Wakeful rest benefits before and after encoding in anterograde amnesia.

Objective: Studies have shown that patients with anterograde amnesia forget less episodic information after a delay if encoding is immediately followed by an unfilled period of wakeful rest. This benefit has been attributed to the reduced interference with the consolidation process. However, this account cannot directly explain improved retention in healthy adults resulting from pre-encoding rest. While benefits resulting from pre- and post-encoding rest can be alternatively explained via improved distinctiveness at retrieval, it has yet to be established whether both benefits are observable in amnesics. The aim of the current study was to assess whether amnesic patients showed improved retention of prose material after 10 min following both pre- and post-encoding unfilled intervals of wakeful rest. Method: Twelve patients with anterograde amnesia were recruited. Participants completed four conditions. A short prose passage was aurally presented in each condition. Prose presentation was preceded and followed by a 9-min delay interval. Delay intervals were either filled (spot-the-difference task) or unfilled (wakeful rest). Prose retention was assessed immediately after presentation and after 10 min. Results: Prose retention was consistently better when wakeful rest followed prose encoding in comparison to a condition where an effortful task was encountered both before and after encoding. Conclusions: Post-encoding wakeful rest alone substantially improves retention in amnesic patients. While pre-encoding wakeful rest elicits inconsistent benefits in amnesics, reduced retention following both pre- and post-encoding task engagement suggests that pre-encoding activity may still be relevant. Overall, our findings support consolidation interference explanations of forgetting in anterograde amnesia. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Pure topographical disorientation in novel environments without anterograde amnesia: a case study.

Topographical disorientation (TD) in novel environments is considered to be a part of anterograde amnesia. A 56-year-old woman presented with pure TD only in novel environments following limbic encephalitis. She could not remember directions inside the hospital on weekly outpatient visits; however, her verbal and visual anterograde memories were normal. In the test of learning photographs of scenes, faces, and objects, only her scores for landscapes were worse than those in healthy controls. These findings suggested that her TD specific to landscapes and directions in novel environments was caused by category-specific memory impairment related to bilateral hippocampal and parahippocampal dysfunction.

Brief Motivational Interventions Are Associated with Reductions in Alcohol-Induced Blackouts Among Heavy Drinking College Students.

BACKGROUND: Alcohol-induced blackouts, a form of anterograde amnesia that restricts the encoding of short-term memories into long-term ones, are among the most severe alcohol-related consequences. College students are at high risk of experiencing alcohol-induced blackouts, and there is a need to determine whether alcohol interventions can effectively reduce blackouts in this population. The current study uses data from 3 randomized clinical trials to examine the effect of various intervention approaches on alcohol-induced blackouts. METHODS: Four interventions were compared over 3 studies: (i) a computerized feedback intervention (electronic Check-Up To Go [e-Chug]; Study 1); (ii) a single-session brief motivational intervention (BMI; Study 1); (iii) a BMI plus behavioral economic session focused on increasing substance-free activities (BMI + Substance-Free Activity Session [SFAS]; Studies 2 and 3); and (iv) a BMI plus supplemental Relaxation Training session (BMI + Relaxation Training; Studies 2 and 3). Studies 1 and 3 also included an assessment-only control condition. For each study, participants reported whether they had experienced an alcohol-induced blackout at each time point; binary logistic regressions examined differential likelihood of experiencing an alcohol-induced blackout over time. RESULTS: Neither the single-session BMI nor e-Chug reduced alcohol-induced blackouts over assessment only; however, participants in the BMI + SFAS or BMI + Relaxation Training condition were significantly less likely to experience an alcohol-induced blackout compared to assessment only at 1-month (Wald = 4.77, odds ratio [OR] = 0.53, p = 0.03) and 6-month follow-ups (Wald = 5.72, OR = 0.52, p = 0.02). Study 2 also revealed a larger effect for the BMI + SFAS over the BMI + Relaxation Training condition at 6 months (Wald = 4.11 OR = 0.22, p = 0.043), although this was not replicated in Study 3. The effects for the 2-session BMIs lasted 6 months, at which point maturation effects diminished differences between assessment-only and intervention conditions. CONCLUSIONS: Two sessions of BMI are a substantial enough dose to result in reductions in alcohol-induced blackouts among college student heavy drinkers.

Fractionating controlled memory processes and recall of context in recognition memory: a case report.

Recollection has been described as both a recognition memory judgment requiring cognitive control and the ability to retrieve contextual information about a prior occurrence. At the core of this article is the question whether or not these two subcomponents of recollection are dissociable in amnesia. In three experiments, we explored the influence of exclusion task instructions on performance in a single case (CJ), with the view to understand the relative contributions of control and source memory to recognition memory decisions. First, contrasting findings were obtained between tasks requiring strategic control or source reports. Second, even though CJ displayed some residual source memory relative to the ability to strategically control this information, his source memory capacity was time-limited. Our findings resonate with the novel proposal that recollection draws heavily upon working memory resources, and provide an example of how amnesic patients might utilize residual working memory capacity to solve episodic memory tasks.

The Day That Went Missing: A First-Person Account of Transient Global Amnesia.

In this vivid first-person case history, political reporter Trip Gabriel describes experiencing a classic episode of transient global amnesia. He was near the average target age of 61. Although no cause has been established for the syndrome, as with many other patients his episode appears to have been triggered by contact with water: He was racing a sailboat. While remaining alert and handling complex sailing maneuvers, he suddenly developed amnesia that left him with no recollection of finishing two races, returning to shore, drinking a beer with his friends, needing help finding his car, and not knowing where he was or where he lived. When he did not arrive home on time, his wife called him and quickly recognized his disorientation. She helped him drive himself home and took him to the hospital, where he was evaluated for a stroke. A brain magnetic resonance imaging scan was normal. He started to become aware again about 9 hours after the start of the attack, but was kept in the hospital until his anterograde amnesia resolved fully about 23 hours after onset. He has no memories of 12 hours (from 3 hours before the attack started through the time he regained awareness in the hospital). He was reassured to learn that a recurrence is unlikely. He finds parallels to his experience in the films Memento and Inside Out. A companion article provides expert commentary on the case report (Kirshner HS. 2017. Cogn Behav Neurol. 30:5-7).

Transient Global Amnesia: Commentary on Trip Gabriel's First-Person Account.

This paper comments on a companion article, a first-person account of an episode of transient global amnesia written by New York Times reporter Trip Gabriel (Gabriel T. 2017. Cogn Behav Neurol. 30:1-4). Mr Gabriel describes having no memories of a cold, rainy day that he had spent on a sailboat competing in two races. The episode may have been triggered by his exposure to water. Afterward, the skipper recalled that Mr Gabriel had functioned fine on the boat, although after returning to shore he needed help finding his car. When he told his wife over the phone that he could not remember where he lived, she got him home and to the hospital. The staff excluded stroke and other causes of amnesia. He felt some awareness after about 9 hours, and the episode ended after about 23 hours. He has been left with a permanent memory gap of 12 hours.The commentary on the case outlines the state of knowledge about transient global amnesia. The diagnosis is well established: a witnessed sudden-onset retrograde and anterograde amnesia lasting <24 hours in a fully conscious person who knows who he/she is and has no other cause for amnesia. Triggers include exposure to water, stress, and sexual intercourse. A normal magnetic resonance imaging scan can help with the often challenging differential diagnosis. Apart from the gap in memory, patients recover fully and only 15% to 20% have recurrences. The underlying pathophysiology has not been explained.

Forgetting "Novel" but Not "Dragon": The Role of Age of Acquisition on Intentional and Incidental Forgetting.

Two experiments studied how the age at which words are acquired (Age of Acquisition, AoA) modulates forgetting. Experiment 1 employed the retrieval-practice paradigm to test the effect of AoA on the incidental forgetting that emerges after solving competition during retrieval (i.e., retrieval-induced forgetting, RIF). Standard RIF appeared with late-acquired words, but this effect disappeared with early-acquired words. Experiment 2 evaluated the effect of AoA on intentional forgetting by employing the list-method directed forgetting paradigm. Results showed a standard directed forgetting effect only when the to-be-forgotten words were late-acquired words. These findings point to the prominent role of AoA in forgetting processes.

Fornix and medial temporal lobe lesions lead to comparable deficits in complex visual perception.

Recent research dealing with the structures of the medial temporal lobe (MTL) has shifted away from exclusively investigating memory-related processes and has repeatedly incorporated the investigation of complex visual perception. Several studies have demonstrated that higher level visual tasks can recruit structures like the hippocampus and perirhinal cortex in order to successfully perform complex visual discriminations, leading to a perceptual-mnemonic or representational view of the medial temporal lobe. The current study employed a complex visual discrimination paradigm in two patients suffering from brain lesions with differing locations and origin. Both patients, one with extensive medial temporal lobe lesions (VG) and one with a small lesion of the anterior fornix (HJK), were impaired in complex discriminations while showing otherwise mostly intact cognitive functions. The current data confirmed previous results while also extending the perceptual-mnemonic theory of the MTL to the main output structure of the hippocampus, the fornix.

A rare case of aortic dissection presenting as pure transient global amnesia.

Transient global amnesia (TGA) is a well-described neurological phenomenon. Clinically, it manifests with the sudden onset of a paroxysmal, transient loss of anterograde memory and disorientation but with intact consciousness. Typically, symptoms last for only a few hours. We present an unusual case of aortic dissection presenting with pure TGA in a patient, who had a positive outcome. This is the second case report of a patient with aortic dissection presenting with pure TGA syndrome, but it is the first case in which the patient survived.

Systemic or intra-amygdala infusion of an endocannabinoid CB1 receptor antagonist AM251 blocked propofol-induced anterograde amnesia.

Propofol is well-known for its anterograde amnesic actions. However, a recent experiment showed that propofol can also produce retrograde memory enhancement effects via an interaction with the endocannabinoid CB1 system. Therefore, the authors hypothesized that the regulating effect of propofol on the endocannabinoid CB1 system might also decrease the anterograde amnesic effect of propofol under some conditions, which might be a risk factor for intraoperative awareness. Since, the basolateral amygdala (BLA) has been confirmed to mediate propofol-induced anterograde amnesia and the BLA contains a high concentration of CB1 receptors, the authors investigated whether and how the endocannabinoid system, particularly the CB1 receptor within BLA, influences propofol-induced anterograde amnesia. Male Sprague-Dawley rats trained with inhibitory avoidance (IA) were systematically pre-trained using a memory-impairing dose of propofol (25 mg/kg). Before propofol administration, rats received an intraperitoneal injection of a CB1 receptor antagonist AM251 (1 mg/kg or 2 mg/kg) or a bilateral intra-BLA injection of AM251 (0.6 ng or 6 ng per 0.5 µl). Twenty-four hours after IA training, the IA retention latency was tested. It was found that systemic or intra-BLA injection of a non-regulating dose of AM251 (2 mg/kg or 6 ng per 0.5 µl, respectively) blocked the memory-impairing effect of propofol. These results indicate that the anterograde amnesic effect of propofol is mediated, in part, by activation of the CB1 cannabinoid receptors in the BLA.

Clinical, neuropsychological, and metabolic characteristics of transient epileptic amnesia syndrome.

OBJECTIVE: Transient epileptic amnesia (TEA) is a recently individualized syndrome occurring in adult patients that includes epileptic seizures with amnestic features and interictal memory disturbances. METHODS: We investigated the clinical, neuropsychological, and 18F-FDG positron emission tomography (18F-FDG-PET) features of 30 consecutive cases of TEA in our center. RESULTS: The mean age of onset of amnestic seizures was 59 years. Pure acute amnesia was the only epileptic manifestation in 17% of cases. Interictal electroencephalography (EEG) abnormalities were present in 57% on awake recording and in most patients in whom sleep EEG was performed (96%). Nine of 30 patients showed anterograde memory deficit and six of 30 exhibited mild executive functioning impairment. On the autobiographical memory interview (AMI), patients showed a significant deficit for the recent period of the episodic subscale. Outcome under treatment was favorable in the majority of cases. A significant improvement was noted on recollection of autobiographical memory. 18F-FDG-PET (22 cases) showed positive correlations between left mesial temporal metabolism levels and anterograde and retrograde memory scores. SIGNIFICANCE: TEA is an emerging epileptic syndrome that likely remains misidentified and misdiagnosed. Neurometabolic data support a dysfunction of a hippocampal-neocortical network sustaining episodic memory.

Persistent anterograde amnesia following limbic encephalitis associated with antibodies to the voltage-gated potassium channel complex.

OBJECTIVE: Limbic encephalitis (LE) associated with antibodies to the voltage-gated potassium channel complex (VGKC) is a potentially reversible cause of cognitive impairment. Despite the prominence of cognitive dysfunction in this syndrome, little is known about patients' neuropsychological profile at presentation or their long-term cognitive outcome. METHODS: We used a comprehensive neuropsychological test battery to evaluate cognitive function longitudinally in 19 patients with VGKC-LE. RESULTS: Before immunotherapy, the group had significant impairment of memory, processing speed and executive function, whereas language and perceptual organisation were intact. At follow-up, cognitive impairment was restricted to the memory domain, with processing speed and executive function having returned to the normal range. Residual memory function was predicted by the antibody titre at presentation. CONCLUSIONS: The results show that, despite broad cognitive dysfunction in the acute phase, patients with VGKC-LE often make a substantial recovery with immunotherapy but may be left with permanent anterograde amnesia.

Retrosplenial amnesia without topographic disorientation caused by a lesion in the nondominant hemisphere.

We report the case of a 68-year-old right-handed man who was admitted to our hospital because of sudden onset of headache. On admission, he presented with left homonymous hemianopsia, disorientation, and recent memory disturbance; however, he had normal remote memory and digit span. He was able to recall the room layout of his house and describe the route from the nearest station to his home on a map. However, at the hospital, he sometimes lost his way because of amnesia. Computed tomography (CT) and magnetic resonance imaging revealed a subcortical hematoma in the right occipital forceps and the parietal lobe, involving the cingulate isthmus. Single-photon emission CT imaging showed reduced perfusion not only in the retrosplenial region but also in the right thalamus. These findings suggested that the retrosplenial amnesia might have been caused by the interruption of hippocampal input into the anterior thalamus.

Profound retrograde but absence of anterograde amnesia for cued place learning in rats with hippocampal lesions.

Previous studies in our lab have shown that slight modifications in the spatial reference memory procedure can overcome the deficit in spatial learning typically observed in rats with hippocampal damage. However, it is unknown if memory acquired under such training circumstances is spared after hippocampal lesions. With this aim a four-arm plus-shaped maze and a spatial reference memory paradigm were used, in which the goal arm was doubly marked: by an intramaze cue (a piece of sandpaper positioned on the floor of the arm) and by the extramaze constellation of stimuli around the maze. Experiment 1 replicated previous findings showing that hippocampally damaged rats can learn a place response just as well as the controls when the intramaze cue is present during the training, but they are unable to do so in the absence of the intramaze signal. When the learning procedure was doubly signaled, a transfer test performed 24h after the end of acquisition demonstrated that lesioned rats showed perfect memory for the goal arm when the intramaze cue was removed. Experiment 2 investigated the effect of hippocampal damage 1 day after the learning. Results showed that regardless of the training procedure employed (with or without the intramaze cue), hippocampal lesions produced a profound retrograde amnesia. Thus, although the absence of anterograde amnesia suggests that structures other that the hippocampus can take charge of the acquisition, the presence of retrograde amnesia indicates the critical role of the normal hippocampus in the long-term formation of allocentric information.

The impairment of recollection in functional amnesic states.

INTRODUCTION: Functional amnesia refers to various forms of amnesia, which have no direct organic brain basis. Psychological stress and trauma were etiologically linked to its development across various cultures. METHODS: We have studied several patients with functional amnesia, employing neuropsychological and neuroimaging methods. Herein we provide a review of the current understanding of the phenomenology, neuropsychology and neurobiology of functional amnesia, which we illustrate by reference to five own case descriptions and other cases presented in the literature. RESULTS: Functional amnesia is mostly of retrograde nature and presents in the form of a memory blockade or repression to recollect episodic-autobiographical events, which may cover the whole past life. Sometimes, the recollection impairment is localized to certain time epochs. In comparison to functional retrograde amnesia, functional isolated anterograde amnesia is much rarer and data on its neurobiology are scant. In patients with functional amnesia with pronounced retrograde episodic-autobiographical memory impairments, we identified changes in brain metabolism, above all reductions in the temporo-frontal regions of the right hemisphere. Recently, even subtle structural changes in the white matter of the (right) frontal cortex were described in functional retrograde amnesia by other researchers. CONCLUSIONS: The disruption in recollection in functional amnesia is often accompanied by changes in personality dimensions, pertaining to cognition (self-related processing, theory of mind), autonoetic consciousness and affectivity. This suggests that functional amnesia is a multifaceted condition. We hypothesize that the recollection deficit in functional retrograde amnesia primarily reflects a desynchronization between a frontal lobe system, important for autonoetic consciousness, and a temporo-amygdalar system, important for evaluation and emotions. Despite assumptions that functional amnesia can always be reversed, several cases of functional amnesia were found to follow a chronic course, suggesting a need for longitudinal prospective studies to quantify possible global cognitive deterioration over time and its neural underpinnings.

Using arterial spin labeling perfusion MRI to explore how midazolam produces anterograde amnesia.

While our previous work suggests that the midazolam-induced memory impairment results from the inhibition of new association formation, little is known about the neural correlates underlying these effects beyond the effects of GABA agonists on the brain. We used arterial spin-labeling perfusion MRI to measure cerebral blood flow changes associated with the effects of midazolam on ability to learn arbitrary word-pairs. Using a double-blind, within-subject cross-over design, subjects studied word-pairs for a later cued-recall test while they were scanned. Lists of different word-pairs were studied both before and after an injection of either saline or midazolam. As expected, recall was severely impaired under midazolam. The contrast of MRI signal before and after midazolam administration revealed a decrease in CBF in the left dorsolateral prefrontal cortex (DLPFC), left cingulate gyrus and left posterior cingulate gyrus/precuneus. These effects were observed even after controlling for any effect of injection. A strong correlation between the midazolam-induced changes in neural activity and memory performance was found in the left DLPFC. These findings provide converging evidence that this region plays a critical role in the formation of new associations and that low functioning of this region is associated with anterograde amnesia.