Conscious Memory Research Articles

The effect of emotional stress on involuntary and voluntary conscious memories

Clinical theories of post-traumatic stress disorder often claim that intrusive (involuntary) memories favour emotionally stressful material and that these memories come with more sensory imagery and emotional reliving compared to voluntary memories. However, these assumptions have not been verified experimentally. Here we obtained recordings of emotional reactions to aversive pictures at the time of encoding, as well as records of involuntary and voluntary memories of these pictures in a subsequent diary study. A comparison of individual ratings, obtained during encoding, of pictures recalled involuntarily and voluntarily showed that emotional stress at encoding increased overall accessibility, independent of whether recall was voluntary or involuntary. However at the time of recall, voluntary memories scored higher on narrative content and on measures of imagery. The findings are compatible with research on emotion and memory in general, but challenge clinical claims of differential involuntary versus voluntary access to emotionally stressful events.

The effect of curcumin on ethanol induced changes in suprachiasmatic nucleus (SCN) and pineal.

(1) Circadian clocks have been localized to discrete sites within the nervous system of several organisms and in mammals to the suprachiasmatic nucleus (SCN) in the anterior hypothalamus. The SCN controls and regulates the production and discharge of melatonin (hormonal message of darkness) from the pineal gland via a multisynaptic efferent pathway. The nocturnal rise in melatonin production from serotonin results due to an increased activity of serotonin N-acetyl transferase (NAT). (2) The complex interaction between alcohol and biological clock need to be understood as alcoholism results in various clock linked neuronal disorders especially loss of memory and amnesia like state of consciousness, sleep disorders, insomnia, dementia etc. (3) Serotonin, 5-Hydroxy-tryptamine (5-HT) plays an important role in mediating alcohol's effects on the brain. Understanding the impact of alcohol consumption on circadian system is a pre-requisite to help in treatment of alcohol induced neurological disorders. We, therefore, studied the effect of ethanol drinking and ethanol withdrawal on daily rhythms of serotonin and its metabolite, 5-hydroxy-indole acetic acid (5-HIAA) in SCN and Pineal of adult male Wistar rats maintained under light-dark (LD, 12:12) conditions. (4) Curcumin is well known for its protective properties such as antioxidant, anti-carcinogenic, anti-viral and anti-infectious etc. Hence, we studied the effect of curcumin on ethanol induced changes on 5-HT and 5-HIAA levels and rhythms in SCN and Pineal. (5) Ethanol withdrawal could not restore either rhythmicity or phases or levels of 5-HT and 5-HIAA. Curcumin administration resulted in partial restoration of daily 5-HT/5-HIAA ratio, with phase shifts in SCN and in Pineal. Understanding the impact of alcohol consumption on circadian system and the role of herbal medication on alcohol withdrawal will help in treatment of alcohol induced neurological disorders.

Neural mechanisms of voluntary and involuntary recall: A PET study

Neuropsychological and neuroimaging studies on episodic memory retrieval have primarily focused on volitional memory tasks. However, some conscious memories arise involuntarily, i.e. without a strategic retrieval attempt, yet little is known about the neural network underlying involuntary episodic memory. The aim of this study was to determine whether voluntary and involuntary recall are mediated by separate cortical networks. We used positron emission tomography (PET) to measure changes in regional cerebral blood flow (rCBF) in 12 healthy subjects during voluntary and involuntary cued recall of pictures and a control condition with no episodic memory requirements. Involuntary recall was elicited by using an incidental memory task. Compared to the control condition, voluntary and involuntary recall were both associated with significant regional cerebral blood flow (rCBF) increases in posterior cingulate gyrus (PCG; BA 23), left precuneus (BA 7), and right parahippocampal gyrus (BA 35/36). In addition, rCBF in right dorsolateral prefrontal cortex (PFC; BA 8/9) and left precuneus (BA 7) was significantly larger during voluntary compared to involuntary recall, while rCBF was enhanced in left dorsolateral PFC (BA 9) during involuntary recall. The findings corroborate an association of the right PFC with a strategic component of episodic memory retrieval. Moreover, they show for the first time that it is possible to activate the medial temporal lobe, the PCG, and the precuneus, regions normally associated with retrieval success, without this strategic element. The relatively higher activity in precuneus during voluntary compared to involuntary recall suggests that activity in this region co-varies not only with retrieval success but also with retrieval intentionality.

The effects of conscious and unconscious memory in temporal lobe damage

目的 探讨颞叶损伤对意识、无意识记忆的影响.方法 选取16例左颞叶损伤患者,12例右颞叶损伤患者和20例正常人进行对照研究,采用Jacoby的加工分离程序,对意识性提取成绩和无意识提取成绩进行分离,同时选用两种图形材料(具体图形和抽象图形)对知觉启动和语义启动进行分离.结果 意识性提取多重比较结果显示,按α=0.05的水准,在具体图形编码条件下,左颞叶损伤组的贡献率(0.475±0.247)低于正常组(0.825±0.130),差异有显著性(F=4.610,P=0.035);右颞叶损伤组与正常组之间差异无显著性.在抽象图形编码条件下,3组之间的差异无显著性.无意识提取多重比较结果显示,按α=0.05的水准,在具体图形编码条件下,右颞叶损伤组的贡献率(0.105±0.148)低于正常组(0.850±0.188),差异有显著性(F=14.858,P=0.001),左颞叶损伤组与正常组之间的差异无显著性;在抽象图形编码条件下,3组之间的差异无显著性.结论 左颞叶损伤导致具体图形的意识性提取受损,右颞叶损伤导致无意识记忆的语义启动受损,颞叶损伤对知觉启动无影响。

Experience-Dependent Eye Movements, Awareness, and Hippocampus-Dependent Memory

We asked what kind of memory is operating when eye movements change as the result of experience. Participants viewed scenes that were either novel, repeated, or manipulated (i.e., a change was introduced in one region of the scene). Eye movements differed depending on the past viewing history of each scene. Participants made fewer fixations and sampled fewer regions when scenes were repeated than when scenes were novel. When scenes were altered, participants made more fixations in the altered region, spent more time looking at the altered region, and made more transitions into and out of the altered region than in unchanged (matched) regions in the repeated scenes. Importantly, these effects occurred only when individuals were aware that a change had occurred. Participants who were unaware that the scene had been altered looked at the changed scenes in the same way that they looked at repeated scenes. Thus, there was no indication that eye movements could reveal an unaware (unconscious) form of memory. Instead, eye movements reflected conscious memory of whether the scene was repeated or manipulated. The findings were the same when awareness was assessed after viewing all the scenes (experiment 1) and when awareness was assessed after each scene was presented (experiment 2). In experiment 3, memory-impaired patients with damage limited to the hippocampus were impaired at deciding whether scenes were novel, repeated, or manipulated. Thus, the ability to consciously recollect recent encounters with scenes reflects a form of hippocampus-dependent memory. The findings show that experience-dependent eye movements in response to altered scenes reflect conscious, declarative memory, and they support the link between aware memory, declarative memory, and hippocampus-dependent memory.

Episodic remembering creates access to involuntary conscious memory: Demonstrating involuntary recall on a voluntary recall task

The idea that involuntary memory retrieval might occur during voluntary memory retrieval can be traced back to Ebbinghaus (1885/1964). However, methodological challenges have stood in the way of testing this idea. Recent diary studies of naturally occurring involuntary memories have provided insights into how this idea could be tested (Berntsen, 1998; Mace, 2005b, 2006). These studies have shown that the contents of an involuntary memory sometimes trigger additional involuntary memories, a process called chaining. It was hypothesised that chaining should also occur on autobiographical memory tasks, and this was tested in the present study by asking participants in an autobiographical memory task to report the presence of involuntary memories while they were performing the task. The results showed that involuntary memories did occur when participants were recalling the past. The results also showed involuntary memories dissociating from voluntary memories on two independent measures, thereby enhancing the credibility of the results.

Posttraumatic Stress Disorder Symptoms During the First Six Months After Traumatic Brain Injury

Posttraumatic Stress Disorder Symptoms During the First Six Months After Traumatic Brain Injury

Deficient memory acquisition in temporal lobe epilepsy is predicted by hippocampal granule cell loss

The hippocampal formation is essentially involved in the formation of conscious memories for facts and events and neurologic diseases affecting the hippocampus associate with severe memory deficits, i.e., temporal lobe epilepsies. We studied the degree of declarative memory dysfunction in 24 human subjects with unilateral mesial temporal lobe epilepsy, using the unique possibility to access memory performance of each isolated hippocampus by intracarotid amobarbital anesthesia. Subsequently, hippocampal specimens from the same patients were available for neuropathologic analysis following surgical treatment of intractable seizures. Neuronal cell loss in the dentate gyrus and all hippocampal subfields correlated with memory performance with the exception of CA2. Moreover, multiple regression and partial correlation analyses identified neuronal cell loss within the internal limb of the dentate gyrus, a developmentally distinct subregion of the hippocampal formation known to generate new neurons throughout life, as highly significant predictor for the patient's ability to learn and recall memories. In accordance with animal studies, the dentate gyrus may play a critical role in the neuronal network associated with memory formation.

The unified theory of repression

Repression has become an empirical fact that is at once obvious and problematic. Fragmented clinical and laboratory traditions and disputed terminology have resulted in a Babel of misunderstandings in which false distinctions are imposed (e.g., between repression and suppression) and necessary distinctions not drawn (e.g., between the mechanism and the use to which it is put, defense being just one). "Repression" was introduced by Herbart to designate the (nondefensive) inhibition of ideas by other ideas in their struggle for consciousness. Freud adapted repression to the defensive inhibition of "unbearable" mental contents. Substantial experimental literatures on attentional biases, thought avoidance, interference, and intentional forgetting exist, the oldest prototype being the work of Ebbinghaus, who showed that intentional avoidance of memories results in their progressive forgetting over time. It has now become clear, as clinicians had claimed, that the inaccessible materials are often available and emerge indirectly (e.g., procedurally, implicitly). It is also now established that the Ebbinghaus retention function can be partly reversed, with resulting increases of conscious memory over time (hypermnesia). Freud's clinical experience revealed early on that exclusion from consciousness was effected not just by simple repression (inhibition) but also by a variety of distorting techniques, some deployed to degrade latent contents (denial), all eventually subsumed under the rubric of defense mechanisms ("repression in the widest sense"). Freudian and Bartlettian distortions are essentially the same, even in name, except for motive (cognitive vs. emotional), and experimentally induced false memories and other "memory illusions" are laboratory analogs of self-induced distortions.

Memory and the Korsakoff syndrome: Not remembering what is remembered

Following the distinction between involuntary unconscious memory, involuntary conscious memory, and intentional retrieval, the focus of the present paper is whether there is an impairment of involuntary conscious memory among Korsakoff patients. At study, participants generated associations versus counted the number of letters with enclosed spaces or the number of vowels in the target words (semantic versus perceptual processing). In the Direct tests, stems were to be used to retrieve the targets with either guessing or no guessing allowed; in the Opposition tests, the stems were to be completed with the first word that came to mind but using another word if that first word was a target word; and in the Indirect tests, no reference was made to the target words from the study phase. In the Direct tests, the performance of Korsakoff patients was not necessarily worse than the one of healthy controls, provided guessing was allowed. More critical for the Korsakoff patients was the deficient involuntary conscious memory. The deficiency explained the suppression failures in the Opposition tests, the absence of performance differences between the Indirect and Opposition tests, the absence of a beneficial effect in providing information about the status of the stem, the performance boost when allowed to guess, and the very low rate of “Know”/“Remember” responses.

Posttraumatic Stress Disorder With Amnesia Following Asphyxiation

We describe five cases of traumatic asphyxiation injury, each meeting diagnostic criteria for posttraumatic stress disorder (PTSD) and characterized by a range of postinjury cognitive impairment. Four patients exhibited dense retrograde amnesia, including absence of conscious memory for the traumatic event. Appreciation of these asphyxiation cases, which involve temporally extended trauma exposure, may help resolve arguments regarding the possibility of co-occurrence of PTSD and neurological amnesia based exclusively on observations of much briefer duration events (specifically, motor vehicle crashes). These five cases also provide evidence that cognitive symptoms of PTSD can develop in the absence of conscious memory for the event.

Conscious and Preconscious Uses of Memory in Patients with Depressive and Somatoform Disorders

This study investigated whether conscious and preconscious memory features contribute to discrimination between depressive and somatoform disorders. Thirty-one participants fulfilling the diagnostic criteria for a somatoform disorder and 28 participants fulfilling the criteria for depression were examined within the framework of the process–dissociation paradigm using neutral, health-threatening, and general threatening words in a lexical decision task. Parameters of conscious memory, preconscious memory, and chance were used to compare memory features of both the groups. There was an inverse relationship between conscious and preconscious memory effects for health-threatening stimuli in the group of patients with somatoform disorders but not in the group of depressive patients. Patients with somatoform disorders showed a significantly lower level of conscious memory for health-threatening stimuli than depressive participants. Compared to depressive patients, a more dynamic relationship between decreased conscious and increased preconscious memory for health-related stimuli seems to be characteristic for patients with somatoform disorders.

Salvaging Locke's Self

Keywords personal identity, Locke, unconscious, narrative self, narrative theory Continuing Commentary This feature in PPP is intended to provide ongoing commentary on main articles previously published in PPP. The essay by Phillips below is a response to Marya Schechtman's paper in "The Unconscious" thematic issue, Philosophy, Psychiatry & Psychology 12, no. 1:9–22. Let me begin by acknowledging Marya Schechtman's admirably clear presentation of Locke's view of personal identity, the problems inherent in that view, the efforts of "psychological continuity theorists" to rectify the flaws in Locke's argument, the problems in their attempted rectifications, and finally her own proposals for rescuing Locke's view of personal identity. My comments focus on the problems I see in her use of the psychoanalytic unconscious to preserve Lockean personal identity and on my own suggestions for sustaining her argument. In her paper, Schechtman first describes Locke's account of personal identity and its problematic dependence on a notion of overlapping conscious memories. She then outlines the unsuccessful attempts of Locke's descendants—the psychological continuity theorists—to make good on his account. In the final section, "An Alternative Account," Schechtman offers her own proposal to compensate for the inadequacies of Locke's account of personal identity by introducing the notion of the unconscious. The gaps in memory that render Locke's version of the self fragmented and discontinuous can be filled in by substituting for Locke's conscious self a self that includes unconscious content. ". . . [I]t is necessary to give an account of the attribution of particular actions and experiences that allows for the attribution of unconscious elements as well as conscious ones" (Schechtman 2005, 18). Schechtman marshals her argument in two steps. First, she argues for replacing a rather passive view of the self as witness to one's past through memory with a version of the self that is actively engaged in making sense of one's life. To have the kind of self-conception that constitutes personal identity on the view I am urging (call it the "self-understanding view"), one must not just know about some collection of past experiences and think of them as hers, she must see life as unfolding according to an intelligible trajectory, where present states follow meaningfully from past ones, and the future is anticipated to bear certain predictable relations to the present. (2005, 18) In a second step, she recognizes that this effort at active self-understanding will come up against roadblocks of incomprehension. Careful self-examination does not reveal why one feels or acts the way one does. It is at this point that Freud and the unconscious enter the picture. "In postulating inner sources for our experiences and actions we recognize that there are [End Page 349] parts of ourselves that we are not conscious of, but that are yet part of our psychological lives in an importantly intimate way. These experiences impact the nature of our conscious experience, and hence should be part of the purview of our self-interested concern. They also influence what we do, and lead to experiences of guilt, shame, or pride, and so are connected to our moral agency. To have an identity-constituting self-conception, then, a person must demand (at least implicitly) a kind of coherence and intelligibility to the course of her life" (2005, 20). It appears that Schechtman salvages the Lockean self by invoking the Freudian unconscious and putting it into the service of expanding Locke's self to include an unconscious dimension. In his classic defense of the unconscious in "The Unconscious" (Freud 1957/1916), Freud articulates a similar argument: It [the unconscious] is necessary because the data of consciousness have a very large number of gaps in them; both in healthy and in sick people psychical acts often occur which can be explained only by presupposing other acts, of which, nevertheless, consciousness affords no evidence. These not only include parapraxes and dreams in healthy people, and everything described as a psychical symptom or an obsession...

Functional Specialization in the Human Medial Temporal Lobe

Investigations of memory in rats and nonhuman primates have demonstrated functional specialization within the medial temporal lobe (MTL), a set of heavily interconnected structures including the hippocampal formation and underlying entorhinal, perirhinal, and parahippocampal cortices. Most studies in humans, however, especially in patients with brain damage, suggest that the human MTL is a unitary memory system supporting all types of declarative memory, our conscious memory for facts and events. To resolve this discrepancy, amnesic patients with either selective hippocampal damage or more extensive MTL damage were tested on variations of an object discrimination task adapted from the nonhuman primate literature. Although both groups were equally impaired on standard recall-based memory tasks, they exhibited different profiles of performance on the object discrimination test, arguing against a unitary view of MTL function. Cases with selective hippocampal damage performed normally, whereas individuals with broader MTL lesions were impaired. Furthermore, deficits in this latter group were related not to the number of discriminations to be learned and remembered, but to the degree of "feature ambiguity," a property of visual discriminations that can emerge when features are part of both rewarded and unrewarded stimuli. These findings resolve contradictions between published studies in humans and animals and introduce a new way of characterizing the impairments that arise after damage to the MTL.

Memory Strength and Repetition Suppression: Multimodal Imaging of Medial Temporal Cortical Contributions to Recognition

Declarative memory permits an organism to recognize stimuli that have been previously encountered, discriminating them from those that are novel. One basis for recognition is item memory strength, which may support the perception of stimulus familiarity. Though the medial temporal lobes are known to be critical for declarative memory, at present the neural mechanisms supporting perceived differences in memory strength remain poorly specified. Here, functional MRI (fMRI) and anatomically constrained magnetoencephalography (MEG) indexed correlates of graded memory strength in the human brain, focusing on medial temporal cortex. fMRI revealed a decrease in medial temporal cortical activation that tracked parametric levels of perceived memory strength. Anatomically constrained MEG current estimates revealed that strength-dependent signal reductions onset within 150-300 ms. Memory strength appears to be rapidly signaled by medial temporal cortex through repetition suppression (activation reductions), providing a basis for the subjective perception of stimulus familiarity or novelty.

Drug-induced amnesia impairs implicit relational memory

Amnesic patients have difficulty consciously recollecting past events, but they perform normally on implicit memory measures that do not require conscious access. Now, an innovative study offers compelling evidence that even implicit memory can be impaired during amnesia, temporarily induced in healthy subjects using a neuropharmacological manipulation (midazolam). Importantly, midazolam impaired implicit, relational memory, whereas non-relational memory was preserved, supporting the characterization of conscious memory in terms of relational encoding.

Experimentally Manipulating the Effects of Involuntary Conscious Memory on a Priming Task

Recent studies showed that involuntary conscious memory can enhance priming in implicit tasks. However, because the results of these studies were based on post hoc selection methods in which subjects were assigned to conditions (aware or unaware) based on their responses on a posttest questionnaire, it is possible that subject selection effects may have influenced the results. The present study used a novel method that experimentally manipulated the effects of involuntary conscious memory on a word stem task. This was accomplished by inducing the experience of word recollection in one test condition while inhibiting it in another. This study showed that subjects who experienced word recollection showed significantly higher rates of priming than those who did not. The results represent the first purely experimental demonstration of involuntary conscious memory's ability to affect priming on implicit tasks.

Conscious control and memory awareness when recognising famous faces

We describe an experiment that investigated levels-of-processing effects in recognition memory for famous faces. The degree of conscious control over the recognition decisions was manipulated by using a response deadline procedure, and memory awareness associated with those decisions was assessed using a standard remember-know paradigm. Levels-of-processing effects were found at both short and long response deadlines, and at both deadlines those effects occurred only in remembering. Moreover, knowing, as well as remembering, increased with the greater opportunity for conscious control over recognition decisions at the long deadline. These results have implications for dual-process theories that distinguish between a slower, more controlled recollection process, reflected in remembering, and a faster, more automatic familiarity process, reflected in knowing.

Noting the Mind: Commonplace Books and the Pursuit of the Self in Eighteenth-Century Britain

Ae for Adversariorum methodus. Be for Beauty, Beneficience, Bread, Bleeding, Blemishes.1 By associating the first letter with the initial vowel of a word, generations of eighteenth-century readers, students, and observers diligently regulated access to information they reputed worth retaining. Following this rule, they organized the notes they took on a certain subject, the thoughts and observations they believed were worth remembering, and the exemplary words of their favorite authors. The rule was devised by John Locke for his method of making commonplace-books, a method characterized by a particular system for indexing the entries of a notebook that became popular in the eighteenth century. Before Locke developed his new method readers had already familiarized themselves with the practice of keeping an account of their readings, excerpting passages of texts, and copying them in their notebooks under a relevant heading. Throughout the early modern period commonplace books provided repositories for arranging notes, excerpts, drawings, and objects.2 Regarded as aids to memory and storehouses of knowledge, they were part of a pedagogic tradition related to rhetoric and the art of memory that dated back to the classical period. Reducing vast amounts of knowledge to a manageable form, they instantiated a special relationship between the accumulation of knowledge and the organization of space. At the turn of the eighteenth century Locke's new method promised to facilitate compilers' task by providing a new way of accumulating multum inparvo at a time of increasing concern for the uncontrollable growth of the Stock of Knowledge.3 It did so by seeking to increase the amount of information one could annotate in the notebook, while also speeding up its retrieval. Many eighteenth-century compilers relied on it in order to reduce the volume of their notebooks and save time. Some were lured by the promise that this technique could also help them to order their minds and thus turn them into better people.Although commonplace books have dropped out of usage today, they were still mentioned in nineteenth-century educational manuals. As tools that lay at the intersection between practices of collecting, reading, classifying, learning, and the arts of rhetoric, they have come to the fore of historical discussion.4 In some cases, commonplace books have been regarded as capable of providing insights into compilers' reading patterns and as biographical sources casting light on compilers' personal idiosyncrasies and cataloguing manias.5 The intellectual and cultural significance of Locke's own new method of compiling has accordingly been discussed in relation to Locke 's own intellectual biography (and in particular his medical interests), in the context of shifting patterns of systematization of knowledge and in light of the dissemination of eighteenthcentury encyclopedic projects.6 However, still little is known about the uses and the popularity of the Lockean method in the eighteenth century.What follows considers the spreading of Lockean commonplacing in the context of eighteenth-century discussions on the nature of the self. Locke himself contributed to these discussions when, in the second edition of his Essay concerning Human Understanding (1694), he famously suggested that selfidentity lay in the mind and resided in the continuity of memory and consciousness.7 Now a widely shared assumption of Western modernity, the view that self lies in the mind has long been dated back to the Age of Enlightenment. Yet early in this period Locke's proposal to make self-identity coextensive with memory and self-knowledge proved controversial. The debate that followed is now part of the canon of the history of philosophy and of the philosophical literature as a whole.8 In the course of the debate some of Locke's critics doubted that it was possible to found the self in conscious memory: they wondered about the destiny of the self during intervals of unconsciousness and found it absurd to define personal identity in terms of something that was inherently discontinuous. …

Different involuntary mechanisms underlie priming and LOP effects in stem completion tests

The role of intentional retrieval, involuntary conscious memory, and lexical processing in priming and levels‐of‐processing (LOP) effects in stem completion tests was investigated in three experiments. First, Experiment 1 provided strong evidence against the intentional retrieval hypothesis for the implicit LOP effects. LOP effects in the explicit test were dependent on intertrial interval at test, whereas LOP effects in the implicit test were not. Second, support was provided for the involuntary conscious memory hypothesis. Implicit memory (priming) was associated with awareness in all three experiments and the implicit LOP effect was associated with awareness in two of the three experiments. Third, it was concluded that lexical processing per se played a limited role in both priming and implicit LOP effects. Although priming was sensitive to normative rates of production in Experiment 1 and the number of solutions in all three experiments, it was insensitive to frequency manipulations. The LOP effect was insensitive to number of solutions, normative rates of production, and frequency manipulations. In addition, LOP and priming effects were uncorrelated in the implicit memory tests. It was concluded that production processes (e.g., Gabrieli et al., 1999), rather than lexical processes, played a crucial role in stem completion priming. In contrast, the LOP effect was attributed to the involuntary interaction of episodic and perceptual memory.