Disturbed memory and amnesia related to intensive care

Patients, when admitted to an intensive care unit (ICU), have one thing in common: their illness is life-threatening. Patients may remain on ICU in a critical condition, needing support with their breathing, circulation, and/or kidneys for varying lengths of time, from days to weeks. During that time the patients will receive sedative and analgesic drugs to ensure compliance with artificial ventilation. Patients recovering from critical illness frequently have little or no recall of their period in ICU, or remember nightmare, hallucinations, or paranoid delusions. The nature, extent and reason for these difficulties, have been under-reported and consequently our purpose was to conduct a review of memory problems experienced by ICU patients. A systematic literature review of computer databases (Medline, PsycLit, and CINAHL) identified 25 relevant papers. In addition, other relevant articles were obtained, citation lists and associated articles retrieved. Due to lack of research on processes underlying memory problems in ICU patients all articles that introduced an insight into possible mechanisms were included in the review. There seem to be two possible processes contributing to memory problems in ICU patients. First the illness and treatment may have a general dampening effect on memory. Delirium and sleep disturbance are both common in ICU patients. Delirium can result in a profound amnesia for the period of confusion. Sleep deprivation exacerbates the confusional state. Slow wave sleep is important for the consolidation of episodic memories. Treatment administered to patients in ICU can have effects on memory. Opiates, benzodiazepines, sedative drugs such as propofol, adrenaline, and corticosteroids can all influence memory. In addition, the withdrawal of drugs, such as benzodiazepines, can cause profound withdrawal reactions, which may contribute to delirium. Second, we hypothesise that there is a process that affects memory negatively for external events but enhances memory for internal events. The physical constraints and social isolation experienced by ICU patients and the life-threatening nature of the illness may increase the experience of hypnagogic hallucinations. Attentional shift during hypnagogic images from external stimuli to internally generated images would explain why ICU patients have such poor recall of external ICU events, but can clearly remember hallucinations and nightmares. Patients describe these memories as being very vivid and this is explored in terms of flashbulb memory formation. The absence of memories for real events on ICU can result in ICU patients remembering paranoid delusions of staff trying to kill them, with little information to reject these vivid memories as unreal. This has implications for patients' future psychological health.     

Missing referents, psychotic symptoms, and discriminating the internal from the externalized

The communicative efficacy of the speech of schizophrenia patients is compromised by the presence of references for which there are no referents. There is evidence that this kind of error is positively associated with the genetic substrate of schizophrenia. The present study was an effort to identify a cognitive process source of these errors by looking at their association with performance on an internal source memory task assessing the ability to remember what one has said out loud versus only thought. Their relationship to psychotic symptoms also was examined. A sample of 110 schizophrenic/schizoaffective outpatients, and 23 nonpsychiatric controls provided 10-min speech samples and completed a battery of memory tests. Patients' symptoms also were rated for severity. Patients performed more poorly than controls on the memory tests, and their speech contained much more frequent references without referents. Frequency of missing referents was associated with scores on the test of internal source memory, even after scores on tests of immediate memory, working memory, and external source memory were regressed out. Missing referents were also related to severity of hallucinations and delusions, and internal source memory performance was related to hallucinations. The findings of this study support the idea that missing referents, hallucinations, and delusions have some common process underpinnings. Impairment in internal source memory appears to be one such process.     

Clinical and non-clinical hallucinations are similarly associated with source memory errors in a visual memory task

Hallucinations have been found to be associated with various types of source memory failure in both schizophrenia patients and hallucination-prone healthy individuals. We investigated the associations of clinical and non-clinical hallucinations with source memory errors in a visual memory task that involved the remembering of picture presentation context. 59 schizophrenia patients and 61 healthy individuals took part in the study. Pictures were presented either at different locations or in association with different visual stimuli. The participants were required afterwards to recognize the target pictures among distractors, and then to remember their spatial location or the visual stimulus that was associated with them. Liberal response bias in picture recognition was associated with hallucination proneness and auditory-verbal hallucinations in subsamples of participants with significant non-clinical or clinical hallucinations. After controlling for overall memory performance, failure to remember the spatial location of the pictures was associated with visual hallucinations in male patients; failure to remember the associated visual stimulus was related to auditory-verbal hallucinations in female patients and to hallucination proneness in healthy women. The findings suggest that both clinical and non-clinical hallucinations are associated with loss of contextual information relative to the acquisition of events.     

Kafka,paranoic doubles and the brain: hypnagogic vs. hyper-reflexive models of disrupted self in neuropsychiatric disorders and anomalous conscious states

Kafka's writings are frequently interpreted as representing the historical period of modernism in which he was writing. Little attention has been paid, however, to the possibility that his writings may reflect neural mechanisms in the processing of self during hypnagogic (i.e., between waking and sleep) states. Kafka suffered from dream-like, hypnagogic hallucinations during a sleep-deprived state while writing. This paper discusses reasons (phenomenological and neurobiological) why the self projects an imaginary double (autoscopy) in its spontaneous hallucinations and how Kafka's writings help to elucidate the underlying cognitive and neural mechanisms. I further discuss how the proposed mechanisms may be relevant to understanding paranoid delusions in schizophrenia. Literature documents and records cognitive and neural processes of self with an intimacy that may be otherwise unavailable to neuroscience. To elucidate this approach, I contrast it with the apparently popularizing view that the symptoms of schizophrenia result from what has been called an operative (i.e., pre-reflective) hyper-reflexivity. The latter approach claims that pre-reflective self-awareness (diminished in schizophrenia) pervades all conscious experience (however, in a manner that remains unverifiable for both phenomenological and experimental methods). This contribution argues the opposite: the "self" informs our hypnagogic imagery precisely to the extent that we are not self-aware.     

Delusions and hallucinations of cocaine abusers and paranoid schizophrenics: a comparative study

We compared delusions and hallucinations of 100 cocaine abusers and 100 paranoid schizophrenic subjects admitted to an East Texas state psychiatric hospital. Subjects in both groups feared that individuals or organized groups might harm them in some way, but delusions of the paranoid schizophrenic subjects were more often bizarre than those of the cocaine abuse subjects. "Cocaine bugs" (parasitosis) were more often found in the cocaine abuse subjects. Command hallucinations were found in both groups, but the commands of the schizophrenic group more often related to harming or killing others. Cocaine abusers had a greater frequency of visual hallucinations (47 to 7), distinguished by shadows, flashing lights ("snow lights"), objects moving and bugs crawling on the arm. Finally, the most distinguishing characteristics were identity delusions, possession delusions, grandiose delusions (other than identities and possessions), and delusions that their families were imposters (Capgras Syndrome) reported by paranoid schizophrenics. No such delusions were reported by the cocaine abusers.     

Imagery and psychotic symptoms: a preliminary investigation

Recent cognitive accounts of psychotic symptoms have suggested that processes involved in the maintenance of emotional disorders may also be implicated in the maintenance of hallucinations and delusions, and particularly emphasise the appraisals of such symptoms as important. Imaginal appraisals have been identified in emotional disorders, and many studies have reported spontaneously occurring images in patients with anxiety disorders. Such images appear to be linked to affect, beliefs and memories. This study examined the occurrence of imagery, using a semi-structured interview, in 35 patients who were experiencing hallucinations and/or delusions and receiving cognitive therapy. The majority of patients (74.3%) reported images, and most of these were recurrent and associated with affect, beliefs and memories. Common themes included images about feared catastrophes associated with paranoia, traumatic memories, and images about the perceived source or content of voices. The theoretical and clinical implications of these findings are discussed and directions for further research considered.     

Effects of stress hormones on traumatic memory formation and the development of posttraumatic stress disorder in critically ill patients

A majority of patients after intensive care treatment report traumatic memories from their stay in the intensive care unit (ICU). Traumatic memories can be associated with the development of posttraumatic stress disorder (PTSD) in a subpopulation of these patients. In contrast to other patient populations at risk for PTSD, patients in the ICU often receive exogenously administered stress hormones like epinephrine, norepinephrine, or cortisol for medical reasons and are extensively monitored. ICU patients therefore represent a suitable population for studying the relationship between stress hormones, traumatic memories, and the development of PTSD. Studies in long-term survivors of ICU treatment demonstrated a clear and vivid recall of different categories of traumatic memory such as nightmares, anxiety, respiratory distress, or pain with little or no recall of factual events. The number of categories of traumatic memory recalled increased with the total administered dosages of stress hormones (both catecholamines and cortisol), and the evaluation of these categories at different time points after discharge from the ICU showed better memory consolidation with higher dosages of stress hormones administered. However, the administration of stress doses of cortisol to critically ill patients resulted in more complex findings as it caused a significant reduction in PTSD symptoms measured after recovery. This effect can possibly be explained by a differential influence of cortisol on memory. Increased serum cortisol levels not only result in consolidation of emotional memory but are also known to cause a temporary impairment in memory retrieval which appears to be independent of glucocorticoid effects on memory formation. Disrupting retrieval mechanisms with glucocorticoids during critical illness may therefore act protectively against the development of PTSD by preventing recall of traumatic memories. Our findings indicate that stress hormones influence the development of PTSD through complex and simultaneous interactions on memory formation and retrieval. Our studies also demonstrate that animal models of aversive learning are useful in analyzing and predicting clinical findings in critically ill humans.     

Distinguishing between memory illusions and actual memories using phenomenological measurements and explicit warnings

Previous research has demonstrated that the false memory effect is robust and that false memories are essentially indistinguishable from memories for events that actually occurred. The current study used several techniques intended to eliminate false memories (source monitoring decisions, confidence ratings, remember/know judgments, and explicit warnings). A robust false memory effect was found in each experiment. However, participants were able to differentiate false memories and actual memories when using specific phenomenological tasks. The current findings provide insight into basic human memory processes.     

History of Religious Delusions and Psychosocial Functioning Among Mexican Patients with Paranoid Schizophrenia

The association between global functionality and religiosity among patients from developing and predominantly Catholic countries warrants attention. To compare religiosity and psychosocial functioning in Mexican schizophrenia patients with and without a history of religious delusions, seventy-four patients with paranoid schizophrenia were recruited. Patients with a history of religious delusions had more psychiatric hospitalizations and poorer psychosocial functioning compared with those without a history of religious delusions. No differences emerged between groups in the total scores of religiosity scales. A history of religious delusions rather than religiosity itself may have an influence on psychosocial functioning among Mexican patients with schizophrenia.     

Observing the transformation of experience into memory

The ability to remember one's past depends on neural processing set in motion at the moment each event is experienced. Memory formation can be observed by segregating neural responses according to whether or not each event is recalled or recognized on a subsequent memory test. Subsequent memory analyses have been performed with various neural measures, including brain potentials extracted from intracranial and extracranial electroencephalographic recordings, and hemodynamic responses from functional magnetic resonance imaging. Neural responses can predict which events, and which aspects of those events, will be subsequently remembered or forgotten, thereby elucidating the neurocognitive processes that establish durable episodic memories.     

A few seemingly harmless routes to a false memory

Since the invention of photography we have learned to rely on photos to help us remember significant moments in our lives. We have come to believe that photographs are accurate and valuable records of events that—years down the track—we may not be able to remember. In this paper, we review recent research demonstrating that photographs can also help us to “remember” events that never really happened. We trace the development of the leading false autobiographical memory paradigm, and we then describe research on the power of both fake narrative stories and fake photographs to cultivate false memories.     

False memories of fabricated political events

In the largest false memory study to date, 5,269 participants were asked about their memories for three true and one of five fabricated political events. Each fabricated event was accompanied by a photographic image purportedly depicting that event. Approximately half the participants falsely remembered that the false event happened, with 27% remembering that they saw the events happen on the news. Political orientation appeared to influence the formation of false memories, with conservatives more likely to falsely remember seeing Barack Obama shaking hands with the president of Iran, and liberals more likely to remember George W. Bush vacationing with a baseball celebrity during the Hurricane Katrina disaster. A follow-up study supported the explanation that events are more easily implanted in memory when they are congruent with a person's preexisting attitudes and evaluations, in part because attitude-congruent false events promote feelings of recognition and familiarity, which in turn interfere with source attributions.     

Episodic recollection in animals: “If it walks like a duck and quacks like a duck…”

In humans, episodic memory is most commonly defined as the subjective experience of recollection, presenting a major challenge to the identification of episodic memory in animals. Here we take the position that episodic memory also has several other distinctive qualities that can be assessed objectively in animals, as well as humans, and the examination of these properties provides insights into underlying mechanisms of episodic memory. We focus on recent evidence accumulated in this laboratory indicating that recognition in rats involves a threshold retrieval process, similar to that observed in human episodic recall. Also, rats can remember the temporal order of unique events, characteristic of the replay of vivid episodic memories in humans. Furthermore, rats combine elements of “when” and “where” events occur, as well as the flow of events within a memory, to distinguish memories that share overlapping features, also characteristic of human episodic memory. Finally, all of these capacities are dependent on the hippocampus, which also plays a critical role in human episodic memory. This combination of findings strongly suggests that animals have the same fundamental information processing functions that underlie episodic recall in humans.     

Intrusive memories and depression in cancer patients

Matched samples of depressed and nondepressed cancer patients were interviewed about past life events, particularly experiences of death and illness. They identified and described any spontaneous intrusive visual memories they had experienced in the past week corresponding to these events. About one quarter reported such memories and, as predicted, the majority of intrusive memories concerned illness, injury and death. The mean levels of intrusion and avoidance were equivalent to patients with post-traumatic stress disorder. Consistent with prediction, depressed patients reported significantly more intrusive memories than controls, and described the memories as typically beginning with or being exacerbated by the onset of depression. Greater numbers of intrusive memories were associated with more maladaptive coping, and greater avoidance with deficits in autobiographical memory functioning.     

Event plausibility does not determine children's false memories

In this paper we ask how the plausibility of an event affects the likelihood that children will develop a false memory for it. Over three interviews 6-year-olds and 10-year-olds were shown two true photos and two false photos-a plausible and less plausible event-and reported what they could remember about those events. Children also rated their confidence that the events happened, and how much they could remember about the events. By the final interview, within each age group, there were no differences in children's confidence ratings for the two false events. In addition, within each age group, the rate of false memories was the same for each event; across age groups, younger children developed more false memories than older children.     

Exploring self-defining memories in schizophrenia

Previous studies have shown that patients with schizophrenia are impaired in recalling specific events from their personal past. However, the relationship between autobiographical memory impairments and disturbance of the sense of identity in schizophrenia has not been investigated in detail. In this study the authors investigated schizophrenic patients’ ability to recall self-defining memories; that is, memories that play an important role in building and maintaining the self-concept. Results showed that patients recalled as many specific self-defining memories as healthy participants. However, patients with schizophrenia exhibited an abnormal reminiscence bump and reported different types of thematic content (i.e., they recalled less memories about past achievements and more memories regarding hospitalisation and stigmatisation of illness). Furthermore, the findings suggest that impairments in extracting meaning from personal memories could represent a core disturbance of autobiographical memory in patients with schizophrenia.     

Psychological processes and paranoia: implications for forensic behavioural science

Paranoid delusions have recently become the focus of empirical research. In this article, we review studies of the psychological mechanisms that might be involved in paranoid thinking and discuss their implications for forensic behaviour science. Paranoia has not been consistently associated with any specific neuropsychological abnormality. However, evidence supports three broad types of mechanism that might be involved in delusional thinking in general and paranoia in particular: anomalous perceptual experiences, abnormal reasoning, and motivational factors. There is some evidence that paranoia may be associated with hearing loss, and good evidence that paranoid patients attend excessively to threatening information. Although general reasoning ability seems to be unaffected, there is strong evidence that a jumping- to-conclusions style of reasoning about data is implicated in delusions in general, but less consistent evidence specifically linking paranoia to impaired theory of mind. Finally, there appears to be a strong association between paranoia and negative self-esteem, and some evidence that attempts to protect self-esteem by attributing negative events to external causes are implicated. Some of these processes have recently been implicated in violent behaviour, and they therefore have the potential to explain the apparent association between paranoid delusions and offending.     

Event plausibility does not determine children's false memories

In this paper we ask how the plausibility of an event affects the likelihood that children will develop a false memory for it. Over three interviews 6-year-olds and 10-year-olds were shown two true photos and two false photos—a plausible and less plausible event—and reported what they could remember about those events. Children also rated their confidence that the events happened, and how much they could remember about the events. By the final interview, within each age group, there were no differences in children's confidence ratings for the two false events. In addition, within each age group, the rate of false memories was the same for each event; across age groups, younger children developed more false memories than older children.     

Field and observer viewpoint in remember-know memories of personal childhood events

This experiment examined the viewpoint and other phenomenal characteristics of childhood memories based on both personal recollections and self-knowledge. Participants were asked to provide examples of remember, know, and uncertain memories, and to rate each memory on a number of dimensions. Remembered events were generally viewed from a field perspective, while known-about events were generally viewed from an observer perspective. In line with earlier research, remembered events received the highest ratings for sensory and contextual detail, emotional content, and memory accuracy, while known-about events were given the lowest ratings. The results are discussed with reference to their possible implications for memory recovery or enhancement techniques that ask people to adopt a different viewpoint. Consideration is given as to whether a switch to a field perspective might encourage the acceptance of suggested details or events.     

Field and observer viewpoint in remember-know memories of personal childhood events

This experiment examined the viewpoint and other phenomenal characteristics of childhood memories based on both personal recollections and self-knowledge. Participants were asked to provide examples of remember, know, and uncertain memories, and to rate each memory on a number of dimensions. Remembered events were generally viewed from a field perspective, while known-about events were generally viewed from an observer perspective. In line with earlier research, remembered events received the highest ratings for sensory and contextual detail, emotional content, and memory accuracy, while known-about events were given the lowest ratings. The results are discussed with reference to their possible implications for memory recovery or enhancement techniques that ask people to adopt a different viewpoint. Consideration is given as to whether a switch to a field perspective might encourage the acceptance of suggested details or events.