The formation of episodic autobiographical memory is predicted by mental imagery, self-reference, and anticipated details.

Introduction: Despite the ecological nature of episodic memory (EM) and the importance of consolidation in its functioning, studies tackling both subjects are still scarce. Therefore, the present study aims at establishing predictions of the future of newly encoded information in EM in an ecological paradigm. Methods: Participants recorded two personal events per day with a SenseCam portable camera, for 10 days, and characterized the events with different subjective scales (emotional valence and intensity, self-concept and self-relevance, perspective and anticipated details at a month, mental images…). They then performed a surprise free recall at 5 days and 1 month after encoding. Machine learning algorithms were used to predict the future of events (episodic or forgotten) in memory at 1 month. Results: The best algorithm showed an accuracy of 78%, suggesting that such a prediction is reliably possible. Variables that best differentiated between episodic and forgotten memories at 1 month were mental imagery, self-reference, and prospection (anticipated details) at encoding and the first free recall. Discussion: These results may establish the basis for the development of episodic autobiographical memory during daily experiences.

Mindfulness and false memories: state and dispositional mindfulness does not increase false memories for naturalistic scenes presented in a virtual environment.

Mindfulness attracted increased research interests in the last decade, reporting an overall beneficial effect of this practice on cognitive performances. Nevertheless, recently a possible detrimental impact of mindfulness has been underlined. While the effect of mindfulness on memory remains under-explored, recent studies have observed an increased false-memory susceptibility after mindfulness practice. A possible explanatory mechanism has been suggested, related to the nature of the studied material. For semantically related information, mindfulness would increase false memories; however, the addition of rich perceptual information could prevent this detrimental effect. The present study aimed to verify this hypothesis by testing the impact of state mindfulness induced by a short meditation session, and dispositional mindfulness on the production of false memory for pictorial material presented in a complex virtual environment. We employed a virtual reality version of the Deese-Roediger-McDermott paradigm (DRM), a classical protocol to induce false memories. Contrary to previous studies, we did not observe any effect of mindfulness on false or correct memories (free recall and recognition) after a short mindfulness practice session compared to a control condition. Nonetheless, we found a beneficial effect of mindfulness practice on memory sensitivity. Additionally, we reported a positive and negative effect of dispositional mindfulness on memory outcomes. While the Non-Reactivity facet was associated with overall better memory performances, we observed an association between the Acting with Awareness facet and an increased recollection of lures. We discuss these findings in line with a recent proposal on the link between mindfulness and episodic memory.

The impact of state and dispositional mindfulness on prospective memory: A virtual reality study.

Prospective memory (PM) consists of remembering to perform an action that was previously planned. The recovery and execution of these actions require attentional resources. Mindfulness, as a state or a dispositional trait, has been associated with better attentional abilities while mind wandering is linked with attentional failures. In this study, we investigated the impact of mindfulness on PM. Eighty participants learned 15 cue-action associations. They were, then, asked to recall the actions at certain moments (time-based items) or places (event-based items) during a walk in a virtual town. Before the PM task, participants were randomly assigned to a mindfulness or mind wandering (control condition) session. Dispositional mindfulness was measured via the Five Facets Mindfulness Questionnaire (FFMQ). Although considered as two opposite states, we did not report any difference between the two groups on PM abilities. Nevertheless, the natural tendency to describe one's own sensations (the Describing facet of the FFMQ) predicted time-based performance in both groups. We discuss different hypotheses to explain this finding in light of recent findings on the impact of mind wandering on future oriented cognition. Our main observation is a positive link between the Describing facet and time-based PM performances. We propose that this link could be due to the common association of this mindfulness facets and PM with attentional and interoceptive abilities. Additional studies are needed to explore this hypothesis.

Dispositional mindfulness attenuates the emotional attentional blink.

Emotional stimuli have been shown to automatically hijack attention, hindering the detection of forthcoming targets. Mindfulness is defined as a present moment non-judgemental attentional stance that can be cultivated by meditation practices, but that may present interindividual variability in the general population. The mechanisms underlying modification in emotional reactivity linked to mindfulness are still a matter of debate. In particular, it is not clear whether mindfulness is associated with a diminished emotional response, or with faster recovery. We presented participants with target pictures embedded in a rapid visual presentation stream. The targets could be preceded by negative, neutral or scrambled critical distractors. We showed that dispositional mindfulness, in particular the Non-reacting facet, was related to faster disengagement of attention from emotional stimuli. These results could have implications for mood disorders characterised by an exaggerated attentional bias toward emotional stimuli, such as anxiety and post-traumatic stress disorders.

Meditation and successful aging: can meditative practices counteract age-related cognitive decline?

Life expectancy is constantly increasing in the developed countries due to medical, hygiene and socio-economic advances. Unfortunately, a longer life not always corresponds to a healthier life. Indeed, aging is associated with growing risk factors for illness associated with societal conditions (isolation, maltreatment), and neurodegenerative diseases. Even normal aging is associated with a cognitive decline that can hinder independence and quality of life of elderly. Thus, one major societal challenge is to build policies that support people of all ages to maintain a maximum health and functional capacity throughout their lives. Meditation could be a promising intervention in contrasting the negative effects of aging. Indeed, it has been shown to enhance cognitive efficiency in several domains, such as attention and executive functions in young adults. Nevertheless, whether these effects extend to old participants is still a matter of debate. Few studies have directly investigated this issue, reporting encouraging results in a large panel of cognitive functions, such as: attention, executive functions and memory. However, a final conclusion about the causal role of meditation and the generalization of these results is made difficult due to several methodological limitations. We propose a roadmap for future studies to pass these limitations with the hope that the present work would contribute to the development of the young research field of meditation in gerontology.

The protective role of long-term meditation on the decline of the executive component of attention in aging: a preliminary cross-sectional study.

Life expectancy is constantly increasing. However, a longer life not always corresponds to a healthier life. Indeed, even normal aging is associated with a decline in different cognitive functions. It has been proposed that a central mechanism that could contribute to this widespread cognitive decline is an ineffective inhibitory attentional control. Meditation, to the other hand, has been associated, in young adults, to enhancement of several attentional processes. Nevertheless, attention is not a unitary construct. An influent model proposed the distinction of three subsystems: the alerting (the ability to reach and maintain a vigilance state), the orienting (the capacity of focusing attention on a subset of stimuli), and the conflict resolution or executive component (the ability to resolve conflict or allocate limited resources between competing stimuli). Here, we investigated, employing the Attentional Network Task (ANT), the specific impact of age on these three subcomponents, and the protective role of long-term meditation testing a group of older adults naïve to meditation, a group of age-matched adults with long-term practice of meditation, and a group of young adults with no previous meditation experience. We reported a specific decline of the efficiency of the executive component in elderly that was not observed in age-matched meditators. Our results are encouraging for the investigation of the potential beneficial impact of meditation on other cognitive processes that decline in aging such as memory. Moreover, they could inform geriatric healthcare prevention and intervention strategies, proposing a new approach for cognitive remediation in elderly populations.

Variable motor imagery training induces sleep memory consolidation and transfer improvements.

Motor-skill practice in repetitive or variable orders leads to better within-day acquisition and facilitates retention and transfer, respectively. This practice pattern effect has been robustly found for physical practice, but little is known about its effect after motor imagery (MI) practice. In the present study, we investigated the effect of constant or variable MI practice, and the consolidation following a day-time or a sleep interval. The physical performance was assessed before (pre-test) and after MI training (post-test), as well as after a night or day-time consolidation (retention test). Finally, a transfer test on an unpracticed task was further performed. Results revealed that in all participants, performance increased significantly in the post-test when compared with the pre-test, while only subjects in the variable MI training showed further gains in performance in the retention test following a night of sleep, and exhibited the best transfer of performance to a novel visuomotor sequence. In contrast, subjects in the constant MI training did not show any delayed performance gain following both day and sleep-consolidation. Overall, and for the first time, these findings partially support the practice pattern effect of motor learning with MI, and further highlight a new difference between mental and physical practice, especially on consolidation. To conclude, variable MI practice, rather than constant, seems to be the valuable condition that should be considered in the practical implications of mental training in motor learning and rehabilitation.

Episodic future thinking in semantic dementia: a cognitive and FMRI study.

Semantic dementia (SD) is characterized by gradual loss of semantic memory. While episodic autobiographical memory seems relatively preserved, behavioral studies suggest that episodic future thinking is impaired. We used fMRI to measure brain activity in four SD patients (JPL, EP, LL, EG) while they envisioned future events and remembered personal past events. Twelve healthy elders served as controls. Episodic quality, emotion, mental imagery and level of consciousness (via remember/know judgements) were checked at debriefing. We analyzed the future compared to the past for each patient. All patients presented lateral temporal atrophy, but varied in terms of frontal and anterior hippocampal atrophy. Patient JPL presented atrophy in bilateral superior medial frontal gyri and left anterior hippocampus and was unable to engage in episodic future thinking, despite hyperactivations in frontal and occipital regions. Patient EP presented no atrophy in the anterior hippocampus, but atrophy in bilateral superior medial frontal gyrus and had difficulties to engage in episodic future thinking. Patient LL presented atrophy in left anterior hippocampus, but hyperactivated its right counterpart for future compared to past thinking, permitting her to project efficiently in the future in an episodic way. Patient EG presented no atrophy in the superior medial frontal gyri or anterior hippocampi and was able to engage in episodic future thinking. Altogether, patients' future projections differed depending on the severity and localization of their atrophy. The functional integrity of bilateral superior medial frontal gyri and anterior hippocampus appear crucial for episodic future thinking: atrophy of both structures strongly impairs future projection, while integrity of these structures or hyperactivation of residual tissue normalizes episodic future projection.

Autobiographical memory in semantic dementia: new insights from two patients using fMRI.

Episodic autobiographical memory (EAM) consists of personal events embedded within a specific spatiotemporal context. Patients with semantic dementia (SD) generally show preserved recent EAMs, but a controversy remains concerning their ability to retrieve remote ones. Only one fMRI study examined remote autobiographical memory in SD through a longitudinal case study (Maguire, Kumaran, Hassabis, & Kopelman, 2010). Here, we propose a cross-sectional study to test the hippocampo-neocortical up-regulation hypothesis, through a multimodal approach (gray matter volume, activation, connectivity analyses), directly comparing recent and remote autobiographical memory retrieval and collecting data to asses phenomelogical re-experiencing. EAM retrieval recruits a distributed network of brain regions, notably the hippocampus which is shown to be atrophied in SD, although some studies report no hippocampal atrophy in SD. Using fMRI, we examined recent and remote EAM retrieval in two SD patients with different profiles of hippocampal atrophy, compared to 12 healthy elders (HE). JPL presented severe bilateral hippocampal atrophy, while EP showed sparing of both hippocampi. Behaviourally, JPL was impaired at retrieving EAMs from both life periods and showed poorer use of visual mental imagery than HE, while EP retrieved memories which were as episodic as those of HE for both periods and relied on greater use of visual mental imagery than HE. Neuroimaging results showed that, for JPL, hyperactivations of the residual hippocampal tissue and of frontal, lateral temporal, occipital and parietal cortices did not efficiently compensate his autobiographical memory deficit. EP however presented hyperactivations in similar neocortical regions which appeared to be more efficient in compensating for atrophy elsewhere, since EP's EAM retrieval was preserved. Functional connectivity analyses focusing on the hippocampus showed how the residual hippocampal activity was connected to other brain areas. For JPL, recent autobiographical retrieval was associated with connectivity between the posterior hippocampus and middle occipital gyrus, while for EP, connectivity was detected between the anterior hippocampus and numerous regions (medial temporal, occipital, temporal, frontal, parietal) for both recent and remote periods. These findings suggest that intensification of hippocampal atrophy in SD strongly affects both recent and remote autobiographical recollection. Up-regulation of neocortical regions and functional hippocampal-neocortical connectivity within the autobiographical network may be insufficient to compensate the lifelong episodic memory deficit for patients with extensive hippocampal atrophy.

A neurocognitive model of meditation based on activation likelihood estimation (ALE) meta-analysis.

Meditation comprises a series of practices mainly developed in eastern cultures aiming at controlling emotions and enhancing attentional processes. Several authors proposed to divide meditation techniques in focused attention (FA) and open monitoring (OM) techniques. Previous studies have reported differences in brain networks underlying FA and OM. On the other hand common activations across different meditative practices have been reported. Despite differences between forms of meditation and their underlying cognitive processes, we propose that all meditative techniques could share a central process that would be supported by a core network for meditation since their general common goal is to induce relaxation, regulating attention and developing an attitude of detachment from one's own thoughts. To test this hypothesis, we conducted a quantitative meta-analysis based on activation likelihood estimation (ALE) of 10 neuroimaging studies (91 subjects) on different meditative techniques to evidence the core cortical network subserving meditation. We showed activation of basal ganglia (caudate body), limbic system (enthorinal cortex) and medial prefrontal cortex (MPFC). We discuss the functional role of these structures in meditation and we tentatively propose a neurocognitive model of meditation that could guide future research.

Influence of suggestion in the DRM paradigm: what state of consciousness is associated with false memory?

We assessed the effect of suggestion on the Deese-Roediger-McDermott paradigm and associated it with the Remember-Know-Guess paradigm. Undergraduate students were given either lists of semantically related words or texts containing these words. After the recall task, if participants did not produce the critical lure, the experimenter suggested that the word had been present, using either a question (moderate suggestion) or an assertion (strong suggestion); these conditions were compared to a condition without suggestion. Afterwards, participants took a recognition test. The results showed that strong suggestions lead to more false recognitions than other conditions and the state of consciousness associated with false recognitions tends to be a feeling of knowing rather than remembering, regardless of the verbal version (list or text). Therefore moderate suggestions did not lead to more false recognitions compare to no suggestion. We discuss the impact of suggestion on consciousness associated with false memories.

Autobiographical memory, the sense of recollection and executive functions after severe traumatic brain injury.

Residual disorders of autobiographical memory long after trauma resulting from head injury are rarely assessed, even though they may affect social adjustment and the resumption of daily life. We conducted a thorough study of autobiographical memory in severe traumatic brain injury (TBI) patients, examined at least one year post-trauma. Twenty-five patients were submitted to a novel and controlled autobiographical procedure specially designed to measure episodic memories (i.e., unique, specific in time and space, and detailed) from their entire life span with two kinds of self-remembering experience. The ability to mentally travel back through time and re-experience the source of acquisition, i.e. autonoetic consciousness, was assessed via the "Remember/Know" paradigm and a checking procedure of sense of remembering. Self-perspective in visual imagery, which is also critically involved in episodic recollection, was assessed by the "Field/Observer perspective" paradigm. In addition, the patients underwent a battery of standardized neuropsychological tests to assess episodic and semantic memory, orientation and executive functions. The results showed that the patients, compared with healthy controls, were significantly impaired in recalling episodic autobiographical memories. This impairment was not related to the life period tested or the patients' ages nor the intellectual impairment. Deficits involved disturbances in sense of remembering, visual imagery self-perspective and recollection of spatiotemporal details. Stepwise-regression analyses carried out in the TBI patients revealed a significant relationship between an abnormal sense of remembering and executive dysfunction covering both anterograde and retrograde components. The novel assessment used in this study provides the first detailed evidence of a more fine-grained deficit of autobiographical memory in TBI patients. Indeed, the results suggest that these patients, long after trauma, present autonoetic consciousness and self-perspective disorders, which include sense of identity (the self) as a continuous entity across time, probably related to frontal dysfunction.

Re-experiencing old memories via hippocampus: a PET study of autobiographical memory.

The time-scale of medial temporal lobe (MTL) involvement in storage and retrieval of episodic memory is keenly debated. To test competitive theories of long-term memory consolidation, the present work aimed at characterizing which cerebral regions are involved during retrieval of recent and remote strictly episodic autobiographical memory. Using positron emission tomography (PET), we examined mental retrieval of recent (0-1 year) and remote (5-10 years) autobiographical memories, controlling for the nature of the autobiographical memories (i.e., specificity, state of consciousness, vividness of mental visual imagery, emotion) retrieved during scanning by behavioral measures assessed at debriefing for each event recalled. Cognitive results showed that specificity and emotion did not change with time interval although both autonoetic consciousness and mental image quality were significantly higher for recent memories, suggesting an underlying shift in the phenomenal experience of remembering with the passage of time. The SPM analysis revealed common activations during the recollection of recent and remote memories that involved a widespread but mainly left-sided cerebral network, consistent with previous studies. Subtraction analysis demonstrated that the retrieval of recent (relative to remote) autobiographical memories principally activated the left dorsolateral prefrontal cortex whereas the retrieval of remote (relative to recent) autobiographical memories activated the inferior parietal cortex bilaterally. ROIs analysis revealed more hippocampal activity for remote memories than for recent ones and a preferentially right-sided involvement of the hippocampal responses whatever the remoteness of autobiographical memories. New insights based on higher hippocampal response to the remoteness of episodic autobiographical memories challenge the standard model and are less discrepant with the multiple trace theory.