Static and Dynamic Accuracy and Occlusion Robustness of SteamVR Tracking 2.0 in Multi-Base Station Setups.

The tracking of objects and person position, orientation, and movement is relevant for various medical use cases, e.g., practical training of medical staff or patient rehabilitation. However, these demand high tracking accuracy and occlusion robustness. Expensive professional tracking systems fulfill these demands, however, cost-efficient and potentially adequate alternatives can be found in the gaming industry, e.g., SteamVR Tracking. This work presents an evaluation of SteamVR Tracking in its latest version 2.0 in two experimental setups, involving two and four base stations. Tracking accuracy, both static and dynamic, and occlusion robustness are investigated using a VIVE Tracker (3.0). A dynamic analysis further compares three different velocities. An error evaluation is performed using a Universal Robots UR10 robotic arm as ground-truth system under nonlaboratory conditions. Results are presented using the Root Mean Square Error. For static experiments, tracking errors in the submillimeter and subdegree range are achieved by both setups. Dynamic experiments achieved errors in the submillimeter range as well, yet tracking accuracy suffers from increasing velocity. Four base stations enable generally higher accuracy and robustness, especially in the dynamic experiments. Both setups enable adequate accuracy for diverse medical use cases. However, use cases demanding very high accuracy should primarily rely on SteamVR Tracking 2.0 with four base stations.

On the influence of informational content and key-response effect mapping on implicit learning and error monitoring in the serial reaction time (SRT) task.

The present experiment was designed to enhance our understanding of how response effects with varying amounts of useful information influence implicit sequence learning. We recorded event-related brain potentials, while participants performed a modified version of the serial reaction time task (SRTT). In this task, participants have to press one of four keys corresponding to four letters on a computer screen. Unknown to participants, in some parts of the experimental blocks, the stimuli appear in a repetitive (structured) deterministic sequence, whereas in other parts, stimuli were determined randomly. Four groups of participants differing in the presentation of tones after each response performed the SRTT. In the no tone group, no tones were presented after a response. The other three groups differed with respect to the melody generated by the key presses: in the unmelodic group, one out of four different tones was chosen randomly and presented immediately after a response. In the consistent melody group, the press of a response key always resulted in the production of the same tone, resulting in a repetitive melody during structured parts of the sequence (consistent redundant effect). In the inconsistent melody group, the "melody" produced in the sequenced parts of the blocks was identical to the consistent melody group, but the same response could produce two different tones depending on the actual position in the stimulus sequence. Thus, during structured sequences, subjects heard the same melody as in the consistent melody group, but every key press could be followed by one out of two different tones. To disentangle effects of sequence awareness from our experimental manipulations, all analyses were restricted to implicit learners. All four groups showed sequence learning, but to a different degree: in general, every kind of tone improved sequence learning relative to the no tone group. However, unmelodic tones were less beneficial for learning than tones forming a melody. Tones mapped consistently to response keys improved learning faster than tones producing the same melody, but not mapped consistently to keys. However, at the end of the learning phase, the two melody groups did not differ in the amount of sequence learning. The error-related negativity (ERN) increased with sequence learning (larger ERN at the end of the experiment for trials following the sequence compared to random trials) and this effect was more pronounced for the groups that showed more learning. These findings indicate that response effects containing useful information foster sequence learning even if the same response can produce different effects. Furthermore, we replicated earlier results showing that the importance of an error with respect to the task at hand modulates the activity of the human performance monitoring system.

Enlarged temporal integration window in schizophrenia indicated by the double-flash illusion.

INTRODUCTION: In the present study we were interested in the processing of audio-visual integration in schizophrenia compared to healthy controls. The amount of sound-induced double-flash illusions served as an indicator of audio-visual integration. We expected an altered integration as well as a different window of temporal integration for patients. METHODS: Fifteen schizophrenia patients and 15 healthy volunteers matched for age and gender were included in this study. We used stimuli with eight different temporal delays (stimulus onset asynchronys (SOAs) 25, 50, 75, 100, 125, 150, 200 and 300 ms) to induce a double-flash illusion. Group differences and the widths of temporal integration windows were calculated on percentages of reported double-flash illusions. RESULTS: Patients showed significantly more illusions (ca. 36-44% vs. 9-16% in control subjects) for SOAs 150-300. The temporal integration window for control participants went from SOAs 25 to 200 whereas for patients integration was found across all included temporal delays. We found no significant relationship between the amount of illusions and either illness severity, chlorpromazine equivalent doses or duration of illness in patients. CONCLUSIONS: Our results are interpreted in favour of an enlarged temporal integration window for audio-visual stimuli in schizophrenia patients, which is consistent with previous research.

Not all errors are created equally: specific ERN responses for errors originating from distractor-based response retrieval.

The binding of stimulus (S) and response (R) features into S-R episodes or 'event files' is a basic process for the regulation of behavior. Recent studies have shown that even irrelevant information is bound into event files. Associating distractors with responses leads to more efficient behavior if irrelevant and relevant stimuli are correlated, but leads to erroneous or inadequate behavior if irrelevant stimuli do not predict relevant ones. In this study, we investigated a control mechanism that is triggered by errors resulting from distractor-based response retrieval. We tested whether the error-related negativity (ERN) differs depending on the error source. In particular, we compared errors due to distractor-based response retrieval with random errors. Errors originating from distractor-based response retrieval elicited a stronger (more negative) ERN than did other types of errors, suggesting that the cognitive system responds in a unique way to this kind of error. This control mechanism is adaptive because it prevents the emergence of inadequate response routines.

Cognitive control in adults with high-functioning autism spectrum disorder: a study with event-related potentials.

Introduction: Little is known about cognitive control in adults with high-functioning forms of autism spectrum disorder because previous research focused on children and adolescents. Cognitive control is crucial to monitor and readjust behavior after errors to select contextually appropriate reactions. The congruency effect and conflict adaptation are measures of cognitive control. Post-error slowing, error-related negativity and error positivity provide insight into behavioral and electrophysiological correlates of error processing. In children and adolescent with autism spectrum disorder deficits in cognitive control and error processing have been shown by changes in post-error slowing, error-related negativity and error positivity in the flanker task. Methods: We performed a modified Eriksen flanker task in 17 adults with high-functioning autism spectrum disorder and 17 healthy controls. As behavioral measures of cognitive control and error processing, we included reaction times and error rates to calculate congruency effects, conflict adaptation, and post-error slowing. Event-related potentials namely error-related negativity and error positivity were measured to assess error-related brain activity. Results: Both groups of participants showed the expected congruency effects demonstrated by faster and more accurate responses in congruent compared to incongruent trials. Healthy controls exhibited conflict adaptation as they obtained performance benefits after incongruent trials whereas patients with autism spectrum disorder did not. The expected slowing in reaction times after errors was observed in both groups of participants. Individuals with autism spectrum disorder demonstrated enhanced electrophysiological error-processing compared to healthy controls indicated by increased error-related negativity and error positivity difference amplitudes. Discussion: Our findings show that adults with high-functioning autism spectrum disorder do not show the expected upregulation of cognitive control in response to conflicts. This finding implies that previous experiences may have a reduced influence on current behavior in these patients which possibly contributes to less flexible behavior. Nevertheless, we observed intact behavioral reactions after errors indicating that adults with high-functioning autism spectrum disorder can flexibly adjust behavior in response to changed environmental demands when necessary. The enhancement of electrophysiological error-processing indicates that adults with high-functioning autism spectrum disorder demonstrate an extraordinary reactivity toward errors reflecting increased performance monitoring in this subpopulation of autism spectrum disorder patients.

Deficient Audiovisual Speech Perception in Schizophrenia: An ERP Study.

In everyday verbal communication, auditory speech perception is often disturbed by background noise. Especially in disadvantageous hearing conditions, additional visual articulatory information (e.g., lip movement) can positively contribute to speech comprehension. Patients with schizophrenia (SZs) demonstrate an aberrant ability to integrate visual and auditory sensory input during speech perception. Current findings about underlying neural mechanisms of this deficit are inconsistent. Particularly and despite the importance of early sensory processing in speech perception, very few studies have addressed these processes in SZs. Thus, in the present study, we examined 20 adult subjects with SZ and 21 healthy controls (HCs) while presenting audiovisual spoken words (disyllabic nouns) either superimposed by white noise (-12 dB signal-to-noise ratio) or not. In addition to behavioral data, event-related brain potentials (ERPs) were recorded. Our results demonstrate reduced speech comprehension for SZs compared to HCs under noisy conditions. Moreover, we found altered N1 amplitudes in SZ during speech perception, while P2 amplitudes and the N1-P2 complex were similar to HCs, indicating that there may be disturbances in multimodal speech perception at an early stage of processing, which may be due to deficits in auditory speech perception. Moreover, a positive relationship between fronto-central N1 amplitudes and the positive subscale of the Positive and Negative Syndrome Scale (PANSS) has been observed.

Intermodal Priming of Cognitive Conflict? A Failed Replication of Mager et al. (2009).

Introduction: The present study was conducted to verify a promising experimental setup which demonstrated an inversed Stroop-effect (much faster responses for incongruent relative to congruent Stroop trials) following a mismatching tone. In the matching condition, which was an almost exact replication of the original study, participants were required to indicate whether word color and word meaning were matching, whereas in the response conflict condition, instruction was the same as in a classical Stroop task and required the participants to respond to the word color. As in the original study, each trial was preceded by a sine tone which was deviant in pitch in 20% of the trials. Results: The main result was that the Stroop effect was not inversed after deviant tones, neither under the matching task instruction nor under the response conflict task instruction. The Stroop effect was unaffected by the previous "conceptual mismatch." Conclusion: The current study failed to replicate the astonishing concept of "conflict priming" reported in previous work and does not open the doors for a new window on sequences of conflicts. Nevertheless, the failed replication is valuable for future research, since it demonstrated that "Conflict Priming" as a facilitation of processing of conflict trials following deviant tones, is not an confirmed finding.

Enhanced attentional processing during speech perception in adult high-functioning autism spectrum disorder: An ERP-study.

Deficits in audiovisual speech perception have consistently been detected in patients with Autism Spectrum Disorder (ASD). Especially for patients with a highly functional subtype of ASD, it remains uncertain whether these deficits and underlying neural mechanisms persist into adulthood. Research indicates differences in audiovisual speech processing between ASD and healthy controls (HC) in the auditory cortex. The temporal dynamics of these differences still need to be characterized. Thus, in the present study we examined 14 adult subjects with high-functioning ASD and 15 adult HC while they viewed visual (lip movements) and auditory (voice) speech information that was either superimposed by white noise (condition 1) or not (condition 2). Subject's performance was quantified by measuring stimulus comprehension. In addition, event-related brain potentials (ERPs) were recorded. Results demonstrated worse speech comprehension for ASD subjects compared to HC under noisy conditions. Moreover, ERP-analysis revealed significantly higher P2 amplitudes over parietal electrodes for ASD subjects compared to HC.

Modulation of the error-related negativity by induction of short-term negative affect.

The present study investigates whether performance monitoring and its electrophysiological indices in a choice reaction time task are modulated by affective information presented briefly prior to the critical stimuli. A flanker task known to elicit a sufficient number of performance errors was used and prior to each flanker stimulus a neutral, pleasant or unpleasant picture from the International Affective Picture System (IAPS) was shown. While behavioral performance to the flanker stimuli was hardly affected by the preceding affective information, the error-related negativity (ERN) of the event-related potential was modulated by affective information: Unpleasant IAPS pictures preceding a performance error led to an increased ERN amplitude compared to trials with neutral and pleasant IAPS pictures. These trial-by-trial modulations of electrophysiological markers of performance monitoring are discussed in terms of the possible influence of affective stimuli on monaminergic neuromodulatory transmitter systems.

Auditory Deficits in Audiovisual Speech Perception in Adult Asperger's Syndrome: fMRI Study.

Audiovisual (AV) integration deficits have been proposed to underlie difficulties in speech perception in Asperger's syndrome (AS). It is not known, if the AV deficits are related to alterations in sensory processing at the level of unisensory processing or at levels of conjoint multisensory processing. Functional Magnetic-resonance images (MRI) was performed in 16 adult subjects with AS and 16 healthy controls (HC) matched for age, gender, and verbal IQ as they were exposed to disyllabic AV congruent and AV incongruent nouns. A simple semantic categorization task was used to ensure subjects' attention to the stimuli. The left auditory cortex (BA41) showed stronger activation in HC than in subjects with AS with no interaction regarding AV congruency. This suggests that alterations in auditory processing in unimodal low-level areas underlie AV speech perception deficits in AS. Whether this is signaling a difficulty in the deployment of attention remains to be demonstrated.

Useful distracting information: ERP correlates of distractors in stimulus-response-episodes.

A basic process in regulating behavior that helps us to disentangle meaningful from distracting information is the binding of stimulus and response features into stimulus-response episodes or "event files". Recent studies have shown that even irrelevant information is bound into event files; distractor repetition on the next trial can trigger the response encoded in this episode, which is indicated by faster reaction times. The present study was conducted to get further insight into the electrophysiological underpinnings of those distractor-based retrieval. For that, we analyzed the N2, a negative deflection in event-related potentials that has been associated with a multitude of processes occurring when relevant and irrelevant stimuli compete with each other within a given trial or even in sequences of trials. Our study showed that distractor which did not provide useful information regarding the required behavior led to more negative N2 amplitudes, whereas distractors that provide useful response-related information were associated with less negative N2 amplitudes. Our results are explained as an adaptive mechanism that helps to hedge against invalid stimulus-response-bindings before an error occurs to increase efficiency of human behavior.

Serial position effects in free memory recall--An ERP-study.

Event-related brain potentials (ERPs) elicited by recalled and non-recalled words were recorded from 18 female subjects to investigate primacy and recency effects in free memory recall. The typical pattern of a serial position curve (SPC) was obtained with words presented at first and final positions in a list recalled better than words presented in the middle of a list. A marked positivity is seen in the ERPs for words on Primacy, but not on Recency positions at frontocentral electrodes. In contrast, ERP amplitudes on parietal electrodes resemble the SPC seen in behavioral data: P300 amplitude is largest for words on Primacy and Recency positions and attenuated on Plateau positions. Furthermore, subjects with a clear Primacy effect in behavioral data show a distinct frontal positive slow wave for Primacy words only, whereas subjects without a clear primacy effect show a frontal "difference due to subsequent memory" (DM) effect for Primacy and Plateau words. These results are discussed in the framework of working memory and distinctiveness.

Memory recall in arousing situations - an emotional von Restorff effect?

BACKGROUND: Previous research has demonstrated a relationship between memory recall and P300 amplitude in list learning tasks, but the variables mediating this P300-recall relationship are not well understood. In the present study, subjects were required to recall items from lists consisting of 12 words, which were presented in front of pictures taken from the IAPS collection. One word per list is made distinct either by font color or by a highly arousing background IAPS picture. This isolation procedure was first used by von Restorff. Brain potentials were recorded during list presentation. RESULTS: Recall performance was enhanced for color but not for emotional isolates. Event-related brain potentials (ERP) showed a more positive P300-component for recalled non-isolated words and color-isolated words, compared to the respective non-remembered words, but not for words isolated by arousing background. CONCLUSION: Our findings indicate that it is crucial to take emotional mediator variables into account, when using the P300 to predict later recall. Highly arousing environments might force the cognitive system to interrupt rehearsal processes in working memory, which might benefit transfer into other, more stable memory systems. The impact of attention-capturing properties of arousing background stimuli is also discussed.

Intertemporal choice behavior is constrained by brain structure in healthy participants and pathological gamblers.

The steepness of the delay discounting function shows considerable interindividual differences. Moreover, faster devaluation of future rewards has been consistently observed in pathological gamblers (PGs). Here, we asked whether variability in delay discounting is at least partially driven by differences in the anatomy of gray and white matter. For 40 healthy young subjects (study 1) as well as 15 PG and 15 age-matched healthy controls (HCs, study 2), the individual discounting parameter k was obtained. Based on 3D T1-weighted high-resolution magnetic resonance scans and diffusion tensor imaging, we performed voxel-based morphometry and tract-based spatial statistics, respectively, to examine the relation of gray matter volume (GMV) and white matter properties (as indicated by fractional anisotropy, FA) to k. Healthy groups from both studies showed a negative correlation between k and FA for the superior longitudinal fascicle and inferior longitudinal fascicle, whereas a positive correlation was found in the PG group for the inferior longitudinal fascicle and left inferior fronto-occipital fascicle. The latter also was significantly different between HC and PG in the group statistics (albeit on the right side), thus suggesting that this is a significant structure for the development of pathological gambling. GMV of the right frontal orbital cortex, left insular cortex and right lateral occipital cortex showed a positive correlation to k HC (studies 1 and 2) and PG, whereas a negative correlation was found for the left frontal pole in all three groups. Group comparison of GMV (study 2) revealed a decrease in PG for several cortical and subcortical areas.

The neural basis of impulsive discounting in pathological gamblers.

Pathological gambling is thought to result from a shift of balance between two competing neurobiological mechanisms: on the one hand the reward system involved in the regulation of the urge to get rewards and on the other hand the top-down control system. Fifteen pathological gamblers (PG) and fifteen healthy controls (HC) were studied in an event-related functional magnetic resonance imaging experiment where participants had to choose either a smaller, but immediately available monetary reward (SIR) or a larger delayed reward (LDR). We examined contrasts between LDR and SIR decisions. Additionally, we contrasted choices near the individual indifference point (indifferent decisions) and clear SIR or LDR choices (sure decisions). Behavioral data confirmed former results of steeper discount rates in PG. Contrasting choices of LDR vs. SIR showed widespread bilateral activations in PG, including postcentral gyrus, thalamus, superior/medial frontal gyrus and cingulate gyrus, whereas HC demonstrated only focal left-sided pre/postcentral activity. Forgoing an immediate reward thus recruits a widespread brain network including typical control areas. Indifferent vs. sure decisions were associated with widespread activation in PG, including the bilateral fronto-parietal cortex, insula, anterior cingulate gyrus, and striatum, whereas in HC, only bilateral frontal cortex and insula were activated. The reverse contrast demonstrated more activity for sure decisions in the cingulate gyrus, insula, and medial frontal gyrus in HC, whereas PG showed inferior parietal and superior temporal activity. The present study demonstrates that pathological gambling is associated with a shift in the interplay between a prefrontal-parietal control network and a brain network involved in immediate reward consumption.

N1 enhancement in synesthesia during visual and audio-visual perception in semantic cross-modal conflict situations: an ERP study.

Synesthesia entails a special kind of sensory perception, where stimulation in one sensory modality leads to an internally generated perceptual experience of another, not stimulated sensory modality. This phenomenon can be viewed as an abnormal multisensory integration process as here the synesthetic percept is aberrantly fused with the stimulated modality. Indeed, recent synesthesia research has focused on multimodal processing even outside of the specific synesthesia-inducing context and has revealed changed multimodal integration, thus suggesting perceptual alterations at a global level. Here, we focused on audio-visual processing in synesthesia using a semantic classification task in combination with visually or auditory-visually presented animated and in animated objects in an audio-visual congruent and incongruent manner. Fourteen subjects with auditory-visual and/or grapheme-color synesthesia and 14 control subjects participated in the experiment. During presentation of the stimuli, event-related potentials were recorded from 32 electrodes. The analysis of reaction times and error rates revealed no group differences with best performance for audio-visually congruent stimulation indicating the well-known multimodal facilitation effect. We found enhanced amplitude of the N1 component over occipital electrode sites for synesthetes compared to controls. The differences occurred irrespective of the experimental condition and therefore suggest a global influence on early sensory processing in synesthetes.

Tracking functional brain changes in patients with depression under psychodynamic psychotherapy using individualized stimuli.

OBJECTIVE: Neurobiological models of depression posit limbic hyperactivity that should normalize after successful treatment. For psychotherapy, though, brain changes in patients with depression show substantial variability. Two critical issues in relevant studies concern the use of unspecific stimulation experiments and relatively short treatment protocols. Therefore changes in brain reactions to individualized stimuli were studied in patients with depression after eight months of psychodynamic psychotherapy. METHODS: 18 unmedicated patients with recurrent major depressive disorder were confronted with individualized and clinically derived content in a functional MRI experiment before (T1) and after eight months (T2) of psychodynamic therapy. A control group of 17 healthy subjects was also tested twice without intervention. The experimental stimuli were sentences describing each participant's dysfunctional interpersonal relationship patterns derived from clinical interviews based on Operationalized Psychodynamic Diagnostics (OPD). RESULTS: At T1 patients showed enhanced activation compared to controls in several limbic and subcortical regions, including amygdala and basal ganglia, when confronted with OPD sentences. At T2 the differences in brain activity between patients and controls were no longer apparent. Concurrently, patients had improved significantly in depression scores. CONCLUSIONS: Using ecologically valid stimuli, this study supports the model of limbic hyperactivity in depression that normalizes after treatment. Without a control group of untreated patients measured twice, though, changes in patients' brain activity could also be attributed to other factors than psychodynamic therapy.

Neural activity in relation to empirically derived personality syndromes in depression using a psychodynamic fMRI paradigm.

OBJECTIVE: The heterogeneity between patients with depression cannot be captured adequately with existing descriptive systems of diagnosis and neurobiological models of depression. Furthermore, considering the highly individual nature of depression, the application of general stimuli in past research efforts may not capture the essence of the disorder. This study aims to identify subtypes of depression by using empirically derived personality syndromes, and to explore neural correlates of the derived personality syndromes. MATERIALS AND METHODS: In the present exploratory study, an individually tailored and psychodynamically based functional magnetic resonance imaging paradigm using dysfunctional relationship patterns was presented to 20 chronically depressed patients. RESULTS from the Shedler-Westen Assessment Procedure (SWAP-200) were analyzed by Q-factor analysis to identify clinically relevant subgroups of depression and related brain activation. RESULTS: The principle component analysis of SWAP-200 items from all 20 patients lead to a two-factor solution: "Depressive Personality" and "Emotional-Hostile-Externalizing Personality." Both factors were used in a whole-brain correlational analysis but only the second factor yielded significant positive correlations in four regions: a large cluster in the right orbitofrontal cortex (OFC), the left ventral striatum, a small cluster in the left temporal pole, and another small cluster in the right middle frontal gyrus. DISCUSSION: The degree to which patients with depression score high on the factor "Emotional-Hostile-Externalizing Personality" correlated with relatively higher activity in three key areas involved in emotion processing, evaluation of reward/punishment, negative cognitions, depressive pathology, and social knowledge (OFC, ventral striatum, temporal pole). RESULTS may contribute to an alternative description of neural correlates of depression showing differential brain activation dependent on the extent of specific personality syndromes in depression.

Validating the truth of propositions: behavioral and ERP indicators of truth evaluation processes.

We investigated processes of truth validation during reading. Participants responded to 'true' and 'false' probes after reading simple true or false sentences. Compatible sentence/probe combinations (true/'true', false/'false') facilitated responding compared with incompatible combinations (true/'false', false/'true'), indicating truth validation. Evidence for truth validation was obtained after inducing an evaluative mindset but not after inducing a non-evaluative mindset, using additional intermixed tasks requiring true/false decisions or sentence comparisons, respectively. Event-related potentials revealed an increased late negativity (500-1000 ms after onset of the last word of sentences) for false compared with true sentences. Paralleling behavioral results, this electroencephalographic marker only obtained in the evaluative mindset condition. Further, mere semantic mismatches between subject and object of sentences led to an elevated N400 for both mindset conditions. Taken together, our findings suggest that truth validation is a conditionally automatic process that is dependent on the current task demands and resulting mindset, whereas the processing of word meaning and semantic relations between words proceeds in an unconditionally automatic fashion.

Why we still don't understand the depressed brain - Not going beyond snapshots.

Although remarkable progress has been made in the search for the brain correlates of depression with neuroimaging methods, we still find a heterogeneity of results and lack of consensus. This short commentary proposes a theoretical reason for this situation linking it to the methods of conducting neuroimaging studies of depression and the ways to interpret findings. If we only take one snapshot of the "depressed brain", the brain activity is presumably the result of four interacting components: neural predispositions, depressogenic pathology, changes caused by (chronic) depression, and compensatory brain mechanisms. The four components will be discussed briefly along with arguments why confusion of them might confuse our view of the brain in depression. After a short presentation of promising new longitudinal studies, this commentary gives first hints how we could go beyond snapshots to better understand the brain in depression.