Conscious Recollection Research Articles

The role of recollection in evaluative conditioning

Attitudes are a core construct of social psychology, and research showed that attitudes can be acquired by merely pairing neutral stimuli with other liked or disliked stimuli (i.e., evaluative conditioning, EC). In this research we address the role of different memory processes contributing to EC. Although it is commonly found that memory for the pairings increases EC, we argue that memory performance data obtained in the standard paradigm remain ambiguous. We hypothesize that memory for stimulus pairings may moderate EC by means of an intentional use of conscious recollection as well as through unintended effects of memory. In two experiments we used modified memory tests that distinguish between these different memory processes on an item-level by identifying recollection as the participant's ability to control memory performance. The analyses of the experiments showed that both intended and unintended influences independently moderate EC. Based on these results we discuss the role of different memory processes in EC, and how memory and learning processes may be related.

Recognition Memory for Colored and Black-and-White Scenes in Normal and Color Deficient Observers (Dichromats)

Color deficient (dichromat) and normal observers’ recognition memory for colored and black-and-white natural scenes was evaluated through several parameters: the rate of recognition, discrimination (A’), response bias (B”D), response confidence, and the proportion of conscious recollections (Remember responses) among hits. At the encoding phase, 36 images of natural scenes were each presented for 1 sec. Half of the images were shown in color and half in black-and-white. At the recognition phase, these 36 pictures were intermixed with 36 new images. The participants’ task was to indicate whether an image had been presented or not at the encoding phase, to rate their level of confidence in his her/his response, and in the case of a positive response, to classify the response as a Remember, a Know or a Guess response. Results indicated that accuracy, response discrimination, response bias and confidence ratings were higher for colored than for black-and-white images; this advantage for colored images was similar in both groups of participants. Rates of Remember responses were not higher for colored images than for black-and-white ones, whatever the group. However, interestingly, Remember responses were significantly more often based on color information for colored than for black-and-white images in normal observers only, not in dichromats.

Interference from mere thinking: mental rehearsal temporarily disrupts recall of motor memory.

Interference between successively learned tasks is widely investigated to study motor memory. However, how simultaneously learned motor memories interact with each other has been rarely studied despite its prevalence in daily life. Assuming that motor memory shares common neural mechanisms with declarative memory system, we made unintuitive predictions that mental rehearsal, as opposed to further practice, of one motor memory will temporarily impair the recall of another simultaneously learned memory. Subjects simultaneously learned two sensorimotor tasks, i.e., visuomotor rotation and gain. They retrieved one memory by either practice or mental rehearsal and then had their memory evaluated. We found that mental rehearsal, instead of execution, impaired the recall of unretrieved memory. This impairment was content-independent, i.e., retrieving either gain or rotation impaired the other memory. Hence, conscious recollection of one motor memory interferes with the recall of another memory. This is analogous to retrieval-induced forgetting in declarative memory, suggesting a common neural process across memory systems. Our findings indicate that motor imagery is sufficient to induce interference between motor memories. Mental rehearsal, currently widely regarded as beneficial for motor performance, negatively affects memory recall when it is exercised for a subset of memorized items.

Role of PFC during retrieval of recognition memory in rodents

One of the challenges for memory researches is the study of the neurobiology of episodic memory which is defined by the integration of all the different components of experiences that support the conscious recollection of events. The features of episodic memory includes a particular object or person (“what”), the context in which the experience took place (“where”) and the particular time at which the event occurred (“when”). Although episodic memory has been mainly studied in humans, there are many studies that demonstrate these features in non-human animals. Here, we summarize a set of studies that employ different versions of recognition memory tasks in animals to study the role of the medial prefrontal cortex in episodic memory.

Increased Risk of Awareness under Anesthesia

Increased Risk of Awareness under Anesthesia

Memory for Past Public Events Depends on Retrieval Frequency but not Memory Age in Alzheimer's Disease

Alzheimer's disease (AD) is characterized by retrograde memory deficits primarily caused by dysfunction of the hippocampal complex. Unresolved questions exist concerning the time course of hippocampal involvement in conscious recollection of declarative knowledge, as reports of temporal gradients of retrograde amnesia have been inconclusive. The aim of this study was to examine whether the extent and severity of retrograde amnesia is mediated by retrieval frequency or, in contrast, whether it depends on the age of the memory according to the assumptions of the main current theories of memory formation. We compared recall of past public events in patients with AD and healthy control (HC) individuals using the Historic Events Test (HET). The HET assesses knowledge about famous public events of the past 60 years divided into four time segments and consists of subjective memory rating, dating accuracy, and contextual memory tasks. Although memory for public events was impaired in AD patients, there was a strong effect of retrieval frequency across all time segments and both groups. As AD and HC groups derived similar benefits from greater retrieval frequency, cortical structures other than the hippocampal complex may mediate memory retrieval. These findings suggest that more frequently retrieved events and facts become more independent of the hippocampal complex and thus better protected against early damage of AD. This could explain why cognitive activity may delay the onset of memory decline in persons who develop AD.

Changes in recognition memory over time: an ERP investigation into vocabulary learning.

Although it seems intuitive to assume that recognition memory fades over time when information is not reinforced, some aspects of word learning may benefit from a period of consolidation. In the present study, event-related potentials (ERP) were used to examine changes in recognition memory responses to familiar and newly learned (novel) words over time. Native English speakers were taught novel words associated with English translations, and subsequently performed a Recognition Memory task in which they made old/new decisions in response to both words (trained word vs. untrained word), and novel words (trained novel word vs. untrained novel word). The Recognition task was performed 45 minutes after training (Day 1) and then repeated the following day (Day 2) with no additional training session in between. For familiar words, the late parietal old/new effect distinguished old from new items on both Day 1 and Day 2, although response to trained items was significantly weaker on Day 2. For novel words, the LPC again distinguished old from new items on both days, but the effect became significantly larger on Day 2. These data suggest that while recognition memory for familiar items may fade over time, recognition of novel items, conscious recollection in particular may benefit from a period of consolidation.

Conscious recollection and binding among context features

Recent research suggests that the subjective feeling of conscious recollection is uniquely characterized by joint memory for several context features while merely familiar memories lack this property (Meiser, Sattler, & Weisser, 2008). In the present research we took the novel approach of extending the dual task paradigm to the simultaneous study of subjective retrieval experience (using the remember/know procedure) and joint memory for two orthogonal context features. While dual task load during encoding lead to reductions in the frequency of the subjective experience of conscious recollection and reductions in overall context memory, joint context memory was not affected. Furthermore, the relation of higher overall context memory for consciously recollected items than for familiar items was preserved even under dual task load. These results have import implications for theories of long-term feature binding and the processes involved in producing the experience of conscious recollection.

Does this sound familiar? Effects of timbre change on episodic retrieval of novel melodies

Three experiments investigated episodic retrieval of novel melodies and tested how a change in timbre between study and test affects the two processes underlying recognition memory, conscious recollection and familiarity. In Experiments 1 and 2, conscious recollection and familiarity were operationalized using the remember/know paradigm. We additionally assessed the influence of the number of presentations during learning in Experiment 1, and the effect of massed versus distributed learning in Experiment 2. Experiment 3 confirmed that participants could also indicate a change in timbre explicitly (same versus different timbre classifications). In all experiments, melodies were better recognized when the timbre at study and test was identical. Effects of timbre change were more pronounced for recollection than familiarity. Distributed learning specifically enhanced the same-timbre advantage on recollection. Together, these results suggest that timbre serves both as a context cue and as an integrated feature of a melody.

Imaging Patients with Psychosis and a Mouse Model Establishes a Spreading Pattern of Hippocampal Dysfunction and Implicates Glutamate as a Driver

The hippocampus in schizophrenia is characterized by both hypermetabolism and reduced size. It remains unknown whether these abnormalities are mechanistically linked. Here we addressed this question by using MRI tools that can map hippocampal metabolism and structure in patients and mouse models. In at-risk patients, hypermetabolism was found to begin in CA1 and spread to the subiculum after psychosis onset. CA1 hypermetabolism at baseline predicted hippocampal atrophy, which occurred during progression to psychosis, most prominently in similar regions. Next, we used ketamine to model conditions of acute psychosis in mice. Acute ketamine reproduced a similar regional pattern of hypermetabolism, while repeated exposure shifted the hippocampus to a hypermetabolic basal state with concurrent atrophy and pathology in parvalbumin-expressing interneurons. Parallel invivo experiments using the glutamate-reducing drug LY379268 and direct measurements of extracellular glutamate showed that glutamate drives both neuroimaging abnormalities. These findings show that hippocampal hypermetabolism leads to atrophy in psychotic disorder and suggest glutamate as a pathogenic driver.

1637 – Recall of previously learned associations and memory generalization in schizophrenia, other psychoses, siblings, and controls. The northern finland 1966 birth cohort study

Introduction Neurocognitive impairments are a core feature of schizophrenia. The medial temporal lobe (MTL) is a brain region associated with declarative memory important in conscious acquisition and recollection of facts and events. The basal ganglia (BG) instead are linked to non-declarative memory functions such as gradual learning of skills and habits. Objective Acquired equivalence (AE) is a phenomenon in which prior training to treat two stimuli as an equivalent increases generalization between them. Our objective was to study this phenomenon in birth cohort setting. Aims To investigate whether the recall of previously learned associations and memory generalization are declined in schizophrenia, other psychoses and siblings compared to healthy controls. Methods The Northern Finland Birth Cohort 1966 is based upon 12, 068 women and their 12, 058 live-born children. The modified Rutger's AE-task was performed for 35 schizophrenia patients, 26 patients suffering from other psychosis, 18 siblings of psychotic subjects and 174 controls. Results The behavioral data showed statistically significant impairment in both recall of learned associations and generalization in schizophrenia and other psychosis groups compared to control subjects. Siblings did not differ significantly from controls in recall of learned associations but they showed impairments in generalization. Conclusions Impairment in recall of learned associations and memory generalization seem to be present also in other psychotic disorders, not only in schizophrenia. Since decline in generalization was seen in addition in siblings the hypothesis that declarative memory could be one of endophenotypes of schizophrenia is supported by this study.

A neurobiology of learning beyond the declarative non-declarative distinction

In neuroscience and psychology it has become common to distinguish between declarative and non-declarative forms of learning (e.g., Squire and Zola, 1996). The perspective (Squire, 2004, p. 173) that declarative learning “refers to the capacity for conscious recollection about facts and events and is the kind of memory that is impaired in amnesia and dependent on structures in the medial temporal lobe” developed when it was observed that patients with hippocampal damage were able to learn and improve on “procedural” tasks, such as hand-eye coordination, without being able to remember the specific learning episodes (e.g., Scoville and Milner, 1957; Squire, 1992). Such evidence led researchers (e.g., Moscovitch, 1995) to suggest that there are two separate learning systems: one involved in declarative, conscious, learning situated in the Medial Temporal Lobe (MTL) comprising the hippocampus, and another involved in non-declarative, implicit, skill/habit learning involving the basal ganglia. An interpretation of the roles of the hippocampus and the basal ganglia in learning independent from the declarative/non-declarative dichotomy may allow understanding the role of neural structures critical in learning without relying on phenomenological categories—difficult to examine from a scientific perspective—such as awareness and consciousness. The very nature of what consciousness is in fact still hotly debated (e.g., Morin, 2006) and grounding an entire taxonomy of learning and memory on consciousness-based criteria might complicate, instead of simplifying, scientific interpretations, and progress. An alternative perspective to the declarative—non-declarative distinction (e.g., Packard and McGaugh, 1992; McDonald and White, 1993) emphasizes the role of the hippocampus in learning stimulus-stimulus relations, and of the dorsal striatum in acquiring stimulus-response relations. Such perspective is consistent with a recent review (Henke, 2010) suggesting that neurobiological models of learning based on consciousness might not be adequate to describe the available experimental evidence.

Sleep Microstructure and Memory Function

Several studies investigated the effect of sleep on memory. In humans, arguably the first experimental description of a ben-eficial role of sleep for memory stabiliza-tion was provided in 1924 (1), indicating a protective benefit of sleep in prevent-ing the normal decay-curve of forgetting that develops across time spent awake. Specific stages of sleep appear to be criti-cal for memory consolidation. Memory is commonly divided into a declarative and a non-declarative memory system (2). Declarative memory is defined by memo-ries accessible to conscious recollection, i.e., memories for events in a spatio-tem-poral context (episodic memory) and fact-based information (semantic memory). Procedural memory for skills is the type of non-declarative memory most thoroughly studied with regard to the effects of sleep. Sleep is characterized by the cyclic occur-rence of REM and NREM sleep comprising SWS (sleep stages 3 and 4) and lighter sleep stages 1 and 2. Two hypotheses were pro-posed regarding sleep stages and memory consolidation (3). The dual process the-ory assumes that the specific sleep stages support consolidation of different types of memories. SWS supports declarative memory consolidation whereas REM sleep does so for procedural memories ( 4). The sequential hypothesis, on the other hand, proposes that sleep benefits memory opti-mally through the cyclic succession of both SWS and REM sleep. The original version of this hypothesis assumed that SWS func-tions to weaken non-adaptive memory traces whereas REM sleep re-stores the remaining traces (5). The dual process hypothesis received support mainly based on the early late sleep comparison, i.e., an approach comparing effects of retention intervals covering the first (SWS-rich) or the second (REM sleep-rich) half of nocturnal sleep. SWS-rich early sleep con-sistently found to support consolidation of hippocampus-dependent declarative memories, whereas REM sleep benefited non-declarative types of memory like priming, and memories for visuo-motor skills ( 6, 7). However, this dichotomy does not fit all results. Several non-declarative tasks, like visual texture discrimination, are also supported by SWS whereas REM sleep in some instances seems to benefit aspects of declarative memory (8).More recently, Genzel and colleagues (9) tried to clarify the link between spe-cific sleep stages and different types of memory consolidation by suppressing sleep stages. They deprived subjects once each of REM sleep and SWS, and once let them sleep undisturbed through the night. After each night, the authors tested declarative and procedural memory con-solidation. Although REM sleep and SWS awakenings led to a significant reduction of the respective sleep stages, memory con-solidation remained unaffected. According to the authors, there are two possible explanations for REM deprivation and SWS deprivation not influencing sleep-dependent consolidation of motor tasks: (1) the diminished amount of REM sleep in the REM deprivation condition was still sufficient for sleep-dependent memory consolidation or (2) the memory con-solidation is dependent on stage 2 sleep. Another explanation of the results is that sleep-associated processes contributing to memory consolidation requires analyses of polysomnographic phenomena, like sleep spindles and slow-wave activity (SWA). This aspect is very important also for the implications for the cognitive decline by increasing age (10, 11). Other factors that change with age, such as hormones and neurotransmitters, or hypoxia related to sleep-disordered breathing (12, 13), may also play an important role.

Effect of emotional valence on episodic memory stages as indexed by event-related potentials.

Several investigations have shown that emotional events show superior recall than non-emotional ones. However, the cortical mechanisms underlying the episodic recall of emotional scenes are still poorly understood. Our main aim was to compare the magnitude of the Event-Related brain Potentials (ERP) old-new effect related to emotionally unpleasant, pleasant and neutral photographic images. As expected, correct recognition of all types of images elicited three topographically distinct ERP components sensitive to the classical old-new recognition effect. The results revealed that the behavioral performances were mainly sensitive to arousal, while the ERP old/new effect over posterior regions (300 – 1000 ms) was exclusively affected by unpleasantness. A later component (1000 – 1400 ms) showed an inverted old/ new effect at parietal sites, which was also sensitive to unpleasantness. These results imply that ERP reflecting episodic conscious recollection and post-retrieval monitoring are clearly affected both by valence and arousal.

Perspectives on Episodic-Like and Episodic Memory

Episodic memory refers to the conscious recollection of a personal experience that contains information on what has happened and also where and when it happened. Recollection from episodic memory also implies a kind of first-person subjectivity that has been termed autonoetic consciousness. Episodic memory is extremely sensitive to cerebral aging and neurodegenerative diseases. In Alzheimer’s disease deficits in episodic memory function are among the first cognitive symptoms observed. Furthermore, impaired episodic memory function is also observed in a variety of other neuropsychiatric diseases including dissociative disorders, schizophrenia, and Parkinson disease. Unfortunately, it is quite difficult to induce and measure episodic memories in the laboratory and it is even more difficult to measure it in clinical populations. Presently, the tests used to assess episodic memory function do not comply with even down-sized definitions of episodic-like memory as a memory for what happened, where, and when. They also require sophisticated verbal competences and are difficult to apply to patient populations. In this review, we will summarize the progress made in defining behavioral criteria of episodic-like memory in animals (and humans) as well as the perspectives in developing novel tests of human episodic memory which can also account for phenomenological aspects of episodic memory such as autonoetic awareness. We will also define basic behavioral, procedural, and phenomenological criteria which might be helpful for the development of a valid and reliable clinical test of human episodic memory.

Hopkins verbal learning test-revised and brief visuospatial memory test-revised: preliminary normative data for the Brazilian population

Memory functions are cognitive processes related to the ability to encode, store and retrieve information associated to the fronto-temporal neurocircuitry1. Episodic memory refers to the system that allows conscious recollection of personal events or episodes and their contexts (time and place)1. Clinical measures of episodic memory include immediate and delayed free recall and recognition of word lists and pictures […] Hopkins verbal learning test-revised and brief visuospatial memory test-revised: preliminary normative data for the Brazilian population

A novel experimental approach to episodic memory in humans based on the privileged access of odors to memories

Episodic memory is defined as the conscious recollection of a personal event (What) in its spatial (Where) and contextual (Which context) environment. In existing approaches, human episodic memory is either explored separately from real-life situations or is not fully controlled. In this study, we propose an intermediate approach, inspired by animal studies, that permits the control of the encoding and recall phases, while still being ecologically valid. As odors are known to be especially evocative reminders, we explored the memory of olfactory episodes. During trial-unique encoding, participants freely explored three episodes, one episode per day, each composed of three unnamable odors (What) that were positioned at specific locations on a board (Where) within a visual context (Which context). On the fourth day, both old and new odors were presented, and when an odor was recognized, the participants had to remember both its spatial location and the visual context in which it occurred. In Experiment 1, the participants were highly proficient at recognizing odors, and they recall the spatio-contextual environment associated with these odors in approximately half of the trials. To adapt the recall procedure to the constraints of fMRI, we conducted Experiment 2 demonstrating that trial repetition did not disturb the memory process. Thus, we first validated our protocol, which investigates the memory of olfactory episodes in a fully controlled way that is as close as possible to real-life situations. Then, we demonstrated the adaptability of our protocol for the future exploration of the neural networks implicated in episodic recall.

Why is there a special issue on perirhinal cortex in a journal called hippocampus? The perirhinal cortex in historical perspective

Despite its small size, the perirhinal cortex (PRh) plays a central role in understanding the cerebral cortex, vision, and memory; it figures in discussions of cognitive capacities as diverse as object perception, semantic knowledge, feelings of familiarity, and conscious recollection. Two conceptual constructs have encompassed PRh. The current orthodoxy incorporates PRh within the medial temporal lobe (MTL) as a memory area; an alternative considers PRh to be a sensory area with a role in both perception and memory. A historical perspective provides insight into both these ideas. PRh came to be included in the MTL because of two accidents of history. In evolutionary history, the hippocampus migrated from its ancestral situation as medial cortex into the temporal lobe; in the history of neuropsychology, a "memory system" that originally consisted of the amygdala and hippocampus came to include PRh. These two histories explain why a part of the sensory neocortex, PRh, entered into the conceptual construct called the MTL. They also explain why some experimental results seem to exclude a perceptual function for this sensory area, while others embrace perception. The exclusion of perceptual functions results from a history of categorizing tasks as perceptual or mnemonic, often on inadequate grounds. By exploring the role of PRh in encoding, representing, and retrieving stimulus information, it can be understood as a part of the sensory neocortex, one that has the same relationship with the hippocampus as do other parts of the neocortex that evolved at about the same time.

Suppression of aversive memories associates with changes in early and late stages of neurocognitive processing

Unwanted memories, such as emotionally negative, can be intentionally suppressed through voluntary control in humans. Memory suppression is thought to be mediated by the interplay of a chain of neurocognitive processes. However, empirical data in support of this notion is lacking. Using high-temporal resolution event-related potential (ERP) technique, we investigated the time course of ERPs associated with suppression of negative and neutral memories in a Think/No-Think paradigm in young, healthy participants. Results showed that participants had greater difficulty in suppressing emotionally negative memories than neutral ones. ERPs and source analyses demonstrated that memory suppression processing for negative and neutral memories were generally associated with changes during early components of a time window of 70–260ms, such as P1 and N2, mainly at the right inferior frontal gyrus and occipital lobe; suppression of aversive memories was associated with two major late ERP components between 380 and 800ms, with significantly smaller later negativity (LN) but larger late parietal positivity (LPP), primarily at the right medial and superior frontal gyri. These results suggest that differences in early components may reflect early stages of suppression processing including visual awareness, attention reallocation, and executive processing. Differences in late components between suppression of aversive and neutral memories may reflect a process of down-regulating conscious recollection of memory representations supported by prefrontal and parietal networks. A less effective control of this process, as evidenced by smaller LN and larger LPP, may explain the fact that emotionally negative memories were harder to be suppressed. Altogether, these findings suggest that suppression of aversive memories requires down-regulation of late conscious recollection, which can be dissociated from early visual and attention processing in memory suppression.

Event-related potential evidence for separable automatic and controlled retrieval processes in proactive interference

Interference between competing memories is a major source of retrieval failure, yet, surprisingly little is known about how competitive memory activation arises in the brain. One possibility is that interference during episodic retrieval might be produced by relatively automatic conceptual priming mechanisms that are independent of strategic retrieval processes. Such priming-driven interference might occur when the competing memories have strong pre-existing associations to the retrieval cue. We used ERPs to measure the neural dynamics of retrieval competition, and investigated whether the ERP correlates of interference were affected by varying task demands for selective retrieval. Participants encoded cue words that were presented either two or four times, paired either with the same or different strongly associated words across repetitions. In a subsequent test, participants either selectively recalled each cue's most recent associate, or simply judged how many times a cue had been presented, without requiring selective recall. Interference effects on test performance were only seen in the recall task. In contrast, ERPs during test revealed an early posterior positivity for high interference items that was present in both retrieval tasks. This early ERP effect likely reflects a conceptual priming-related N400 reduction when many associations to a cue were pre-activated. A later parietal positivity resembling the ERP correlate of conscious recollection was found only in the recall task. The results suggest that early effects of proactive interference are relatively automatic and independent of intentional retrieval processes, consistent with suggestions that interference can arise through conceptual priming.