Sustained posterior contralateral activity indicates re-entrant target processing in visual change detection: an EEG study

Camouflage patterning modulates neural signatures of attention and decision-making

Many animals rely on visual camouflage to avoid detection and increase their chances of survival. Edge disruption is commonly seen in the natural world, with animals evolving high-contrast markings that are incongruent with their real body outline in order to avoid recognition. While many studies have investigated how camouflage properties influence viewer performance and eye movement in predation search tasks, researchers in the field have yet to consider how camouflage may directly modulate visual attention and object processing. To examine how disruptive coloration modulates attention, we use a visual object recognition model to quantify object saliency. We determine if object saliency is predictive of human behavioural performance and subjective certainty, as well as neural signatures of attention and decision-making. We show that increasing edge disruption not only reduces detection and identification performance but is also associated with a dampening of neurophysiological signatures of attentional filtering. Increased self-reported certainty regarding decisions corresponds with neurophysiological signatures of evidence accumulation and decision-making. In summary, we have demonstrated a potential mechanism by which edge disruption increases the evolutionary fitness of animals by reducing the brain's ability to distinguish signal from noise, and hence to detect and identify the camouflaged animal.

On the Relevance of Posterior and Midfrontal Theta Activity for Visuospatial Attention

The aim of this study was to examine whether oscillatory activity in the theta-band is relevant for selective visuospatial attention when there is a need for the suppression of interfering and distracting information. A variant of the Eriksen flanker task was employed with bilateral arrays: one array consisting of a target and congruent or incongruent flankers and the second array consisting of neutral distractors. The bilateral arrays were preceded either by a 100% valid spatial cue or by a neutral cue. In the cue-target interval, a major burst in medial frontal theta power was observed, which was largest in the spatial cue condition. In the latter condition, additionally a posterior theta increase was observed that was larger over sites ipsilateral to the forthcoming target array. Functional connectivity analyses revealed that this pretarget posterior theta was related to the midfrontal theta. No such effects were observed in the neutral cue condition. After onset of the bilateral arrays, a major burst in posterior theta activity was observed in both cue conditions, which again was larger above sites ipsilateral to the target array. Furthermore, this posterior theta was in all cases related to the midfrontal theta. Taken together, the findings suggest that a fronto-posterior theta network plays an important role in the suppression of irrelevant and conflicting visual information. The results also suggest that the reciprocal relation between visuospatial attention and executive response control may be closer than commonly thought.

Cross-modal interactions at the audiovisual cocktail-party revealed by behavior, ERPs, and neural oscillations

Theories of attention argue that objects are the units of attentional selection. In real-word environments such objects can contain visual and auditory features. To understand how mechanisms of selective attention operate in multisensory environments, in this pre-registered study, we created an audiovisual cocktail-party situation, in which two speakers (left and right of fixation) simultaneously articulated brief numerals. In three separate blocks, informative auditory speech was presented (a) alone or paired with (b) congruent or (c) uninformative visual speech. In all blocks, subjects localized a pre-defined numeral. While audiovisual-congruent and uninformative speech improved response times and speed of information uptake according to diffusion modeling, an ERP analysis revealed that this did not coincide with enhanced attentional engagement. Yet, consistent with object-based attentional selection, the deployment of auditory spatial attention (N2ac) was accompanied by visuo-spatial attentional orienting (N2pc) irrespective of the informational content of visual speech. Notably, an N2pc component was absent in the auditory-only condition, demonstrating that a sound-induced shift of visuo-spatial attention relies on the availability of audio-visual features evolving coherently in time. Additional exploratory analyses revealed cross-modal interactions in working memory and modulations of cognitive control.

Selective spatial attention in lateralized multi-talker speech perception: EEG correlates and the role of age

Speech comprehension under dynamic cocktail party conditions requires auditory search for relevant speech content and focusing spatial attention on the target talker. Here, we investigated the development of these cognitive processes in a population of 329 participants aged 20-70 years. We used a multi-talker speech detection and perception task in which pairs of words (each consisting of a cue and a target word) were simultaneously presented from lateralized positions. Participants attended to predefined cue words and responded to the corresponding target. Task difficulty was varied by presenting cue and target stimuli at different intensity levels. Decline in performance was observed only in the oldest group (age range 53-70 years) and only in the most difficult condition. The EEG analysis of neurocognitive correlates of lateralized auditory attention and stimulus evaluation (N2ac, LPCpc, alpha power lateralization) revealed age-associated changes in focussing on and processing of task-relevant information, while no such deficits were found on early auditory search and target segregation. Irrespective of age, more challenging listening conditions were associated with an increased allocation of attentional resources.

Violated Expectations for Spatial and Feature Attributes of Visual Trajectories Modulate Event-Related Potential Amplitudes across the Visual Processing Hierarchy

During visual perception the brain must combine its predictions about what is to be perceived with incoming relevant information. The present study investigated how this process interacts with attention by using event-related potentials that index these cognitive mechanisms. Specifically, this study focused on examining how the amplitudes of the N170, N2pc, and N300 would be modulated by violations of expectations for spatial and featural attributes of visual stimuli. Participants viewed a series of shape stimuli in which a salient shape moved across a set of circular locations so that the trajectory of the shape implied the final position and shape of the stimulus. The final salient stimuli occurred in one of four possible outcomes: predictable position and shape, predictable position but unpredictable shape, unpredictable position but predictable shape, and unpredictable position and shape. The N170 was enhanced by unpredictable positions and shapes, whereas the N300 was enlarged only by unpredictable positions. The N2pc was not modulated by violations of expectation for shapes or positions. Additionally, it was observed post-hoc that the P1pc amplitude was increased by unpredictable shapes. These findings revealed that incorrect prediction increases neural activity. Furthermore, they suggest that prediction and attention interact differently in different stages of visual perception, depending on the type of attention being engaged: The N170 indexes initial prediction error signalling irrespective of the type of information (spatial or featural) in which error occurs, followed by the N300 as a marker of prediction updating involving reorientation of spatial attention.

Neural Underpinnings of Proactive and Preemptive Adjustments of Action Control

This study aimed to trace the neural basis of proactive and preemptive adjustments of executive control and their effects on online processing of response conflict. In two EEG experiments, participants performed the flanker task with predictive cueing of conflict. The following questions were addressed: "Does conflict cueing improve performance?" We observed improved behavioral performance in the predictive condition, suggesting that participants proactively utilized the cues to prepare for the upcoming demands. "How is conflict processing affected by predictive cueing?" Conflict-related modulations of midfrontal N2 and theta power were smaller in the predictive than in the neutral condition. This suggests that proactive control suppressed the impact of incongruent flankers so that the conflict was reduced, and so was the involvement of online control. "Is proactive control implemented through preactivation of online control?" Conflict cueing increased midfrontal theta power also before target onset, suggesting preactivation of the control processes beforehand. "Do proactive and reactive control depend on common or unique processes?" Unlike the online control, the proactive control triggered a burst of theta power in the right hemisphere's dorsal and ventral lateral prefrontal cortices, connected with the midfrontal area via theta phase coherence. This indicates that the two control modes involve partially unique but coordinated neural processes. "Is preemptive control implemented through modulations of visual processing?" Predictive cueing modulated both the pretarget preparatory alpha desynchronization and the target selection-related posterior contralateral negativity (N2pc and sustained posterior contralateral negativity), in line with the hypothesis of preemptive tuning of sensory selection aimed at reducing the impact of conflicting stimuli.

Did you even see that? visual sensory processing of single stimuli under different locomotor loads

Modern living and working environments are more and more interspersed with the concurrent execution of locomotion and sensory processing, most often in the visual domain. Many job profiles involve the presentation of visual information while walking, for example in warehouse logistics work, where a worker has to manage walking to the correct aisle to pick up a package while being presented with visual information over data-glasses concerning the next order. Similar use-cases can be found in manufacturing jobs, for example in car montage assembly lines where next steps are presented via augmented reality headsets while walking at a slow pace. Considering the overall scarcity of cognitive resources available to be deployed to either the cognitive or motor processes, task performance decrements were found when increasing load in either domain. Interestingly, the walking motion also had beneficial effects on peripheral contrast detection and the inhibition of visual stream information. Taking these findings into account, we conducted a study that comprised the detection of single visual targets (Landolt Cs) within a broad range of the visual field (-40° to +40° visual angle) while either standing, walking, or walking with concurrent perturbations. We used questionnaire (NASA-TLX), behavioral (response times and accuracy), and neurophysiological data (ERPs and ERSPs) to quantify the effects of cognitive-motor interference. The study was conducted in a Gait Real-time Analysis Interactive Laboratory (GRAIL), using a 180° projection screen and a swayable and tiltable dual-belt treadmill. Questionnaire and behavioral measures showed common patterns. We found increasing subjective physical workload and behavioral decrements with increasing stimulus eccentricity and motor complexity. Electrophysiological results also indicated decrements in stimulus processing with higher stimulus eccentricity and movement complexity (P3, Theta), but highlighted a beneficial role when walking without perturbations and processing more peripheral stimuli regarding earlier sensory components (N1pc/N2pc, N2). These findings suggest that walking without impediments can enhance the visual processing of peripheral information and therefore help with perceiving non-foveal sensory content. Also, our results could help with re-evaluating previous findings in the context of cognitive-motor interference, as increased motor complexity might not always impede cognitive processing and performance.

Selection for Action: The Medial Frontal Cortex Is an Executive Hub for Stimulus and Response Selection

This EEG study investigates the electrophysiological activity underlying processes of stimulus and response selection, and their executive orchestration via long-range functional connectivity under conflict condition, in order to shed more light on how these brain dynamics shape individual behavioral performance. Participants (n = 91) performed a modified flanker task, in which bilateral visual stimulation and a bimanual response pattern were employed to isolate the stimulus and response selection-related lateralized activity. First, we identified conflict-related markers of task-relevant processes; most importantly, the stimulus and response selection were evidenced by contra-ipsilateral differences in visual and motor activity, respectively, and executive control was evidenced by modulations of midfrontal activity. Second, we identified conflict-related functional connectivity between midfrontal and other task-relevant areas. The results showed that interregional phase synchronization in theta band was centered at the midfrontal site, interpreted here as a "hub" of executive communication. Importantly, the theta functional connectivity was more robust under the condition of increased demands for stimulus and response selection, including connectivity between the medial frontal cortex and the lateral frontal and motor areas, as well as cross-frequency theta-alpha coupling between the medial frontal cortex and contralateral visual areas. Third, we showed that individual differences in the measured conflict-related EEG activity, particularly the midfrontal N2, theta power, and global theta connectivity, predict the behavioral efficiency in conflict resolution.

Phasic alerting facilitates endogenous orienting of spatial attention: Evidence from event-related lateralizations of the EEG

Alerting has been hypothesized to affect spatial orienting either by accelerating the speed of attentional shift toward the cued target location (the accelerating hypothesis) or by enhancing the orienting effect without changing its time course (the enhancing hypothesis). To investigate the neural underpinnings of the effect of phasic alerting on endogenous orienting, we recorded the electroencephalogram (EEG) in a variant of the spatial cueing task with a tone presented 100 ms before the cue as a phasic alerting signal, and calculated cue-evoked event-related lateralizations (ERLs) providing a precise assessment of preparatory visuospatial attention. Behavioral results showed that the spatial orienting effect was increased under the phasic alerting condition, as expected. The EEG results showed that an orienting-related ERL component called a late directing attention positivity (LDAP) had shorter onset latency and larger amplitude in the alerting condition than in the no-alerting (no-tone) condition. In conclusion, phasic alerting seems to both accelerate and enhance orienting-related preparatory modulations within the ventral visual stream.

The Psychophysiology of Action: A Multidisciplinary Endeavor for Integrating Action and Cognition

There is a vast amount of literature concerning the integration of action and cognition. Although this broad research area is of great interest for many disciplines like sports, psychology and cognitive neuroscience, only a few attempts tried to bring together different perspectives so far. Our goal is to provide a perspective to spark a debate across theoretical borders and integration of different disciplines via psychophysiology. In order to boost advances in this research field it is not only necessary to become aware of the different areas that are relevant but also to consider methodological aspects and challenges. We briefly describe the most relevant theoretical accounts to the question of how internal and external information processes or factors interact and, based on this, argue that research programs should consider the three dimensions: (a) dynamics of movements; (b) multivariate measures and; (c) dynamic statistical parameters. Only with an extended perspective on theoretical and methodological accounts, one would be able to integrate the dynamics of actions into theoretical advances.

Association between heart rhythm and cortical sound processing

Sound signal processing signifies an important factor for human conscious communication and it may be assessed through cortical auditory evoked potentials (CAEP). Heart rate variability (HRV) provides information about heart rate autonomic regulation. We investigated the association between resting HRV and CAEP. We evaluated resting HRV in the time and frequency domain and the CAEP components. The subjects remained at rest for 10 minutes for HRV recording, then they performed the CAEP examinations through frequency and duration protocols in both ears. Linear regression indicated that the amplitude of the N2 wave of the CAEP in the left ear (not right ear) was significantly influenced by standard deviation of normal-to-normal RR-intervals (17.7%) and percentage of adjacent RR-intervals with a difference of duration greater than 50 milliseconds (25.3%) time domain HRV indices in the frequency protocol. In the duration protocol and in the left ear the latency of the P2 wave was significantly influenced by low (LF) (20.8%) and high frequency (HF) bands in normalized units (21%) and LF/HF ratio (22.4%) indices of HRV spectral analysis. The latency of the N2 wave was significantly influenced by LF (25.8%), HF (25.9%) and LF/HF (28.8%). In conclusion, we promote the supposition that resting heart rhythm is associated with thalamo-cortical, cortical-cortical and auditory cortex pathways involved with auditory processing in the right hemisphere.

On the neural mechanisms underlying the protective function of retroactive cuing against perceptual interference: Evidence by event-related potentials of the EEG

This EEG study investigated the protective effect of retroactive attentional focusing on working memory. To this effect, we used a visuo-spatial working memory task and presented block-wise distractor displays after working memory contents had been updated by means of a retroactive cue (retro-cue). Retroactive attention attenuated the interfering effect of distractors on memory precision. The reduction of working memory load by means of a selective retro-cue was reflected by a decline of a negative slow wave over parietal sites. Posterior N1 to the distractor was reduced following a selective retro-cue compared to a neutral retro-cue condition, most notably at left hemispheric sites. P3b referred to the distractor was suppressed completely only following a selective retro-cue. This suggests that focusing on only a subset of visuo-spatial information represented in working memory releases cognitive resources for preventing the in-depth processing of subsequently irrelevant visual events, thereby inhibiting their transfer into working memory.

From Capture to Inhibition: How does Irrelevant Information Influence Visual Search? Evidence from a Spatial Cuing Paradigm

Even though information is spatially and temporally irrelevant, it can influence the processing of subsequent information. The present study used a spatial cuing paradigm to investigate the origins of this persisting influence by means of event-related potentials (ERPs) of the EEG. An irrelevant color cue that was either contingent (color search) or non-contingent (shape search) on attentional sets was presented prior to a target array with different stimulus-onset asynchronies (SOA; 200, 400, 800 ms). Behavioral results indicated that color cues captured attention only when they shared target-defining properties. These same-location effects persisted over time but were pronounced when cue and target array were presented in close succession. N2 posterior contralateral (N2pc) showed that the color cue generally drew attention, but was strongest in the contingent condition. A subsequently emerging contralateral posterior positivity referred to the irrelevant cue (i.e., distractor positivity, Pd) was unaffected by the attentional set and therefore interpreted as an inhibitory process required to enable a re-direction of the attentional focus. Contralateral delay activity (CDA) was only observable in the contingent condition, indicating the transfer of spatial information into working memory and thus providing an explanation for the same-location effect for longer SOAs. Inhibition of this irrelevant information was reflected by a second contralateral positivity triggered through target presentation. The results suggest that distracting information is actively maintained when it resembles a sought-after object. However, two independent attentional processes are at work to compensate for attentional distraction: the timely inhibition of attentional capture and the active inhibition of mental representation of irrelevant information.

Electrophysiological correlates of cocktail-party listening

Detecting, localizing, and selectively attending to a particular sound source of interest in complex auditory scenes composed of multiple competing sources is a remarkable capacity of the human auditory system. The neural basis of this so-called "cocktail-party effect" has remained largely unknown. Here, we studied the cortical network engaged in solving the "cocktail-party" problem, using event-related potentials (ERPs) in combination with two tasks demanding horizontal localization of a naturalistic target sound presented either in silence or in the presence of multiple competing sound sources. Presentation of multiple sound sources, as compared to single sources, induced an increased P1 amplitude, a reduction in N1, and a strong N2 component, resulting in a pronounced negativity in the ERP difference waveform (N2d) around 260 ms after stimulus onset. About 100 ms later, the anterior contralateral N2 subcomponent (N2ac) occurred in the multiple-sources condition, as computed from the amplitude difference for targets in the left minus right hemispaces. Cortical source analyses of the ERP modulation, resulting from the contrast of multiple vs. single sources, generally revealed an initial enhancement of electrical activity in right temporo-parietal areas, including auditory cortex, by multiple sources (at P1) that is followed by a reduction, with the primary sources shifting from right inferior parietal lobule (at N1) to left dorso-frontal cortex (at N2d). Thus, cocktail-party listening, as compared to single-source localization, appears to be based on a complex chronology of successive electrical activities within a specific cortical network involved in spatial hearing in complex situations.