Olympic team rowers and team swimmers show altered functional brain activation during working memory and action inhibition.

BACKGROUND: High-level expertise in team-sports is associated with superior performance on executive functions (EFs) such as working memory (WM) and action inhibition, and with altered activation of brain areas related to these EFs. In most such studies, athletes were sampled from the domain of dynamic (i.e., open-skill) team-sports (e.g., soccer players). Whether static (i.e., closed-skill) team-sports athletes (e.g., rowers and synchronized swimmers) also show superior EFs performance and differential EF-related functional brain activation remains unknown. METHODS: We recruited 14 elite closed-skill athletes, all national champions, and internationally competitive in various rowing disciplines, as well as 14 controls matched on gender, age, and education, and had them perform working memory and action inhibition (stop-signal) tasks during fMRI scanning. RESULTS: Group differences in performance in either task failed to obtain statistical significance, although athletes showed a numerical trend toward higher WM capacity than controls. Importantly, task-related BOLD responses suggested that Olympic closed-skill team athletes show stronger recruitment of brain areas that emphasize relatively stable task demands and weaker engagement of brain areas that emphasize rapidly changing demands imposed by extraneous stimulation. CONCLUSION: Functional brain imaging data suggest elite closed-skill athletes may employ different cognitive strategies.

The effect of individual characteristics on susceptibility to aggressive and/or intimidating approaches: quantifying probability pathways by creating a victimization model.

Background: A significant body of literature has identified multiple factors that contribute to established victimization by aggressive and/or intimidating behaviours. These studies primarily originate from the fields of intimate partner violence (IPV), bullying, sexual abuse, and/or commercial sexual exploitation (CSE), and generally focus on female victims. It appears, however, complicated to quantify the cumulative contribution of these factors on susceptibility to intimidating and/or hostile engagements on an individual level.Objective: To develop a comprehensive risk model to quantify, on an individual level, the cumulative effects of previously reported characteristics on susceptibility to aggressive/intimidating approaches, leading to victimization (e.g. in the context of IPV/sexual abuse).Methods: A Bayesian belief network was developed using data from previous studies, capturing the multivariate contribution of previously reported characteristics on the likelihood of becoming victimized by aggressive and/or intimidating approaches (e.g. in the IPV/CSE context) in female victims aged 12-24 years.Results: The model showed that specific combinations of characteristics may contribute to an increased likelihood of victimization (e.g. in the context of IPV/bullying/sexual abuse or CSE). This likelihood could be quantified and categorized into specific clusters of factors differentiating between victimization by physically violent, non-physical, and/or sexual aggressive/intimidating approaches.Conclusion: The present model appears to be the first to successfully quantify the cumulative contribution of individual characteristics on the likelihood of becoming victimized by aggressive and/or intimidating approaches, typically leading to victimization. Moreover, the present scientific effort and resulting model suggest that there may be a latent variable mediating between the implemented factors and overall outcome, i.e. the susceptibility to aggressive and/or intimidating approaches. From that perspective, the model may also be considered as an initial outline to effectively indicate susceptibility to such approaches.

This study constructed a Bayesian belief network of published statistics to quantify the cumulative effects of individual characteristics on victimization (e.g. in the context of IPV/sexual abuse/bullying/CSE).The model showed that the likelihood of victimization following aggressive and/or intimidating approaches could be quantified and categorized into three different features: the likelihood of becoming victimized by physically violent, non-physical, and/or sexual aggressive/intimidating approaches. The likelihood of becoming victimized by physically violent and non-physical aggressive/intimidating approaches seems to be predominantly characterized by risk factors such as depressive symptoms and elevated neuroticism. The likelihood of victimization by sexual intimidating approaches seems to be primarily associated with externalizing risk factors (e.g. impulsivity), strengthened by factors related to previous (negative) sexual experiences and early-onset puberty.This model could be considered as an initial outline to effectively indicate susceptibility to aggressive/intimidating approaches. The model may therefore be considered an applicable framework for future research to further unravel the complicated aggressive and/or intimidating victim­perpetrator interactions related to victimization.

The brains of elite soccer players are subject to experience-dependent alterations in white matter connectivity.

Soccer is the only major sport with voluntary unprotected head-to-ball contact. It is crucial to determine if head impact through long-term soccer training is manifested in brain structure and connectivity, and whether such alterations are due to sustained training per se. Using diffusion tensor imaging, we documented a comprehensive view of soccer players' brains in a sample of twenty-five right-handed male elite soccer players aged from 18 to 22 years and twenty-five non-athletic controls aged 19-24 years. Importantly, none had recalled a history of concussion. We performed a whole-brain tract-based spatial statistical analysis, and a tract-specific probabilistic tractography method to measure the differences of white matter properties between groups. Whole-brain integrity analysis showed stronger microstructural integrity within the corpus callosum tract in soccer players compared to controls. Further, tract-specific probabilistic tractography revealed that the anterior part of corpus callosum may be the brain structure most relevant to training experience, which may put into perspective prior evidence showing corpus callosum alteration in retired or concussed athletes practicing contact sports. Intriguingly, experience-related alterations showed left hemispheric lateralization of potential early signs of concussion-like effects. In sum, we concluded that the observed gains and losses may be due to a consequence of engagement in protracted soccer training that incurs prognostic hallmarks associated with minor injury-induced neural inflammation.

Conscious perception of natural images is constrained by category-related visual features.

Conscious perception is crucial for adaptive behaviour yet access to consciousness varies for different types of objects. The visual system comprises regions with widely distributed category information and exemplar-level representations that cluster according to category. Does this categorical organisation in the brain provide insight into object-specific access to consciousness? We address this question using the Attentional Blink approach with visual objects as targets. We find large differences across categories in the attentional blink. We then employ activation patterns extracted from a deep convolutional neural network to reveal that these differences depend on mid- to high-level, rather than low-level, visual features. We further show that these visual features can be used to explain variance in performance across trials. Taken together, our results suggest that the specific organisation of the higher-tier visual system underlies important functions relevant for conscious perception of differing natural images.

Memory-related perceptual illusions directly affect physical activity in humans.

Perceptual illusions help us understand deficits in human perception, but they also have the potential to serve as treatment methods; e.g., to alleviate phantom limb pain. Treatment effects are usually the direct result of a mismatch between false visual feedback and somatosensory/proprioceptive feedback. We aimed to influence physical activity (walking distance) using a memory-related perceptual illusion that relies on a mismatch between a spatially manipulated virtual reality environment and a weakness of memory for a similar, previously experienced environment. Participants' main task was to reproduce a baseline distance three times, by walking on a treadmill while moving through a virtual reality environment. Depending on condition, the environment was either stretched or compressed relative to the previous session, but participants were not informed about these manipulations. Because false, suggestive information can lead to alterations in memory, especially when conveyed through 'rich' forms of media such as virtual reality, we expected each manipulation to alter memory for the previous environment(s) and we hypothesized that this would influence walking distance. The results for the first time showed that memory-related perceptual illusions can directly affect physical activity in humans. The effects we found are substantial; stretching previously experienced virtual environments led participants to almost double their initial walking distance, whereas compressing the environments resulted in about half of the initial distance. Possible clinical applications arising from these findings are discussed.

Dual cognitive pathways to voice quality: Frequent voicers improvise, infrequent voicers elaborate.

We investigate the involvement of Working Memory Capacity (WMC, the cognitive resource necessary for controlled elaborate thinking) in voice behavior (speaking up with suggestions, problems, and opinions to change the organization). While scholars assume voice requires elaborate thinking, some empirical evidence suggests voice might be more automatic. To explain this discrepancy, we distinguish between voice quantity (frequency of voice) and voice quality (novelty and value of voiced information) and propose that WMC is important for voice quality, but less for voice quantity. Furthermore, we propose that frequent voicers rely less on WMC to reach high voice quality than people who voice rarely. To test our ideas, we conducted three studies: a between-participant lab-study, a within-participant experiment, and a multi-source field-study. All studies supported our expectation that voice quantity is unrelated to WMC, and that voice quality is positively related to WMC, but only for those who rarely voice. This indicates that the decision to voice (quantity) might be more automatic and intuitive than often assumed, whereas its value to the organization (quality), relies more on the degree of cognitive elaboration of the voicer. It also suggests that frequent and infrequent voicers use distinct cognitive pathways to voice high-quality information: frequent voicers improvise, while infrequent voicers elaborate.

Conscious visual memory with minimal attention.

Is conscious visual perception limited to the locations that a person attends? The remarkable phenomenon of change blindness, which shows that people miss nearly all unattended changes in a visual scene, suggests the answer is yes. However, change blindness is found after visual interference (a mask or a new scene), so that subjects have to rely on working memory (WM), which has limited capacity, to detect the change. Before such interference, however, a much larger capacity store, called fragile memory (FM), which is easily overwritten by newly presented visual information, is present. Whether these different stores depend equally on spatial attention is central to the debate on the role of attention in conscious vision. In 2 experiments, we found that minimizing spatial attention almost entirely erases visual WM, as expected. Critically, FM remains largely intact. Moreover, minimally attended FM responses yield accurate metacognition, suggesting that conscious memory persists with limited spatial attention. Together, our findings help resolve the fundamental issue of how attention affects perception: Both visual consciousness and memory can be supported by only minimal attention. (PsycINFO Database Record

Modulating prefrontal control in humans reveals distinct pathways to competitive success and collective waste.

Competitive decision making may require controlling and calculative mind-sets. We examined this possibility in repeated predator-prey contests by up- or down-regulating the individual's right inferior frontal gyrus (rIFG), a brain region involved in impulse inhibition and mentalizing. Following brain stimulation, subjects invested as predator or prey against a non-treated antagonist. Relative to sham-treatment (i) prey-defense was relatively frequent, strong and unaffected by stimulation, (ii) down-regulating predator rIFG produced a high-firing strategy-predators earned more because they attacked more frequently, while (iii) up-regulating predator rIFG produced a track-and-attack strategy-predators earned more because they attacked especially when their (non-stimulated) antagonist lowered its prey-defense. Results suggest that calculative mindsets are not needed to compete effectively, especially not when the goal is to survive. Enhanced prefrontal control enables individuals to appear less aggressive without sacrificing competitive effectiveness-it provides human predators with an iron fist in a velvet glove.

Frequency Band-Specific Electrical Brain Stimulation Modulates Cognitive Control Processes.

A large body of findings has tied midfrontal theta-band (4-8 Hz) oscillatory activity to adaptive control mechanisms during response conflict. Thus far, this evidence has been correlational. To evaluate whether theta oscillations are causally involved in conflict processing, we applied transcranial alternating current stimulation (tACS) in the theta band to a midfrontal scalp region, while human subjects performed a spatial response conflict task. Conflict was introduced by incongruency between the location of the target stimulus and the required response hand. As a control condition, we used alpha-band (8-12 Hz) tACS over the same location. The exact stimulation frequencies were determined empirically for each subject based on a pre-stimulation EEG session. Behavioral results showed general conflict effects of slower response times (RT) and lower accuracy for high conflict trials compared to low conflict trials. Importantly, this conflict effect was reduced specifically during theta tACS, which was driven by slower response times on low conflict trials. These results show how theta tACS can modulate adaptive cognitive control processes, which is in accordance with the view of midfrontal theta oscillations as an active mechanism for cognitive control.

Neural Correlates of Visual Short-term Memory Dissociate between Fragile and Working Memory Representations.

Evidence is accumulating that the classic two-stage model of visual STM (VSTM), comprising iconic memory (IM) and visual working memory (WM), is incomplete. A third memory stage, termed fragile VSTM (FM), seems to exist in between IM and WM [Vandenbroucke, A. R. E., Sligte, I. G., & Lamme, V. A. F. Manipulations of attention dissociate fragile visual STM from visual working memory. Neuropsychologia, 49, 1559-1568, 2011; Sligte, I. G., Scholte, H. S., & Lamme, V. A. F. Are there multiple visual STM stores? PLoS One, 3, e1699, 2008]. Although FM can be distinguished from IM using behavioral and fMRI methods, the question remains whether FM is a weak expression of WM or a separate form of memory with its own neural signature. Here, we tested whether FM and WM in humans are supported by dissociable time-frequency features of EEG recordings. Participants performed a partial-report change detection task, from which individual differences in FM and WM capacity were estimated. These individual FM and WM capacities were correlated with time-frequency characteristics of the EEG signal before and during encoding and maintenance of the memory display. FM capacity showed negative alpha correlations over peri-occipital electrodes, whereas WM capacity was positively related, suggesting increased visual processing (lower alpha) to be related to FM capacity. Furthermore, FM capacity correlated with an increase in theta power over central electrodes during preparation and processing of the memory display, whereas WM did not. In addition to a difference in visual processing characteristics, a positive relation between gamma power and FM capacity was observed during both preparation and maintenance periods of the task. On the other hand, we observed that theta-gamma coupling was negatively correlated with FM capacity, whereas it was slightly positively correlated with WM. These data show clear differences in the neural substrates of FM versus WM and suggest that FM depends more on visual processing mechanisms compared with WM. This study thus provides novel evidence for a dissociation between different stages in VSTM.

Forgotten but not gone: Retro-cue costs and benefits in a double-cueing paradigm suggest multiple states in visual short-term memory.

Visual short-term memory (VSTM) performance is enhanced when the to-be-tested item is cued after encoding. This so-called retro-cue benefit is typically accompanied by a cost for the noncued items, suggesting that information is lost from VSTM upon presentation of a retrospective cue. Here we assessed whether noncued items can be restored to VSTM when made relevant again by a subsequent second cue. We presented either 1 or 2 consecutive retro-cues (80% valid) during the retention interval of a change-detection task. Relative to no cue, a valid cue increased VSTM capacity by 2 items, while an invalid cue decreased capacity by 2. Importantly, when a second, valid cue followed an invalid cue, capacity regained 2 items, so that performance was back on par. In addition, when the second cue was also invalid, there was no extra loss of information from VSTM, suggesting that those items that survived a first invalid cue, automatically also survived a second. We conclude that these results are in support of a very versatile VSTM system, in which memoranda adopt different representational states depending on whether they are deemed relevant now, in the future, or not at all. We discuss a neural model that is consistent with this conclusion.

Accurate metacognition for visual sensory memory representations.

The capacity to attend to multiple objects in the visual field is limited. However, introspectively, people feel that they see the whole visual world at once. Some scholars suggest that this introspective feeling is based on short-lived sensory memory representations, whereas others argue that the feeling of seeing more than can be attended to is illusory. Here, we investigated this phenomenon by combining objective memory performance with subjective confidence ratings during a change-detection task. This allowed us to compute a measure of metacognition--the degree of knowledge that subjects have about the correctness of their decisions--for different stages of memory. We show that subjects store more objects in sensory memory than they can attend to but, at the same time, have similar metacognition for sensory memory and working memory representations. This suggests that these subjective impressions are not an illusion but accurate reflections of the richness of visual perception.

Seeing without knowing: neural signatures of perceptual inference in the absence of report.

Every day, we experience a rich and complex visual world. Our brain constantly translates meaningless fragmented input into coherent objects and scenes. However, our attentional capabilities are limited, and we can only report the few items that we happen to attend to. So what happens to items that are not cognitively accessed? Do these remain fragmentary and meaningless? Or are they processed up to a level where perceptual inferences take place about image composition? To investigate this, we recorded brain activity using fMRI while participants viewed images containing a Kanizsa figure, an illusion in which an object is perceived by means of perceptual inference. Participants were presented with the Kanizsa figure and three matched nonillusory control figures while they were engaged in an attentionally demanding distractor task. After the task, one group of participants was unable to identify the Kanizsa figure in a forced-choice decision task; hence, they were "inattentionally blind." A second group had no trouble identifying the Kanizsa figure. Interestingly, the neural signature that was unique to the processing of the Kanizsa figure was present in both groups. Moreover, within-subject multivoxel pattern analysis showed that the neural signature of unreported Kanizsa figures could be used to classify reported Kanizsa figures and that this cross-report classification worked better for the Kanizsa condition than for the control conditions. Together, these results suggest that stimuli that are not cognitively accessed are processed up to levels of perceptual interpretation.

Bottom-up and top-down attention are independent.

What is the relationship between top-down and bottom-up attention? Are both types of attention tightly interconnected, or are they independent? We investigated this by testing a large representative sample of the Dutch population on two attentional tasks: a visual search task gauging the efficiency of top-down attention and a singleton capture task gauging bottom-up attention. On both tasks we found typical performance--i.e., participants displayed a significant search slope on the search task and significant slowing caused by the unique, but irrelevant, object on the capture task. Moreover, the high levels of significance we observed indicate that the current set-up provided very high signal to noise ratios, and thus enough power to accurately unveil existing effects. Importantly, in this robust investigation we did not observe any correlation in performance between tasks. The use of Bayesian statistics strongly confirmed that performance on both tasks was uncorrelated. We argue that the current results suggest that there are two attentional systems that operate independently. We hypothesize that this may have implications beyond our understanding of attention. For instance, it may be that attention and consciousness are intertwined differently for top-down attention than for bottom-up attention.

Fragile visual short-term memory is an object-based and location-specific store.

Fragile visual short-term memory (FM) is a recently discovered form of visual short-term memory. Evidence suggests that it provides rich and high-capacity storage, like iconic memory, yet it exists, without interference, almost as long as visual working memory. In the present study, we sought to unveil the functional underpinnings of this memory storage. We found that FM is only completely erased when the new visual scene appears at the same location and consists of the same objects as the to-be-recalled information. This result has two important implications: First, it shows that FM is an object- and location-specific store, and second, it suggests that FM might be used in everyday life when the presentation of visual information is appropriately designed.

Non-attended representations are perceptual rather than unconscious in nature.

Introspectively we experience a phenomenally rich world. In stark contrast, many studies show that we can only report on the few items that we happen to attend to. So what happens to the unattended objects? Are these consciously processed as our first person perspective would have us believe, or are they - in fact - entirely unconscious? Here, we attempt to resolve this question by investigating the perceptual characteristics of visual sensory memory. Sensory memory is a fleeting, high-capacity form of memory that precedes attentional selection and working memory. We found that memory capacity benefits from figural information induced by the Kanizsa illusion. Importantly, this benefit was larger for sensory memory than for working memory and depended critically on the illusion, not on the stimulus configuration. This shows that pre-attentive sensory memory contains representations that have a genuinely perceptual nature, suggesting that non-attended representations are phenomenally experienced rather than unconscious.

Two critical periods in early visual cortex during figure-ground segregation.

The ability to distinguish a figure from its background is crucial for visual perception. To date, it remains unresolved where and how in the visual system different stages of figure-ground segregation emerge. Neural correlates of figure border detection have consistently been found in early visual cortex (V1/V2). However, areas V1/V2 have also been frequently associated with later stages of figure-ground segregation (such as border ownership or surface segregation). To causally link activity in early visual cortex to different stages of figure-ground segregation, we briefly disrupted activity in areas V1/V2 at various moments in time using transcranial magnetic stimulation (TMS). Prior to stimulation we presented stimuli that made it possible to differentiate between figure border detection and surface segregation. We concurrently recorded electroencephalographic (EEG) signals to examine how neural correlates of figure-ground segregation were affected by TMS. Results show that disruption of V1/V2 in an early time window (96-119 msec) affected detection of figure stimuli and affected neural correlates of figure border detection, border ownership, and surface segregation. TMS applied in a relatively late time window (236-259 msec) selectively deteriorated performance associated with surface segregation. We conclude that areas V1/V2 are not only essential in an early stage of figure-ground segregation when figure borders are detected, but subsequently causally contribute to more sophisticated stages of figure-ground segregation such as surface segregation.

Manipulations of attention dissociate fragile visual short-term memory from visual working memory.

People often rely on information that is no longer in view, but maintained in visual short-term memory (VSTM). Traditionally, VSTM is thought to operate on either a short time-scale with high capacity - iconic memory - or a long time scale with small capacity - visual working memory. Recent research suggests that in addition, an intermediate stage of memory in between iconic memory and visual working memory exists. This intermediate stage has a large capacity and a lifetime of several seconds, but is easily overwritten by new stimulation. We therefore termed it fragile VSTM. In previous studies, fragile VSTM has been dissociated from iconic memory by the characteristics of the memory trace. In the present study, we dissociated fragile VSTM from visual working memory by showing a differentiation in their dependency on attention. A decrease in attention during presentation of the stimulus array greatly reduced the capacity of visual working memory, while this had only a small effect on the capacity of fragile VSTM. We conclude that fragile VSTM is a separate memory store from visual working memory. Thus, a tripartite division of VSTM appears to be in place, comprising iconic memory, fragile VSTM and visual working memory.

Magnetic stimulation of the dorsolateral prefrontal cortex dissociates fragile visual short-term memory from visual working memory.

To guide our behavior in successful ways, we often need to rely on information that is no longer in view, but maintained in visual short-term memory (VSTM). While VSTM is usually broken down into iconic memory (brief and high-capacity store) and visual working memory (sustained, yet limited-capacity store), recent studies have suggested the existence of an additional and intermediate form of VSTM that depends on activity in extrastriate cortex. In previous work, we have shown that this fragile form of VSTM can be dissociated from iconic memory. In the present study, we provide evidence that fragile VSTM is different from visual working memory as magnetic stimulation of the right dorsolateral prefrontal cortex (DLPFC) disrupts visual working memory, while leaving fragile VSTM intact. In addition, we observed that people with high DLPFC activity had superior working memory capacity compared to people with low DLPFC activity, and only people with high DLPFC activity really showed a reduction in working memory capacity in response to magnetic stimulation. Altogether, this study shows that VSTM consists of three stages that have clearly different characteristics and rely on different neural structures. On the methodological side, we show that it is possible to predict individual susceptibility to magnetic stimulation based on functional MRI activity.