulus in conditions of higher stimulus complexity was associated with higher severity of social interaction difficulties (in Study 1). Conclusions Reduced attention to novelty in autism might partly be driven by difficulties in processing more complex information, which might contribute to the development of social interaction difficulties in autism. Replication in larger samples and longitudinal research using younger age groups are recommended.

Study of sensory information processing depending on visual stimulus complexity based on multichannel EEG signals

Introduction: Analysis of electrical activity in the cortical neural network during the processing of visual information is one ofthe most interesting issues in modern neuroscience. The particular attention of the researchers is attracted by the study of neuralactivity during complex visual stimuli processing. Purpose: Studying the process of sensory information processing in the corticalneural network based on recorded electrical activity signals (EEG). Results: We have studied neural activity during visual informationprocessing based on the stimulus-related change in the spectral EEG energy in the 15–30 Hz frequency band. Using the developedapproach, we analyzed the influence of the visual stimulus complexity on the features of spatio-temporal neural activity. It has beenfound that at low complexity the spectral amplitude of the EEG in the range of 15–30 Hz increases mainly in the parietal zone. Withincreasing complexity, the spectral amplitude of the EEG increases simultaneously in different parts of the cortex, mainly in the frontalregion. Practical relevance: The identified features of neural dynamics can be used in the development of passive brain-computerinterfaces to monitor a person’s cognitive state and evaluate the cognitive load in real time.