Retrieval of pictures and words from long-term memory: Effects upon short-term memory

On each of a series of Brown-Peterson short-term memory (STM) tests, the presentation of a verbal to-be-remembered (TBR) item (a five-letter quintogram in Experiment 1 and an eight-letter octogram in Experiment 2) was followed immediately by a 10-sec retention interval. During the retention interval, subjects recalled and reproduced previously learned paired associate response triads that consisted of three concrete pictures, concrete words, abstract pictures, or abstract words. Following selective retrieval of one of the four types of response triads from long-term memory (LTM), subjects attempted to recall the TBR items from STM. In both experiments, the intervening retrieval of abstract words resulted in significantly poorer retention of the TBR items than did the intervening retrieval of concrete words; the retrieval of concrete words resulted, in turn, in significantly poorer retention of the TBR items than did the retrieval of concrete or abstract pictures. Retrieval of the latter two types of materials appeared not to interfere with the short-term retention of the TBR verbal material (i.e., the quintograms and octograms). The results reflect the occurrence of selective interference effects, and, except for one discrepant finding, appear to be consistent with Paivio’s 11971) dual-coding hypothesis and Shiffrin and Schneider’s (1977) general theory of memory.     

Effects of protein synthesis inhibitors on sleep and amygdala-kindled seizure thresholds in cats

This study examined the effects of protein synthesis inhibitors on sleep and seizure susceptibility in amygdala-kindled cats. Six cats with stable seizure thresholds were treated with 150 mg/kg of chloramphenicol or its cogener, thiamphenicol, at 12-h intervals over a 30-h period. State pattern variables were monitored continuously during the first 18 h. At 30 h, kindled seizure thresholds were measured in terms of minimum stimulus intensities (microA) required to elicit generalized tonic clonic convulsions. All cats were exposed to both drugs, with a 1-week intertrial interval and the order of drug treatment counterbalanced. Rapid eye movement (REM) sleep was significantly attenuated after chloramphenicol but was unaffected by thiamphenicol, as previously shown. Seizure thresholds were unaltered regardless of changes in sleep state physiology. The results extend previous work showing that protein synthesis inhibitors which suppress REM sleep increase seizure susceptibility only in animals that are either highly predisposed to seizures or that display REM sleep disruption as the sole sleep deficit associated with their seizure condition.     

Temporal organization of the brain: Neurocognitive mechanisms and clinical implications

The synchrony between the individual brain and its environment is maintained by a system of internal clocks that together reflect the temporal organization of the organism. Extending the theoretical work of Edelman and others, the temporal organization of the brain is posited as functioning through "re-entry" and "temporal tagging" and binds the wide range of possible times to a unified cognitive experience which is held in unison with the outside world. Dysfunction in this system is reflected in the temporal discord seen in cases of aging, sleep disorder, jet-lag, and shift-work, as well as in mental disorders and drug-induced changes in consciousness. The extent to which neuroendocrine structures contribute to the neurocognitive mechanisms which underlie consciousness has so far not been explored. Therefore, neuroendocrine mechanisms contributing to the temporal organization of the brain are reviewed. It is concluded that time-and its neuroendocrine correlate melatonin-is a binding principle for organizing conscious experience.     

Effects and mechanisms of working memory training: a review

Can cognitive abilities such as reasoning be improved through working memory training? This question is still highly controversial, with prior studies providing contradictory findings. The lack of theory-driven, systematic approaches and (occasionally serious) methodological shortcomings complicates this debate even more. This review suggests two general mechanisms mediating transfer effects that are (or are not) observed after working memory training: enhanced working memory capacity, enabling people to hold more items in working memory than before training, or enhanced efficiency using the working memory capacity available (e.g., using chunking strategies to remember more items correctly). We then highlight multiple factors that could influence these mechanisms of transfer and thus the success of training interventions. These factors include (1) the nature of the training regime (i.e., intensity, duration, and adaptivity of the training tasks) and, with it, the magnitude of improvements during training, and (2) individual differences in age, cognitive abilities, biological factors, and motivational and personality factors. Finally, we summarize the findings revealed by existing training studies for each of these factors, and thereby present a roadmap for accumulating further empirical evidence regarding the efficacy of working memory training in a systematic way.     

Long-term autobiographical memory across middle childhood: patterns,predictors, and implications for conceptualizations of childhood amnesia

ABSTRACT

We examined recall of events by children 4–11 years to inform patterns of retention of autobiographical memories as well as factors that predict their survival. 101 children participated in a 4-year prospective study. At study inception, children were 4, 6, and 8 years. They were tested annually for three more years for a total of four waves of data collection. At each wave, we obtained narrative reports of recent (all waves) and distant (Waves 2–4) events, resulting in virtually continuous sampling of memories formed by 4- to 11-year-olds and recalled after 1–3-year delays. We also measured children's language, and domain-general and memory-specific cognitive skills. Multi-level modelling revealed age-related increases in the likelihood of survival of memories over the delays. Critically, the rate of increase in retention of individual memories was the same across the cohorts. In addition to age, thematic coherence of original memory reports predicted memory survivability. Other factors were not predictive. The dense sampling and prospective tracking of memories across the 4–11-year age period permitted an especially strong test for continuity versus discontinuity in autobiographical memory across the second half of the first decade of life. The data are strongly indicative of continuity and gradual change.     

Bridging the gap between brain and behavior: cognitive and neural mechanisms of episodic memory

The notion that non-human animals are capable of episodic memory is highly controversial. Here, we review recent behavioral work from our laboratory showing that the fundamental features of episodic memory can be observed in rats and that, as in humans, this capacity relies on the hippocampus. We also discuss electrophysiological evidence, from our laboratory and that of others, pointing to associative and sequential coding in hippocampal cells as potential neural mechanisms underlying episodic memory.     

Strategy-dependent changes in memory: Effects on behavior and brain activity

In the present study, an implicit strategy manipulation was used to explore the contribution of memory strategy to brain activation and behavioral performance. Participants were biased to use either a short-term (maintenance-focused) or long-term (retrieval-focused) memory strategy within a single memory task through manipulation of task context. In comparing directly matched trials across the different task contexts, we observed clear changes in both behavioral performance and brain activity across a network of regions located primarily within lateral and medial frontal cortex. These effects of the memory strategy manipulation suggest that when a retrieval-focused strategy is induced, mnemonic processes are preferentially engaged during the encoding period. In contrast, when a maintenance-focused strategy is induced, mnemonic processes are preferentially engaged during the delay and response periods. Taken together, the results imply that covert cognitive strategies play an important role in modulating brain activation and behavior during memory tasks.     

Visual and tactile memory for 2-D patterns: Effects of changes in size and left-right orientation

Visual identification of 3-D objects depends on representations that are invariant across changes in size and left-right orientation. We examined whether this finding reflects the unique demands of processing 3-D objects, or whether it generalizes to 2-D patterns and to the tactile modality. Our findings suggest that object representation for identification is influenced greatly by the processing demands of stimulus materials (e.g., 2-D vs. 3-D objects) and stimulus modality (touch vs. vision). Identification of 2-D patterns in vision is adversely affected by left-right orientation changes, but not size changes. Identification of the same patterns in touch is adversely affected by both changes. Together, the results suggest that the unique processing demands of stimulus materials and modality shape the representation of objects in memory.     

Effects of prior knowledge and response bias upon recognition memory for a story: Implications for children's eyewitness testimony

Abstract: The present study was designed to evaluate the integration hypothesis and the response bias hypothesis for explaining the fragility of children's eyewitness memory, by varying the plausibility of postevent information and the strength of response bias in recognition tests. Preschool children were told a story in which a boy named Ken saw a housebreaker stealing various objects and the postevent information was also incorporated into the story. The first recognition test was administered immediately following the presentation of an interpolated story, and the second recognition test was administered 10 weeks later. The results indicated that high-plausibility objects tended to be recognized as the stolen objects in the second recognition test, and that recognition accuracy was higher for a new-distractor condition than for a misleading-distractor condition. These findings were interpreted as suggesting that the memory representation of the story might be changed through the integration processes and/or rendered inaccessible in terms of the response bias.     

Quantifying precision and availability of location memory in everyday pictures and some implications for picture database design

The authors investigated whether memory for object locations in pictures could be exploited to address known difficulties of designing query languages for picture databases. M. W. Lansdale's (1998) model of location memory was adapted to 4 experiments observing memory for everyday pictures. These experiments showed that location memory is quantified by 2 parameters: a probability that memory is available and a measure of its precision. Availability is determined by controlled attentional processes, whereas precision is mostly governed by picture composition beyond the viewer's control. Additionally, participants' confidence judgments were good predictors of availability but were insensitive to precision. This research suggests that databases using location memory are feasible. The implications of these findings for database design and for further research and development are discussed.     

Imaging episodic memory: implications for cognitive theories and phenomena

Functional neuroimaging studies are beginning to identify neuroanatomical correlates of various cognitive functions. This paper presents results relevant to several theories and phenomena of episodic memory, including component processes of episodic retrieval, encoding specificity, inhibition, item versus source memory, encoding-retrieval overlap, and the picture-superiority effect. Overall, by revealing specific activation patterns, the results provide support for existing theoretical views and they add some unique information which may be important to consider in future attempts to develop cognitive theories of episodic memory.     

Ordered short-term memory differs in signers and speakers: implications for models of short-term memory

Capacity limits in linguistic short-term memory (STM) are typically measured with forward span tasks in which participants are asked to recall lists of words in the order presented. Using such tasks, native signers of American Sign Language (ASL) exhibit smaller spans than native speakers ([Boutla, M., Supalla, T., Newport, E. L., & Bavelier, D. (2004). Short-term memory span: Insights from sign language. Nature Neuroscience, 7(9), 997-1002]). Here, we test the hypothesis that this population difference reflects differences in the way speakers and signers maintain temporal order information in short-term memory. We show that native signers differ from speakers on measures of short-term memory that require maintenance of temporal order of the tested materials, but not on those in which temporal order is not required. In addition, we show that, in a recall task with free order, bilingual subjects are more likely to recall in temporal order when using English than ASL. We conclude that speakers and signers do share common short-term memory processes. However, whereas short-term memory for spoken English is predominantly organized in terms of temporal order, we argue that this dimension does not play as great a role in signers' short-term memory. Other factors that may affect STM processes in signers are discussed.     

Therapist memory and reverie: implications for the clinical setting

In this work, the author considers reveries to be ‘dream-like-memories’. In the course of a session they appear as proto-memory – the therapist’s early traumatic object relations that are recorded in the unconscious at an almost bodily level (a type of unthought known) and which are resurrected between therapist and patient when a similar traumatic subject arises between them. The therapist’s reveries are recollections in the form of dream-like allusions to his past experience. A clinical vignette from the psychotherapy of a child whose father suffered from PTSD (following a wartime experience in Afghanistan and Iraq) is discussed. Dissociative dynamics were repeated in the therapeutic relationship, in the form of an obsessive game intending to preserve the state in which there was no need to remember what had been unconsciously transmitted to the child: his father’s wartime experience. The projection of the primary elements which had been silenced evoked in the therapist allusions to his unconscious identification with his ancestor’s post-traumatic experiences. These allusions helped in overcoming the dissociated state. The role of memory in child psychotherapists’ receptivity of trauma is revisited.     

Effects of verbal labeling and exposure duration on implicit memory for visual patterns.

The present study investigated the role of verbal labeling and exposure duration in implicit memory for novel visual patterns. Encoding condition was varied in Experiment 1. Two encoding conditions discouraged verbal labeling and a third required it. In Experiment 2, exposure duration was manipulated to determine whether a new memory representation could be formed after a single 1-s exposure. The results suggest that verbal labeling is not necessary to support priming. Type of encoding did not affect implicit memory, but had a pronounced effect on explicit memory. Furthermore, a single 1-s exposure was sufficient to support priming, and priming was not further enhanced by longer stimulus exposures. In contrast, recognition performance was enhanced by a longer stimulus duration. Thus, priming effects with these novel figures are likely to be supported by newly acquired representations rather than by preexisting memory representations.     

Memory-modulatory effects of centrally acting noradrenergic drugs: possible involvement of brain cholinergic mechanisms.

Post-training administration of the centrally acting muscarinic agonist oxotremorine (50.0 microgram/kg, ip) facilitated 48-hr retention, in mice, of a one-trial step-through inhibitory avoidance response. Oxotremorine-induced memory facilitation was not prevented by the simultaneous post-training administration of the central beta-adrenoceptor antagonist propranolol (2.0 mg/kg, ip). In contrast, post-training administration of atropine (0.5 mg/kg, ip), but not methylatropine (0.5 mg/kg, ip), completely prevented the facilitatory effects of the central beta-adrenoceptor agonist clenbuterol (30.0 micrograms/kg, ip) on retention. Low subeffective doses of clenbuterol (3.0 micrograms/kg, ip) and oxotremorine (6.25 or 12.5 micrograms/kg, ip) potentiated their effects and facilitated retention when given simultaneously immediately post-training. These results suggest that clenbuterol may induce memory facilitation through an increase of the release of acetylcholine in the brain. Post-training administration of a high dose of clenbuterol (1.0 mg/kg, ip) significantly impaired retention. Clenbuterol (1.0 mg/kg, ip)-induced impairment of retention was completely prevented by simultaneous post-training administration of oxotremorine (6.25, 12.5, or 50.0 micrograms/kg, ip). The centrally acting anticholinesterase physostigmine (21.5 or 68.0 micrograms/kg, ip) partially prevented clenbuterol-induced impairment of memory. The peripherally acting anticholinesterase neostigmine (68.0 micrograms/kg, ip) modified neither retention nor the amnestic effects of clenbuterol. Considered together, these findings are consistent with the view that brain muscarinic cholinergic mechanisms are involved in both the facilitatory and impairing effect of post-training clenbuterol on the modulation of memory storage.     

Context preexposure prevents forgetting of a contextual fear memory: implication for regional changes in brain activation patterns associated with recent and remote memory tests

Contextual fear conditioning was maintained over a 15-day retention interval suggesting no forgetting of the conditioning experience. However, a more subtle generalization test revealed that, as the retention interval increased, rats showed enhanced generalized fear to an altered context. Preexposure to the training context prior to conditioning, however, prevented this enhanced generalized fear from developing. These results support the hypothesis that the memory representation of the context degrades as the memory ages and is responsible for enhanced generalization. The implications of these results for systems consolidation versus forgetting interpretations of regional changes in neural activation patterns that occur as memories age are discussed.     

Complexity effects in visuo-spatial working memory: implications for the role of long-term memory

Several studies have shown that the capacity of visuo-spatial working memory is limited by complexity. Using a variant of the Corsi blocks task, this paper investigates the effect of complexity of the to-be-remembered path on visuo-spatial memory span. Redundancy was determined by three Gestalt principles: symmetry, repetition, and continuation. Experiment 1 revealed an effect of path complexity. The subsequent experiments explored whether the superiority for recall of structured over complex paths can be attributed solely to the operation of visuo-spatial working memory, or whether it also reflects the use of long-term knowledge. Experiment 2 demonstrated that the effect of complexity remained, even when the mechanisms for visuo-spatial coding were removed by a secondary visuo-spatial task. In Experiments 3 and 4 subjects were trained in the recall of complex paths. This led to the creation of long-term memory representations for these paths, as shown by an improvement in their span, and a concomitant lack of transfer to new paths. Finally, Experiment 5 showed that one prior repetition of a complex path was sufficient to produce specific and long-term learning effects. These results point to the involvement of long-term memory processes in the temporary retention of visuo-spatial material for which representations exist in long-term memory. They also suggest that the effect of complexity may provide a tractable technique for investigating the mechanisms underlying the limits of visuo-spatial short-term storage.     

Effects of food deprivation upon behavioral patterns and time budgeting of Aplysia fasciata

Effects of food deprivation upon time devoted to different behaviors in Aplysia fasciata were investigated. Time invested in mating, egg-laying, swimming, and movement in place was increased, and time spent immobile and crawling was decreased. Time of occurrence of behaviors was highly synchronized, but differed from that seen when food was available. Changes in behavior seem to be adaptive to conditions in which food is scarce: increased motility may lead to finding sites where food is present, while increased egg-laying and mating may ensure survival of progeny. Behavioral changes can be readily accounted for by removal of postingestive stimuli signaling satiation.