Roles of the Default Mode Network in Different Aspects of Self-representation When Remembering Social Autobiographical Memories.

Autobiographical memory (AM) is episodic memory for personally experienced events, in which self-representation is more important than that in laboratory-based memory. Theoretically, self-representation in a social context is categorized as the interpersonal self (IS) referred to in a social interaction with a person or the social-valued self (SS) based on the reputation of the self in the surrounding society. Although functional neuroimaging studies have demonstrated the involvement of the default mode network (DMN) in self-representation, little is known about how the DMN subsystems contribute differentially to IS-related and SS-related AMs. To elucidate this issue, we used fMRI to scan healthy young adults during the recollection of AMs. We performed multivariate pattern analysis (MVPA) and assessed functional connectivity in the DMN subsystems: the midline core, medial temporal lobe (MTL), and dorsomedial pFC (dmPFC) subsystems. The study yielded two main sets of findings. First, MVPA revealed that all DMN subsystems showed significant classification accuracy between IS-related and nonsocial-self-related AMs, and IS-related functional connectivity of the midline core regions with the retrosplenial cortex of the MTL subsystem and the dmPFC of the dmPFC subsystem was significant. Second, MVPA significantly distinguished between SS-related and nonsocial-self-related AMs in the midline core and dmPFC subsystems but not in the MTL subsystem, and SS-related functional connectivity with the midline core regions was significant in the temporal pole and TPJ of the dmPFC subsystem. Thus, dissociable neural mechanisms in the DMN could contribute to different aspects of self-representation in social AMs.

Remembering unexpected beauty: Contributions of the ventral striatum to the processing of reward prediction errors regarding the facial attractiveness in face memory.

The COVID-19 pandemic has led people to predict facial attractiveness from partially covered faces. Differences in the predicted and observed facial attractiveness (i.e., masked and unmasked faces, respectively) are defined as reward prediction error (RPE) in a social context. Cognitive neuroscience studies have elucidated the neural mechanisms underlying RPE-induced memory improvements in terms of monetary rewards. However, little is known about the mechanisms underlying RPE-induced memory modulation in terms of social rewards. To elucidate this, the present functional magnetic resonance imaging (fMRI) study investigated activity and functional connectivity during face encoding. In encoding trials, participants rated the predicted attractiveness of faces covered except for around the eyes (prediction phase) and then rated the observed attractiveness of these faces without any cover (outcome phase). The difference in ratings between these phases was defined as RPE in facial attractiveness, and RPE was categorized into positive RPE (increased RPE from the prediction to outcome phases), negative RPE (decreased RPE from the prediction to outcome phases), and non-RPE (no difference in RPE between the prediction and outcome phases). During retrieval, participants were presented with individual faces that had been seen and unseen in the encoding trials, and were required to judge whether or not each face had been seen in the encoding trials. Univariate activity in the ventral striatum (VS) exhibited a linear increase with increased RPE in facial attractiveness. In the multivariate pattern analysis (MVPA), activity patterns in the VS and surrounding areas (extended VS) significantly discriminated between positive/negative RPE and non-RPE. In the functional connectivity analysis, significant functional connectivity between the extended VS and the hippocampus was observed most frequently in positive RPE. Memory improvements by face-based RPE could be involved in functional networks between the extended VS (representing RPE) and the hippocampus, and the interaction could be modulated by RPE values in a social context.

Effects of Long-Chain Polyunsaturated Fatty Acids in Combination with Lutein and Zeaxanthin on Episodic Memory in Healthy Older Adults.

Arachidonic acid (ARA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA), which are long-chain polyunsaturated fatty acids (LCPUFAs), as well as lutein (L) and zeaxanthin (Z), can potentially improve brain function. However, the effect of a combination of these components (LCPUFAs + LZ) on memory function in healthy older individuals remains unclear. This study aimed to determine if LCPUFAs + LZ-supplemented food could improve memory function. Exploratory and confirmatory trials (Trials 1 and 2, respectively) were conducted in healthy older Japanese individuals with memory complaints. We conducted randomized, double-blind, placebo-controlled, parallel-group trials. Participants were randomly allocated to two groups: placebo or LCPUFAs + LZ. LCPUFAs + LZ participants were provided with supplements containing ARA, DHA, EPA, L, and Z for 24 weeks in Trial 1 and 12 weeks in Trial 2. Memory functions were evaluated using Cognitrax before and after each trial. Combined analyses were performed for subgroups of participants with cognitive decline in Trials 1 and 2. The results showed that supplementation with LCPUFAs + LZ did not significantly affect memory function in healthy, non-demented, older individuals with memory complaints whereas it improved memory function in healthy, non-demented, older individuals with cognitive decline.

Neural Mechanisms of Perceiving and Subsequently Recollecting Emotional Facial Expressions in Young and Older Adults.

It is known that emotional facial expressions modulate the perception and subsequent recollection of faces and that aging alters these modulatory effects. Yet, the underlying neural mechanisms are not well understood, and they were the focus of the current fMRI study. We scanned healthy young and older adults while perceiving happy, neutral, or angry faces paired with names. Participants were then provided with the names of the faces and asked to recall the facial expression of each face. fMRI analyses focused on the fusiform face area (FFA), the posterior superior temporal sulcus (pSTS), the OFC, the amygdala (AMY), and the hippocampus (HC). Univariate activity, multivariate pattern (MVPA), and functional connectivity analyses were performed. The study yielded two main sets of findings. First, in pSTS and AMY, univariate activity and MVPA discrimination during the processing of facial expressions were similar in young and older adults, whereas in FFA and OFC, MVPA discriminated facial expressions less accurately in older than young adults. These findings suggest that facial expression representations in FFA and OFC reflect age-related dedifferentiation and positivity effect. Second, HC-OFC connectivity showed subsequent memory effects (SMEs) for happy expressions in both age groups, HC-FFA connectivity exhibited SMEs for happy and neutral expressions in young adults, and HC-pSTS interactions displayed SMEs for happy expressions in older adults. These results could be related to compensatory mechanisms and positivity effects in older adults. Taken together, the results clarify the effects of aging on the neural mechanisms in perceiving and encoding facial expressions.

Effects of Aging on the Neural Mechanisms Underlying the Recollection of Memories Encoded by Social Interactions With Persons in the Same and Different Age Groups.

Memories related to ingroup members are remembered more accurately than those related to outgroup members. However, little is known about the age-dependent differences in neural mechanisms underlying the retrieval of memories shared with ingroup or outgroup members that are categorized by age-group membership. The present functional magnetic resonance imaging (fMRI) study investigated this issue. Healthy young and older adults participated in a 2-day experiment. On the first day outside fMRI, participants were presented with words by unfamiliar persons in movie clips and exchanged each word with persons belonging to the same age group (SAG) or different age group (DAG). On the second day during fMRI, participants were randomly presented with learned and new words one by one, and they judged whether each word had been encoded with either SAG or DAG members or neither. fMRI results demonstrated that an age-dependent decrease in successful retrieval activation of memories presented by DAG was identified in the anterior temporal lobe (ATL) and hippocampus, whereas with memories presented by SAG, an age-dependent decrease in activation was not found in any regions. In addition, an age-dependent decrease in functional connectivity was significant between the hippocampus/ATL and posterior superior temporal sulcus (pSTS) during the successful retrieval of memories encoded with the DAG people. The "other"-related mechanisms including the hippocampus, ATL, and pSTS with memories learned with the outgroup members could decrease in older adults, whereas with memories learned with the ingroup members, the "self"-related mechanisms could be relatively preserved in older adults.

Memory of my victory and your defeat: Contributions of reward- and memory-related regions to the encoding of winning events in competitions with others.

Social interactions enhance human memories, but little is known about how the neural mechanisms underlying episodic memories are modulated by rewarding outcomes in social interactions. To investigate this, fMRI data were recorded while healthy young adults encoded unfamiliar faces in either a competition or a control task. In the competition task, participants encoded opponents' faces in the rock-paper-scissors game, where trial-by-trial outcomes of Win, Draw, and Lose for participants were shown by facial expressions of opponents (Angry, Neutral, and Happy). In the control task, participants encoded faces by assessing facial expressions. After encoding, participants recognized faces previously learned. Behavioral data showed that emotional valence for opponents' Angry faces as the Win outcome was rated positively in the competition task, whereas the rating for Angry faces was rated negatively in the control task, and that Angry faces were remembered more accurately than Neutral or Happy faces in both tasks. fMRI data showed that activation in the medial orbitofrontal cortex (mOFC) paralleled the pattern of valence ratings, with greater activation for the Win than Draw or Lose conditions of the competition task, and the Angry condition of the control task. Moreover, functional connectivity between the mOFC and hippocampus was increased in Win compared to Angry, and the mOFC-hippocampus functional connectivity predicted individual differences in subsequent memory performance only in Win of the competition task, but not in any other conditions of the two tasks. These results demonstrate that the memory enhancement by context-dependent social rewards involves interactions between reward- and memory-related regions.

Intrinsic functional network contributions to the relationship between trait empathy and subjective happiness.

Subjective happiness (well-being) is a multi-dimensional construct indexing one's evaluations of everyday emotional experiences and life satisfaction, and has been associated with different aspects of trait empathy. Despite previous research identifying the neural substrates of subjective happiness and empathy, the mechanisms mediating the relationship between the two constructs remain largely unclear. Here, we performed a data-driven, multi-voxel pattern analysis of whole-brain intrinsic functional connectivity to reveal the neural mechanisms of subjective happiness and trait empathy in a sample of young females. Behaviorally, we found that subjective happiness was negatively associated with personal distress (i.e., self-referential experience of others' feelings). Consistent with this inverse relationship, subjective happiness was associated with the dorsolateral prefrontal cortex exhibiting decreased functional connectivity with regions important for the representation of unimodal sensorimotor information (e.g., primary sensory cortices) or multi-modal summaries of brain states (e.g., default mode network) and increased functional connectivity with regions important for the attentional modulation of these representations (e.g., frontoparietal, attention networks). Personal distress was associated with the medial prefrontal cortex exhibiting functional connectivity differences with similar networks--but in the opposite direction. Finally, intrinsic functional connectivity within and between these networks fully mediated the relationship between the two behavioral measures. These results identify an important contribution of the macroscale functional organization of the brain to human well-being, by demonstrating that lower levels of personal distress lead to higher subjective happiness through variation in intrinsic functional connectivity along a neural representation vs. modulation gradient.

Effects of combining exercise with long-chain polyunsaturated fatty acid supplementation on cognitive function in the elderly: a randomised controlled trial.

Multifactorial lifestyle intervention is known to be more effective for ameliorating cognitive decline than single factor intervention; however, the effects of combining exercise with long-chain polyunsaturated fatty acids (LCPUFA) on the elderlies' cognitive function remain unclear. We conducted a randomised, single-masked placebo-controlled trial in non-demented elderly Japanese individuals. Participants were randomly allocated to the exercise with LCPUFA, placebo, or no exercise with placebo (control) groups. Participants in the exercise groups performed 150 min of exercise per week, comprised resistance and aerobic training, for 24 weeks with supplements of either LCPUFA (docosahexaenoic acid, 300 mg/day; eicosapentaenoic acid, 100 mg/day; arachidonic acid, 120 mg/day) or placebo. Cognitive functions were evaluated by neuropsychological tests prior to and following the intervention. The per-protocol set analysis (n = 76) revealed no significant differences between the exercise and the control groups in changes of neuropsychological tests. Subgroup analysis for participants with low skeletal muscle mass index (SMI) corresponding to sarcopenia cut-off value showed changes in selective attention, while working memory in the exercise with LCPUFA group was better than in the control group. These findings suggest that exercise with LCPUFA supplementation potentially improves attention and working memory in the elderly with low SMI.

Reduced Enhancement of Memory for Faces Encoded by Semantic and Socioemotional Processes in Patients with Parkinson's Disease.

OBJECTIVES: Patients with Parkinson's disease (PD) exhibit impaired semantic and socioemotional processes, which are thought to be related to dysfunctions in the fronto-striatal circuit. However, little is known about how the memory enhancement by these processes was reduced in PD. The present study investigated this issue. METHODS: The retrieval performance of face memories encoded by semantic and socioemotional processes was compared between 24 PD patients and 24 age-matched healthy controls (HC). During encoding, participants were presented with unfamiliar faces and made judgment about them in three encoding conditions of semantic judgment (Semantics), attractiveness judgment (Attractiveness), and form judgment (Form). In Semantics, participants rated to what degree each face looked like an office worker, whereas in Attractiveness, participants rated how attractive each face was. The Form condition as a control required participants to judge the shape of each face. During retrieval after encoding, participants made old or new judgment for target and distracter faces. RESULTS: In HC, the retrieval of faces encoded by Semantics and Attractiveness was significantly more accurate than that encoded by Form, whereas this memory enhancement was not identified in PD. In addition, individual scores in frontal lobe function and long-term memory correlated with the retrieval performance of memories encoded in Semantics and Attractiveness but not Form. CONCLUSIONS: These findings suggest that the processing of semantic and socioemotional signals conveyed from faces could be impaired in PD and that the impairment of these processes could decrease the enhancement of face memories by semantic and socioemotional elaborations.

[Time and Self in Episodic Memory and Confabulation].

Confabulation is defined as the production of narrative descriptions of events that never happened, and is often observed in amnesia with basal forebrain lesions. However, little is known about the possible mechanisms related to confabulation. In this review article, we summarized previous neuropsychological and neuroimaging studies associated with confabulation, and proposed a hypothetical mechanism of confabulation. Previous studies have demonstrated that amnesic patients with confabulation after basal forebrain damage are impaired in the processing of time-related information in episodic memory and that activation of this region is significant during the processing of time-related information in episodic memory. In addition, confabulating patients with basal forebrain lesions extending to the medial prefrontal cortex (mPFC), medial temporal, and thalamic regions are likely to show significant disturbances in age-awareness and significant false memories in personally experienced events. Given the importance of the mPFC in the self-referential process and of the hippocampus in the integration of episodic components, the basal forebrain region could play an important role in orienting the self in time by acting as an interface between the mPFC and the hippocampus. Confabulation in basal forebrain amnesia could be caused by a decline of the time-self interaction.

[Contribution of the Medial Prefrontal Cortex to Social Memory].

Social memory is a form of episodic memories in multiple domains of social context. Functional neuroimaging studies have demonstrated that the medial prefrontal cortex (mPFC) plays an important role in social memories. However, little is known about the dissociable roles within mPFC in social memories. The purpose of this article was to summarize functional neuroimaging studies investigating social memories, and to propose a hypothetical model regarding the contribution of mPFC sub-regions to social memories. In this article, we divided mPFC into three sub-regions of the orbital, ventral, and dorsal regions. Functional neuroimaging studies have shown that the orbital mPFC (orbitofrontal cortex) contributes to the reward process in episodic memory, and that the reward-related activation is identified in primary, secondary, and social rewards. A role of the ventral mPFC has been found in the self-referential process, and the encoding operation of this process produces the self-reference effect in episodic memory. Activation in the dorsal mPFC has been observed in high demanding processes including cognitive control and in social cognition such as impression formation for others during episodic encoding and retrieval. The interactive mechanisms within three sub-regions of mPFC and between mPFC and the medial temporal lobe could contribute to social memories.

Approach or avoidance: Neural correlates of intelligence evaluation from faces.

Intelligence is among the key determinants of power and social status in modern societies. In this functional magnetic resonance imaging study, we examined the neural correlates of intelligence evaluation from faces. Participants underwent scans while they evaluated the perceived intelligence and friendliness of faces. We found that medial orbitofrontal cortex activity increased linearly with friendliness ratings. The relationship between perceived intelligence and brain activity was positively linear in the right caudate nucleus and U-shaped (i.e., strong responses to unintelligent-looking or intelligent-looking faces) in the right anterior insula/inferior frontal gyrus. Perceived intelligence was also significantly positively correlated with both friendliness and attractiveness. Furthermore, intelligence rating scores had a positive linear effect on reaction times in the friendliness rating task, suggesting that participants had greater conflicts when making friendliness judgments for faces that appeared to belong to intelligent individuals. In addition, the degree of this effect predicted individual differences in the positive linear modulatory effect of intelligence scores in the right caudate nucleus. Our interpretation was that the activity in the caudate nucleus revealed an approach-avoidance conflict with regard to highly intelligent people, that is, they were perceived as attractive but also potentially threatening. Although our interpretations are merely suggestive because we did not measure the approach-avoidance behaviors directly, our findings have important implications for understanding the dynamics of human interaction in modern societies that increasingly allocate power and status based on intelligence.

Emerging Directions in Emotional Episodic Memory.

Building upon the existing literature on emotional memory, the present review examines emerging evidence from brain imaging investigations regarding four research directions: (1) Social Emotional Memory, (2) The Role of Emotion Regulation in the Impact of Emotion on Memory, (3) The Impact of Emotion on Associative or Relational Memory, and (4) The Role of Individual Differences in Emotional Memory. Across these four domains, available evidence demonstrates that emotion- and memory-related medial temporal lobe brain regions (amygdala and hippocampus, respectively), together with prefrontal cortical regions, play a pivotal role during both encoding and retrieval of emotional episodic memories. This evidence sheds light on the neural mechanisms of emotional memories in healthy functioning, and has important implications for understanding clinical conditions that are associated with negative affective biases in encoding and retrieving emotional memories.

[Neural Mechanisms Underlying the Processing of Temporal Information in Episodic Memory and Its Disturbance].

Episodic memory is defined as memory for personally experienced events, and includes memory content and contextual information of time and space. Previous neuroimaging and neuropsychological studies have demonstrated three possible roles of the temporal context in episodic memory. First, temporal information contributes to the arrangement of temporal order for sequential events in episodic memory, and this process is involved in the lateral prefrontal cortex. The second possible role of temporal information in episodic memory is the segregation between memories of multiple events, which are segregated by cues of different time information. The role of segregation is associated with the orbitofrontal regions including the orbitofrontal cortex and basal forebrain region. Third, temporal information in episodic memory plays an important role in the integration of multiple components into a coherent episodic memory, in which episodic components in the different modalities are combined by temporal information as an index. The role of integration is mediated by the medial temporal lobe including the hippocampus and parahippocampal gyrus. Thus, temporal information in episodic memory could be represented in multiple stages, which are involved in a network of the lateral prefrontal, orbitofrontal, and medial temporal lobe regions.

Remembering my friends: Medial prefrontal and hippocampal contributions to the self-reference effect on face memories in a social context.

Memories associated with the self are remembered more accurately than those associated with others. The memory enhancement related to the self is known as the self-reference effect (SRE). However, little is known regarding the neural mechanisms underlying the SRE in a social context modulated by social relationships. In the present fMRI study, we investigated encoding-related activation of face memories encoded with the self-referential process in a social context that was manipulated by imagining a person-to-person relationship. Healthy young adults participated in the present study. During encoding, participants encoded unfamiliar target faces by imagining a future friendship with themselves (Self), their friends (Friend), or strangers (Other). During retrieval, participants were presented with target and distracter faces one by one, and they judged whether each face had been previously learned. In the behavioral results, target faces encoded in the Self condition were remembered more accurately than those encoded in the Other condition. fMRI results demonstrated that encoding-related activation in the medial prefrontal cortex (mPFC) was significantly greater in the Self condition than in the Friend or Other conditions. In addition, the generalized psycho-physiological interaction (gPPI) analysis showed that functional connectivity between activation in the hippocampus and the cortical midline structures (CMSs), including the mPFC and precuneus, was significant in the Self but not in the Other condition. These findings suggest that the SRE in a social context could be involved in the interaction between the CMS regions, which are related to the self-referential process, and the hippocampus related to the memory process. Hum Brain Mapp 38:4256-4269, 2017. © 2017 Wiley Periodicals, Inc.

Neural mechanisms underlying the reward-related enhancement of motivation when remembering episodic memories with high difficulty.

The motivation to receive rewards enhances episodic memories, and the motivation is modulated by task difficulty. In episodic retrieval, however, functional neuroimaging evidence regarding the motivation that mediates interactions between reward and task difficulty is scarce. The present fMRI study investigated this issue. During encoding performed without fMRI, participants encoded Japanese words using either deep or shallow strategies, which led to variation in difficulty level during subsequent retrieval. During retrieval with fMRI, participants recognized the target words in either high or low monetary reward conditions. In the behavioral results, a reward-related enhancement of memory was found only when the memory retrieval was difficult, and the rewarding effect on subjective motivation was greater in the retrieval of memories with high difficulty than those with low difficulty. The fMRI data showed that reward-related increases in the activation of the substantia nigra/ventral tegmental area (SN/VTA), medial temporal lobe (MTL), dorsomedial prefrontal cortex (dmPFC), and dorsolateral prefrontal cortex (dlPFC) were greater during the retrieval of memories with high difficulty than those with low difficulty. Furthermore, reward-related enhancement of functional connectivity between the SN/VTA and MTL and between the SN/VTA and dmPFC during the retrieval of memories with high difficulty was significantly correlated with reward-related increases of retrieval accuracy and subjective motivation. The reward-related enhancement of episodic retrieval and retrieval-related motivation could be most effective when the level of retrieval difficulty is optimized. Such reward-related enhancement of memory and motivation could be modulated by a network including the reward-related SN/VTA, motivation-related dmPFC, and memory-related MTL. Hum Brain Mapp 38:3428-3443, 2017. © 2017 Wiley Periodicals, Inc.

Lateral and medial prefrontal contributions to emotion generation by semantic elaboration during episodic encoding.

Memories for emotion-laden stimuli are remembered more accurately than those for neutral stimuli. Although this enhancement reflects stimulus-driven modulation of memory by emotions, functional neuroimaging evidence of the interacting mechanisms between emotions generated by intentional processes, such as semantic elaboration, and memory is scarce. The present fMRI study investigated how encoding-related activation is modulated by emotions generated during the process of semantic elaboration. During encoding with fMRI, healthy young adults viewed neutral (target) pictures either passively or with semantic elaboration. In semantic elaboration, participants imagined background stories related to the pictures. Encoding trials with semantic elaboration were subdivided into conditions in which participants imagined negative, positive, or neutral stories. One week later, memories for target pictures were tested. In behavioral results, memories for target pictures were significantly enhanced by semantic elaboration, compared to passive viewing, and the memory enhancement was more remarkable when negative or positive stories were imagined. fMRI results demonstrated that activations in the left inferior frontal gyrus and dorsal medial prefrontal cortex (dmPFC) were greater during the encoding of target pictures with semantic elaboration than those with passive viewing, and that these activations further increased during encoding with semantic elaboration of emotional stories than of neutral stories. Functional connectivity between the left inferior frontal gyrus and dmPFC/hippocampus during encoding significantly predicted retrieval accuracies of memories encoded with self-generated emotional stories. These findings suggest that networks including the left inferior frontal region, dmPFC, and hippocampus could contribute to the modulation of memories encoded with the emotion generation.

Competing against a familiar friend: Interactive mechanism of the temporo-parietal junction with the reward-related regions during episodic encoding.

Competition enhances learning under certain circumstances. However, little is known about how the neural mechanisms involved in a competition during the episodic encoding are modulated by the social distance of personal relationships with opponents. To investigate this issue, using functional magnetic resonance imaging (fMRI), we scanned healthy young adults during a competition with their familiar friends and unfamiliar others in the episodic encoding. Three major findings emerged from this study. First, activations in the right temporo-parietal junction (rTPJ) were significantly greater in the competition with familiar friends than with unfamiliar others, and the activations in this region were significantly correlated with the subjective ratings of motivation. Second, striatum and amygdala activations increased by the competition with familiar friends were significantly correlated with the increased ratings of pleasantness, which reflected emotionally positive feelings in victory for the competition with familiar opponents. Third, the functional connectivity between the rTPJ and reward-related regions, including the striatum and substantia nigra, was higher in the competition with familiar friends than with unfamiliar others. Taken together with our behavioral findings, in which memories encoded by competing with familiar friends were remembered more accurately than those with unfamiliar others, the interacting mechanisms between the rTPJ that is involved in social motivation and the reward-related regions that are involved in social reward could contribute to the enhancement of memories encoded in the competition with familiar others.

Disturbance of time orientation, attention, and verbal memory in amnesic patients with confabulation.

Confabulation is often observed in amnesic patients after brain damage. However, evidence regarding the relationship between confabulation and other neuropsychological functions is scarce. In addition, previous studies have proposed two possibilities of the relationship between confabulation and false memory, in which patients with confabulation are likely to retrieve false memories, or confabulations are relatively independent of false memories. The present study investigated how confabulation is related to various cognitive functions, including orientation, attention, frontal lobe function, memory, and mental status, and to false memories, as assessed by the Deese-Roediger-Mcdermott (DRM) paradigm. Patients with organic amnesia participated, and confabulations were evaluated using the Confabulation Battery. Amnestic patients were classified into two groups: confabulating (CP) and nonconfabulating patients (NCP). The CP group was significantly impaired in time orientation, attention, and verbal memory, compared to the NCP group and age-matched healthy controls (HC). Results of the DRM paradigm revealed no significant difference in false memory retrieval induced by critical lures across CP, NCP, and HC groups. Confabulating responses in organic amnesia could be in part induced by disturbance of time consciousness and attention control in severe impairment of verbal memories, and confabulation and false memory could be modulated by different cognitive systems.

Remembering with gains and losses: effects of monetary reward and punishment on successful encoding activation of source memories.

The motivation of getting rewards or avoiding punishments reinforces learning behaviors. Although the neural mechanisms underlying the effect of rewards on episodic memory have been demonstrated, there is little evidence of the effect of punishments on this memory. Our functional magnetic resonance imaging (fMRI) study investigated the effects of monetary rewards and punishments on activation during the encoding of source memories. During encoding, participants memorized words (item) and locations of presented words (source) under 3 conditions (Reward, Punishment, and Control). During retrieval, participants retrieved item and source memories of the words and were rewarded or penalized according to their performance. Source memories encoded with rewards or punishments were remembered better than those without such encoding. fMRI data demonstrated that the ventral tegmental area and substantia nigra and nucleus accumbens activations reflected both the processes of reward and punishment, whereas insular activation increased as a linear function of punishment. Activation in the hippocampus and parahippocampal cortex predicted subsequent retrieval success of source memories. Additionally, correlations between these reward/punishment-related regions and the hippocampus were significant. The successful encoding of source memories could be enhanced by punishments and rewards, and interactions between reward/punishment-related regions and memory-related regions could contribute to memory enhancement by reward and/or punishment.