P300 Response Research Articles

Effect of Supplemental Language Therapy on Cortical Neuroplasticity and Language Outcomes in Children with Hearing Loss

Background/Objectives: The cortical auditory evoked potential P1 response is a biomarker of cortical auditory maturation for tracking longitudinal cortical maturation in children with hearing loss after treatment with hearing aids and/or cochlear implants. In conjunction with hearing treatments, children with hearing loss commonly receive language therapy services. However, the effect of language therapy on cortical maturation in hearing loss is less well studied. Methods: This study explored auditory cortical maturation changes, using the P1 response, with coinciding language changes, utilizing the Preschool Language Scales test, following approximately six months of supplemental listening and spoken language therapy services in 39 children with hearing aids or cochlear implants. Results: Following supplemental language therapy, P1 latencies significantly decreased in all children, at a rate found to be significantly faster than expected for typical maturation. Language scores also significantly improved beyond expected maturation effects and were correlated with P1 latencies following supplemental therapy. Overall, with approximately six months of therapy, the children in this study made significantly greater gains of 9 to 10 months in total language and expressive communication. A subgroup analysis revealed that children with cochlear implants showed significantly lower language scores than their chronological age following supplemental therapy, while children with hearing aids obtained language scores that were not significantly different to their chronological age at follow-up. Conclusions: Overall, the results from this study showed that supplemental language therapy resulted in more typical auditory cortical maturation and improved language abilities and that the P1 CAEP response can objectively track neuroplastic changes in children as a function of language therapy provided in conjunction with hearing aids and CIs.

Decoding imagined movement in people with multiple sclerosis for brain–computer interface translation

Objective.Multiple sclerosis (MS) is a heterogeneous autoimmune-mediated disorder affecting the central nervous system, commonly manifesting as fatigue and progressive limb impairment. This can significantly impact quality of life due to weakness or paralysis in the upper and lower limbs. A brain-computer interface (BCI) aims to restore quality of life through control of an external device, such as a wheelchair. However, the limited BCI research in people with MS has been confined to exploring the P300 response and brain signals associated with attempted movement. The current study aims to expand the MS-BCI literature by highlighting the feasibility of decoding MS imagined movement.Approach.We collected electroencephalography data from eight participants with various symptoms of MS and ten neurotypical control participants. Participants made imagined movements of the hands and feet as directed by a go no-go protocol. Binary regularised linear discriminant analysis was used to classify imagined movement vs. rest and vs. movement at individual time-frequency points. The frequency bands which provided the maximal accuracy, and the associated latency, were compared.Main Results.In all MS participants, the classification algorithm achieved above 70% accuracy in at least one imagined movement vs. rest classification and most movement vs. movement classifications. There was no significant difference between classification of limbs with weakness or paralysis to neurotypical controls. Both the MS and control groups possessed decodable information within the alpha (7-13 Hz) and beta (16-30 Hz) bands at similar latency.Significance.This study is the first to demonstrate the feasibility of decoding imagined movements in people with MS. As an alternative to the P300 response, motor imagery-based control of a BCI may also be combined with existing motor imagery therapy to supplement MS rehabilitation. These promising results merit further long term BCI studies to investigate the effect of MS progression on classification performance.

Competition modulates the effects of social comparison on ERP responses during face processing.

Little is known about the effect of prior social performance feedback on face processing. Our previous study explored how equal and unequal social comparison-related outcomes modulate event-related potential (ERP) responses to subsequently-presented faces, where interests between oneself and others were independent (noncompetitive situations). Here, we aimed to extend this investigation by assessing how different unequal social comparison-related outcomes affect face processing under noncompetitive and competitive situations (i.e., a conflict of interest exists between the self and others). To address this issue, 39 participants were exposed with self-related and social comparison-related outcomes, categorized as positive or negative, after performing an attentional task with peers. Rewards and punishments depended on social comparison-related outcomes in the competition condition and on self-related outcomes in the noncompetition condition. ERP results showed that social comparison-related outcomes influenced P100 responses to faces in the self-positive condition. More notably, the effects on N170 responses observed in the noncompetition condition was absent in the competition condition. There was an effect on LPP responses only in the competition and self-negative condition. These findings suggest that social comparison-related outcomes influence early face processing irrespective of competition, while competition subsequently disrupts this processing but later, enhances depending on self-related outcomes.

Error monitoring and response inhibition in adolescents with bipolar disorders: An ERP study.

Cognitive control develops throughout adolescence, a high-risk period for bipolar disorders (BD) onset. Despite neurobehavioral abnormalities in adults with BD, there is minimal research investigating deviations in cognitive control in adolescents with BD. Cognitive control involves numerous processes. Identifying the specific neural abnormalities in adolescent BD could provide precise targets for novel interventions that improve illness outcomes. The present study administered a Go/No-Go (GNG) task to 98 adolescents (44 BD; 54 controls) to activate response inhibition and error processes and recorded EEG for event-related potentials (ERPs) analysis. Stimulus-locked N2 and P3 (response inhibition) and response-locked error-related negativity (ERN; early error detection) and error positivity (Pe; conscious error detection) were analyzed. Adolescents with BD had attenuated Pe mean amplitudes following failed inhibition trials. There were no group differences in other ERP amplitudes, including N2, P3, and ERN. The pattern of findings implicates conscious error detection impairment in adolescents with BD, without support for deficits in more automatic, earlier error detection. Impaired conscious error detection in adolescents with BD may be an early expression of BD pathophysiology and a possible intervention target for cognitive rehabilitation. Further studies are needed to examine Pe in BD across the lifetime.

Objective Visual Acuity Estimates in Amblyopia Are More Accurate With Optotype-Based P300 Than With VEP Measurements.

Traditional visual acuity (VA) measurements depend on subjective responses, which can be unreliable, especially with uncooperative participants. Objective measurements with visual evoked potentials (VEP) address this issue but can overestimate VA in amblyopia. This study aims to establish the P300 component of the event-related potential as an objective VA test for amblyopia and compare its performance to subjective (psychophysical) and VEP-based VA estimates. Psychophysical, VEP-based, and P300-based VA estimates were obtained for amblyopic and fellow eyes of 18 participants (aged 19-65) in a bicentric study. VEP-based VA was determined from the spatial frequency threshold derived from occipital cortex pattern-pulse responses to check-sizes ranging from 0.048° to 8.95°. P300 responses were collected using visual oddball sequences with circular optotypes. The threshold was estimated from the sigmoid function of parietal P300 amplitude versus optotype gap size. Mean VA values for amblyopic eyes were compared across methods. VEP-based VA of the amblyopic eyes overestimated psychophysical VA by 0.18 ± 0.06 logMAR (P = 0.0016). In contrast, P300-based VA showed no significant difference from psychophysical VA (0.00 ± 0.04 logMAR, P > 0.05). In amblyopia, P300-based optotype VA aligns more closely with psychophysical VA than VEP-based VA, suggesting that P300-based VA is a valid objective alternative for estimating VA in amblyopic eyes. This study highlights the potential of P300-based VA testing as a reliable and objective method for assessing VA in amblyopic eyes, offering a promising tool for clinical and research applications where traditional methods fall short.

Emotional Evaluations from Partners and Opponents Differentially Influence the Perception of Ambiguous Faces.

The influence of contextual valence and interpersonal distance on facial expression perception remains unclear despite their significant role in shaping social perceptions. In this event-related potential (ERP) study, we investigated the temporal dynamics underlying the processing of surprised faces across different interpersonal distances (partner, opponent, or stranger) and contextual valence (positive, neutral, or negative) contexts. Thirty-five participants rated the valence of surprised faces. An advanced mass univariate statistical approach was utilized to analyze the ERP data. Behaviorally, surprised faces in partner-related negative contexts were rated more negatively than those in opponent- and stranger-related contexts. The ERP results revealed an increased P1 amplitude for surprised faces in negative relative to neutral contexts. Both the early posterior negativity (EPN) and late positive potentials (LPP) were also modulated by contextual valence, with larger amplitudes for faces in positive relative to neutral and negative contexts. Additionally, when compared to stranger-related contexts, faces in partner-related contexts exhibited enhanced P1 and EPN responses, while those in opponent-related contexts showed amplified LPP responses. Taken together, these findings elucidate the modulation of intricate social contexts on the perception and interpretation of ambiguous facial expressions, thereby enhancing our understanding of nonverbal communication and emotional cognition.

The Effects of Hearing One's Own Name on Subsequent Attention to Visual Stimuli in Autistic and Neurotypical Children: An ERP Study.

Hearing one's own name produces unique patterns of brain activation which triggers attention and orienting responses to the caller. Children with autism spectrum disorder (ASD) rarely orientate towards people calling their own name, but the extent to which it may facilitate processing of the following external stimuli are not yet clear. The current study consisted of both auditory and visual stimuli. Electroencephalogram (EEG) was measured in 28 autistic and neurotypical children (aged 3-7years) to investigate auditory event-related brain potentials (ERPs) while hearing either their own or an unfamiliar name, and subsequent visual ERPs when viewing objects after hearing them. The results demonstrated that, unlike neurotypical children, autistic children did not show enhanced P300 responses upon hearing their own name, but exhibited more negative N1 response in the left frontal region to hearing their own name than an unfamiliar name. However, both autistic and neurotypical children showed equivalent changes in N2, P3 and Late positive potential (LPP) visual ERPs when viewing objects after hearing their own name relative to an unfamiliar name. These findings suggest that autistic children who do not overtly respond to their own name (characterized by a head-turn), nevertheless exhibit increased attention to visual objects in their environment after hearing it. This implies that autistic children do recognize the sound of their name as important but may not understand the social meaning of it.

Musicianship Modulates Cortical Effects of Attention on Processing Musical Triads.

Background: Many studies have demonstrated the benefits of long-term music training (i.e., musicianship) on the neural processing of sound, including simple tones and speech. However, the effects of musicianship on the encoding of simultaneously presented pitches, in the form of complex musical chords, is less well established. Presumably, musicians' stronger familiarity and active experience with tonal music might enhance harmonic pitch representations, perhaps in an attention-dependent manner. Additionally, attention might influence chordal encoding differently across the auditory system. To this end, we explored the effects of long-term music training and attention on the processing of musical chords at the brainstem and cortical levels. Method: Young adult participants were separated into musician and nonmusician groups based on the extent of formal music training. While recording EEG, listeners heard isolated musical triads that differed only in the chordal third: major, minor, and detuned (4% sharper third from major). Participants were asked to correctly identify chords via key press during active stimulus blocks and watched a silent movie during passive blocks. We logged behavioral identification accuracy and reaction times and calculated information transfer based on the behavioral chord confusion patterns. EEG data were analyzed separately to distinguish between cortical (event-related potential, ERP) and subcortical (frequency-following response, FFR) evoked responses. Results: We found musicians were (expectedly) more accurate, though not faster, than nonmusicians in chordal identification. For subcortical FFRs, responses showed stimulus chord effects but no group differences. However, for cortical ERPs, whereas musicians displayed P2 (~150 ms) responses that were invariant to attention, nonmusicians displayed reduced P2 during passive listening. Listeners' degree of behavioral information transfer (i.e., success in distinguishing chords) was also better in musicians and correlated with their neural differentiation of chords in the ERPs (but not high-frequency FFRs). Conclusions: Our preliminary results suggest long-term music training strengthens even the passive cortical processing of musical sounds, supporting more automated brain processing of musical chords with less reliance on attention. Our results also suggest that the degree to which listeners can behaviorally distinguish chordal triads is directly related to their neural specificity to musical sounds primarily at cortical rather than subcortical levels. FFR attention effects were likely not observed due to the use of high-frequency stimuli (>220 Hz), which restrict FFRs to brainstem sources.

Early visual modulation and selection predict saccadic timing during visual search: An ERP study.

Saccadic eye movements, a critical aspect of real-world visual behavior, are preceded by an initial accumulation of visual information followed by the selection of a single location to move one's eyes. However, it is currently unclear how each of these stages uniquely affects saccadic timing. In this study, participants searched for a contour integration target while EEG was used to measure posterior cortical activity between search display onset and first saccade initiation. The goal was to determine whether saccade timing could be attributed to differences in early ERP amplitudes, with the P1 reflecting the magnitude of early perceptual information accumulation and the N1 reflecting the strength of selection leading to the saccadic decision. EOG was used to measure saccade timing, and trials were divided into fast, middle, and slow bins. The N1 response was smallest in the slow saccade tertile, relative to both the fast and middle tertiles, suggesting weak selection. In contrast, the P1 response was largest for this same slow saccadic tertile relative to the middle saccadic tertile, suggesting vigorous information accumulation. Therefore, delays in saccadic behavior may occur when the visual system is overwhelmed with visual input, thus increasing the time to reach a saccadic decision. These findings reconcile models of eye movement behavior which often prioritize either the impact of information accrual or selection, rather than regarding both as an integrated whole.

Event-related potentials of stimuli inhibition and access in cross-modal distractor-induced blindness.

Distractor-induced blindness (DIB) describes a reduced access to a cued visual target-if multiple target-like distractors have been presented beforehand. Previous ERP data suggest a cumulative frontal inhibition triggered by distractors, which affects the updating process of the upcoming target. In the present study, we examine whether the modality of the cue-formerly defined in the visual domain-affects the expression of these neural signatures. 27 subjects were tested in a cross-modal DIB task: Distractors and targets were defined by a transient change of stimuli shape in a random-dot kinematogram. The onset of the target was announced by a rise in amplitude of a sinusoidal tone. Behavioral results confirmed that detection of the target relies on the number of preceding distractor episodes. Replicating previous unimodal results, ERP responses to distractors were characterized by a frontal negativity starting at 100 ms, which increases with an increasing number of distractor episodes. However, the processing-and detection-of the target was not characterized by a more-expressed P3 response, but by an occipital negativity. The current data confirm that the neural signatures of target awareness depend on the experimental setup used: In case of the DIB, the cross-modal setting might lead to a reduction of attentional resources in the visual domain.

Relevance of Prosodic Focus and Lexical Stress for Discourse Comprehension in Turkish: Evidence from Psychometric and Electrophysiological Data.

Prosody underpins various linguistic domains ranging from semantics and syntax to discourse. For instance, prosodic information in the form of lexical stress modifies meanings and, as such, syntactic contexts of words as in Turkish kaz-má "pickaxe" (noun) versus káz-ma "do not dig" (imperative). Likewise, prosody indicates the focused constituent of an utterance as the noun phrase filling the wh-spot in a dialogue like What did you eat? I ate----. In the present study, we investigated the relevance of such prosodic variations for discourse comprehension in Turkish. We aimed at answering how lexical stress and prosodic focus mismatches on critical noun phrases-resulting in grammatical anomalies involving both semantics and syntax and discourse-level anomalies, respectively-affect the perceived correctness of an answer to a question in a given context. To that end, 80 native speakers of Turkish, 40 participating in a psychometric experiment and 40 participating in an EEG experiment, were asked to judge the acceptability of prosodic mismatches that occur either separately or concurrently. Psychometric results indicated that lexical stress mismatch led to a lower correctness score than prosodic focus mismatch, and combined mismatch received the lowest score. Consistent with the psychometric data, EEG results revealed an N400 effect to combined mismatch, and this effect was followed by a P600 response to lexical stress mismatch. Conjointly, these results suggest that every source of prosodic information is immediately available and codetermines the interpretation of an utterance; however, semantically and syntactically relevant lexical stress information is assigned more significance by the language comprehension system compared with prosodic focus information.

Face and face pareidolia in patients with temporal lobe epilepsy indicates different neural processing: an event-related potential study

BackgroundVisual perception of face images or face pareidolia can be evaluated with event-related potentials (ERP) for healthy subjects and patients with neurological conditions. In this study, we aimed to analyse event-related potential components such as P100, N100, N170, and vertex-positive potential (VPP) in response to face pareidolia perception in temporal lobe epilepsy (TLE) patients.MethodsERPs were recorded during the pareidolia test. Waveforms were analzyed and current source density (CSD) maps were generated.ResultsCSD profiles were shown to be interpretable when face and face pareidolia conditions. N100, P100, and N170 components showed larger amplitudes and longer latency in epilepsy patients in response to face pareidolia stimuli compared to real face images. However, the N170 component latency did not differ significantly between epilepsy patients and healthy participants, while the larger amplitude and longer latency of N100 and P100 responses were evoked in healthy patients.ConclusionsOur results indicate a difference in the neural mechanisms of processing real face information and pareidolia face-like information in TLE patients.

The Development of a Multicommand Tactile Event-Related Potential-Based Brain–Computer Interface Utilizing a Low-Cost Wearable Vibrotactile Stimulator

A tactile event-related potential (ERP)-based brain–computer interface (BCI) system is an alternative for enhancing the control and communication abilities of quadriplegic patients with visual or auditory impairments. Hence, in this study, we proposed a tactile stimulus pattern using a vibrotactile stimulator for a multicommand BCI system. Additionally, we observed a tactile ERP response to the target from random vibrotactile stimuli placed in the left and right wrist and elbow positions to create commands. An experiment was conducted to explore the location of the proposed vibrotactile stimulus and to verify the multicommand tactile ERP-based BCI system. Using the proposed features and conventional classification methods, we examined the classification efficiency of the four commands created from the selected EEG channels. The results show that the proposed vibrotactile stimulation with 15 stimulus trials produced a prominent ERP response in the Pz channels. The average classification accuracy ranged from 61.9% to 79.8% over 15 stimulus trials, requiring 36 s per command in offline processing. The P300 response in the parietal area yielded the highest average classification accuracy. The proposed method can guide the development of a brain–computer interface system for physically disabled people with visual or auditory impairments to control assistive and rehabilitative devices.

The LCLAT1/LYCAT acyltransferase is required for EGF-mediated phosphatidylinositol-3,4,5-trisphosphate generation and Akt signaling.

Receptor tyrosine kinases such as EGF receptor (EGFR) stimulate phosphoinositide 3 kinases to convert phosphatidylinositol-4,5-bisphosophate [PtdIns(4,5)P2] into phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P3]. PtdIns(3,4,5)P3 then remodels actin and gene expression, and boosts cell survival and proliferation. PtdIns(3,4,5)P3 partly achieves these functions by triggering activation of the kinase Akt, which phosphorylates targets like Tsc2 and GSK3β. Consequently, unchecked upregulation of PtdIns(3,4,5)P3-Akt signaling promotes tumor progression. Interestingly, 50-70% of PtdIns and PtdInsPs have stearate and arachidonate at sn-1 and sn-2 positions of glycerol, respectively, forming a species known as 38:4-PtdIns/PtdInsPs. LCLAT1 and MBOAT7 acyltransferases partly enrich PtdIns in this acyl format. We previously showed that disruption of LCLAT1 lowered PtdIns(4,5)P2 levels and perturbed endocytosis and endocytic trafficking. However, the role of LCLAT1 in receptor tyrosine kinase and PtdIns(3,4,5)P3 signaling was not explored. Here, we show that LCLAT1 silencing in MDA-MB-231 and ARPE-19 cells abated the levels of PtdIns(3,4,5)P3 in response to EGF signaling. Importantly, LCLAT1-silenced cells were also impaired for EGF-driven and insulin-driven Akt activation and downstream signaling. Thus, our work provides first evidence that the LCLAT1 acyltransferase is required for receptor tyrosine kinase signaling.

Electrophysiological correlates of why humans deviate from rational decision-making: A registered replication study.

In contrast to rational choice theory predicting humans to optimize expected utilities of choices, humans deviate from rational behavior in decision-making paradigms. Hewig etal. (2011) explored affective correlates of decision-making in the ultimatum game (UG) and the dictator game (DG). They found that feedback-related negativity (FRN), subjective valence ratings, and autonomic nervous system activity predicted rejection of monetary offers. This registered replication aimed to validate and extend these findings. Although behavioral patterns and results of subjective ratings closely matched the original study, not all psychophysiological effects were successfully replicated. Firstly, we could not replicate the reported effects of autonomic nervous system activity. Secondly, a quadratic instead of the originally proposed linear relation between the offer and the FRN emerged, possibly driven by the offer evaluation in economic games and the rewarding anticipation of successful punishment for low offers. Thirdly, P3 amplitudes mirrored the quadratic offer response pattern, generally peaking for the lowest offer. In contrast to the original study, P3 responses were larger in the UG compared with the DG. Finally, our findings indicate that participant-related higher midfrontal theta activation predicted lower acceptance behavior in the UG, with a systematic dampening effect for fairer offers. This highlights cognitive control as a crucial mechanism in economic decision-making to overcome behavioral defaults. Overall, our results conceptually support the original conclusion that decision-making in economic games is non-rational and dependent on the objective situation as well as emotional and neural markers, though not precisely as suggested by Hewig etal. (2011).

Risk avoidance and social anxiety in adolescence: Examination of event-related potentials and theta-dynamics on the Balloon Risk Avoidance Task

Adolescents are at relatively high-risk for developing anxiety, particularly social anxiety. A primary hallmark of social anxiety is the impulse to avoid situations that introduce risk. Here, we examined the neural and behavioral correlates of risk avoidance in adolescents (N=59) 11 to 19 years of age. The Balloon Risk Avoidance Task was used with concurrent electroencephalography to measure event-related potentials (frontal P2; late slow-wave; N2, feedback-related negativity, FRN; posterior P3) and oscillatory dynamics (midfrontal theta, 4–7 Hz) in response to unsuccessful and successful risk avoidance conditions. Social anxiety was measured using the Social Phobia and Anxiety Inventory for Children. Results indicated that, across the whole sample, youth exhibited smaller P3, larger FRN, and larger theta responses to unsuccessful risk avoidance. Youth reporting high (compared to low) levels of social anxiety exhibited larger P2, slow-wave, and FRN responses to unsuccessful, compared to successful, risk avoidance. Further, greater social anxiety was associated with reduced theta responses to successful avoidance. Youth with higher levels of social anxiety showed smaller theta responses to both conditions compared to those with low levels of social anxiety. Taken together, the ERP-component differences and weakened theta power in socially anxious youth following unsuccessful avoidance are informative neural correlates for socially anxious youth during risk avoidance.

Perceptual anchoring: Children with dyslexia benefit less than controls from contextual repetitions in speech processing

ObjectivesIndividuals with dyslexia perceive and utilize statistical features in the auditory input deficiently. The present study investigates whether affected children also benefit less from repeating context tones as perceptual anchors for subsequent speech processing. MethodsIn an event-related potential study, eleven-year-old children with dyslexia (n = 21) and without dyslexia (n = 20) heard syllable pairs, with the first syllable either receiving a constant pitch (anchor) or variable pitch (no-anchor), while second syllables were identical across conditions. ResultsChildren with and without dyslexia showed smaller auditory P2 responses to constant-pitch versus variable-pitch first syllables, while only control children additionally showed smaller N1 and faster P1 responses. This suggests less automatic processing of anchor repetitions in dyslexia. For the second syllables, both groups showed faster P2 responses following anchor than no-anchor first syllables, but only controls additionally showed smaller P2 responses. ConclusionsChildren with and without dyslexia show differences in anchor effects. While both groups seem to allocate less attention to speech stimuli after contextual repetitions, children with dyslexia display less facilitation in speech processing from acoustic anchors. SignificanceAltered anchoring in the linguistic domain may contribute to the difficulties of individuals with dyslexia in establishing long-term representations of speech.

P300 Responses to Speech and Music Stimuli: Effect of Musical Training

P300 Responses to Speech and Music Stimuli: Effect of Musical Training

Effects of Transcutaneous Auricular Vagus Nerve Stimulation on the P300: Do Stimulation Duration and Stimulation Type Matter?

Non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) has attracted increasing interest as a neurostimulation tool with potential applications in modulating cognitive processes such as attention and memory, possibly through the modulation of the locus-coeruleus noradrenaline system. Studies examining the P300 brain-related component as a correlate of noradrenergic activity, however, have yielded inconsistent findings, possibly due to differences in stimulation parameters, thus necessitating further investigation. In this event-related potential study involving 61 participants, therefore, we examined how changes in taVNS parameters, specifically stimulation type (interval vs. continuous stimulation) and duration, influence P300 amplitudes during a visual novelty oddball task. Although no effects of stimulation were found over the whole cluster and time window of the P300, cluster-based permutation tests revealed a distinct impact of taVNS on the P300 response for a small electrode cluster, characterized by larger amplitudes observed for easy targets (i.e., stimuli that are easily discernible from standards) following taVNS compared to sham stimulation. Notably, our findings suggested that the type of stimulation significantly modulated taVNS effects on the P300, with continuous stimulation showing larger P300 differences (taVNS vs. sham) for hard targets and standards compared to interval stimulation. We observed no interaction effects of stimulation duration on the target-related P300. While our findings align with previous research, further investigation is warranted to fully elucidate the influence of taVNS on the P300 component and its potential utility as a reliable marker for neuromodulation in this field.

The FreiBurger: a new optotype for P300-based acuity estimation.

Accurate objective assessment of visual acuity is crucial, particularly in cases of suspected malingering, or when the patient's inability to cooperate makes standard psychophysical acuity tests unreliable. The P300 component of the event-related potentials offers a potential solution and even allows for the use of standard optotypes like the Landolt C. However, low-vision patients with large eccentric visual field defects often struggle to locate the Landolt C gap quickly enough for a P300 to be reliably produced. Addressing this challenge, we introduce a novel optotype (the "FreiBurger") with a critical detail that extends through the optotype's center. Two experiments, with 16 and 12 participants, respectively, were conducted. In the first, psychophysical acuity estimates were obtained with both the FreiBurger and the Landolt C. In the second, we tested the performance of the FreiBurger, relative to the Landolt C, in eliciting a P300 with undegraded vision, simulated low vision, and in a simulated combination of low vision and visual field constriction. Comparable psychophysical acuity values (average difference 0.03 logMAR) were obtained for both optotypes. In the P300 recordings, both optotypes produced similar P300 responses under conditions of undegraded vision and low vision. However, with the combination of low vision and constricted visual field, the P300 could only be reliably obtained with the FreiBurger, while the amplitude was drastically reduced with the Landolt C (9.1µV vs. 2.2µV; p < 0.0005). The new optotype extends the applicability of P300-based acuity estimation to the frequently encountered combination of low vision and constricted visual field, where Landolt C optotypes fail. Although impairments were simulated in the present study, we assume that the advantages of the new optotype will also manifest in patients with such impairments. We furthermore expect the advantages to apply to time-sensitive psychophysical examinations as well.