Do Miniature Eye Movements Affect Neurofeedback Training Performance? A Combined EEG-Eye Tracking Study.

EEG-based neurofeedback is a prominent method to modulate one's own brain activity in a desired direction. However, the EEG signal can be disturbed by artifacts, e.g., eye movements, which can consequently confound the neurofeedback performance. Involuntary miniature eye movements can be hardly detected by conventional EEG correction methods such as recording the electro-oculogram (EOG) and subtracting EOG activity from the EEG signal. However, such miniature eye movements can influence EEG activity, especially in the Gamma frequency range, enormously. In the present study, we investigated whether power in different EEG frequencies can be effectively modulated by self-control of brain signals during neurofeedback training and/or whether changes in EEG power are provoked by miniature eye movements during the training. To this end, 24 participants performed one session of SMR and one session of Gamma neurofeedback training. Additionally, in each training session sham feedback was performed. An eye tracker was used to detect miniature eye movements (< 1°) during neurofeedback training. About two thirds of the participants were able to increase their SMR power over the course of NF training, while one third was able to increase Gamma power. Generally, miniature eye movements induced a strong Gamma power increase. The number of eye movements also increased numerically over the course of the NF training. However, we did not find a significant relationship with the NF training performance. This is a first indication that miniature saccades do not affect NF training performance, but should not be neglected during NF training. Our results have to be confirmed in future studies.

Increased insula activity precedes the formation of subjective illusory Gestalt.

The constructive nature of human perception sometimes leads us to perceiving rather complex impressions from simple sensory input: for example, recognizing animal contours in cloud formations or seeing living creatures in shadows of objects. A special type of bistable stimuli gives us a rare opportunity to study the neural mechanisms behind this process. Such stimuli can be visually interpreted either as simple or as more complex illusory content on the basis of the same sensory input. Previous studies demonstrated increased activity in the superior parietal cortex during the perception of an illusory Gestalt impression compared to a simpler interpretation. Here, we examined the role of slow fluctuations of resting-state fMRI activity in shaping the subsequent illusory interpretation by investigating activity related to the illusory Gestalt not only during, but also prior to its perception. We presented 31 participants with a bistable motion stimulus, which can be perceived either as four moving dot pairs (local) or two moving illusory squares (global). fMRI was used to measure brain activity in a slow event-related design. We observed stronger IPS and putamen responses to the stimulus when participants perceived the global interpretation compared to the local, confirming the findings of previous studies. Most importantly, we also observed that the global stimulus interpretation was preceded by an increased activity of the bilateral dorsal insula, which is known to process saliency and gate information for conscious access. Our data suggest an important role of the dorsal insula in shaping complex illusory interpretations of the sensory input.

The development of visual attention in early infancy: Insights from a free-viewing paradigm.

Theories of visual attention suggest a cascading development of subfunctions such as alertness, spatial orientation, attention to object features, and endogenous control. Here, we aimed to track infants' visual developmental steps from a primarily exogenously to more endogenously controlled processing style during their first months of life. In this repeated measures study, 51 infants participated in seven fortnightly assessments at postterm ages of 4-16 weeks. Infants were presented with the same set of static and dynamic paired comparison stimuli in each assessment. Visual behavior was evaluated by a newly introduced scoring scheme. Our results confirmed the suggested visual developmental hierarchy and clearly demonstrated the suitability of our scoring scheme for documenting developmental changes in visual attention during early infancy. Besides the general ontogenetic course of development, we also discuss intra- and interindividual differences which may affect single assessments, and highlight the importance of repeated measurements for reliable evaluation of developmental changes.

The effects of transcranial alternating current stimulation (tACS) at individual alpha peak frequency (iAPF) on motor cortex excitability in young and elderly adults.

Transcranial alternating current stimulation (tACS) can modulate brain oscillations, cortical excitability and behaviour. In aging, the decrease in EEG alpha activity (8-12 Hz) in the parieto-occipital and mu rhythm in the motor cortex are correlated with the decline in cognitive and motor functions, respectively. Increasing alpha activity using tACS might therefore improve cognitive and motor function in the elderly. The present study explored the influence of tACS on cortical excitability in young and old healthy adults. We applied tACS at individual alpha peak frequency for 10 min (1.5 mA) to the left motor cortex. Transcranial magnetic stimulation was used to assess the changes in cortical excitability as measured by motor-evoked potentials at rest, before and after stimulation. TACS increased cortical excitability in both groups. However, our results also suggest that the mechanism behind the effects was different, as we observed an increase and decrease in intracortical inhibition in the old group and young group, respectively. Our results indicate that both groups profited similarly from the stimulation. There was no indication that tACS was more effective in conditions of low alpha power, that is, in the elderly.

Looking for ideas: Eye behavior during goal-directed internally focused cognition.

Humans have a highly developed visual system, yet we spend a high proportion of our time awake ignoring the visual world and attending to our own thoughts. The present study examined eye movement characteristics of goal-directed internally focused cognition. Deliberate internally focused cognition was induced by an idea generation task. A letter-by-letter reading task served as external task. Idea generation (vs. reading) was associated with more and longer blinks and fewer microsaccades indicating an attenuation of visual input. Idea generation was further associated with more and shorter fixations, more saccades and saccades with higher amplitudes as well as heightened stimulus-independent variation of eye vergence. The latter results suggest a coupling of eye behavior to internally generated information and associated cognitive processes, i.e. searching for ideas. Our results support eye behavior patterns as indicators of goal-directed internally focused cognition through mechanisms of attenuation of visual input and coupling of eye behavior to internally generated information.

Guidance toward and away from distractors in repeated visual search.

When searching for two targets consecutively in the same display, participants use memory of recently fixated distractors that become the target in the second search to find that target more quickly. Here we ask whether participants are also using memory for fixated distractors that do not become the target. In Experiment 1 we show that search is faster overall in the second search regardless of whether or not the second search target was fixated in the first search. We replicate this effect in Experiment 2 for different display sizes and further show that the effect is a result of the prioritization of locations that are more likely to contain the target. This suggests that representations of the fixated distractor items are retained across the two searches and that these representations can be used flexibly to optimize search performance. Furthermore, this suggests that the short-term memory processes that support search across consecutive searches not only facilitate guidance toward the target but also allow distractors to be excluded from the search process.

Decoupling of the pupillary light response during internal attention: The modulating effect of luminance intensity.

In a world full of sensory stimuli, attention guides us between the external environment and our internal thoughts. While external attention involves processing sensory stimuli, internal attention is devoted to self-generated representations such as planning or spontaneous mind wandering. They both draw from common cognitive resources, thus simultaneous engagement in both often leads to interference between processes. In order to maintain internal focus, an attentional mechanism known as perceptual decoupling takes effect. This mechanism supports internal cognition by decoupling attention from the perception of sensory information. Two previous studies of our lab investigated to what extent perceptual decoupling is evident in voluntary eye movements. Findings showed that the effect is mediated by the internal task modality and workload (visuospatial > arithmetic and high > low, respectively). However, it remains unclear whether it extends to involuntary eye behavior, which may not share cognitive resources with internal activities. Therefore, the present experiment aimed to further elucidate attentional dynamics by examining whether internal attention affects the pupillary light response (PLR). Specifically, we consistently observed that workload and task modality of the internal task reduced the PLR to luminance changes of medium intensity. However, the PLR to strong luminance changes was less or not at all affected by the internal task. These results suggest that perceptual decoupling effects may be less consistent in involuntary eye behavior, particularly in the context of a salient visual stimulus.

How workload and availability of spatial reference shape eye movement coupling in visuospatial working memory.

Eyes are active in memory recall and visual imagination, yet our grasp of the underlying qualities and factors of these internally coupled eye movements is limited. To explore this, we studied 50 participants, examining how workload, spatial reference availability, and imagined movement direction influence internal coupling of eye movements. We designed a visuospatial working memory task in which participants mentally moved a black patch along a path within a matrix and each trial involved one step along this path (presented via speakers: up, down, left, or right). We varied workload by adjusting matrix size (3 × 3 vs. 5 × 5), manipulated availability of a spatial frame of reference by presenting either a blank screen (requiring participants to rely solely on their mental representation of the matrix) or spatial reference in the form of an empty matrix, and contrasted active task performance to two control conditions involving only active or passive listening. Our findings show that eye movements consistently matched the imagined movement of the patch in the matrix, not driven solely by auditory or semantic cues. While workload influenced pupil diameter, perceived demand, and performance, it had no observable impact on internal coupling. The availability of spatial reference enhanced coupling of eye movements, leading more frequent, precise, and resilient saccades against noise and bias. The absence of workload effects on coupled saccades in our study, in combination with the relatively high degree of coupling observed even in the invisible matrix condition, indicates that eye movements align with shifts in attention across both visually and internally represented information. This suggests that coupled eye movements are not merely strategic efforts to reduce workload, but rather a natural response to where attention is directed.

Interruption in visual search: a systematic review.

Visual search, the process of trying to find a target presented among distractors, is a much-studied cognitive task. Less well-studied is the condition in which the search task is interrupted before the target is found. The consequences of such interruptions in visual search have been investigated across various disciplines, which has resulted in diverse and at times contradictory findings. The aim of this systematic review is to provide a more cohesive understanding of the effects of interruptions in visual search. For this purpose, we identified 28 studies that met our inclusion criteria. To facilitate a more organized and comprehensive analysis, we grouped the studies based on three dimensions: the search environment, the interruption aftermath, and the type of the interrupting event. While interruptions in visual search are variable and manifest differently across studies, our review provides a foundational scheme for a more cohesive understanding of the subject. This categorization serves as a starting point for exploring potential future directions, which we delineate in our conclusions.

The effects of type and workload of internal tasks on voluntary saccades in a target-distractor saccade task.

When we engage in internally directed cognition, like doing mental arithmetic or mind wandering, fewer cognitive resources are assigned for other activities like reacting to perceptual input-an effect termed perceptual decoupling. However, the exact conditions under which perceptual decoupling occurs and its underlying cognitive mechanisms are still unclear. Hence, the present study systematically manipulated the task type (arithmetic, visuospatial) and workload (control, low, high) of the internal task in a within-subject design and tested its effects on voluntary saccades in a target-distractor saccade task. As expected, engagement in internal tasks delayed saccades to the target. This effect was moderated by time, task, and workload: The delay was largest right after internal task onset and then decreased, potentially reflecting the intensity of internal task demands. Saccades were also more delayed for the high compared to the low workload condition in the arithmetic task, whereas workload conditions had similarly high effects in the visuospatial task. Findings suggests that perceptual decoupling of eye behavior gradually increases with internal demands on general resources and that perceptual decoupling is specifically sensitive to internal demands on visuospatial resources. The latter may be mediated by interference due to eye behavior elicited by the internal task itself. Internal tasks did not affect the saccade latency-deviation trade-off, indicating that while the internal tasks delayed the execution of the saccade, the perception of the saccade stimuli and spatial planning of the saccade continued unaffected in parallel to the internal tasks. Together, these findings shed further light on the specific mechanisms underlying perceptual decoupling by suggesting that perceptual decoupling of eye behavior increases as internal demands on cognitive resources overlap more strongly with demands of the external task.

Effects of internally directed cognition on smooth pursuit eye movements: A systematic examination of perceptual decoupling.

Eye behavior differs between internally and externally directed cognition and thus is indicative of an internal versus external attention focus. Recent work implicated perceptual decoupling (i.e., eye behavior becoming less determined by the sensory environment) as one of the key mechanisms involved in these attention-related eye movement differences. However, it is not yet understood how perceptual decoupling depends on the characteristics of the internal task. Therefore, we systematically examined effects of varying internal task demands on smooth pursuit eye movements. Specifically, we evaluated effects of the internal workload (control vs. low vs. high) and of internal task (arithmetic vs. visuospatial). The results of multilevel modelling showed that effects of perceptual decoupling were stronger for higher workload, and more pronounced for the visuospatial modality. Effects also followed a characteristic time-course relative to internal operations. The findings provide further support of the perceptual decoupling mechanism by showing that it is sensitive to the degree of interference between external and internal information.

Believing Processes during the COVID-19 Pandemic: A Qualitative Analysis.

Cognition, emotion, emotional regulation, and believing play a special role in psychosocial functioning, especially in times of crisis. So far, little is known about the process of believing during the COVID-19 pandemic. The aim of this study was to examine the process of believing (using the Model of Credition) and the associated psychosocial strain/stress during the first lockdown in the COVID-19 pandemic. An online survey via LimeSurvey was conducted using the Brief Symptom Inventory-18 (BSI-18), the Pittsburgh Sleep Quality Index (PSQI), and a dedicated Believing Questionnaire, which assesses four parameters of credition (propositions, certainty, emotion, mightiness) between April and June, 2020, in Austria. In total, n = 156 mentally healthy participants completed all questionnaires. Negative credition parameters were associated with higher global symptom load (from BSI-18): narratives: r = 0.29, p < 0.001; emotions r = 0.39, p < 0.001. These findings underline the importance of credition as a link between cognition and emotion and their impact on psychosocial functioning and stress regulation in implementing novel strategies to promote mental health.

Believing processes during the COVID-19 pandemic in individuals with bipolar disorder: An exploratory study.

BACKGROUND: Believing or "credition" refers to psychological processes that integrate the cognitions and emotions that influence our behavior. In the credition model by Angel and Seitz, four parameters are postulated: proposition, certainty, emotion and mightiness. It is assumed that believing processes are influenced by both the individual as well as socio-cultural factors and external circumstances. External or environmental circumstances can include threatening situations such as the ongoing pandemic. It has been hypothesized that believing processes related to the pandemic differ between individuals with bipolar disorder (BD) and healthy controls (HC). AIM: To investigate credition in individuals with BD during the coronavirus disease 2019 (COVID-19) pandemic. METHODS: Psychiatrically stable individuals with BD (n = 52) and age- and sex matched HC (n = 52) participated in an online survey during the first lockdown of the COVID-19 pandemic. The survey took place between April 9th and June 4th, 2020, in Austria. Participants completed the Brief Symptom Inventory-18, the Beck Depression Inventory-II, the Altman Self-Rating Mania Scale, the Pittsburgh Sleep Quality Index and a dedicated Believing Questionnaire assessing four parameters of credition (proposition, certainty, emotion and mightiness). The MAXQDA software was used to analyze the qualitative data. Statistical analyses included analyses of variance, a multivariate analysis of variance and a multivariate analysis of co-variance. RESULTS: Individuals with BD reported significantly more negative propositions [F (1,102) = 8.89, P = 0.004, η2 p = 0.08] and negative emotions [Welch´s F (1,82.46) = 18.23, P < 0.001, η2 p = 0.18], while HC showed significantly more positive propositions [F (1,102) = 7.78, P = 0.006, η2 p = 0.07] and emotions [F (1,102) = 14.31, P < 0.001, η2 p = 0.12]. In addition, individuals with BD showed a higher incongruence between their propositions and their emotions [F (1,102) = 9.42, P = 0.003, η2 p = 0.08] and showed strong correlations between the parameters of the Believing Questionnaire and their psychiatric symptoms (r = 0.51-0.77, all P < 0.001). Positive as well as negative emotions and propositions were associated with scores measuring symptoms of depression, anxiety and sleep quality. CONCLUSION: Believing parameters were associated with psychiatric symptoms in BD during the pandemic. Findings broaden knowledge about the susceptibility of believing processes for ambient challenges in individuals with BD.

Target processing in overt serial visual search involves the dorsal attention network: A fixation-based event-related fMRI study.

In serial visual search we shift attention successively from location to location in search for the target. Although such search has been investigated using fMRI, overt attention (i.e., eye movements) was usually neglected or discouraged. As a result, it is unclear what happens in the instant when our gaze falls upon a target as compared to a distractor. In the present experiment, we used a multiple target search task that required eye movements and employed an analysis based on fixations as events of interest to investigate differences between target and distractor processing. Twenty young healthy adults indicated the number of targets (0-3) among distractors in a 20-item display. Compared to distractor fixations, we found that target fixations gave rise to wide-spread activation in the dorsal attention system, as well as in the visual cortex. Targets that were found later during the search activated the left inferior frontal gyrus and the left supramarginal gyrus more strongly than those that were found earlier. Finally, areas associated with visual and verbal working memory showed increased activation with a larger number of targets in the display.

Saccadic and manual response time data on inhibition of return during and after a visual search.

In the present paper we present a dataset that provides data of two experiments in which we investigated the presence of Inhibition of Return (IOR) during and after a visual search. Participants either had to saccade (Experiment 1 and 2) or make a manual response (Experiment 2) to a probe during a visual search task (searching for a target letter among a set of distractors) or immediately after its completion. The data consist of the unprocessed raw data and one csv-file of the processed eye tracking data on eight (Experiment 1) and 18 (Experiment 2) participants, respectively. In total, we obtained 5,116 trials in Experiment 1 and 18,424 in Experiment 2. The data set is stored at the repository DOOR hosted by the University of Krems (https://door.donau-uni.ac.at/view/o:1014). Detailed information about the experiments and the interpretation of the data can be found in the paper "Post-search IOR: Searching for inhibition of return after search" (Höfler et al., 2019) [1].

Neurophysiological indicators of internal attention: An fMRI-eye-tracking coregistration study.

Many goal-directed, as well as spontaneous everyday activities (e.g., planning, mind-wandering), rely on an internal focus of attention. This fMRI-eye-tracking coregistration study investigated brain mechanisms and eye behavior related to internally versus externally directed cognition. Building on an established paradigm, we manipulated internal attention demands within tasks utilizing conditional stimulus masking. Internally directed cognition involved bilateral activation of the lingual gyrus and inferior parietal lobe areas as well as wide-spread deactivation of visual networks. Moreover, internally directed cognition was related to greater pupil diameter, pupil diameter variance, blink duration, fixation disparity variance, and smaller amounts of microsaccades. FMRI-eye-tracking covariation analyses further revealed that larger pupil diameter was related to increased activation of basal ganglia and lingual gyrus. It can be concluded that internally and externally directed cognition are characterized by distinct neurophysiological signatures. The observed neurophysiological differences indicate that internally directed cognition is associated with reduced processing of task-irrelevant information and increased mental load. These findings shed further light on the interplay between neural and perceptual mechanisms contributing to an internal focus of attention.

How Reliably Do Eye Parameters Indicate Internal Versus External Attentional Focus?

Eye behavior is increasingly used as an indicator of internal versus external focus of attention both in research and application. However, available findings are partly inconsistent, which might be attributed to the different nature of the employed types of internal and external cognition tasks. The present study, therefore, investigated how consistently different eye parameters respond to internal versus external attentional focus across three task modalities: numerical, verbal, and visuo-spatial. Three eye parameters robustly differentiated between internal and external attentional focus across all tasks. Blinks, pupil diameter variance, and fixation disparity variance were consistently increased during internally directed attention. We also observed substantial attentional focus effects on other parameters (pupil diameter, fixation disparity, saccades, and microsaccades), but they were moderated by task type. Single-trial analysis of our data using machine learning techniques further confirmed our results: Classifying the focus of attention by means of eye tracking works well across participants, but generalizing across tasks proves to be challenging. Based on the effects of task type on eye parameters, we discuss what eye parameters are best suited as indicators of internal versus external attentional focus in different settings.

Eye behavior predicts susceptibility to visual distraction during internally directed cognition.

When we engage in internally directed cognition (e.g., planning or imagination), our eye behavior decouples from external stimuli and couples to internal representations (e.g., internal visualizations of ideas). Here, we investigated whether eye behavior predicts the susceptibility to visual distraction during internally directed cognition. To this end, participants performed a divergent thinking task, which required internally directed attention, and we measured distraction in terms of attention capture by unrelated images. We used multilevel mixed models to predict visual distraction by eye behavior right before distractor onset. In Study 1 (N = 38), visual distraction was predicted by increased saccade and blink rate, and higher pupil dilation. We replicated these findings in Study 2 using the same task, but with less predictable distractor onsets and a larger sample (N = 144). We also explored whether individual differences in susceptibility to visual distraction were related to cognitive ability and task performance. Taken together, variation in eye behavior was found to be a consistent predictor of visual distraction during internally directed cognition. This highlights the relevance of eye parameters as objective indicators of internal versus external attentional focus and distractibility during complex mental tasks.

Age-Dependent Effect of Transcranial Alternating Current Stimulation on Motor Skill Consolidation.

Transcranial alternating current stimulation (tACS) is the application of subthreshold, sinusoidal current to modulate ongoing brain rhythms related to sensory, motor and cognitive processes. Electrophysiological studies suggested that the effect of tACS applied at an alpha frequency (8-12 Hz) was state-dependent. The effects of tACS, that is, an increase in parieto-occipital electroencephalography (EEG) alpha power and magnetoencephalography (MEG) phase coherence, was only observed when the eyes were open (low alpha power) and not when the eyes were closed (high alpha power). This state-dependency of the effects of alpha tACS might extend to the aging brain characterized by general slowing and decrease in spectral power of the alpha rhythm. We additionally hypothesized that tACS will influence the motor cortex, which is involved in motor skill learning and consolidation. A group of young and old healthy adults performed a serial reaction time task (SRTT) with their right hand before and after the tACS stimulation. Each participant underwent three sessions of stimulation: sham, stimulation applied at the individual participant's alpha peak frequency or individual alpha peak frequency (iAPF; α-tACS) and stimulation with iAPF plus 2 Hz (α2-tACS) to the left motor cortex for 10 min (1.5 mA). We measured the effect of stimulation on general motor skill (GMS) and sequence-specific skill (SS) consolidation. We found that α-tACS and α2-tACS improved GMS and SS consolidation in the old group. In contrast, α-tACS minimally improved GMS consolidation but impaired SS consolidation in the young group. On the other hand, α2-tACS was detrimental to the consolidation of both skills in the young group. Our results suggest that individuals with aberrant alpha rhythm such as the elderly could benefit more from tACS stimulation, whereas for young healthy individuals with intact alpha rhythm the stimulation could be detrimental.

Neurophysiological indicators of internal attention: An electroencephalography-eye-tracking coregistration study.

INTRODUCTION: Many goal-directed and spontaneous everyday activities (e.g., planning, mind wandering) rely on an internal focus of attention. Internally directed cognition (IDC) was shown to differ from externally directed cognition in a range of neurophysiological indicators such as electroencephalogram (EEG) alpha activity and eye behavior. METHODS: In this EEG-eye-tracking coregistration study, we investigated effects of attention direction on EEG alpha activity and various relevant eye parameters. We used an established paradigm to manipulate internal attention demands in the visual domain within tasks by means of conditional stimulus masking. RESULTS: Consistent with previous research, IDC involved relatively higher EEG alpha activity (lower alpha desynchronization) at posterior cortical sites. Moreover, IDC was characterized by greater pupil diameter (PD), fewer microsaccades, fixations, and saccades. These findings show that internal versus external cognition is associated with robust differences in several indicators at the neural and perceptual level. In a second line of analysis, we explored the intrinsic temporal covariation between EEG alpha activity and eye parameters during rest. This analysis revealed a positive correlation of EEG alpha power with PD especially in bilateral parieto-occipital regions. CONCLUSION: Together, these findings suggest that EEG alpha activity and PD represent time-sensitive indicators of internal attention demands, which may be involved in a neurophysiological gating mechanism serving to shield internal cognition from irrelevant sensory information.