Decoding the content of working memory in school-aged children.

Developmental improvements in working memory (WM) maintenance predict many real-world outcomes, including educational attainment. It is thus critical to understand which WM mechanisms support these behavioral improvements, and how WM maintenance strategies might change through development. One challenge is that specific WM neural mechanisms cannot easily be measured behaviorally, especially in a child population. However, new multivariate decoding techniques have been designed, primarily in adult populations, that can sensitively decode the contents of WM. The goal of this study was to deploy multivariate decoding techniques known to decode memory representations in adults to decode the contents of WM in children. We created a simple computerized WM game for children, in which children maintained different categories of information (visual, spatial or verbal). We collected electroencephalography (EEG) data from 20 children (7-12-year-olds) while they played the game. Using Multivariate Pattern Analysis (MVPA) on children's EEG signals, we reliably decoded the category of the maintained information during the sensory and maintenance period. Across exploratory reliability and validity analyses, we examined the robustness of these results when trained on less data, and how these patterns generalized within individuals throughout the testing session. Furthermore, these results matched theory-based predictions of WM across individuals and across ages. Our proof-of-concept study proposes a direct and age-appropriate potential alternative to exclusively behavioral WM maintenance measures in children. Our study demonstrates the utility of MVPA to measure and track the uninstructed representational content of children's WM. Future research could use our technique to investigate children's WM maintenance and strategies.

The effect of multisensory distraction on working memory: A role for task relevance?

There is growing recognition that working memory and selective attention are highly related. However, a key function of selective attention-ignoring distractors-is much less understood in the domain of working memory. In the attention domain, it is now clear that distractors' task relevance and stimulation of multiple senses at a time (i.e., being multisensory), affect how much such information can distract from the main task, and that load modulates these effects. Here, we examined the effects of the task relevance and multisensory nature of distractors on working memory performance under high and low memory load, aiming to clarify whether distracting information similarly affects selective attention performance and working memory performance. We proposed a multiexperiment research plan involving up to three consecutive experiments, based on an initial online study (Experiment 0) with fully task-irrelevant distractors. There, we found conclusive evidence against a difference in how unisensory and multisensory distractors affected working memory performance. The next study, Experiment 1, replicated these results. However, when distractors were made partly task relevant in the subsequent Experiment 2d, multisensory distractors disrupted working memory performance more than unisensory distractors on average. However, closer nonpreregistered inspection revealed that multisensory distractors were actually only more disruptive than auditory distractors, and similarly as disruptive as visual distractors. Thus, overall, there was no strong evidence for multisensory distractors being more disruptive to working memory performance than unisensory distractors. Taken together, these experiments constitute a novel and detailed investigation of the impact of distracting information on working memory performance. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Decoding the content of working memory in school-aged children.

Developmental improvements in working memory (WM) maintenance predict many real-world outcomes, including educational attainment. It is thus critical to understand which WM mechanisms support these behavioral improvements, and how WM maintenance strategies might change through development. One challenge is that specific WM neural mechanisms cannot easily be measured behaviorally, especially in a child population. However, new multivariate decoding techniques have been designed, primarily in adult populations, that can sensitively decode the contents of WM. The goal of this study was to deploy multivariate decoding techniques known to decode memory representations in adults to decode the contents of WM in children. We created a simple computerized WM game for children, in which children maintained different categories of information (visual, spatial or verbal). We collected electroencephalography (EEG) data from 20 children (7-12-year-olds) while they played the game. Using Multivariate Pattern Analysis (MVPA) on children's EEG signals, we reliably decoded the category of the maintained information during the sensory and maintenance period. Across exploratory reliability and validity analyses, we examined the robustness of these results when trained on less data, and how these patterns generalized within individuals throughout the testing session. Furthermore, these results matched theory-based predictions of WM across individuals and across ages. Our proof-of-concept study proposes a direct and age-appropriate potential alternative to exclusively behavioral WM maintenance measures in children. Our study demonstrates the utility of MVPA to measure and track the uninstructed representational content of children's WM. Future research could use our technique to investigate children's WM maintenance and strategies.

Digital haptics improve speed of visual search performance in a dual-task setting.

Dashboard-mounted touchscreen tablets are now common in vehicles. Screen/phone use in cars likely shifts drivers' attention away from the road and contributes to risk of accidents. Nevertheless, vision is subject to multisensory influences from other senses. Haptics may help maintain or even increase visual attention to the road, while still allowing for reliable dashboard control. Here, we provide a proof-of-concept for the effectiveness of digital haptic technologies (hereafter digital haptics), which use ultrasonic vibrations on a tablet screen to render haptic perceptions. Healthy human participants (N = 25) completed a divided-attention paradigm. The primary task was a centrally-presented visual conjunction search task, and the secondary task entailed control of laterally-presented sliders on the tablet. Sliders were presented visually, haptically, or visuo-haptically and were vertical, horizontal or circular. We reasoned that the primary task would be performed best when the secondary task was haptic-only. Reaction times (RTs) on the visual search task were fastest when the tablet task was haptic-only. This was not due to a speed-accuracy trade-off; there was no evidence for modulation of VST accuracy according to modality of the tablet task. These results provide the first quantitative support for introducing digital haptics into vehicle and similar contexts.

Towards understanding how we pay attention in naturalistic visual search settings.

Research on attentional control has largely focused on single senses and the importance of behavioural goals in controlling attention. However, everyday situations are multisensory and contain regularities, both likely influencing attention. We investigated how visual attentional capture is simultaneously impacted by top-down goals, the multisensory nature of stimuli, and the contextual factors of stimuli's semantic relationship and temporal predictability. Participants performed a multisensory version of the Folk et al. (1992) spatial cueing paradigm, searching for a target of a predefined colour (e.g. a red bar) within an array preceded by a distractor. We manipulated: 1) stimuli's goal-relevance via distractor's colour (matching vs. mismatching the target), 2) stimuli's multisensory nature (colour distractors appearing alone vs. with tones), 3) the relationship between the distractor sound and colour (arbitrary vs. semantically congruent) and 4) the temporal predictability of distractor onset. Reaction-time spatial cueing served as a behavioural measure of attentional selection. We also recorded 129-channel event-related potentials (ERPs), analysing the distractor-elicited N2pc component both canonically and using a multivariate electrical neuroimaging framework. Behaviourally, arbitrary target-matching distractors captured attention more strongly than semantically congruent ones, with no evidence for context modulating multisensory enhancements of capture. Notably, electrical neuroimaging of surface-level EEG analyses revealed context-based influences on attention to both visual and multisensory distractors, in how strongly they activated the brain and type of activated brain networks. For both processes, the context-driven brain response modulations occurred long before the N2pc time-window, with topographic (network-based) modulations at ∼30 ms, followed by strength-based modulations at ∼100 ms post-distractor onset. Our results reveal that both stimulus meaning and predictability modulate attentional selection, and they interact while doing so. Meaning, in addition to temporal predictability, is thus a second source of contextual information facilitating goal-directed behaviour. More broadly, in everyday situations, attention is controlled by an interplay between one's goals, stimuli's perceptual salience, meaning and predictability. Our study calls for a revision of attentional control theories to account for the role of contextual and multisensory control.

The development of attentional control mechanisms in multisensory environments.

Outside the laboratory, people need to pay attention to relevant objects that are typically multisensory, but it remains poorly understood how the underlying neurocognitive mechanisms develop. We investigated when adult-like mechanisms controlling one's attentional selection of visual and multisensory objects emerge across childhood. Five-, 7-, and 9-year-olds were compared with adults in their performance on a computer game-like multisensory spatial cueing task, while 129-channel EEG was simultaneously recorded. Markers of attentional control were behavioural spatial cueing effects and the N2pc ERP component (analysed traditionally and using a multivariate electrical neuroimaging framework). In behaviour, adult-like visual attentional control was present from age 7 onwards, whereas multisensory control was absent in all children groups. In EEG, multivariate analyses of the activity over the N2pc time-window revealed stable brain activity patterns in children. Adult-like visual-attentional control EEG patterns were present age 7 onwards, while multisensory control activity patterns were found in 9-year-olds (albeit behavioural measures showed no effects). By combining rigorous yet naturalistic paradigms with multivariate signal analyses, we demonstrated that visual attentional control seems to reach an adult-like state at ∼7 years, before adult-like multisensory control, emerging at ∼9 years. These results enrich our understanding of how attention in naturalistic settings develops.

Mental Rotation of Digitally-Rendered Haptic Objects.

Sensory substitution is an effective means to rehabilitate many visual functions after visual impairment or blindness. Tactile information, for example, is particularly useful for functions such as reading, mental rotation, shape recognition, or exploration of space. Extant haptic technologies typically rely on real physical objects or pneumatically driven renderings and thus provide a limited library of stimuli to users. New developments in digital haptic technologies now make it possible to actively simulate an unprecedented range of tactile sensations. We provide a proof-of-concept for a new type of technology (hereafter haptic tablet) that renders haptic feedback by modulating the friction of a flat screen through ultrasonic vibrations of varying shapes to create the sensation of texture when the screen is actively explored. We reasoned that participants should be able to create mental representations of letters presented in normal and mirror-reversed haptic form without the use of any visual information and to manipulate such representations in a mental rotation task. Healthy sighted, blindfolded volunteers were trained to discriminate between two letters (either L and P, or F and G; counterbalanced across participants) on a haptic tablet. They then tactually explored all four letters in normal or mirror-reversed form at different rotations (0°, 90°, 180°, and 270°) and indicated letter form (i.e., normal or mirror-reversed) by pressing one of two mouse buttons. We observed the typical effect of rotation angle on object discrimination performance (i.e., greater deviation from 0° resulted in worse performance) for trained letters, consistent with mental rotation of these haptically-rendered objects. We likewise observed generally slower and less accurate performance with mirror-reversed compared to prototypically oriented stimuli. Our findings extend existing research in multisensory object recognition by indicating that a new technology simulating active haptic feedback can support the generation and spatial manipulation of mental representations of objects. Thus, such haptic tablets can offer a new avenue to mitigate visual impairments and train skills dependent on mental object-based representations and their spatial manipulation.

Brain and Cognitive Mechanisms of Top-Down Attentional Control in a Multisensory World: Benefits of Electrical Neuroimaging.

In real-world environments, information is typically multisensory, and objects are a primary unit of information processing. Object recognition and action necessitate attentional selection of task-relevant from among task-irrelevant objects. However, the brain and cognitive mechanisms governing these processes remain not well understood. Here, we demonstrate that attentional selection of visual objects is controlled by integrated top-down audiovisual object representations ("attentional templates") while revealing a new brain mechanism through which they can operate. In multistimulus (visual) arrays, attentional selection of objects in humans and animal models is traditionally quantified via "the N2pc component": spatially selective enhancements of neural processing of objects within ventral visual cortices at approximately 150-300 msec poststimulus. In our adaptation of Folk et al.'s [Folk, C. L., Remington, R. W., & Johnston, J. C. Involuntary covert orienting is contingent on attentional control settings. Journal of Experimental Psychology: Human Perception and Performance, 18, 1030-1044, 1992] spatial cueing paradigm, visual cues elicited weaker behavioral attention capture and an attenuated N2pc during audiovisual versus visual search. To provide direct evidence for the brain, and so, cognitive, mechanisms underlying top-down control in multisensory search, we analyzed global features of the electrical field at the scalp across our N2pcs. In the N2pc time window (170-270 msec), color cues elicited brain responses differing in strength and their topography. This latter finding is indicative of changes in active brain sources. Thus, in multisensory environments, attentional selection is controlled via integrated top-down object representations, and so not only by separate sensory-specific top-down feature templates (as suggested by traditional N2pc analyses). We discuss how the electrical neuroimaging approach can aid research on top-down attentional control in naturalistic, multisensory settings and on other neurocognitive functions in the growing area of real-world neuroscience.

Sounds enhance visual completion processes.

Everyday vision includes the detection of stimuli, figure-ground segregation, as well as object localization and recognition. Such processes must often surmount impoverished or noisy conditions; borders are perceived despite occlusion or absent contrast gradients. These illusory contours (ICs) are an example of so-called mid-level vision, with an event-related potential (ERP) correlate at ∼100-150 ms post-stimulus onset and originating within lateral-occipital cortices (the ICeffect). Presently, visual completion processes supporting IC perception are considered exclusively visual; any influence from other sensory modalities is currently unknown. It is now well-established that multisensory processes can influence both low-level vision (e.g. detection) as well as higher-level object recognition. By contrast, it is unknown if mid-level vision exhibits multisensory benefits and, if so, through what mechanisms. We hypothesized that sounds would impact the ICeffect. We recorded 128-channel ERPs from 17 healthy, sighted participants who viewed ICs or no-contour (NC) counterparts either in the presence or absence of task-irrelevant sounds. The ICeffect was enhanced by sounds and resulted in the recruitment of a distinct configuration of active brain areas over the 70-170 ms post-stimulus period. IC-related source-level activity within the lateral occipital cortex (LOC), inferior parietal lobe (IPL), as well as primary visual cortex (V1) were enhanced by sounds. Moreover, the activity in these regions was correlated when sounds were present, but not when absent. Results from a control experiment, which employed amodal variants of the stimuli, suggested that sounds impact the perceived brightness of the IC rather than shape formation per se. We provide the first demonstration that multisensory processes augment mid-level vision and everyday visual completion processes, and that one of the mechanisms is brightness enhancement. These results have important implications for the design of treatments and/or visual aids for low-vision patients.

Symmetry and its role in the crossmodal correspondence between shape and taste.

Despite the rapid growth of research on the crossmodal correspondence between visually presented shapes and basic tastes (e.g., sweet, sour, bitter, and salty), most studies that have been published to date have focused on shape contour (roundness/angularity). Meanwhile, other important features, such as symmetry, as well as the underlying mechanisms of the shape-taste correspondence, have rarely been studied. Over two experiments, we systematically manipulated the symmetry and contours of shapes and measured the influences of these variables on shape-taste correspondences. Furthermore, we investigated a potential underlying mechanism, based on the common affective appraisal of stimuli in different sensory modalities. We replicated the results of previous studies showing that round shapes are associated with sweet taste, whereas angular shapes are associated with sour and bitter tastes. In addition, we demonstrated a novel effect that the symmetry group of a shape influences how it is associated with taste. A significant relationship was observed between the taste and appraisal scores of the shapes, suggesting that the affective factors of pleasantness and threat underlie the shape-taste correspondence. These results were consistent across cultures, when we compared participants from Taiwanese and Western (UK, US, Canada) cultures. Our findings highlight that perceived pleasantness and threat are culturally common factors involved in at least some crossmodal correspondences.

Glyph guessing for 'oo' and 'ee': spatial frequency information in sound symbolic matching for ancient and unfamiliar scripts.

In three experiments, we asked whether diverse scripts contain interpretable information about the speech sounds they represent. When presented with a pair of unfamiliar letters, adult readers correctly guess which is /i/ (the 'ee' sound in 'feet'), and which is /u/ (the 'oo' sound in 'shoe') at rates higher than expected by chance, as shown in a large sample of Singaporean university students (Experiment 1) and replicated in a larger sample of international Internet users (Experiment 2). To uncover what properties of the letters contribute to different scripts' 'guessability,' we analysed the visual spatial frequencies in each letter (Experiment 3). We predicted that the lower spectral frequencies in the formants of the vowel /u/ would pattern with lower spatial frequencies in the corresponding letters. Instead, we found that across all spatial frequencies, the letter with more black/white cycles (i.e. more ink) was more likely to be guessed as /u/, and the larger the difference between the glyphs in a pair, the higher the script's guessability. We propose that diverse groups of humans across historical time and geographical space tend to employ similar iconic strategies for representing speech in visual form, and provide norms for letter pairs from 56 diverse scripts.