Successful learning depends on various factors such as depth of processing, motivation, or curiosity about information. A strong drive to learn something or the expectation of receiving a reward can be crucial to enhance learning. However, the influence of curiosity on the processing of new information and its similarity with reward processing is not well understood. This study examined whether states of curiosity influence specific ERPs associated with reward processing and whether these ERPs are related with later memory benefits. In an initial screening phase, participants indicated their curiosity and confidence in prior knowledge about answers to various trivia questions. In a subsequent study phase, we targeted different time windows related to reward processing during the presentation of trivia answers containing the reward positivity (RewP; 250–350 msec), the P3 (250–500 msec), and the late-positive-potential (LPP; 600–1000 msec). In a following surprise memory test, we found that participants recalled more high- than low-curiosity answers. The RewP, P3, and LPP showed greater positive mean amplitudes for high compared with low curiosity, reflecting increased reward processing. In addition, we found that the RewP and the P3 showed more positive mean amplitudes for later recalled compared with later forgotten answers, but curiosity did not modulate this encoding-related results. These findings support the view that the satisfaction of curiosity resembles reward processing, indicated by ERPs.

ERP old/new effects have been associated with different subprocesses of episodic recognition memory. The notion that recollection is reflected in the left parietal old/new effect seems to be uncontested. However, an association between episodic familiarity and the mid-frontal old/new effect is not uncontroversial. It has been argued that the mid-frontal old/new effect is functionally equivalent to the N400 and hence merely reflects differences in conceptual fluency between old and new items. Therefore, it is related to episodic familiarity only in situations in which conceptual fluency covaries with familiarity. Alternatively, the old/new effect in this time window reflects an interaction of episodic familiarity and conceptual processing with each making a unique functional contribution. To test this latter account, we manipulated conceptual fluency and episodic familiarity orthogonally in an incidental recognition test: Visually presented old and new words were preceded by either conceptually related or unrelated auditory prime words. If the mid-frontal old/new effect is functionally distinguishable from conceptual priming effects, an ERP contrast reflecting pure priming (correct rejections in the related vs. unrelated condition) and a contrast reflecting priming plus familiarity (hits in the related vs. correct rejections in the unrelated condition) should differ in scalp distribution. As predicted, the pure priming contrast had a right-parietal distribution, as typically observed for the N400 effect, whereas the priming plus familiarity contrast was significantly more frontally accentuated. These findings implicate that old/new effects in this time window are driven by unique functional contributions of episodic familiarity and conceptual processing.

The left-lateralized N170 component of ERPs for words compared with various control stimuli is considered as an electrophysiological manifestation of visual expertise for written words. To understand the information sensitivity of the effect, researchers distinguish between coarse tuning for words (the N170 amplitude difference between words and symbol strings) and fine tuning for words (the N170 amplitude difference between words and consonant strings). Earlier developmental ERP studies demonstrated that the coarse tuning for words occurred early in children (8 years old), whereas the fine tuning for words emerged much later (10 years old). Given that there are large individual differences in reading ability in young children, these tuning effects may emerge earlier than expected in some children. This study measured N170 responses to words and control stimuli in a large group of 7-year-olds that varied widely in reading ability. In both low and high reading ability groups, we observed the coarse neural tuning for words. More interestingly, we found that a stronger N170 for words than consonant strings emerged in children with high but not low reading ability. Our study demonstrates for the first time that fine neural tuning for orthographic properties of words can be observed in young children with high reading ability, suggesting that the emergent age of this effect is much earlier than previously assumed. The modulation of this effect by reading ability suggests that fine tuning is flexible and highly related to experience. Moreover, we found a correlation between this tuning effect at left occipitotemporal electrodes and children's reading ability, suggesting that the fine tuning might be a biomarker of reading skills at the very beginning of learning to read.

Contrasts between ERPs elicited by new items from tests with distinct episodic retrieval requirements index preretrieval processing. Preretrieval operations are thought to facilitate the recovery of task-relevant information because they have been shown to correlate with response accuracy in tasks in which prioritizing the retrieval of this information could be a useful strategy. This claim was tested here by contrasting new item ERPs from two retrieval tasks, each designed to explicitly require the recovery of a different kind of mnemonic information. New item ERPs differed from 400 msec poststimulus, but the distribution of these effects varied markedly, depending upon participants' response accuracy: A protracted posteriorly located effect was present for higher performing participants, whereas an anteriorly distributed effect occurred for lower performing participants. The magnitude of the posterior effect from 400 to 800 msec correlated with response accuracy, supporting the claim that preretrieval processes facilitate the recovery of task-relevant information. Additional contrasts between ERPs from these tasks and an old/new recognition task operating as a relative baseline revealed task-specific effects with nonoverlapping scalp topographies, in line with the assumption that these new item ERP effects reflect qualitatively distinct retrieval operations. Similarities in these effects were also used to reason about preretrieval processes related to the general requirement to recover contextual details. These insights, alongside the distinct pattern of effects for the two accuracy groups, reveal the multifarious nature of preretrieval processing while indicating that only some of these classes of operation are systematically related to response accuracy in recognition memory tasks.

We examined the ERP correlates of familiarity and recollection and their development in 8- to 10-year-old children and a control group of young adults. Capitalizing on the different temporal dynamics of familiarity and recollection, we tested recognition memory in both groups with a speeded and nonspeeded response condition. Consistent with the view that familiarity is available earlier than recollection and by this more relevant for speeded recognition judgments, adults and children showed an early frontal old/new effect, the putative ERP correlate of familiarity in the speeded response condition. No parietal old/new effect, the putative ERP correlate of recollection was obtained in the speeded condition in neither group. Conversely, in the nonspeeded condition, both groups showed the parietal old/new effect, and a frontal effect was additionally observed for adults. In light of the generally lower memory accuracy of the children, these data suggested that children use a weaker and less matured version of the same explicit memory network used by adults in which familiarity and recollection differentially contribute to speeded and nonspeeded recognition memory judgments.

Recognition memory based on familiarity judgments is a form of declarative memory that has been repeatedly associated with the anterior medial temporal lobe. It has been argued that this region sustains familiarity-based recognition not only by retrieving item-specific information but also by coding for those semantic aspects of an event that support later familiarity-based recognition. Here, we used event-related fMRI to directly examine whether the contribution of anterior medial temporal lobe to declarative memory indeed results from its role in processing semantic aspects of an event. For this purpose, a sentence comprehension task was employed which varied the demands of semantic and syntactic processing of the sentence-final word. By presenting those sentence-final words together with new words in a subsequent incidental recognition memory test, we were able to determine the mnemonic consequences of presenting words in different sentential contexts. Results showed that enhanced semantic processing during comprehension activates regions in medial temporal lobe cortex and leads to response suppression in partly overlapping regions when the word is successfully retrieved. Data from a behavioral follow-up study support the view that enhanced semantic processing at study enhances familiarity-based remembering in a subsequent test phase.

Retrieval practice on a subset of previously studied material enhances later memory for practiced material but can inhibit memory for related unpracticed material. The present study examines the effects of prior retrieval practice on evoked (ERPs) and induced (oscillatory power) measures of electrophysiological activity underlying recognition of practiced and unpracticed words. Compared to control material, recognition of unpracticed words was characterized by reduced amplitudes of the P2 ERP component and by reduced early (200–400 msec) oscillatory theta power. The reduction in P2 amplitude was associated with decreased evoked theta power but not with decreased theta phase locking (phase-locking index). Recognition of unpracticed material was further accompanied by a reduction in occipital gamma power (>250 msec). In contrast, the beneficial effects of retrieval practice on practiced words were reflected by larger parietal ERP positivity (>500 msec) and by a stronger decrease in oscillatory alpha power in a relatively late time window (>700 msec). The results suggest that the beneficial and detrimental effects of retrieval practice are mediated by different processes. In particular, they suggest that reduced theta (4–7 Hz) and gamma (60–90 Hz) power reflect the specific effects of inhibitory processes on the unpracticed material's memory representation.

In this experiment, we examined the extent to which error-driven learning may operate under implicit learning conditions. We compared error monitoring in a sequence learning task in which stimuli consisted of regular, irregular, or random sequences. Subjects were either informed (explicit condition) or not informed (implicit condition) about the existence of the sequence. For both conditions, reaction times were faster to stimuli from regular sequences than from random sequences, thus supporting the view that sequence learning occurs irrespective of learning condition. Response-locked event-related potentials (ERPs) showed a pronounced ERN/Ne, thereby signaling the detection of committed errors. Deviant stimuli from irregular sequences elicited an N2b component that developed in the course of the experiment, albeit faster for explicit than implicit learners. This observation supports the view that deviant events acquire the status of perceived errors during explicit and implicit learning, and thus, an N2b is generated resembling the ERN/Ne to committed errors. While performing the task, expectations about upcoming events are generated, compared to the actual events, and evaluated on the dimension “better or worse than expected.” The accuracy of this process improves with learning, as shown by a gradual increase in N2b amplitude as a function of learning. Additionally, a P3b, which is thought to mirror conscious processing of deviant stimuli and is related to updating of working memory representations, was found for explicit learners only.

This study examined emotional influences on the hypothesized event-related potential (ERP) correlates of familiarity and recollection (Experiment 1) and the states of awareness (Experiment 2) accompanying recognition memory for faces differing in facial affect. Participants made gender judgments to positive, negative, and neutral faces at study and were in the test phase instructed to discriminate between studied and nonstudied faces. Whereas old–new discrimination was unaffected by facial expression, negative faces were recollected to a greater extent than both positive and neutral faces as reflected in the parietal ERP old–new effect and in the proportion of remember judgments. Moreover, emotion-specific modulations were observed in frontally recorded ERPs elicited by correctly rejected new faces that concurred with a more liberal response criterion for emotional as compared to neutral faces. Taken together, the results are consistent with the view that processes promoting recollection are facilitated for negative events and that emotion may affect recognition performance by influencing criterion setting mediated by the prefrontal cortex.

A central issue in the research of directed forgetting is whether the differential memory performance for to-be-remembered (TBR) and to-be-forgotten (TBF) items is solely due to differential encoding or whether retrieval inhibition of TBF items plays an additional role. In this study, recognition-related event-related brain potentials (ERPs) were used to examine this issue. The spatio-temporal distributions of the old/new ERP effects obtained in Experiment 1 that employed a directed forgetting paradigm were compared with those recorded in Experiment 2 in which the level of processing was manipulated. In Experiment 1, participants were instructed to remember or to forget words by means of a cue presented after each word. ERPs recorded in the recognition test revealed early phasic frontal and parietal old/new effects for TBR items, whereas TBF items elicited only a frontal old/new effect. Moreover, a late right-frontal positive slow wave was more pronounced for TBF items, suggesting that those items were associated with a larger amount of post-retrieval processing. In Experiment 2, the same cueing method and the same stimulus materials were used, and memory encoding was manipulated by cueing participants to process the words either deeply or shallowly. Both deeply and shallowly encoded items elicited phasic frontal and parietal old/new effects followed by a late right-frontal positive slow wave. However, in contrast to TBR and TBF items, these effects differed only quantitatively. The results suggest that differential encoding alone cannot account for the effects of directed forgetting. They are more consistent with the view that items followed by an instruction to forget become inhibited and less accessible, and, therefore, more difficult to retrieve.