Imagine Yourself Dancing Waltz: The Effect of Imagination on Memory in Alzheimer's Disease.

BACKGROUND: Self-imagination refers to a mnemonic strategy of imagining oneself at a scene related to a cue. OBJECTIVE: We tested the effect of self-imagination on memory recall in Alzheimer's disease (AD) Methods: Individuals with AD and healthy controls were invited to perform two conditions. In the control (i.e., semantic elaboration) condition, participants were asked to define to which semantic category (e.g., dance) words (e.g., waltz) belong. However, in a self-imagining condition, participants were asked to imagine themselves in a scene related to the stimuli (e.g., dancing waltz). Both conditions were followed by two free memory tests with two different intervals (20 seconds vs. 20 minutes). RESULTS: Analysis showed a beneficial effect of self-imagination for the 20-second but not for the 20- minute recall in AD participants and controls. CONCLUSION: Clinicians can incorporate our findings when assessing, especially when trying to rehabilitate, episodic memory in AD.

The recombined memory: associative inference in Alzheimer's disease.

BACKGROUND: Associative inference refers to an adaptive ability that allows flexible recombination of information acquired during previous experiences to make new connections that they have not directly experienced. This cognitive ability has been widely associated with the hippocampus. AIMS: We investigated associative inference in patients with Alzheimer's disease and control participants. METHODS: The task has two phases. In the training phase, participants learned to encode overlapping pairs of objects (AB + BC). In the test phase, participants were invited to retrieve previously see associations (i.e., AB, BC) as well as novel associations between the previously exposed objects (i.e., AC). In addition, we test the relationship between associative inference and cognitive flexibility. RESULTS: Analysis demonstrated lower associative inference in AD patients than in control participants. Interestingly, performance on the associative inference task was significantly correlated with low performance on a cognitive flexibility task in AD patients. DISCUSSION: Our findings demonstrate a compromise of the ability to flexibly combine new representations from prior memories in AD, which is likely related to the hippocampal dysfunction in AD.

False Memories in Individuals With Stabilized Schizophrenia.

This study aimed to examine the false memories in individuals with stabilized schizophrenia. Using the Deese, Roediger, and McDermott (DRM) task, schizophrenia patients and matched healthy controls had to recall words from each DRM list. Following the presentation of the DRM lists, the participants performed a recognition task. Neuropsychological tests were also administered. Results demonstrated that patients with schizophrenia recalled and recognized significantly fewer studied words than the healthy participants. This failure in retrieval is likely to result from a lack of encoding strategies. Results also showed that a stabilized schizophrenic pathology neither increased nor reduced false memories. Patients and controls showed high levels of false memories. Signal detection analyses revealed that patients discarded the critical word as not having been studied, relying on a lax decision criterion (based on familiarity, best guess or chance). Although false memories fell within the normal range for both groups, in individuals with schizophrenia they probably result from deficient encoding processes. Nevertheless, correlational analyses did not show which cognitive deficits contribute to false memories in schizophrenia.

"Remember to take your medication": Prospective memory in Korsakoff's syndrome.

BACKGROUND: While event-based prospective memory refers to enacting intending action in response to a specific event or cue ("e.g., When I tell you there are 10 minutes left, please give me this stopwatch"), time-based prospective memory refers to enacting intending action in relation to a specific time ("In 10 minutes time, please ask me for a pencil"). Relative to event-based prospective memory, little is known about time-based prospective memory in Korsakoff's syndrome (KS). METHOD: We used behavioral tasks to investigate event- and time-based prospective memory as well as episodic memory and executive function in patients with KS and control participants. RESULTS: Analysis demonstrated lower event- and time-based prospective memory in patients with KS than in control participants. Interestingly, we found lower time-based than event-based prospective memory in patients with KS. Further, significant correlations were observed between prospective memory and episodic memory and executive function in the patients. CONCLUSIONS: Prospective memory is important for everyday life tasks, and failures of prospective memory can endanger patients' safety. One clinical implication of our findings is the importance of including an evaluation of prospective memory in cognitive evaluation of KS.

The fabricated past: intentionally fabricated autobiographical memories in Alzheimer's disease.

OBJECTIVE: We investigated intentionally fabricated autobiographical memories in Alzheimer's Disease (AD). METHOD: We invited AD patients and control participants to construct real events as well as fabricated events describing fictitious personal events that occurred in the past. RESULTS: Results demonstrated slower retrieval time for intentionally fabricated memories than for real ones in both AD patients and control participants. The analysis also showed similar vividness for intentionally fabricated memories and real ones in AD patients but lower vividness for intentionally fabricated memories than for real ones in control participants. CONCLUSIONS: The slow retrieval time of intentionally fabricated memories may be attributed to the cognitive effort required to retrieve elements from autobiographical memory and edit them to construct a new memory. We suggest that the vividness of intentionally fabricated memories observed in AD may induce confusion with real memories. In addition to the experimental approach of our study, we offer a theoretical rationale for intentionally fabricated autobiographical memories by situating them in the wider context of different facets of false memories in AD (e.g. confabulations, source monitoring errors).

The eyes of the past: larger pupil size for autobiographical memories retrieved from field perspective.

BACKGROUND: Visual perspective during memory retrieval has mainly been evaluated with methodologies based on introspection and subjective reports. The current study investigates whether visual perspective can be evaluated with a physiological measurement: pupil dilation. METHODS: While their pupil diameter was measured with an eye-tracker, forty-five participants retrieved one memory from a field perspective (i.e., as viewed through our own eyes) and one memory from an observer perspective (i.e., as viewed from a spectator's standpoint). After retrieval, participants rated the emotional intensity of the memories. RESULTS: Analysis demonstrated larger pupils during the retrieval of memories from a field perspective and higher emotional intensity for memories retrieved from a field perspective. DISCUSSION: The larger pupils for memories recalled from a field perspective could, however, not be attributed to their higher emotional intensity. These findings suggest that pupil dilation could be used as a physiological assessment of visual perspective during memory retrieval.

Effects of visual imagery on false memories in DRM and misinformation paradigms.

This study examined the possibility that moderators of false memories in the Deese-Roediger-McDermott (DRM) paradigm affect the occurrence of false memories in the misinformation paradigm. More precisely, the purpose was to determine to what extent an imaging instruction modulates false memories in the DRM and misinformation paradigms. A sample of young adults was assigned to the DRM or the misinformation tasks, either in control conditions or in conditions including an imaging instruction. Findings revealed that an imaging instruction decreases false memories in DRM whereas there is no evidence about imaging effects in the misinformation task. These observations tally with previous studies, reporting a weak or no correlation between false memories in these paradigms, and are discussed in the light of current theories.

The image of memory: relationship between autobiographical memory and mental imagery in Korsakoff syndrome.

We evaluated the relationship between autobiographical memory and mental imagery in Korsakoff syndrome (KS). We invited patients with KS and control participants to retrieve personal events and to perform measures of visual imagery (Taller/Wilder task), and spatial imagery (Clock Angles task). On the Taller/Wilder task, participants had to generate a mental image of an object presented as a word and determine whether the object was taller than it was wide. On the Clock Angles task, participants had to imagine the angle created by the hands on a clock set to a certain time and determine whether that angle was <90°. Analyses showed impaired spatial imagery and autobiographical memory but intact visual imagery in KS. Analyses also demonstrated significant correlations between visual imagery, spatial imagery and autobiographical memory in patients with KS and control participants. Our findings demonstrate that autobiographical retrieval in KS is associated with the ability to retrieve (visual imagery) and manipulate mental images (spatial imagery).

Repeated recall on source misattribution in Alzheimer's disease.

We assessed the effect of repeated recall on item memory and source monitoring in Alzheimer's disease (AD). AD patients and controls were instructed to either look at or imagine items. They then had to either retrieve the items without indicating their source in three consecutive free recall tests, or to remember the source of the retrieved items in three consecutive source tests. Results showed a significant increase in item memory across all three free recall tests and all three source monitoring tests in control participants, but not in AD patients. More source misattributions were observed in AD patients and controls in the third source test than in the first and second tests. The absence of beneficial effect of repeated recall on item memory in AD patients may be attributed to compromise in memory consolidation processes, while the increase in source misattributions due to repetitions may be attributed to the inflation effect.

Stochastic nonlinear model for somatic cell population dynamics during ovarian follicle activation.

In mammals, female germ cells are sheltered within somatic structures called ovarian follicles, which remain in a quiescent state until they get activated, all along reproductive life. We investigate the sequence of somatic cell events occurring just after follicle activation, starting by the awakening of precursor somatic cells, and their transformation into proliferative cells. We introduce a nonlinear stochastic model accounting for the joint dynamics of the two cell types, and allowing us to investigate the potential impact of a feedback from proliferative cells onto precursor cells. To tackle the key issue of whether cell proliferation is concomitant or posterior to cell awakening, we assess both the time needed for all precursor cells to awake, and the corresponding increase in the total cell number with respect to the initial cell number. Using the probabilistic theory of first passage times, we design a numerical scheme based on a rigorous finite state projection and coupling techniques to compute the mean extinction time and the cell number at extinction time. We find that the feedback term clearly lowers the number of proliferative cells at the extinction time. We calibrate the model parameters using an exact likelihood approach. We carry out a comprehensive comparison between the initial model and a series of submodels, which helps to select the critical cell events taking place during activation, and suggests that awakening is prominent over proliferation.

The thin line between reality and imagination: The imagination inflation effect in Korsakoff's syndrome.

OBJECTIVE: The imagination inflation effect, which is a form of memory distortion, occurs when imagining an event that never happened may increase the tendency to falsely remember that it really occurred. We investigated this effect in Korsakoff's syndrome. METHOD: Our procedures consisted of 2 sessions and a recognition test. In Session 1, patients with Korsakoff's syndrome and controls listened to statements of actions (e.g., "hold the pen"), enacted the actions, or imagined performing the actions. In Session 2, participants imagined statements of actions from Session 1 as well as new statements of actions once or 3 times. On the recognition test, participants had to decide whether statements of actions were or were not enacted during Session 1. RESULTS: Analysis demonstrated that imagining performing the actions increased the tendency of both patients with Korsakoff's syndrome and controls to falsely recall the actions as having been enacted. DISCUSSION: Our findings suggest that patients with Korsakoff's syndrome are prone to the imagination inflation effect, an effect that can be attributed to difficulties with source monitoring. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Analysis and numerical simulation of an inverse problem for a structured cell population dynamics model.

In this work, we study a multiscale inverse problem associated with a multi-type model for age structured cell populations. In the single type case, the model is a McKendrick-VonFoerster like equation with a mitosis-dependent death rate and potential migration at birth. In the multi-type case, the migration term results in an unidirectional motion from one type to the next, so that the boundary condition at age 0 contains an additional extrinsic contribution from the previous type. We consider the inverse problem of retrieving microscopic information (the division rates and migration proportions) from the knowledge of macroscopic information (total number of cells per layer), given the initial condition. We first show the well-posedness of the inverse problem in the single type case using a Fredholm integral equation derived from the characteristic curves, and we use a constructive approach to obtain the lattice division rate, considering either a synchronized or non-synchronized initial condition. We take advantage of the unidirectional motion to decompose the whole model into nested submodels corresponding to self-renewal equations with an additional extrinstic contribution. We again derive a Fredholm integral equation for each submodel and deduce the well-posedness of the multi-type inverse problem. In each situation, we illustrate numerically our theoretical results.

Visual imagery: The past and future as seen by patients with Alzheimer's disease.

We investigated visual imagery for past and future thinking in Alzheimer's Disease (AD). We invited AD patients and controls to retrieve past events and to imagine future events. Participants also provided a "Field" response if they see the event through their own eyes, or an "Observer" response if they see themselves in the scene as a spectator would. Less "Field" and more "Observer" responses were observed in AD participants than in controls during past and future thinking, suggesting a diminished ability to mentally visualize past and future events in AD. Results also demonstrated significant positive correlations between the production of "Field" responses and specificity during past and future thinking, suggesting a relationship between the ability to mentally visualize past and future events and autobiographical overgenerality in AD.

The effects of emotional content on source monitoring in fibromyalgia patients.

Source confusion refers to a person's failure to distinguish whether an event has been actually seen or simply imagined. Nevertheless, prior research has demonstrated a reduction of source confusion for negative arousing information. According to the emotional-congruence effect, this emotional benefit is likely observed in patients suffering from chronic pain. This hypothesis was tested on 15 patients suffering of fibromyalgia syndrome (FMS) and 15 healthy women. In a source-monitoring task, participants had to decide whether positive, negative, and neutral words were imagined or seen with a picture. The results showed recognition deficits and more source confusion for FMS patients compared to controls. Contrary to the hypothesis of negativity bias in fibromyalgia, patients exhibited enhanced recognition for both positive and negative words. Moreover, they showed better source memory for the imagined items than for those seen with a picture. Overall, these results indicate that FMS affects episodic memory.

Effect of Expertise on Boundary Extension in Approach Sequences.

In a constantly changing environment, one of the conditions for adaptation is based on the visual system's ability to realize predictions. In this context, a question that arises is the evolution of the processes allowing anticipation with regard to the acquisition of knowledge relative to specific situations. We sought to study this question by focusing on boundary extension, the tendency to overestimate the scope of a previously perceived scene. We presented to novice, beginner, and expert car drivers road scenes in the form of approach sequences constituting very briefly displayed photographs (i.e., 250 milliseconds each), in order to determine the effect of expertise at an early stage of scene perception. After three presentations, participants had to judge whether a fourth photograph was the same, closer up, or further away than the third one. When experts and beginners showed a classical boundary extension effect, novices presented no directional memory distortion. Different hypotheses are discussed.

[French norms of imagery for pictures, for concrete and abstract words]. / Normes françaises d'imagerie pour des dessins, des noms concrets et des noms abstraits.

This paper deals with French norms for mental image versus picture agreement for 138 pictures and the imagery value for 138 concrete words and 69 abstract words. The pictures were selected from Snodgrass et Vanderwart's norms (1980). The concrete words correspond to the dominant naming response to the pictorial stimuli. The abstract words were taken from verbal associative norms published by Ferrand (2001). The norms were established according to two variables: 1) mental image vs. picture agreement, and 2) imagery value of words. Three other variables were controlled: 1) picture naming agreement; 2) familiarity of objects referred to in the pictures and the concrete words, and 3) subjective verbal frequency of words. The originality of this work is to provide French imagery norms for the three kinds of stimuli usually compared in research on dual coding. Moreover, these studies focus on figurative and verbal stimuli variations in visual imagery processes.