Self-reference during explicit memory retrieval: an event-related potential analysis

Late frontal positivity effects in Self-referential Memory: Unique to the Self?

The self-reference effect in memory (SRE), in which stimuli related to self are better remembered than other stimuli, has been studied often in the fMRI literature, but much less with EEG. In two experiments, we investigated how self-referencing modulated event-related potential (ERP) markers of the subsequent memory effect, testing whether the same components that reflect memory success are impacted or whether unique components are modulated by self-referencing. Participants were asked to evaluate whether an adjective accurately described either the self or a given other by making a yes/no key press during EEG recording. Then participants were given a surprise recognition memory test where they judged each adjective as old or new. We observed a main effect of self-relevance on a late positivity at right frontal electrodes. A very similar effect was observed when comparing words subsequently remembered to those that were forgotten. However, no interaction was found between self-relevance and subsequent memory, suggesting the frontal positivity is not exclusive to the SRE, but instead a reflection of deeper encoding that leads to better memory. Thus, this frontal positivity may be a marker of a deeper encoding process that is elicited by self-referencing but not exclusive to the SRE.

May the source be with you! Electrophysiological correlates of retrieval orientation are associated with source memory performance

Successful source memory retrieval is assumed to rely on intact preretrieval processes, such as retrieval orientation (RO). RO is the specialized processing of retrieval cues, depending on the type of information, memory is searched for. In a previous study, a positive frontal slow wave RO ERP effect was interpreted as reflecting memory search for self-relevant information. However, such a functional interpretation is hampered by the use of retrieval strategies as a consequence of which target source information can be indirectly inferred from the correct classification of non-target source information. To overcome this limitation, the present study compared two types of source information (i.e. color or character information) by asking participants to remember details within each source type and thus enforcing the selective retrieval of target information. Consistent with previous research, a positive frontal ERP component (600-800 ms post-stimulus) differentiated between correct rejections in both tasks, probably reflecting memory search for self-relevant information. Moreover, the RO ERP effect was associated with better source memory performance, providing evidence for the beneficial effect of ROs for memory retrieval. This relationship might be covered in memory exclusion tasks due to non-target retrieval.

Electrophysiological evidence of encoding in self-referential effect

Although the self-referential effect was widely supported by several previous studies, there was few event-related potential (ERP) evidence for the encoding mechanism of the self-referential effect. The present study employed ERPs to investigate whether the electrophysiological indices of the encoding processing could predict the retrieval processing in the self-referential paradigm. Behavioral results demonstrated better performance in the self-reference condition than other-reference condition. The N400 and LPP for the subsequent memory effect (the Dm effect) were observed in both self-referential and other-referential trials as shown in the ERP results of the encoding processing. Moreover, the self-referential information had higher amplitudes for subsequently remembered trials. The study also showed correlation between the ERP components in the encoding phase and those in retrieval. These findings suggest that the self-referential effect can be due to more effective encoding process, which in turn predicts better later recall performance.

Self-Referential Information Alleviates Retrieval Inhibition of Directed Forgetting Effects-An ERP Evidence of Source Memory

Directed forgetting (DF) assists in preventing outdated information from interfering with cognitive processing. Previous studies pointed that self-referential items alleviated DF effects due to the elaboration of encoding processes. However, the retrieval mechanism of this phenomenon remains unknown. Based on the dual-process framework of recognition, the retrieval of self-referential information was involved in familiarity and recollection. Using source memory tasks combined with event-related potential (ERP) recording, our research investigated the retrieval processes of alleviative DF effects elicited by self-referential information. The FN400 (frontal negativity at 400 ms) is a frontal potential at 300–500 ms related to familiarity and the late positive complex (LPC) is a later parietal potential at 500–800 ms related to recollection. The FN400 effects of source memory suggested that familiarity processes were promoted by self-referential effects without the modulation of to-be-forgotten (TBF) instruction. The ERP results of DF effects were involved with LPCs of source memory, which indexed retrieval processing of recollection. The other-referential source memory of TBF instruction caused the absence of LPC effects, while the self-referential source memory of TBF instruction still elicited the significant LPC effects. Therefore, our neural findings suggested that self-referential processing improved both familiarity and recollection. Furthermore, the self-referential processing advantage which was caused by the autobiographical retrieval alleviated retrieval inhibition of DF, supporting that the self-referential source memory alleviated DF effects.

Principal components of electrocortical activity during self-evaluation indicate depressive symptom severity

Negative self-evaluation is an important psychological characteristic of depression. In order to study the underlying neural mechanisms, we examined event-related potentials (ERPs) during a self-evaluation task in a community sample (N = 150) of adults reporting a range of depressive symptoms. Principal components analysis (PCA) was used to separate processes that overlap in the average ERP, and neural source analysis was applied to localize the ERP components, with a particular focus on the frontal networks that are thought to be critical to affective self-regulation in depression. Consistent with previous research, individuals reporting greater depression showed enhanced negativity over medial frontal regions as well as attenuation of the late positive potential over parietal regions. Examining loadings of frontal sources on the ERP components showed that activity in the right inferior frontal region may be particularly important for depressed individuals: activity in this region declined as symptoms became more severe. Characterizing brain mechanisms of self-evaluation on the timescale of cognitive events may provide insight into the neural mechanisms of self-regulation that are important in cognitive therapy, and that could be made more amenable to change through increasing neuroplasticity with targeted non-invasive neuromodulation.

Learning-induced plasticity in medial prefrontal cortex predicts preference malleability

Learning induces plasticity in neuronal networks. As neuronal populations contribute to multiple representations, we reasoned plasticity in one representation might influence others. We used human fMRI repetition suppression to show that plasticity induced by learning another individual’s values impacts upon a value representation for oneself in medial prefrontal cortex (mPFC), a plasticity also evident behaviorally in a preference shift. We show this plasticity is driven by a striatal “prediction error,” signaling the discrepancy between the other’s choice and a subject’s own preferences. Thus, our data highlight that mPFC encodes agent-independent representations of subjective value, such that prediction errors simultaneously update multiple agents’ value representations. As the resulting change in representational similarity predicts interindividual differences in the malleability of subjective preferences, our findings shed mechanistic light on complex human processes such as the powerful influence of social interaction on beliefs and preferences.

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Learning the values of another causes plasticity in a mPFC value representation

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This plasticity predicts how much subjects’ own preferences change

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Plasticity is explained by a striatal surprise signal

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Value coding in mPFC occurs independently of the agent for whom a decision is made

Oxytocin effects on neural correlates of self-referential processing

Oxytocin (OT) influences how humans process information about others. Whether OT affects the processing of information about oneself remains unknown. Using a double-blind, placebo-controlled within-subject design, we recorded event-related potentials (ERPs) from adults during trait judgments about oneself and a celebrity and during judgments on word valence, after intranasal OT or placebo administration. We found that OT vs. placebo treatment reduced the differential amplitudes of a fronto-central positivity at 220-280 ms (P2) during self- vs. valence-judgments. OT vs. placebo treatment tended to reduce the differential amplitude of a late positive potential at 520-1000 ms (LPP) during self-judgments but to increase the differential LPP amplitude during other-judgments. OT effects on the differential P2 and LPP amplitudes to self- vs. celebrity-judgments were positively correlated with a measure of interdependence of self-construals. Thus OT modulates the neural correlates of self-referential processing and this effect varies as a function of interdependence.

Neural oscillations dissociate between self-related attentional orientation versus evaluation

To investigate whether self-reflection on personality traits engages distinct neural mechanisms of self-related attentional orientation and self-related evaluation, we recorded electroencephalograms from adults while they made trait judgments about themselves and an age- and gender-matched friend, or judgments of word valence. Each trial consisted of a cue word that indicated a target person for trait judgment or instructed valence judgment, followed by a trait adjective to be evaluated. Using a wavelet analysis, we calculated time-frequency power at each electrode and phase synchrony between electrode pairs associated with self-, friend- or valence-cues and with trait adjectives during trait or valence judgments. Relative to friend- and valence-cues, self-cues elicited increased synchronous activity in delta (2-4Hz), theta (5-7Hz), alpha (8-13Hz), beta (14-26Hz), and gamma (28-40Hz) bands, and increased large-scale phase synchrony in these frequency bands. Self-related evaluation compared to friend-related evaluation during trait judgments induced stronger desynchronization in alpha, beta and gamma band activities, and decreased phase synchrony in alpha and gamma band activities. Our findings suggest that self-related attentional orientation and self-related evaluation engage distinct neural mechanisms that are respectively characterized by synchrony and desynchrony of neural activity in local assemblies and between long-distance brain regions.

It's All About You: an ERP study of emotion and self-relevance in discourse

Accurately communicating self-relevant and emotional information is a vital function of language, but we have little idea about how these factors impact normal discourse comprehension. In an event-related potential (ERP) study, we fully crossed self-relevance and emotion in a discourse context. Two-sentence social vignettes were presented either in the third or the second person (previous work has shown that this influences the perspective from which mental models are built). ERPs were time-locked to a critical word toward the end of the second sentence which was pleasant, neutral, or unpleasant (e.g., A man knocks on Sandra's/your hotel room door. She/You see(s) that he has agift/tray/gunin his hand.). We saw modulation of early components (P1, N1, and P2) by self-relevance, suggesting that a self-relevant context can lead to top-down attentional effects during early stages of visual processing. Unpleasant words evoked a larger late positivity than pleasant words, which evoked a larger positivity than neutral words, indicating that, regardless of self-relevance, emotional words are assessed as motivationally significant, triggering additional or deeper processing at post-lexical stages. Finally, self-relevance and emotion interacted on the late positivity: a larger late positivity was evoked by neutral words in self-relevant, but not in non-self-relevant, contexts. This may reflect prolonged attempts to disambiguate the emotional valence of ambiguous stimuli that are relevant to the self. More broadly, our findings suggest that the assessment of emotion and self-relevance are not independent, but rather that they interactively influence one another during word-by-word language comprehension.

Self-specific processing in the default network: a single-pulse TMS study

In examining neural processing specific to the self, primarily by contrasting self-related stimuli with non-self-related stimuli (i.e., self vs. other), neuroimaging studies have activated a consistent set of regions, including medial prefrontal cortex (MPFC), precuneus, and right and left inferior parietal cortex. However, criticism has arisen that this network may not be specific to self-related processing, but instead reflects a more general aspect of cortical processing. For example, it is almost identical to the active network of the resting state, the "default" mode, when the subject is free to think about anything at all. We tested the self-specificity of this network by using transcranial magnetic stimulation (TMS) to briefly disrupt local cortical processing while subjects rated adjectives as like or unlike themselves or their best friend. Healthy volunteers show a self-reference effect (SRE) in this task, in which performance with self-related items is superior to that with other-related items. As individual adjectives appeared on a monitor, single-pulse TMS was applied at five different times relative to stimulus onset (SOA: stimulus onset asynchrony) ranging from 0 to 480 ms. In 18 subjects, TMS to left parietal cortex suppressed the SRE from 160 to 480 ms. SRE suppression occurred at later SOA with TMS to the right parietal cortex. In contrast, no effects were seen with TMS to MPFC. Together with our previous work, these results provide evidence for a self-specific processing system in which midline and lateral inferior parietal cortices, as elements of the default network, play a role in ongoing self-awareness.

Self-involvement modulates the effective connectivity of the autobiographical memory network

Neuroimaging studies have revealed a consistent overlap between brain regions involved in self-processing and those implicated in autobiographical memory. However, no study has directly tested how the degree of self-involvement with an event being remembered alters the neural circuitry engaged during memory retrieval. The present study compared hockey players' memories for game elements in which they were highly involved (e.g. scoring a goal) versus less involved (e.g. watching a goal from the bench). Specifically, we examined how the effective connectivity of a network of brain regions known to be involved in autobiographical memory retrieval varied based upon the players' level of self-involvement with the remembered event. During remembering of high self-involvement events, connections between the left hippocampus and medial prefrontal cortex were 'in synchrony' with connections between the medial prefrontal cortex and the right amygdala-hippocampal complex. By contrast, the hippocampal-prefrontal connection was 'out-of-sync' with the prefrontal-amygdala connection during retrieval of low self-involvement memories. This result is discussed in terms of two memory systems (one that is hippocampal-based and one that is amygdala-hippocampal-based) that may be involved to varying degrees depending upon the characteristics of a remembered event.