The role of semantic memory in prospective memory and episodic future thinking: new insights from a case of semantic dementia.

Prospective memory (PM), the ability to remember to execute planned actions, and episodic future thinking (EFT), the ability to imagine future personal events, are two core aspects of future-oriented cognition. The present study aimed for the first time at examining the role of semantic memory loss in PM and EFT in a single case patient (SL) at the early stage of semantic dementia.First, we investigated various types of PM as well as episodic memory of new events using a validated ecological assessment via virtual reality. Second, we examined EFT using a temporally extended version of the TEMPau task, which measures episodic aspects of remembering the past and imagining the future taking temporal distance into account.Patient SL was deficient in semantically linked event-based PM and was unable to provide any EFT for the most distant period but was preserved in other types of PM and near and intermediate EFT.These findings provide new evidence on the role of semantic memory in PM depending on the type of intention and in EFT depending on the temporal distance mirroring autobiographical memory. Finally, they point out a specific link between PM and near EFT in future-oriented cognition.

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.

Temporosylvian arachnoid cysts in children. Part 2: Postoperative neuropsychological and clinical improvement.

OBJECTIVE: The authors' objective was to study clinical, imaging, and neuropsychological changes in children who underwent surgery for a temporal arachnoid cyst (TAC). METHODS: Thirty-four children were prospectively assessed similarly at diagnosis and postoperatively (mean 14 months) with clinic visits, images, cognitive tests, and parental questionnaires on mood/behavior and executive functions. The scores were compared pre- and postoperatively for the entire cohort and individually. The scores of 25 children were also compared with a control group of 23 healthy age-matched children. Parents were administered an outcome questionnaire on average 4 years postoperatively. RESULTS: The 34 children selected for surgery had signs of raised intracranial pressure (74%) and/or selective neuropsychological disorders presumably linked to cyst location (learning difficulties in 65%, cognitive difficulties in 56%, and mood/behavior difficulties in 47%). The majority of patients had a convex cyst (85%) and underwent microsurgical fenestration (85%). The TAC volume decreased ≥ 50% for 59% of children. On the Wechsler Intelligence Scale, the entire cohort significantly improved on Full Scale IQ and verbal and perceptual nonverbal indexes. Individually, nearly half of the children (47%) highly increased their scores (≥ 15 points) on at least one IQ index and 26% on at least two indexes. Language, working memory, episodic memory, and executive functions were also significantly improved. Improvements were more pronounced in patients with a preoperative heterogeneous profile with isolated lower scores and a left-sided cyst. Parental questionnaires showed reduction in anxiety, aggressiveness, social problems, and daily life executive disorders. Preschool-aged children improved significantly in language and verbal IQ, as did middle/high school-aged children in many domains. Individual analyses revealed improvement in 76% of cases. Cognitive scores were lower for patients preoperatively than for controls and were no longer significantly different postoperatively in verbal fluency, visual memory, and working memory. Four years later, 97% of parents described an improvement in their child, correlated with cognitive improvements. CONCLUSIONS: Among children with a TAC, some have no clinical signs or neuropsychological difficulties, and others may show signs of raised intracranial pressure and/or specific neuropsychological disorders that impact daily life and require significant and long-lasting rehabilitation. In these cases, consideration may be given to surgical decompression. It is interesting to note that 76% of this surgically treated cohort improved regardless of the child's age, particularly in patients with selective disorders and an impact on daily life. However, a larger number of children will need to be investigated before the true benefit of such treatment can be known.

Intermittent theta burst stimulation over left BA10 enhances virtual reality-based prospective memory in healthy aged subjects.

Prospective memory (PM) refers to a complex cognitive ability that underpins the delayed execution of previously formulated intentions. PM performance declines early in normal aging and this process is accentuated in Alzheimer's disease. The left frontopolar cortex (BA10) has been consistently assigned a major role in PM functioning, but whether it can be noninvasively modulated to enhance PM performance in aged people has not been addressed so far. Here, we investigated the effects of modulating left BA10 by means of theta burst stimulation (TBS), using either excitatory (intermittent TBS), inhibitory (continuous TBS) or control (vertex) TBS in healthy aged subjects. The behavioral effects were assessed using a reliable and ecological virtual reality PM task that included both event- and time-based retrievals. As compared with vertex stimulation, event-based PM performance significantly improved after excitatory stimulation, whereas inhibitory stimulation had no significant effect. Additionally, and across the different types of stimulation, performance for congruent links between the event-based PM cue and the action to be performed was significantly better as compared with incongruent links. In conclusion, intermittent TBS might provide a relevant interventional strategy to counteract the decline of cognitive functions and memory abilities in normal aging.

Functional independence within the self-memory system: new insights from two cases of developmental amnesia.

Neuropsychological and neuroimaging data suggest that the self-memory system can be fractionated into three functionally independent systems processing personal information at several levels of abstraction, including episodic memories of one's life (episodic autobiographical memory, EAM), semantic knowledge of facts about one's life (semantic autobiographical memory, SAM), and semantic knowledge of one's personality [conceptual self, (CS)]. Through the study of two developmental amnesic patients suffering of neonatal brain injuries, we explored how the different facets of the self-memory system develop when growing up with bilateral hippocampal atrophy. Neuropsychological evaluations showed that both of them suffered from dramatic episodic learning disability with no sense of recollection (Remember/Know procedure), whereas their semantic abilities differed, being completely preserved (Valentine) or not (Jocelyn). Magnetic resonance imaging, including quantitative volumetric measurements of the hippocampus and adjacent (entorhinal, perirhinal, and temporopolar) cortex, showed severe bilateral atrophy of the hippocampus in both patients, with additional atrophy of adjacent cortex in Jocelyn. Exploration of EAM and SAM according to lifetime periods covering the entire lifespan (TEMPAu task, Piolino et al., 2009) showed that both patients had marked impairments in EAM, as they lacked specificity, details and sense of recollection, whereas SAM was completely normal in Valentine, but impaired in Jocelyn. Finally, measures of patients' CS (Tennessee Self-Concept Scale, Fitts and Warren, 1996), checked by their mothers, were generally within normal range, but both patients showed a more positive self-concept than healthy controls. These two new cases support a modular account of the medial-temporal lobe with episodic memory and recollection depending on the hippocampus, and semantic memory and familiarity on adjacent cortices. Furthermore, they highlight developmental episodic and semantic functional independence within the self-memory system suggesting that SAM and CS may be acquired without episodic memories.

[What about the mental time travel and age-related effects?]. / Quid du voyage mental dans le temps subjectif et effets de l'âge ?

According to Tulving, episodic memory allows humans to travel mentally through subjective time into either the past or the future, this ability being at the origin of adaptation, organization and planning of future behavior. The main aim of this review is to present a state of art of episodic mental time travel and a lifespan perspective from children to elderly people. We examine the numerous similarities between remembering the past and envisioning the future which have been highlighted in cognitive, neuroimaging, and neuropsychological studies. We also present studies that have given evidence that remembering the past and imagining the future differ somewhat. We focus on demonstrating that hippocampal dysfunction is associated with disturbances in the recall of episodic autobiographical details in past memories, but also in the imagining of episodic detailed future events. More specifically, we discuss that the future seems to involve higher semantic processes mediated by the inferior frontal and lateral temporal gyri. We propose that the study of mental travel in personal time could be undertaken in line with the distinction between the memory of (episodic) experiences and (semantic) personal knowledge of one's life, which constitutes a major part of the self and constraints what we have been, what we are now, and what we might yet become.