Human Event-related Brain Potential Research Articles

Pathologists aren't pigeons: exploring the neural basis of visual recognition and perceptual expertise in pathology.

Visual (perceptual) reasoning is a critical skill in many medical specialties, including pathology, diagnostic imaging, and dermatology. However, in an ever-compressed medical curriculum, learning and practicing this skill can be challenging. Previous studies (including work with pigeons) have suggested that using reward-feedback-based activities, novices can gain expert levels of visual diagnostic accuracy in shortened training times. But is this level of diagnostic accuracy a result of image recognition (categorization) or is it the acquisition of diagnostic expertise? To answer this, the authors measured electroencephalographic data (EEG) and two components of the human event-related brain potential (reward positivity and N170) to explore the nature of visual expertise in a novice-expert study in pathology visual diagnosis. It was found that the amplitude of the reward positivity decreased with learning in novices (suggesting a decrease in reliance on feedback, as in other studies). However, this signal remained significantly different from the experts whose reward positivity signal did not change over the course of the experiment. There were no changes in the amplitude of the N170 (a reported neural marker of visual expertise) in novices over time. Novice N170 signals remained statistically and significantly lower in amplitude compared to experts throughout task performance. These data suggest that, while novices gained the ability to recognize (categorize) pathologies through reinforcement learning as quantified by the change in reward positivity, increased accuracy, and decreased time for responses, there was little change in the neural marker associated with visual expertise (N170). This is consistent with the multi-dimensional and complex nature of visual expertise and provides insight into future training programs for novices to bridge the expertise gap.

How low can you go? Measuring human event-related brain potentials from a two-channel EEG system

Over the past ten years, there has been a rapid increase in the availability and use of mobile electroencephalography (mEEG) in research. Indeed, researchers using mEEG have recorded EEG and event-related brain potentials in a wide range of environments - for example, while walking (Debener et al., 2012), riding a bike (Scanlon et al., 2020), or even in a shopping mall (Krigolson et al., 2021). However, given that low-cost, ease-of-use, and setup speed provide the primary advantages of an mEEG system over large array traditional EEG systems, an important and unresolved question is just how many electrodes does an mEEG system need to collect research-quality EEG data? Here, we tested whether or not a two-channel forehead-mounted mEEG system – the “Patch” – could measure event-related brain potentials within their established amplitude and latency characteristics (Luck, 2014). In the present study, participants performed a visual oddball task while we recorded EEG data from the Patch. Our results demonstrated that we could capture and quantify the N200 and P300 event-related brain potential components using a minimal electrode array forehead-mounted EEG system. Our data further support the idea that mEEG can be used for quick and rapid EEG-based assessments, such as measuring the impact of concussions on the sports field (Fickling et al., 2021) or assessing the impact of stroke severity in a hospital (Wilkinson et al., 2020).

Using Muse: Rapid Mobile Assessment of Brain Performance.

The advent of mobile electroencephalography (mEEG) has created a means for large scale collection of neural data thus affording a deeper insight into cognitive phenomena such as cognitive fatigue. Cognitive fatigue – a neural state that is associated with an increased incidence of errorful performance – is responsible for accidents on a daily basis which at times can cost human lives. To gain better insight into the neural signature of cognitive fatigue in the present study we used mEEG to examine the relationship between perceived cognitive fatigue and human-event related brain potentials (ERPs) and electroencephalographic (EEG) oscillations in a sample of 1,000 people. As a secondary goal, we wanted to further demonstrate the capability of mEEG to accurately measure ERP and EEG data. To accomplish these goals, participants performed a standard visual oddball task on an Apple iPad while EEG data were recorded from a Muse EEG headband. Counter to traditional EEG studies, experimental setup and data collection was completed in less than seven minutes on average. An analysis of our EEG data revealed robust N200 and P300 ERP components and neural oscillations in the delta, theta, alpha, and beta bands. In line with previous findings we observed correlations between ERP components and EEG power and perceived cognitive fatigue. Further, we demonstrate here that a linear combination of ERP and EEG features is a significantly better predictor of perceived cognitive fatigue than any ERP or EEG feature on its own. In sum, our results provide validation of mEEG as a viable tool for research and provide further insight into the impact of cognitive fatigue on the human brain.

Early cortical processing of vection-inducing visual stimulation as measured by event-related brain potentials (ERP)

Visual motion stimuli can induce the perception of self-motion in stationary observers (known as vection). In the present study, we investigated the sensory processing underlying vection by measuring the human event-related brain potentials (ERPs) elicited by the movement onset of a visual stimulus. We presented participants a visual stimulus consisting of alternating black-and-white vertical bars that moved in horizontal direction, creating the sensation of vection. The stimulus was presented on a screen that was divided into a central and a surrounding peripheral visual area. Both areas moved independently from each other, resulting in four different movement patterns: the peripheral and the central stimulus moved in the same or opposite direction, or one of the two visual areas of the stimulus moved while the other remained stable. In addition, two different stimulus types varying with respect to the bars’ width (narrow vs. wide) were used. Participants were presented with these stimuli in two phases of the experiment: During EEG-recording, only short phases (2.5–3.5 ms) of visual motion were applied. In a separate rating phase, visual motion was presented for 45 s. In this phase, vection onset, intensity, and duration were verbally recorded. Overall, the visual stimulation generated vection with different intensities (i.e., weakest vection with sole central stimulus movement). Stimulus type did not affect vection. In the ERPs, stimulus onset elicited parieto-occipital P2 and N2 components. The amplitudes of the ERP components differed significantly between the four movement patterns (irrespective of stimulus type), however, they did not fully align with the subjective vection ratings. Since the ERPs are associated with early sensory processing preceding vection, we argue that the ERPs mirror the contribution of sensory cortical processes to vection rather than the subjective sensation of vection per se.

Electrophysiological responses of medial prefrontal cortex to feedback at different levels of hierarchy

Recent advances in computational reinforcement learning suggest that humans and animals can learn from different types of reinforcers in a hierarchically organised fashion. According to this theoretical framework, while humans learn to coordinate subroutines based on external reinforcers such as food rewards, simple actions within those subroutines are reinforced by an internal reinforcer called a pseudo-reward. Although the neural mechanisms underlying these processes are unknown, recent empirical evidence suggests that the medial prefrontal cortex (MPFC) is involved. To elucidate this issue, we measured a component of the human event-related brain potential, called the reward positivity, that is said to reflect a reward prediction error signal generated in the MPFC. Using a task paradigm involving reinforcers at two levels of hierarchy, we show that reward positivity amplitude is sensitive to the valence of low-level pseudo-rewards but, contrary to our expectation, is not modulated by high-level rewards. Further, reward positivity amplitude to low-level feedback is modulated by the goals of the higher level. These results, which were further replicated in a control experiment, suggest that the MPFC is involved in the processing of rewards at multiple levels of hierarchy.

Visual mismatch negativity (vMMN) is elicited with para-foveal hemifield oddball stimulation: An event-related brain potential (ERP) study

The visual mismatch negativity (vMMN) is a component of the human event-related brain potential (ERP) that indicates the automatic processing and detection of changes in the visual sensory input. The study tested whether the vMMN was observable when the visual input is restricted to one visual hemifield and, with this, only para-foveal input to one of the two primary sensory cortices in the visual system is available for stimulus processing. The vMMN was elicited by the stimulation restricted to a small portion of the visual field. This demonstrates that in general vMMN elicitation is not confined to stimulations covering a broad range of the visual field or to the propagation of sensory information to both sensory visual cortices. In addition, the vMMN amplitudes showed a high variability between the different conditions, including non-significant vMMN amplitudes. This suggests that pronounced vMMNs observed in experimental settings relies on salient visual stimuli covering different channels of sensory information in vision.

The application of reward learning in the real world: Changes in the reward positivity amplitude reflect learning in a medical education context.

Evidence ranging from behavioural adaptations to neurocognitive theories has made significant advances into our understanding of feedback-based learning. For instance, over the past twenty years research using electroencephalography has demonstrated that the amplitude of a component of the human event-related brain potential - the reward positivity - appears to change with learning in a manner predicted by reinforcement learning theory (Holroyd and Coles, 2002; Sutton and Barto, 1998). However, while the reward positivity (also known as the feedback related negativity) is well studied, whether the component reflects an underlying learning process or whether it is simply sensitive to feedback evaluation is still unclear. Here, we sought to provide support that the reward positivity is reflective of an underlying learning process and further we hoped to demonstrate this in a real-world medical education context. In the present study, students with no medical training viewed a series of patient cards that contained ten physiological readings relevant for diagnosing liver and biliary disease types, selected the most appropriate diagnostic classification, and received feedback as to whether their decisions were correct or incorrect. Our behavioural results revealed that our participants were able to learn to diagnose liver and biliary disease types. Importantly, we found that the amplitude of the reward positivity diminished in a concomitant manner with the aforementioned behavioural improvements. In sum, our data support theoretical predictions (e.g., Holroyd and Coles, 2002), suggest that the reward positivity is an index of a neural learning system, and further validate that this same system is involved in learning across a wide range of contexts.

When theory and biology differ: The relationship between reward prediction errors and expectancy

Comparisons between expectations and outcomes are critical for learning. Termed prediction errors, the violations of expectancy that occur when outcomes differ from expectations are used to modify value and shape behaviour. In the present study, we examined how a wide range of expectancy violations impacted neural signals associated with feedback processing. Participants performed a time estimation task in which they had to guess the duration of one second while their electroencephalogram was recorded. In a key manipulation, we varied task difficulty across the experiment to create a range of different feedback expectancies − reward feedback was either very expected, expected, 50/50, unexpected, or very unexpected. As predicted, the amplitude of the reward positivity, a component of the human event-related brain potential associated with feedback processing, scaled inversely with expectancy (e.g., unexpected feedback yielded a larger reward positivity than expected feedback). Interestingly, the scaling of the reward positivity to outcome expectancy was not linear as would be predicted by some theoretical models. Specifically, we found that the amplitude of the reward positivity was about equivalent for very expected and expected feedback, and for very unexpected and unexpected feedback. As such, our results demonstrate a sigmoidal relationship between reward expectancy and the amplitude of the reward positivity, with interesting implications for theories of reinforcement learning.

Switching Attention Within Working Memory is Reflected in the P3a Component of the Human Event-Related Brain Potential.

The flexible access to information in working memory is crucial for adaptive behavior. It is assumed that this is realized by switching the focus of attention within working memory. Switching of attention is mirrored in the P3a component of the human event-related brain potential (ERP) and it has been argued that the processes reflected by the P3a are also relevant for selecting information within working memory. The aim of the present study was to further evaluate whether the P3a mirrors genuine switching of attention within working memory by applying an object switching task: Participants updated a memory list of four digits either by replacing one item with another digit or by processing the stored digit. ERPs were computed separately for two types of trials: (1) trials in which an object was repeated and (2) trials in which a switch to a new object was required in order to perform the task. Object-switch trials showed increased response times compared with repetition trials in both task conditions. In addition, switching costs were increased in the processing compared with the replacement condition. Pronounced P3a’s were obtained in switching trials but there were no difference between the two updating tasks (replacement or processing). These results were qualified by the finding that the magnitude of the visual location shift also affects the ERPs in the P3a time window. Taken together, the present pattern of results suggest that the P3a reflects an initial process of selecting information in working memory but not the memory updating itself.

The impact of cognitive load on reward evaluation

The neural systems that afford our ability to evaluate rewards and punishments are impacted by a variety of external factors. Here, we demonstrate that increased cognitive load reduces the functional efficacy of a reward processing system within the human medial–frontal cortex. In our paradigm, two groups of participants used performance feedback to estimate the exact duration of one second while electroencephalographic (EEG) data was recorded. Prior to performing the time estimation task, both groups were instructed to keep their eyes still and avoid blinking in line with well established EEG protocol. However, during performance of the time-estimation task, one of the two groups was provided with trial-to-trial-feedback about their performance on the time-estimation task and their eye movements to induce a higher level of cognitive load relative to participants in the other group who were solely provided with feedback about the accuracy of their temporal estimates. In line with previous work, we found that the higher level of cognitive load reduced the amplitude of the feedback-related negativity, a component of the human event-related brain potential associated with reward evaluation within the medial–frontal cortex. Importantly, our results provide further support that increased cognitive load reduces the functional efficacy of a neural system associated with reward processing.

Sensitivity of frontal beta oscillations to reward valence but not probability

Reward feedback elicits a brief increase in power in the high-beta frequency range of the human electroencephalogram (EEG) over frontal areas of the scalp, but the functional role of this oscillatory activity remains unclear. An observed sensitivity to reward expectation (HajiHosseini, Rodríguez-Fornells, and Marco-Pallarés, 2012; [2]) suggests that reward-related beta may index a reward prediction error (RPE) signal for reinforcement learning. To investigate this possibility we reanalyzed EEG data from two prior experiments that revealed RPEs in the human event-related brain potential (Holroyd and Krigolson, 2007 [12]; Holroydet al., 2008 [13]). We found that feedback stimuli that indicated reward, when compared to feedback stimuli that indicated no-reward, elicited relatively more beta power (20–30Hz) over a frontal area of the scalp. However, beta power was not sensitive to feedback probability. These results indicate that reward-related beta does not index an RPE but rather relates to a different reward processing function.

Hierarchical Error Evaluation: The Role of Medial-Frontal Cortex in Postural Control

ABSTRACTMotor error evaluation appears to be a hierarchically organized process subserved by 2 distinct systems: a higher level system within medial-frontal cortex responsible for movement outcome evaluation (high-level error evaluation) and a lower level posterior system(s) responsible for the mediation of within-movement errors (low-level error evaluation). While a growing body of evidence suggests that a reinforcement learning system within medial-frontal cortex plays a crucial role in the evaluation of high-level errors made during discrete reaching movements and continuous motor tracking, the role of this system in postural control is currently unclear. Participants learned a postural control task via a feedback-driven trial-and-error shaping process. In line with previous findings, electroencephalographic recordings revealed that feedback about movement outcomes elicited a feedback error–related negativity: a component of the human event-related brain potential associated with high-level outcome evaluation within medial-frontal cortex. Thus, the data provide evidence that a high-level error-evaluation system within medial-frontal cortex plays a key role in learning to control our body posture.

Differences in sensory processing of German vowels and physically matched non-speech sounds as revealed by the mismatch negativity (MMN) of the human event-related brain potential (ERP)

We compared processing of speech and non-speech by means of the Mismatch Negativity (MMN). For this purpose, the MMN elicited by vowels was compared to those elicited by two non-speech stimulus types: spectrally rotated vowels, having the same stimulus complexity as the speech stimuli, and sounds based on the bands of formants of the vowels, representing non-speech stimuli of lower complexity as compared to the other stimulus types. This design allows controlling for effects of stimulus complexity when comparing neural correlates of processing speech to non-speech. Deviants within a modified multi-feature design differed either in duration or spectral property. Moreover, the difficulty to discriminate between the standard and the two deviants was controlled for each stimulus type by means of an additional active discrimination task. Vowels elicited a larger MMN compared to both non-speech stimulus types, supporting the concept of language-specific phoneme representations and the role of the participants’ prior experience.

Explaining the high voice superiority effect in polyphonic music: Evidence from cortical evoked potentials and peripheral auditory models

Natural auditory environments contain multiple simultaneously-sounding objects and the auditory system must parse the incoming complex sound wave they collectively create into parts that represent each of these individual objects. Music often similarly requires processing of more than one voice or stream at the same time, and behavioral studies demonstrate that human listeners show a systematic perceptual bias in processing the highest voice in multi-voiced music. Here, we review studies utilizing event-related brain potentials (ERPs), which support the notions that (1) separate memory traces are formed for two simultaneous voices (even without conscious awareness) in auditory cortex and (2) adults show more robust encoding (i.e., larger ERP responses) to deviant pitches in the higher than in the lower voice, indicating better encoding of the former. Furthermore, infants also show this high-voice superiority effect, suggesting that the perceptual dominance observed across studies might result from neurophysiological characteristics of the peripheral auditory system. Although musically untrained adults show smaller responses in general than musically trained adults, both groups similarly show a more robust cortical representation of the higher than of the lower voice. Finally, years of experience playing a bass-range instrument reduces but does not reverse the high voice superiority effect, indicating that although it can be modified, it is not highly neuroplastic. Results of new modeling experiments examined the possibility that characteristics of middle-ear filtering and cochlear dynamics (e.g., suppression) reflected in auditory nerve firing patterns might account for the higher-voice superiority effect. Simulations show that both place and temporal AN coding schemes well-predict a high-voice superiority across a wide range of interval spacings and registers. Collectively, we infer an innate, peripheral origin for the higher-voice superiority observed in human ERP and psychophysical music listening studies.This article is part of a Special Issue entitled <Music: A window into the hearing brain>.

Auditory event-related potentials (P3a, P3b) and genetic variants within the dopamine and serotonin system in healthy females

The late positive components of the human event-related brain potential comprise electrocortical reflections of stimulus-driven attentional capture (the anteriorly distributed P3a) and top–down control detection of relevant events (the posteriorly distributed P3b). As of yet, the neuropharmacologic and neurogenetic origin of the P3a and P3b is not fully understood.In this study, we address the contribution of dopaminergic and serotoninergic mechanisms. Sixty healthy females completed an active auditory novelty oddball paradigm while EEG was recorded. In all subjects, genetic polymorphisms within the dopamine system (dopamine transporter [DAT1], catecholamine-O-methyltransferase val158met [COMT val158met]) and the serotonin system (serotonin transporter [5HTTLPR]) were assessed.Across genotypes, novels (relative to standards) elicited a fronto-centrally distributed P3a, and targets (relative to standards) a parieto-centrally distributed P3b. Genotypes effects were observed for both P3a (COMT, 5HTTPLR) and P3b (DAT1, COMT, 5HTTLPR) only at prefrontal electrode location (Fz). Specifically, the frontal P3a was enhanced in COMT met/met homozygotes, but not in DAT1 9R. The target-related P3b was enhanced in COMT met/met and DAT1 9R relative to its genetic counterparts, but only at frontal electrodes. This ‘anteriorized’ enhancement may reflect either an additional frontal component in the target-related P3 dependent on dopamine, or a more subtle shift in the neural ensemble that generates the target-related P3. Results for 5HTTLPR short allele homozygotes mimicked those in COMT met/met homozygotes.In all, the present findings suggest involvement of frontal-cortical dopaminergic and serotoninergic mechanisms in bottom-up attentional capture (COMT val158met, 5HTTLPR), with an additional top–down component sensitive to striatal signals (DAT1).

How human electrophysiology informs psychopharmacology: from bottom-up driven processing to top-down control.

This review surveys human event-related brain potential (ERP) and event-related magnetic field (ERF) approaches to psychopharmacology and psychopathology, and the way in which they complement behavioral studies and other neuroimaging modalities. The major paradigms involving ERP/ERF are P50 suppression, loudness-dependent auditory evoked potential (LDAEP), mismatch negativity (MMN), P300, mental chronometry, inhibitory control, and conflict processing (eg, error-related negativity (ERN)). Together these paradigms cover a range of more bottom-up driven to more top-down controlled processes. A number of relationships between the major neurotransmitter systems and electrocortical mechanisms are highlighted. These include the role of dopamine in conflict processing, and perceptual processing vs motor preparation; the role of serotonin in P50 suppression, LDAEP, and MMN; glutamate/NMDA and MMN; and the role of acetylcholine in P300 generation and memory-related processes. A preliminary taxonomy for these relationships is provided, which should be helpful in attuning possible new treatments or new applications of existing treatments to various disorders.

Activation and application of an obligatory phonotactic constraint in German during automatic speech processing is revealed by human event-related potentials

In auditory speech processing, implicit linguistic knowledge is activated and applied on phonetic and segment-related phonological processing level even if the perceived sound sequence is outside the focus of attention. In this study, the effects of language-specific phonotactic restrictions on pre-attentive auditory speech processing were investigated, using the Mismatch Negativity component of the human event-related brain potential. In German grammar, the distribution of the velar and the palatal dorsal fricative is limited by an obligatory phonotactic constraint, Dorsal Fricative Assimilation, which demands that a vowel and a following dorsal fricative must have the same specifications for articulatory backness. For passive oddball stimulation, we used three phonotactically correct VC syllables and one incorrect VC syllable, composed of the vowels [ε] and [ɔ] and the fricatives [ç] and [ʃ]. Stimuli were contrasted pairwise in experimental oddball blocks in a way that they differed in regard to their respective vowel but shared the fricative. Additionally to the usual Mismatch Negativity which is attributable to the change of the initial vowel and which was elicited by all deviants, we observed a second negative deflection in the deviant ERP elicited by the phonotactically ill-formed syllable only. This negativity cannot be attributed to any acoustical or phonemic difference between standard and deviant, it rather reflects the effect of a phonotactic evaluation process after both sounds of the syllable were identified. Our finding suggests that implicit phonotactic knowledge is activated and applied even outside the focus of the participants' attention.

Position but not color deviants result in visual mismatch negativity in an active oddball task

Changes in the visual environment might be detected automatically. This function is provided by the sensory systems and showed, for instance, by the pop-out phenomenon. Automatic change detection is also observable within visual oddball paradigms, where rare changes are introduced in an irrelevant stimulus feature; the detection of deviant stimuli is accompanied by a negative component (so-called visual mismatch negativity) in the human event-related brain potential. In this study, the deviating stimulus feature was embedded in a task-relevant object presented in the focus of attention. With this, visual mismatch negativity was observable only with position deviants presented in the upper visual half field but not by lower half field presentation or color deviants.

Breaking the rule: mismatch negativity is affected by top-down predictive information

Event Abstract Back to Event Breaking the rule: mismatch negativity is affected by top-down predictive information Andreas Widmann1* and E. Schroger1 1 Institute of Psychology I, University of Leipzig, Germany The mismatch negativity component (MMN) of the human event related brain potential reflects neural processes related to the detection of irregularities in acoustic stimulation. MMN was supposed to be unaffected by top-down predictive information as it is also elicited when participants have full knowledge about an upcoming deviation, e.g. when it was predicted by an attended visual cue. Here, however, we show that top-down predictive information can affect the processes underlying MMN generation. MMN amplitude was found to be smaller in response to self-generated expected deviants compared to unexpected deviants and deviants where no top-down predictive information was available. It is argued that the processes underlying MMN generation, in particular the generation of the memory trace serving for the memory comparison, are accessible to top-down predictive information and not restricted to bottom-up driven regularity violations. Conference: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: Widmann A and Schroger E (2009). Breaking the rule: mismatch negativity is affected by top-down predictive information. Conference Abstract: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications. doi: 10.3389/conf.neuro.09.2009.05.105 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Mar 2009; Published Online: 26 Mar 2009. * Correspondence: Andreas Widmann, Institute of Psychology I, University of Leipzig, Leipzig, Germany, widmann@uni-leipzig.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Andreas Widmann E. Schroger Google Andreas Widmann E. Schroger Google Scholar Andreas Widmann E. Schroger PubMed Andreas Widmann E. Schroger Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Which Way Do I Go? Neural Activation in Response to Feedback and Spatial Processing in a Virtual T-Maze

In 2 human event-related brain potential (ERP) experiments, we examined the feedback error-related negativity (fERN), an ERP component associated with reward processing by the midbrain dopamine system, and the N170, an ERP component thought to be generated by the medial temporal lobe (MTL), to investigate the contributions of these neural systems toward learning to find rewards in a "virtual T-maze" environment. We found that feedback indicating the absence versus presence of a reward differentially modulated fERN amplitude, but only when the outcome was not predicted by an earlier stimulus. By contrast, when a cue predicted the reward outcome, then the predictive cue (and not the feedback) differentially modulated fERN amplitude. We further found that the spatial location of the feedback stimuli elicited a large N170 at electrode sites sensitive to right MTL activation and that the latency of this component was sensitive to the spatial location of the reward, occurring slightly earlier for rewards following a right versus left turn in the maze. Taken together, these results confirm a fundamental prediction of a dopamine theory of the fERN and suggest that the dopamine and MTL systems may interact in navigational learning tasks.