Source localization (LORETA) of the error-related-negativity (ERN/Ne) and positivity (Pe)

We investigated error processing of 39 subjects engaging the Eriksen flanker task. In all 39 subjects a pronounced negative deflection (ERN/Ne) and a later positive component (Pe) were observed after incorrect as compared to correct responses. The neural sources of both components were analyzed using LORETA source localization. For the negative component (ERN/Ne) we found significantly higher brain electrical activity in medial prefrontal areas for incorrect responses, whereas the positive component (Pe) was localized nearby but more rostral within the anterior cingulate cortex (ACC). Thus, different neural generators were found for the ERN/Ne and the Pe, which further supports the notion that both error-related components represent different aspects of error processing.     

Unavoidable errors: a spatio-temporal analysis of time-course and neural sources of evoked potentials associated with error processing in a speeded task

The detection of errors is known to be associated with two successive neurophysiological components in EEG, with an early time-course following motor execution: the error-related negativity (ERN/Ne) and late positivity (Pe). The exact cognitive and physiological processes contributing to these two EEG components, as well as their functional independence, are still partly unclear. Furthermore, these components are typically obtained in conditions where errors are rare events relative to correct trials, and thus presumably implicate other cognitive and motivational processes besides error monitoring. Here, we investigated error processing using high-density scalp ERPs and advanced topographical analyses in healthy participants, during a new Go/noGo task that led to many errors within a relatively short period of time, yet without generating frustration or insufficient motivation. ERP results showed the presence of two distinct electrophysiological markers of error monitoring (ERN/Ne and Pe) during this task, even though errors were practically as frequent as correct responses. Topographic mapping analyses showed for the first time that both the ERN/Ne and Pe elicited a specific distribution of electrical activity relative to correct responses (not just a change in the amplitude of electric signals), suggesting the activation of a distinct configuration of intracranial generators during error detection. This was confirmed by additional analyses using dipole source localization, showing generators in anterior cingulate cortex contributing to the ERN/Ne, but in more posterior cingulate regions for Pe. Moreover, we found that, across all participants, the magnitude of the ERN/Ne correlated with the level of state anxiety, even in the subclinical range, whereas the Pe was correlated negatively with the total number of errors and positively with the improvement of response speed on correct trials. By contrast, no significant relation was found between error monitoring ERPs and individual measures of impulsivity. Taken together, these data suggest that these two successive EEG components associated with errors reflect different monitoring processes, with distinct neural substrates in cingulate cortex. While ERN/Ne processes in anterior cingulate might primarily mediate error detection, Pe processes in posterior cingulate might be more directly related to behavioral adjustment based on the outcome of current actions.     

Resting anterior cingulate activity and abnormal responses to errors in subjects with elevated depressive symptoms: a 128-channel EEG study

Depression has been associated with dysfunctional executive functions and abnormal activity within the anterior cingulate cortex (ACC), a region critically involved in action regulation. Prior research invites the possibility that executive deficits in depression may arise from abnormal responses to negative feedback or errors, but the underlying neural substrates remain unknown. We hypothesized that abnormal reactions to error would be associated with dysfunctional rostral ACC activity, a region previously implicated in error detection and evaluation of the emotional significance of events. To test this hypothesis, subjects with low and high Beck Depression Inventory (BDI) scores performed an Eriksen Flanker task. To assess whether tonic activity within the rostral ACC predicted post-error adjustments, 128-channel resting EEG data were collected before the task and analyzed with low-resolution electromagnetic tomography (LORETA) using a region-of-interest approach. High BDI subjects were uniquely characterized by significantly lower accuracy after incorrect than correct trials. Mirroring the behavioral findings, high BDI subjects had significantly reduced pretask gamma (36.5-44 Hz) current density within the affective (rostral; BA24, BA25, BA32) but not cognitive (dorsal; BA24', BA32') ACC subdivision. For low, but not high, BDI subjects pretask gamma within the affective ACC subdivision predicted post-error adjustments even after controlling for activity within the cognitive ACC subdivision. Abnormal responses to errors may thus arise due to lower activity within regions subserving affective and/or motivational responses to salient cues. Because rostral ACC regions have been implicated in treatment response in depression, our findings provide initial insight into putative mechanisms fostering treatment response.     

The role of cingulate cortex in the detection of errors with and without awareness: a high-density electrical mapping study

Error-processing research has demonstrated that the brain uses a specialized neural network to detect errors during task performance but the brain regions necessary for conscious awareness of an error are poorly understood. In the present study we show that two well-known error-related event-related potential (ERP) components, the error-related negativity (ERN) and error positivity (Pe) have a differential relationship with awareness during performance of a manual response inhibition task optimized to examine error awareness. While the ERN was unaffected by the participants' conscious experience of errors, the Pe was only seen when participants were aware of committing an error. Source localization of these components indicated that the ERN was generated by a caudal region of the anterior cingulate cortex (ACC) while the Pe was associated with contributions from a more anterior ACC region and the posterior cingulate-precuneus. Tonic EEG measures of cortical arousal were correlated with individual rates of error awareness and showed a specific relationship with the amplitude of the Pe. The latter finding is consistent with evidence that the Pe represents a P3-like facilitation of information processing modulated by subcortical arousal systems. Our data suggest that the ACC might participate in both preconscious and conscious error detection and that cortical arousal provides a necessary setting condition for error awareness. These findings may be particularly important in the context of clinical studies in which a proper understanding of self-monitoring deficits requires an explicit measurement of error awareness.     

A neurophysiological study of the detrimental effects of alprazolam on human action monitoring

In order to adapt their behavior to different unexpected situations, humans need to be able to monitor their performance and detect and correct errors. Benzodiazepines have long been shown to impair performance in humans, but the performance-related neurophysiological processes targeted by these drugs remain largely unknown. In the present article, we assessed the impact of alprazolam administration on relevant aspects of action monitoring, i.e., the monitoring of response conflict and the detection and correction of errors by means of neurophysiological measures. Multichannel event-related brain potentials (ERPs) were recorded to assess the impact of the benzodiazepine alprazolam (0.25 mg and 1.00 mg) on action monitoring and motor preparation in a group of twelve healthy male volunteers who participated in a double-blind cross-over placebo-controlled clinical trial involving a letter flanker task. Error detection was evaluated using the error-related negativity (ERN); response conflict on correct trials was measured by means of the N2 amplitude difference between congruent and incongruent trials; motor preparation was assessed by means of the lateralized readiness potentials (LRPs); and post-error adjustments were assessed by measuring post-error slowing in reaction time. Alprazolam significantly reduced the amplitude of the ERN and the number of corrective responses and increased reaction time and LRP latencies. The drug had no effect on amplitude differences in the N2 component between congruent and incongruent trials or on post-error slowing. Thus, alprazolam was shown to affect brain correlates of error detection (ERN) and motor preparation (LRPs), while it did not disturb conflict monitoring on correct trials (N2) or post-error adjustments of behavior.     

Altered cingulate sub-region activation accounts for task-related dissociation in ERN amplitude as a function of obsessive-compulsive symptoms

Larger error-related negativities (ERNs) have been consistently found in obsessive-compulsive disorder (OCD) patients, and are thought to reflect the activities of a hyperactive cortico-striatal circuit during action monitoring. We previously observed that obsessive-compulsive (OC) symptomatic students (non-patients) have larger ERNs during errors in a response competition task, yet smaller ERNs in a reinforcement learning task. The finding of a task-specific dissociation suggests that distinct yet partially overlapping medio-frontal systems underlie the ERN in different tasks, and that OC symptoms are associated with functional differences in these systems. Here, we used EEG source localization to identify why OC symptoms are associated with hyperactive ERNs to errors yet hypoactive ERNs when selecting maladaptive actions. At rest, OC symptomatology predicted greater activity in rostral anterior cingulate cortex (rACC) and lower activity in dorsal anterior cingulate cortex (dACC). When compared to a group with low OC symptom scores, the high OC group had greater rACC reactivity during errors in the response competition task and less deactivation of dACC activity during errors in the reinforcement learning task. The degree of activation in these areas correlated with ERN amplitudes during both tasks in the high OC group, but not in the low group. Interactive anterior cingulate cortex (ACC) systems associated avoidance of maladaptive actions were intact in the high OC group, but were related to poorer performance on a third task: probabilistic reversal learning. These novel findings link both tonic and phasic activities in the ACC to action monitoring alterations, including dissociation in performance deficits, in OC symptomatic participants.     

Error negativity does not reflect conflict: a reappraisal of conflict monitoring and anterior cingulate cortex activity

Our ability to detect and correct errors is essential for our adaptive behavior. The conflict-loop theory states that the anterior cingulate cortex (ACC) plays a key role in detecting the need to increase control through conflict monitoring. Such monitoring is assumed to manifest itself in an electroencephalographic (EEG) component, the "error negativity" (Ne or "error-related negativity" [ERN]). We have directly tested the hypothesis that the ACC monitors conflict through simulation and experimental studies. Both the simulated and EEG traces were sorted, on a trial-by-trial basis, as a function of the degree of conflict, measured as the temporal overlap between incorrect and correct response activations. The simulations clearly show that conflict increases as temporal overlap between response activation increases, whereas the experimental results demonstrate that the amplitude of the Ne decreases as temporal overlap increases, suggesting that the ACC does not monitor conflict. At a functional level, the results show that the duration of the Ne depends on the time needed to correct (partial) errors, revealing an "on-line" modulation of control on a very short time scale.     

To bet or not to bet? The error negativity or error-related negativity associated with risk-taking choices

The functional significance of error-related negativity (Ne/ERN), which occurs at approximately the same time as erroneous responses, has been investigated extensively using reaction time (RT) tasks. The error detection theory assumes that the Ne/ERN reflects the mismatch detected by comparing representations of the intended and the actually performed actions. The conflict monitoring theory asserts that the Ne/ERN reflects the detection of response conflict between intended and actually performed actions during response selection. In this study, we employed a gambling task in which participants were required to choose whether they would take part in betting in each trial and they were presented with gain or loss feedback in both the "to bet" and the "not to bet" trials. The response-locked ERP magnitudes were more negative for "to bet" than for "not to bet" choices for both large and small stakes and were more negative for choices involving large rather than small stakes. Dipole source analysis localized the ERP responses to the anterior cingulate cortex (ACC). These findings suggest that the ACC signals the riskiness of choices and may function as an early warning system that alerts the brain to prepare for the potential negative consequence associated with a risky action.     

Brain error-monitoring activity is affected by semantic relatedness: an event-related brain potentials study

Speakers continuously monitor what they say. Sometimes, self-monitoring malfunctions and errors pass undetected and uncorrected. In the field of action monitoring, an event-related brain potential, the error-related negativity (ERN), is associated with error processing. The present study relates the ERN to verbal self-monitoring and investigates how the ERN is affected by auditory distractors during verbal monitoring. We found that the ERN was largest following errors that occurred after semantically related distractors had been presented, as compared to semantically unrelated ones. This result demonstrates that the ERN is sensitive not only to response conflict resulting from the incompatibility of motor responses but also to more abstract lexical retrieval conflict resulting from activation of multiple lexical entries. This, in turn, suggests that the functioning of the verbal self-monitoring system during speaking is comparable to other performance monitoring, such as action monitoring.     

Adaptive control deficits in attention-deficit/hyperactivity disorder (ADHD): the role of error processing

Cognitive performance of children with attention-deficit hyperactivity disorder (ADHD) is characterized by large moment-to-moment fluctuations in cognitive control reflected by a highly inconsistent and inaccurate response style. It has been suggested that abnormal error processing underlies this failure to implement adequate control. We investigated the error-related negativity (ERN), a negative deflection in the event-related potential (ERP) time-locked to erroneous responses in 16 rigorously screened ADHD boys aged 8-12 years and 16 age-matched normal control boys during a modified Eriksen flanker paradigm with two levels of time pressure. Children with ADHD responded as fast and regularly as controls, but committed significantly more errors, particularly when facing time pressure and response conflict. ADHD children produced shorter runs of correct responses than controls. In addition, with high time pressure, error runs were prolonged relative to control children, suggesting an increase in both frequency and magnitude of temporary lapses of control. ERP amplitude differences between correct and incorrect responses were diminished in ADHD children, whereas post-error slowing remained unaffected. This pattern of results indicates that a specific deficit in monitoring ongoing behaviour, rather than insufficient strategic adjustments, gave rise to performance limitations in ADHD. Findings are discussed in terms of anterior cingulate cortex (ACC) dysfunction, leading to a failure to predict the likelihood that an error occurs in a given context.     

Performance monitoring following conflict: Internal adjustments in cognitive control?

The purpose of this study was to investigate the effects of strategic conflict-related adjustments in cognitive control processes on indices of performance monitoring. Previous research has examined the ability of parametric task-related manipulations to bias attention to errors; however, the present study sought to elucidate the effects of internal adjustments in control mediated by the anterior cingulate cortex on error-related conflict processing. High-density event-related potentials (ERPs) were obtained from 124 healthy individuals (68 female, 66 male) during a modified Eriksen flanker task. Behavioral measures (i.e., error rates, response times [RTs]) and N2 amplitudes showed significant conflict adaptation (i.e., previous-trial congruencies influenced current-trial measures). For error trials, the error-related negativity (ERN) was more negative for errors on high-conflict (i.e., incongruent) trials following high-conflict trials relative to errors on high-conflict trials following low-conflict (i.e., congruent) trials. These findings indicate that error-related conflict-monitoring processes adjust according to the post-conflict recruitment of strategic cognitive control and suggest an ongoing interplay between conflict and internal adjustments in control resources. Interpretations from the perspective of the conflict monitoring theory of cognitive control, the reinforcement learning theory, and the response-outcome theory of the ERN are discussed.     

Dissociable correlates of response conflict and error awareness in error-related brain activity

Errors in speeded decision tasks are associated with characteristic patterns of brain activity. In the scalp-recorded EEG, error processing is reflected in two components, the error-related negativity (ERN) and the error positivity (Pe). These components have been widely studied, but debate remains regarding the precise aspects of error processing they reflect. The present study investigated the relation between the ERN and the Pe using a novel version of the flanker task to allow a comparison between errors reflecting different causes—response conflict versus stimulus masking. The conflict and mask conditions were matched for overall behavioural performance but differed in underlying response dynamics, as indexed by response time distributions and measures of lateralised motor activity. ERN amplitude varied in relation to these differing response dynamics, being significantly larger in the conflict condition compared to the mask condition. Furthermore, differences in response dynamics between participants were predictive of modulations in ERN amplitude. In contrast, Pe activity varied little between conditions, but varied across trials in relation to participants’ awareness of their errors. Taken together, these findings suggest a dissociation between the ERN and the Pe, with the former reflecting the dynamics of response selection and conflict, and the latter reflecting conscious recognition of an error.     

Dynamics of response-conflict monitoring and individual differences in response control and behavioral control: an electrophysiological investigation using a stop-signal task.

OBJECTIVES: The aim of the present study was to investigate the functional significance of error (related) negativity Ne/ERN and individual differences in human action monitoring. A response-conflict model of Ne/ERN should be tested applying a stop-signal paradigm. After a few modifications of Ne/ERN response-conflict theory (Yeung N, Botvinick MM, Cohen JD. The neural basis of error detection: conflict monitoring and the error-related negativity. Psychological Review 2004:111(4);931-959), strength and time course of response conflict could be modeled as a function of stop-signal delay. METHOD: In Experiment 1, 35 participants performed a visual two-choice response-time task but tried to withhold the response if an auditory stop signal was presented. Probability of stopping errors was held at 50% using variable delays between visual and auditory stimuli. Experiment 2 (n=10) employed both auditory go and stop signals and confirmed that Ne/ERN effects are due to conflict induced by the auditory stop signal, and not the mere presence or absence of an additional stimulus. RESULTS: As predicted, amplitudes of both the stimulus-locked and response-locked Ne/ERN were largest for non-stopped responses, followed by successfully stopped and go responses. However, independently of response type Ne/ERN also increased with increasing stop-signal delay. Since longer delay invokes stronger response conflict, results specifically support the notion of Ne/ERN reflecting response-conflict monitoring. Furthermore, individual differences related to measures of response control and behavioral control were observed. Both low response control estimated from stop-task performance and high psychometric impulsivity were accompanied by smaller Ne/ERN amplitude on stop trials, suggesting reduced response-conflict monitoring. CONCLUSIONS: The present study supported the response-conflict view of Ne/ERN. Furthermore, the observed relationship between impulsivity and Ne/ERN amplitude suggested that individuals with low behavioral control were characterized by lower activity in anterior cingulate cortex, the neural generator of Ne/ERN, in situations of strong response conflict. SIGNIFICANCE: The present study, for the first time, employed a stop-signal paradigm to verify predictions regarding the temporal dynamics of response-conflict processing as derived from response-conflict theory of ERN.     

Evaluation-related frontocentral negativity evoked by correct responses and errors

An event-related potential (ERP) with frontocentral negativity is known to be evoked by error responses, but may also occur on correct response trials. The error-related negativity (ERN) is thought to be generated in the anterior cingulate cortex (ACC). The current study aimed to further elucidate its functional significance as well as its neuronal correlates by directly comparing its amplitude and time course on correct and error trials in a continuous performance task (CPT). Results yielded a frontocentral positive potential preceding correct responses and a high amplitude post-response frontocentral negative potential during conditions involving response competition. To remove potential no-confounding effects of the positive component preceding the motor response, a second experiment was conducted where a red fixation cross served as a cue for potential response competition tendencies. Again, results yielded highest post-response amplitudes on correct trials involving response competition. The positive pre-response potential was eliminated by the visual cue. Interestingly, the cue led to an enhancement of the negative post-response component on trials without response competition. Taken together, the frontocentral post-response negativity might reflect evaluative rather than error-related processing.     

Reduced error monitoring in children with autism spectrum disorder: an ERP study

This study investigated self-monitoring in children with autism spectrum disorder (ASD) with event-related potentials looking at both the error-related negativity (ERN) and error-related positivity (Pe). The ERN is related to early error/conflict detection, and the Pe has been associated with conscious error evaluation or attention allocation. In addition, post-error slowing in reaction times (RTs) was measured. Children with ASD and age- and IQ- matched controls were administered an easy and a hard version of an auditory decision task. Results showed that the ERN was smaller in children with ASD but localized in the anterior cingulate cortex (ACC) in both groups. In addition we found a negativity on correct trials (CRN) that did not differ between the groups. Furthermore, a reduced Pe and a lack of post-error slowing in RTs were found in children with ASD. The reduced ERN in children with ASD, in the presence of an intact CRN, might suggest a specific insensitivity to detect situations in which the chance of making errors is enhanced. This might in turn lead to reduced error awareness/attention allocation to the erroneous event (reduced Pe) and eventually in a failure in change of strategy to deal with a situation, as becomes evident from the lack of post-error slowing in the ASD group. This relates well to the perseverative behaviour that is seen in children with ASD. We discuss these results in terms of a general deficit in self-monitoring, underlying social disturbance in ASD and the involvement of the ACC.     

Anterior cingulate and the monitoriing of response conflict: evidence from an fMRI study of overt verb generation

Studies of a range of higher cognitive functions consistently activate a region of anterior cingulate cortex (ACC), typically posterior to the genu and superior to the corpus collosum. In particular, this ACC region appears to be active in task situations where there is a need to override a prepotent response tendency, when responding is underdetermined, and when errors are made. We have hypothesized that the function of this ACC region is to monitor for the presence of "crosstalk" or competition between incompatible responses. In prior work, we provided initial support for this hypothesis, demonstrating ACC activity in the same region both during error trials and during correct trials in task conditions designed to elicit greater response competition. In the present study, we extend our testing of this hypothesis to task situations involving underdetermined responding. Specifically, 14 healthy control subjects performed a verb-generation task during event-related functional magnetic resonance imaging (fMRI), with the on-line acquisition of overt verbal responses. The results demonstrated that the ACC, and only the ACC, was more active in a series of task conditions that elicited competition among alternative responses. These conditions included a greater ACC response to: (1) Nouns categorized as low vs. high constraint (i.e., during a norming study, multiple verbs were produced with equal frequency vs. a single verb that produced much more frequently than any other); (2) the production of verbs that were weak associates, rather than, strong associates of particular nouns; and (3) the production of verbs that were weak associates for nouns categorized as high constraint. We discuss the implication of these results for understanding the role that the ACC plays in human cognition.     

Theta EEG dynamics of the error-related negativity.

OBJECTIVE: The error-related negativity (ERN) is a response-locked brain potential (ERP) occurring 80-100ms following response errors. This report contrasts three views of the genesis of the ERN, testing the classic view that time-locked phasic bursts give rise to the ERN against the view that the ERN arises from a pure phase-resetting of ongoing theta (4-7Hz) EEG activity and the view that the ERN is generated - at least in part - by a phase-resetting and amplitude enhancement of ongoing theta EEG activity. METHODS: Time-domain ERP analyses were augmented with time-frequency investigations of phase-locked and non-phase-locked spectral power, and inter-trial phase coherence (ITPC) computed from individual EEG trials, examining time courses and scalp topographies. Simulations based on the assumptions of the classic, pure phase-resetting, and phase-resetting plus enhancement views, using parameters from each subject's empirical data, were used to contrast the time-frequency findings that could be expected if one or more of these hypotheses adequately modeled the data. RESULTS: Error responses produced larger amplitude activity than correct responses in time-domain ERPs immediately following responses, as expected. Time-frequency analyses revealed that significant error-related post-response increases in total spectral power (phase- and non-phase-locked), phase-locked power, and ITPC were primarily restricted to the theta range, with this effect located over midfrontocentral sites, with a temporal distribution from approximately 150-200ms prior to the button press and persisting up to 400ms post-button press. The increase in non-phase-locked power (total power minus phase-locked power) was larger than phase-locked power, indicating that the bulk of the theta event-related dynamics were not phase-locked to response. Results of the simulations revealed a good fit for data simulated according to the phase-locking with amplitude enhancement perspective, and a poor fit for data simulated according to the classic view and the pure phase-resetting view. CONCLUSIONS: Error responses produce not only phase-locked increases in theta EEG activity, but also increases in non-phase-locked theta, both of which share a similar topography. SIGNIFICANCE: The findings are thus consistent with the notion advanced by Luu et al. [Luu P, Tucker DM, Makeig S. Frontal midline theta and the error-related negativity; neurophysiological mechanisms of action regulation. Clin Neurophysiol 2004;115:1821-35] that the ERN emerges, at least in part, from a phase-resetting and phase-locking of ongoing theta-band activity, in the context of a general increase in theta power following errors.     

Neural correlates of impulsive responding in borderline personality disorder: ERP evidence for reduced action monitoring

Patients with borderline personality disorder (BPD) are characterized by marked impulsive behaviour. The impulsive response style of patients with BPD may be associated with diminished action monitoring, which can be investigated by measuring the error-related negativity (ERN). The ERN is an ERP component generated in the anterior cingulate cortex (ACC) following erroneous responses. Behavioural and ERP measurements were obtained during performance on a speeded two-choice reaction task in a group of patients with BPD (N=12) and in a group of age-matched controls (N=12). The ERP results showed that ERN amplitudes were reduced for patients with BPD, as were the P300 amplitudes after late feedback. The behavioural results confirmed a more impulsive response style for the BPD group, reflected in larger RT differences between correct and incorrect responses and in an increase in erroneous responses to the easy congruent stimuli. Additionally, analyses on post-error congruency effects demonstrated that controls adjusted their behaviour following errors, but patients with BPD did not. The attenuated ERNs indicate reduced action monitoring in patients with BPD. This suggests that the ACC, or the action-monitoring network it is part of, is not functioning optimally. Due to this reduced action monitoring, patients with BPD do not learn from their errors as well as controls. Consequently, they do not adjust their behaviour when necessary and thus maintain their impulsive response style.     

Developmental changes in error monitoring: an event-related potential study

The aim of the study was to investigate the developmental trajectory of error monitoring. For this purpose, children (age 7-8), young adolescents (age 13-14) and adults (age 23-24) performed a Go/No-Go task and were compared on overt reaction time (RT) performance and on event-related potentials (ERPs), thought to reflect error detection (error-related negativity: ERN) and conscious evaluation (error positivity: Pe) of the error. RT on correct trials, variability of responding and percentage of errors decreased with age. The latencies of incorrect responses, compared to correct responses, were shorter in children and adolescents than in adults, indicative of developmental changes in impulsive response style. Groups did not differ in the ability to adjust response strategies after making an error (post-error slowing). The ERN amplitude increased with age, the Pe amplitude did not change with age. Possible explanations for the developmental changes in ERN are discussed.     

Attention for learning signals in anterior cingulate cortex

Learning theory suggests that animals attend to pertinent environmental cues when reward contingencies unexpectedly change so that learning can occur. We have previously shown that activity in basolateral nucleus of amygdala (ABL) responds to unexpected changes in reward value, consistent with unsigned prediction error signals theorized by Pearce and Hall. However, changes in activity were present only at the time of unexpected reward delivery, not during the time when the animal needed to attend to conditioned stimuli that would come to predict the reward. This suggested that a different brain area must be signaling the need for attention necessary for learning. One likely candidate to fulfill this role is the anterior cingulate cortex (ACC). To test this hypothesis, we recorded from single neurons in ACC as rats performed the same behavioral task that we have used to dissociate signed from unsigned prediction errors in dopamine and ABL neurons. In this task, rats chose between two fluid wells that produced varying magnitudes of and delays to reward. Consistent with previous work, we found that ACC detected errors of commission and reward prediction errors. We also found that activity during cue sampling encoded reward size, but not expected delay to reward. Finally, activity in ACC was elevated during trials in which attention was increased following unexpected upshifts and downshifts in value. We conclude that ACC not only signals errors in reward prediction, as previously reported, but also signals the need for enhanced neural resources during learning on trials subsequent to those errors.