Spontaneous Retrieval Research Articles

The role of cue salience in prospective memory commission errors in nonperformed nonfocal tasks.

Prospective memory (PM) refers to the ability to remember to execute an intention in the future without having a permanent reminder. These intentions can be performed when they are not relevant or become no-longer needed, the so-called "commission errors". The present study aims to understand the effect of cue salience on PM commission errors with unperformed intentions and on the ongoing task performance-associated costs. Through a between-subjects design, eighty-one participants were assigned to 3 conditions: the no-PM condition, which served as control, and the salient and nonsalient conditions, which were asked to perform a lexical decision task and an incomplete nonfocal prospective memory task (i.e. no PM cues were presented). Subsequently, participants were instructed to no longer execute the prospective intention. In the second phase, a lexical decision task occurred again, including irrelevant PM cues, which should not be answered as such. In the salient condition, cues were salient (i.e. presented in red or blue background). In contrast, in the nonsalient condition, PM cues appeared on a black background, as any other stimuli. In the no-PM control condition, participants only performed an LDT. A commission error occurred when the (irrelevant) intention was performed in this second phase. Results showed that more participants performed a commission error in the presence of salient cues, even when PM intentions became irrelevant. Additionally, when cues were not salient, participants took longer to answer the LDT, as reasoned by the spontaneous retrieval theory. These findings are discussed according to the dual-mechanism account.

On second thoughts: Testing the underlying mechanisms of spontaneous future thought

The human capacity to imagine possible future events unintentionally, with minimal cognitive effort, is termed spontaneous future thought (SFT). This paper addresses an important theoretical question for cognitive science: What are the possible cognitive mechanisms underlying such SFT experiences? We contrasted three hypotheses present in the literature: the online construction hypothesis, the recasting hypothesis, and the memories of future thoughts hypothesis. Study 1 (N = 41) used novel subjective ratings which challenged the recasting mechanism: SFTs were mostly rated as dissimilar to autobiographical memories, suggesting they are not simply past experiences ‘recast’ as future events. Study 2 (N = 90) used a novel experimental paradigm, comparing effects of voluntary episodic future constructions and non-personal narratives upon subsequent spontaneous thought sampling. Results suggested that voluntary future constructions remain accessible to spontaneous retrieval, supporting the memories of future thoughts hypothesis. This finding, and other data presented across the two studies, still indicates a role for online construction processes in SFT, but further empirical work is needed to clarify how and when constructive processes are engaged in SFT. Taken together, these two studies represent initial efforts to elucidate the mechanisms underlying SFT, providing the first proof-of-principle that deliberately envisioned future events can reappear, without intention, in consciousness at some later time, and further supporting the dual process account of future thinking. These methods and findings provide a firm basis for subsequent experimental and longitudinal research on SFT.

Chemogenetic activation of histamine neurons promotes retrieval of apparently lost memories

Memory retrieval can become difficult over time, but it is important to note that memories that appear to be forgotten might still be stored in the brain, as shown by their occasional spontaneous retrieval. Histamine in the central nervous system is a promising target for facilitating the recovery of memory retrieval. Our previous study demonstrated that histamine H3 receptor (H3R) inverse agonists/antagonists, activating histamine synthesis and release, enhance activity in the perirhinal cortex and help in retrieving forgotten long-term object recognition memories. However, it is unclear whether enhancing histaminergic activity alone is enough for the recovery of memory retrieval, considering that H3Rs are also located in other neuron types and affect the release of multiple neurotransmitters. In this study, we employed a chemogenetic method to determine whether specifically activating histamine neurons in the tuberomammillary nucleus facilitates memory retrieval. In the novel object recognition test, control mice did not show a preference for objects based on memory 1 week after training, but chemogenetic activation of histamine neurons before testing improved memory retrieval. This selective activation did not affect the locomotor activity or anxiety-related behavior. Administering an H2R antagonist directly into the perirhinal cortex inhibited the recovery of memory retrieval induced by the activation of histamine neurons. Furthermore, we utilized the Barnes maze test to investigate whether chemogenetic activation of histamine neurons influences the retrieval of forgotten spatial memories. Control mice explored all the holes in the maze equally 1 week after training, whereas mice with chemogenetically activated histamine neurons spent more time around the target hole. These findings indicate that chemogenetic activation of histamine neurons in the tuberomammillary nucleus can promote retrieval of seemingly forgotten object recognition and spatial memories.

13 Verbal Memory and Learning Strategies in an Autistic Sample Using the CVLT

Objective:The present study aims to better understand learning strategies and difficulties in autistic youth. Previous studies have found that autistic youth have difficulties with executive function skills and poorer performance in memory and learning tasks, especially those that require spontaneous retrieval of information compared to memory tasks that provide external retrieval cues. Additionally, it has been theorized that autistic youth employ a serial approach rather than a semantic approach to learning. The current study hypothesized that the autistic sample will have (a) significant difficulties in learning and memory, (b) employ a serial approach more frequently and a semantic approach less frequently than the CVLT normative sample, and (c) will benefit significantly when provided with external retrieval cues.Participants and Methods:Archival data from a mixed clinical and research database were examined for this study. Participants include 740 autistic individuals between the ages of 5.50 and 24.3 (M = 10.90, SD = 2.98). The sample consisted of 22.2% girls and 34.0% Black, Indigenous, and people of color (BIPOC). All individuals had a FSIQ > 70 (M = 99.91, SD = 16.09) and were clinically diagnosed with autism using DSM-IV-TR or DSM-V criteria by a clinician at an autism diagnostic center. Participants completed the age-appropriate California Verbal Learning Test (CVLT, Delis et al. 1987) which is a neuropsychological measure that examines verbal memory and learning. One-sample t-tests were used to examine the sample's verbal memory abilities and their learning strategies. A paired sample t-test was used to evaluate the sample's performance before and after an external retrieval cue was given.Results:Results from the one-sample t-tests indicate that the autistic sample performed worse than the CVLT normative data with a large effect size (t(739)= -9.440, p <.001, Cohen's d = 1.292). Secondly, the autistic sample was less likely to use a semantic learning approach (t(739) = -1.841, p = .033, Cohen's d = 1.234), but not more likely to use a serial approach (t(739)=-.040, p=.484) compared to the normative sample. Lastly, the paired sample t-test results show that the sample performed significantly better after receiving the external retrieval cue (t(739)=-2.570, p=.005, Cohen's d = .770).Conclusions:The data supported the first hypothesis; autistic individuals have increased difficulties with learning and verbal memory. However, the data only partially support the second hypothesis. The sample was less likely to use a semantic approach to learning but was not more likely to use serial learning. This finding is opposed to the Weak Central Coherence (WCC) theory, which suggests that autistic individuals are more likely to have detail-oriented, bottom-up cognitive thinking styles, consistent with a serial learning strategy. Lastly, data showed improvement when autistic individuals received a retrieval cue. This result supports the Task Support Hypothesis (TSH) and indicates that autistic individuals benefit from cues for memory recall, particularly those that capitalize on their areas of strength. This study did not use a control group and is limited in ethno-racial diversity; therefore, these are preliminarily findings that require further replication.

Parietal cortical alpha/beta suppression during prospective memory retrieval.

Prospective memory (PM) impairment is among the most frequent memory complaints, yet little is known about the underlying neural mechanisms. PM for a planned intention may be achieved through strategic monitoring of the environment for cues, involving ongoing attentional processes, or through spontaneous retrieval. We hypothesized that parietal spectral power modulation accompanies prospectively encoded intention retrieval, irrespective of PM retrieval approach. A cognitively engaging arithmetic-based ongoing task (OGT) was employed to encourage spontaneous retrieval, with a focal, internally generated PM cue to eliminate OGT/PM trial differentiation based on perceptual or conceptual PM cue features. Two PM repetition frequencies were used to vary the extent of strategic monitoring. We observed a transient parietal alpha/beta spectral power reduction directly preceding the response, which was distinguishable on a single trial basis, as revealed by an OGT/PM trial classification rate exceeding 70% using linear discriminant analysis. The alpha/beta idling rhythm reflects cortical inhibition. A disengagement of task-relevant neural assemblies from this rhythm, reflected in alpha/beta power reduction, is deemed to increase information content, facilitate information integration, and enable engagement of neural assemblies in task-related cortical networks. The observed power reduction is consistent with the Dual Pathways model, where PM strategies converge at the PM retrieval stage.

Investigating the relationship between periodontitis and specific memory processes in the search for cognitive markers of Alzheimer’s disease risk

The spontaneous retrieval deficit (SRD) hypothesis argues that individuals in the preclinical stages of Alzheimer’s disease (AD) are particularly impaired in spontaneous retrieval, which manifests in reduced mind-wandering. Our main purpose was to provide novel evidence to support the SRD hypothesis by investigating, for the first time, the relationship between mind-wandering and periodontitis, the latter being the risk factor for AD. The second objective was to address the lack of deeper understanding of the relationship between oral health and specific cognitive abilities by investigating whether periodontitis would be primarily associated with memory. Sixty community-dwelling dementia-free older adults completed neuropsychological tests that focused on various cognitive abilities and a computerised task, during which mind-wandering was evaluated. Periodontal health was assessed subjectively, and through an oral examination by a qualified dentist that focused on visible periodontitis-related changes in gingival tissues and the number of periodontitis bacteria. In line with our predictions, objective and subjective symptoms of poorer periodontal health were associated with less mind-wandering, providing further support for the SRD hypothesis. Again in line with predictions, poorer periodontal health was associated with worse episodic memory, with no relationship between periodontitis and the measure targeting various cognitive abilities, from which memory was excluded.

Can Feedback Boost Prospective Memory Performance?

Abstract Prospective memory (PM) refers to remembering to perform intended actions in the future. Although there is ample evidence supporting the benefits of feedback for memory, it is unclear whether these benefits can be extended to the field of PM. Therefore, 2 experiments were conducted to investigate the role of feedback in PM. Experiment 1 compared PM performance in 3 feedback conditions (no feedback, ongoing task feedback, PM feedback). Experiment 2 further examined the effects of feedback valence (positive feedback or negative feedback) on PM performance under different task loads (task variability). Results suggested that providing feedback improved PM performance. The fluctuation of costs to PM during different feedback phases reflected the dynamically strategic monitoring for PM, especially in the PM feedback condition. Additionally, a significant PM performance difference between positive feedback and negative feedback in the invariable condition was observed. More importantly, only under the variable condition did the fluctuation of costs to PM task with positive feedback increase from the baseline phase to the second feedback phase. This finding indicated positive feedback promoted PM performance accompanied by more cognitive resources needed for strategic monitoring, and negative feedback boosted PM performance, relying on spontaneous retrieval independent of cognitive resources. Altogether, feedback boosted PM, and this benefit varies depending on the type of feedback and task variability. These results reflected a flexible change in PM processes and supported the dynamic multiprocess view of PM.

Prospective Memory Function Predicts Future Cognitive Decline and Incident Dementia.

This study aimed to test whether prospective memory (PM) was an early cognitive marker of future cognitive decline and incident dementia using longitudinal data spanning 8years from the Sydney Memory and Ageing Study. At baseline, 121 participants aged 72-91years were tested in PM using a validated PM task, Virtual Week, which included time- and event-based tasks presented with varying regularity. Responses were scored "Correct" if completed accurately and "Missed" if the target was not remembered at any time. Measures of cognition were taken at baseline and 2-year intervals over 8years. Dementia diagnoses were made by expert consensus panels using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria. Linear mixed models and Cox proportional hazards regression models were used to analyze the data, controlling for potential confounds. Both decreased PM accuracy and missed PM responses were associated with rate of cognitive decline measured by Mini-Mental State Examination over 8years and global cognitive decline over 4years. Risk of incident dementia increased with poorer baseline PM ability and missed responses. These effects remained significant after controlling for baseline cognition and were strongest for event-based and regular PM tasks. PM is a sensitive early marker of future cognitive decline and risk of incident dementia. PM tasks supported by spontaneous retrieval (event-based) and those with lower retrospective memory demands (regular tasks) function as particularly sensitive predictors. In other words, deficits in performing less effortful PM tasks best predicted cognitive decline. These findings may encourage clinicians to incorporate PM tasks in clinical assessments.

Children below two years of age spontaneously recall an event with Magical Teddies

It is typically challenging for two-year-olds to recollect memories upon demand. However, we know from diary studies that children spontaneously, ‘out of the blue’, recall memories about their past. Spontaneous retrieval may be less cognitively demanding because it is less dependent on prefrontal cortex and mainly relies on associative processes. However, spontaneous retrieval remains to be examined experimentally in children younger than age 3. We examined spontaneous retrieval by means of both verbal and nonverbal measures in fifty-two 23-months-old children in a controlled lab-setting. When returning to a distinct lab setting after one week, more than 44 % of the children had spontaneous recollections of a unique one-off Magical Teddies Event. This finding demonstrates that spontaneous recall of past events is present very early in childhood, which has implications for the understanding of memory development in young children.

Deficits in spontaneous and stimulus-dependent retrieval as an early sign of abnormal aging

Research on early cognitive markers of Alzheimer’s disease is primarily focused on episodic memory tests that involve deliberate retrieval. Our purpose was to provide clear evidence to support a novel Spontaneous Retrieval Deficit hypothesis, which predicts that people at pre-clinical stages of dementia, including those with amnestic Mild Cognitive Impairment (aMCI), are particularly impaired on tasks based on spontaneous retrieval. We compared 27 aMCI individuals and 27 healthy controls on mind-wandering while performing a task during which there were exposed to either highly meaningful or unmeaningful pictures. The substantial reduction in mind-wandering among individuals with aMCI was found with exposure to highly meaningful stimuli, but not to unmeaningful pictures, and it was most pronounced for past-oriented thoughts, i.e., involuntary autobiographical memories. Those findings provide strong support for this novel hypothesis, and show that it is the spontaneous, but bottom-up and cue-driven processes, for which meaningful environmental stimuli are crucial, that are very promising early markers of the disease.

Dissociating sub-processes of aftereffects of completed intentions and costs to the ongoing task in prospective memory: A mouse-tracking approach

In the present study, we used mouse tracking to investigate two processes underlying prospective memory (PM) retrieval: First, we aimed to explore to what extent spontaneous retrieval of already completed PM intentions is supported by reflexive-associative and discrepancy-plus-search processes. Second, we aimed to disentangle whether costs to an ongoing task during the pursuit of a PM intention are associated with presumably resource-demanding monitoring processes or with a presumably resource-sparing strategic delay of ongoing-task responses. Our third aim was to explore the interaction of processes underlying costs to the ongoing task and processes of spontaneous retrieval. Our analyses replicated response-time patterns from previous studies indicating aftereffects of completed intentions and costs to ongoing-task performance, as well as increased aftereffects while pursuing a PM intention. Notably, based on our mouse-tracking analyses, we argue that aftereffects of completed intentions are best explained by a reflexive initiation of an already completed intention. If the completed intention is not performed in its entirety (i.e., no commission error), the reflexive initiation of the completed intention is followed by a subsequent movement correction that most likely represents a time-consuming response-verification process. Regarding performance costs in the ongoing task, our analyses suggest that actively pursuing a PM intention most likely leads to a strategic delay of ongoing activities. Lastly, we found that pursuing a novel PM task after intention completion exacerbated orienting responses to all deviant stimuli, exacerbated the readiness to initiate the completed intention reflexively, and substantially prolonged the response-verification process following this reflexive intention retrieval.

Distinct environmental cues trigger spontaneous recall of past events in 3- and 4-year-old children even after long delays.

Verbally reported long-term memory for past events typically improves with age. However, such findings are based exclusively on studies, where children are directly asked to recall. The present study showed that when 3- (n=113, 59 girls) and 4-year-olds (n=113, 62 girls), predominantly White, were brought back to a distinct laboratory-setting after either 1-, 4.5-, or 13-weeks, children-regardless of age and delay-spontaneously recalled the distinct event experienced at their first visit (all Cohen's ds>1.00). Meanwhile, the oldest children outperformed the youngest when being asked directly to retrieve the event ( ). These findings suggest that spontaneous retrieval facilitated by distinct environmental cues provides a short-cut to young children's event memories.

Dementia-Free Older Adults with Subjective Cognitive Impairment Show Lower Mood and No Deficits of Spontaneous Memory Retrieval.

The aim of the present study was to investigate whether spontaneous retrieval deficits could be found in individuals with Subjective Cognitive Impairment (SCI). The sample consisted of 52 participants over 65 years of age (mean age = 76.00; SD = 7.48) with 11 males. We asked 26 individuals with SCI and 26 individuals without SCI to perform a prospective memory (PM) task that had previously demonstrated spontaneous retrieval deficits in individuals with Mild Cognitive Impairment. The results did not demonstrate the expected differences in a PM task based on spontaneous retrieval [t(50) = -.05; p = .964, d = .01]. However, participants' mood did predict their subjective memory complaints (β = -.51; p < .001) and their subjective assessment of their future memory performance (r = -.38; p < .01). The findings are in line with numerous studies which have shown that SCI is more related to mood disturbance than to objective cognitive functioning.

Moving forward: Exploring the role of interference on prospective memory deactivation

Recent prospective memory (PM) studies have shown that an intention may be erroneously executed despite no-longer-needed (i.e., commission errors), especially under demanding ongoing activities. In the current study, we examined whether PM deactivation benefits from a retroactive interference mechanism. For this, we set up a procedure in which participants are first asked to perform a PM task which is critically declared finished afterwards. Next, they encoded a new and dissimilar PM intention to accomplish later (Experiment 1) or performed filler tasks with increased working memory difficulty levels (Experiment 2). Lastly, all participants encountered several (but irrelevant) PM cues. Together, our findings provide evidence that the efficiency of the deactivation process can be modulated by encoding novel and dissimilar PM tasks and by the type of processing after intention completion. These findings are discussed in terms of strategic or spontaneous retrieval processes and linked to a retroactive interference mechanism which helps to overwrite or deteriorate the old-PM task representation.

Episodic-semantic interactions in spontaneous thought.

The distinction between a semantic memory system, encompassing conceptual knowledge, and an episodic memory system, characterized by specific episodes, is one of the most important theoretical proposals in cognitive science. However, the distinction between systems has rarely been discussed in relation to spontaneous thought that comes to mind with reduced cognitive effort and intentionality. In this review, we propose that the growing research on spontaneous thought can contribute to current discussions on the interaction between the episodic and semantic systems. Firstly, we review research that shows that, as in deliberate retrieval, spontaneous thoughts are influenced by both episodic and semantic memory, as reflected by the mix of semantic and episodic elements in descriptions of spontaneous thoughts, as well as semantic priming effects in spontaneous thoughts. We integrate the current evidence based on the interplay between cues and semantic activation. Namely, we suggest that cues are key to access episodic memory and modulate the frequency of spontaneous thought, while semantic activation modulates the content of spontaneous thought. Secondly, we propose that spontaneous retrieval is a privileged area to explore the question of functional independence between systems, because it provides direct access to the episodic system. We review the evidence for spontaneous thought in semantic dementia, which suggests that episodic and semantic systems are functionally independent. We acknowledge the scarcity of evidence and suggest that future studies examine the contents of spontaneous thought descriptions and their neural correlates to test the functional relationship and inform the interaction between episodic and semantic systems.

Real-time assessment of looking time at central environmental cues for spontaneous recall in 35-month-olds

Evidence supporting the assumption that spontaneous recall of previously experienced events is triggered by distinct, environmental cues has hitherto exclusively been based on post-hoc reasoning and not on direct, in vivo examination. Using a novel experimental paradigm, we present the first real-time analyses of 35-month-old’s looking time as spontaneous retrieval unfolds. Twenty-nine middle-to-higher SES children (out of 114 participating) spontaneously recalled having taken part in either a Teddy or a Game event (adjacently placed in two unique boxes) when returning to the lab one week later. Naïve coders registered looking time towards the two dissimilar looking boxes 10 s preceding spontaneous recall. The children having spontaneous recollections looked reliably longer at their Target box (relative to Foil), whereas this was not the case for a group of matched (by gender, event, and CDI) controls producing no spontaneous memories. The findings are important for understanding how visual attention facilitates spontaneous recall.

Sustained and Transient Processes in Event-based Prospective Memory in Adolescence and Adulthood.

Prospective memory (PM) refers to the cognitive processes associated with remembering to perform an intended action after a delay. Varying the salience of PM cues while keeping the intended response constant, we investigated the extent to which participants relied on strategic monitoring, through sustained, top-down control, or on spontaneous retrieval via transient bottom-up processes. There is mixed evidence regarding developmental improvements in event-based PM performance after the age of 13 years. We compared PM performance and associated sustained and transient neural correlates in 28 typically developing adolescents (12-17 years old) and 19 adults (23-30 years old). Lower PM cue salience associated with slower ongoing task (OT) RTs, reflected by increased μ ex-Gaussian parameter, and sustained increases in frontoparietal activation during OT blocks, both thought to reflect greater proactive control supporting cue monitoring. Behavioral and neural correlates of PM trials were not specifically modulated by cue salience, revealing little difference in reactive control between conditions. The effect of cue salience was similar across age groups, suggesting that adolescents are able to adapt proactive control engagement to PM task demands. Exploratory analyses showed that younger, but not older, adolescents were less accurate and slower in PM trials relative to OT trials than adults and showed greater transient activation in PM trials in an occipito-temporal cluster. These results provide evidence of both mature and still maturing aspects of cognitive processes associated with implementation of an intention after a delay during early adolescence.

Long-term memory of real-world episodes is independent of recency effects: magic tricks as ecological tasks

How episodic memories decay is an unresolved question in cognitive neuroscience. The role of short-term mechanisms regarding the decay of episodic memories is circumscribed to set the maximum recall from which a monotonic decay occurs. However, this sequential view from the short to the long-term is not compulsory, as short-term dependent memory gains (like recency effects when memorizing a list of elements; serial-position effects) may not be translated into long-term memory differences. Moreover, producing memorable events in the laboratory faces important challenges, such as recreating realistic conditions with elevated recall, or avoiding spontaneous retrievals during memory retention (sociocultural hooks). The current study proposes the use of magic to enhance the study of memory. We designed a sequence of magic tricks performed live on stage to evaluate the interaction between memory decay and serial-position effects of those tricks. The audience was asked to freely recall the tricks at four different timepoints: just after the show, 10 days, 1.5 months and 4.5 months. We discovered serial-position differences after the show that were no longer present later on, suggesting that short-term memory gains do not translate into the long-term. Illustrating the power of naturalistic stimuli to study long-term memory while interrogating the interaction between short-term and long-term mechanisms, this work is, to our knowledge, the first scientific study of the memorability of magic tricks.

The effects of aging and an episodic specificity induction on spontaneous task-unrelated thought.

When voluntarily describing their past or future, older adults typically show a reduction in episodic specificity (e.g., including fewer details reflecting a specific event, time and/or place). However, aging has less impact on other types of tasks that place minimal demands on strategic retrieval such as spontaneous thoughts. In the current study, we investigated age-related differences in the episodic specificity of spontaneous thoughts using experimenter-based coding of thought descriptions. Additionally, we tested whether an episodic specificity induction, which increases episodic detail during deliberate retrieval of events in young and older adults, has the same effect under spontaneous retrieval. Twenty-four younger and 24 healthy older adults performed two counterbalanced sessions including a video, the episodic specificity or control induction, and a vigilance task. In the episodic specificity induction, participants recalled the details of the video while in the control they solved math exercises. The impact of this manipulation on the episodic specificity of spontaneous thoughts was assessed in the subsequent vigilance task, in which participants were randomly stopped to describe their thoughts and classify them as deliberate/spontaneous. We found no differences in episodic specificity between age groups in spontaneous thoughts, supporting the prediction that automatic retrieval attenuates the episodic specificity decrease in aging. The lack of age differences was present regardless of the induction, showing no interactions. For the induction, we also found no main effect, indicating that automatic retrieval bypasses event construction and accesses pre-stored events. Overall, our evidence suggests that spontaneous retrieval is a promising strategy to support episodic specificity in aging.

Age Affects Strategic But Not Spontaneous Recall in 35- and 46-Month-old Children

ABSTRACT It is well documented that young children have difficulties with strategically remembering past events. Recent evidence on event memory in 35- and 46-month-old children suggests that strategic retrieval (yes/no questions) improves with age, whereas spontaneous retrieval is relatively unaffected by age. We here replicate and extend those findings (N = 124): First, a novel free (strategic) recall test was added to improve ecological validity. Second, the free recall procedure allowed us to make direct comparisons between spontaneous and free strategic recall relative to age. The free recall test revealed similar results in the standard yes/no questions (older children outperformed younger). The direct comparison between spontaneous and free recall revealed a reliable interaction between age and retrieval mode: While the children’s age did not affect spontaneous recall, the 46-month-olds outperformed the 35-month-olds on the free recall test. The results add to the accumulating evidence that spontaneous recall of events is an early developmental achievement.