Competitive short-term and long-term memory processes in spatial habituation

Exposure to a spatial location leads to habituation of exploration such that, in a novelty preference test, rodents subsequently prefer exploring a novel location to the familiar location. According to Wagner's (1981) theory of memory, short-term and long-term habituation are caused by separate and sometimes opponent processes. In the present study, this dual-process account of memory was tested. Mice received a series of exposure training trials to a location before receiving a novelty preference test. The novelty preference was greater when tested after a short, rather than a long, interval. In contrast, the novelty preference was weaker when exposure training trials were separated by a short, rather than a long interval. Furthermore, it was found that long-term habituation was determined by the independent effects of the amount of exposure training and the number of exposure training trials when factors such as the intertrial interval and the cumulative intertrial interval were controlled. A final experiment demonstrated that a long-term reduction of exploration could be caused by a negative priming effect due to associations formed during exploration. These results provide evidence against a single-process account of habituation and suggest that spatial habituation is determined by both short-term, recency-based memory and long-term, incrementally strengthened memory.     

Enhanced long-term and impaired short-term spatial memory in GluA1 AMPA receptor subunit knockout mice: Evidence for a dual-process memory model

The GluA1 AMPA receptor subunit is a key mediator of hippocampal synaptic plasticity and is especially important for a rapidly-induced, short-lasting form of potentiation. GluA1 gene deletion impairs hippocampus-dependent, spatial working memory, but spares hippocampus-dependent spatial reference memory. These findings may reflect the necessity of GluA1-dependent synaptic plasticity for short-term memory of recently visited places, but not for the ability to form long-term associations between a particular spatial location and an outcome. This hypothesis is in concordance with the theory that short-term and long-term memory depend on dissociable psychological processes. In this study we tested GluA1^−/− mice on both short-term and long-term spatial memory using a simple novelty preference task. Mice were given a series of repeated exposures to a particular spatial location (the arm of a Y-maze) before their preference for a novel spatial location (the unvisited arm of the maze) over the familiar spatial location was assessed. GluA1^−/− mice were impaired if the interval between the trials was short (1 min), but showed enhanced spatial memory if the interval between the trials was long (24 h). This enhancement was caused by the interval between the exposure trials rather than the interval prior to the test, thus demonstrating enhanced learning and not simply enhanced performance or expression of memory. This seemingly paradoxical enhancement of hippocampus-dependent spatial learning may be caused by GluA1 gene deletion reducing the detrimental effects of short-term memory on subsequent long-term learning. Thus, these results support a dual-process model of memory in which short-term and long-term memory are separate and sometimes competitive processes.     

The effects of retention interval on preschool children's short-term memory of verbal items

The short-term recall of word-triads was tested, comparing retention over three types of intervals within 24 preschoolers. Retention was significantly lower in the 16 sec unfilled interval condition than in the immediate test condition. This result, predicted from preschoolers' rehearsal deficiency, differs from those obtained in previous adult and child studies. A filled interval condition, requiring irrelevant verbal activity during the 16 sec period, significantly reduced recall from that of the unfilled interval condition. Recognition of the word items on a subsequent recognition test was greater than chance and was not affected by interval condition. This suggests that the condition effects in short-term recall did not disrupt the long-term storage of the items.     

Dual trace theory and the consolidation of long-term memory

Retention functions were determined for four Ss for recognition memory of letters at 14 different delays from 3 sec to 5 min and two levels of storage load (1 and 6 letter lists), the retention interval being filled with backward counting. Memory strength retention functions were fit extremely well by assuming that two traces, short-term memory and long-term memory, are operative in this type of memory task. Only the short-term memory trace appears to be present during the first 8 or 10 sec of the retention interval, and this short-term trace decays exponentially with a time constant in the vicinity of 10 sec. Long-term memory is subject to a consolidation process which does not begin until about 10 sec after the study period and which is substantially complete at about 30 sec after the study period. Storage load has a very large effect on the degree of acquisition (learning) for both short and long-term traces, but storage load appears to have only a moderate effect or no effect on the decay rate of the short-term trace. There is some suggestion that the duration of the consolidation phase is shortened by an increase in storage load.     

PILLS OR SKILLS FOR HYPERACTIVE CHILDREN

The controversial nature of drug treatment of hyperactivity, the incidence and sequelae of hyperactivity, and problems of differential diagnosis of hyperactivity versus aggression were discussed. The effects of psychostimulant medication and behavior therapy on hyperactive children were reviewed with regard to effects on their social and academic behavior. Both treatments have resulted in clear short-term changes in social behavior but neither long-term academic nor long-term social effects have been shown with either treatment. Short-term effects on academic behavior have resulted from behavioral interventions but not from psychostimulants. However, the interventions have been too brief to allow one to draw unequivocal conclusions about the clinical efficacy of behavioral treatments. Although there have been long-term evaluations of psychostimulant therapy, there have not been any evaluations of long-term behavioral treatment programs for hyperactive children. Given the salutary short-term effects of behavior therapy with hyperactive children, extended clinical trials of behavior therapy need to be conducted. Finally, specific directions are suggested for future research.     

Visual memory and stimulus repetition effects

Recent investigations of memory for randomly configured patterns indicate that visual memory can involve distinct short-term and long-term components. The appearance of a visual recency effect that is confined to the last-presented item is believed to result from the active visualization of this item during the retention interval. Studies of the retention of familiar visual information have also suggested that the short-term effects observed are a result of active visualization. In a review of these studies, however, we argue that the effects obtained with familiar visual information are not necessarily a result of active visualization and, indeed, may not involve anything other than long-term visual memory. For example, Rabbitt and Vyas (1979) observed a visual recency effect in a serial choice reaction time task involving familiar information. That this recency effect was confined to the final item accords with the results obtained with unfamiliar visual information. However, this choice reaction time task did not require subjects to remember previous stimuli, so it is unlikely that they actively visualized them. With the case for a distinct short-term visual memory currently resting on the recency effect interpreted as reflecting a process of active visualization, this result is especially important. In the second part of the present paper, we report a series of experiments that provides an understanding of the visual recency effect in the serial choice reaction time task. We conclude from these studies that this effect is not due to visualization or to a visual trace either decaying or being overwritten by a succeeding stimulus.     

Adult age differences in short-term memory and subsequent long-term memory for actions.

Short-term memory for actions was investigated for young adult and elderly adult subjects with the Brown-Peterson procedure at retention intervals of 0 and 15 s. The short-term memory trials were followed by the long-term recall of the prior to-be-remembered actions. The 15-s retention interval was filled either with no activity or with 1 of 3 different interfering activities. Verbal interference had little effect on short-term memory at either age level. Actions performed in the interval either by the subjects or by the experimenter produced significantly lower recall scores at each age level, with the decrement being more pronounced for the elderly than for the young subjects. The long-term memory results indicated that successful short-term recall enhanced later long-term recall, regardless of age level.     

The Effects on Skill Acquisition of an Interpolated Motor Short-Term Memory Task During The Kr-Delay Interval

The effects of an interpolated motor short-term memory task during the KR-delay interval on skill acquisition was investigated. On each trial subjects estimated two positions on a linear-positioning apparatus. One group of subjects was presented two biasing movements, which they immediately recalled, during the KR-delay interval. The interpolated motor short-term memory task interfered with skill acquisition and retention.     

Rorschach Changes in Long-Term Short-Term Psychotherapy

Over a period of several years, repeat Korschach testing was done with two groups of patients receiving outpatient psychotherapy, a long-term group (n = 88) engaged in intensive, dynamically oriented psychotherapy and a short-term group (n = 88) involved in behavioral or gestalt therapy. Rorschach protocols were obtained at the beginning of the treatment and on three subsequent occasions, 1 year, 21/2 years, and 4 years later, when most of the long-term and all of the short-term patients had completed their therapy. The findings demonstrate generally beneficial effects of psychotherapy, greater change in long-term than in short-term therapy, and the validity of the Rorschach for measuring these effects and changes.     

Rorschach changes in long-term and short-term psychotherapy

Over a period of several years, repeat Korschach testing was done with two groups of patients receiving outpatient psychotherapy, a long-term group (n = 88) engaged in intensive, dynamically oriented psychotherapy and a short-term group (n = 88) involved in behavioral or gestalt therapy. Rorschach protocols were obtained at the beginning of the treatment and on three subsequent occasions, 1 year, 2 1/2 years, and 4 years later, when most of the long-term and all of the short-term patients had completed their therapy. The findings demonstrate generally beneficial effects of psychotherapy, greater change in long-term than in short-term therapy, and the validity of the Rorschach for measuring these effects and changes.     

Effects of proactive interference and rehearsal on the primary and secondary components of short-term retention

Under the conditions of the distractor paradigm, short-term retention declines to a minimum in a very brief period. The rapid forgetting can be said to reflect the declining contribution of the short-term store or primary memory and the asymptote can be taken as a measure of the contribution of the long-term store or secondary memory. It was shown that manipulating proactive effects by varying the recency of prior material affected only the primary memory component of the short-term retention function. On the other hand manipulating the difficulty of the subsidiary task performed during the retention period with proactive effects held constant affected both the primary and the secondary components. The results were discussed with respect to the relation between the two memory components and the idea that proactive effects are limited to long-term store.     

Working memory, long-term memory, and medial temporal lobe function

Early studies of memory-impaired patients with medial temporal lobe (MTL) damage led to the view that the hippocampus and related MTL structures are involved in the formation of long-term memory and that immediate memory and working memory are independent of these structures. This traditional idea has recently been revisited. Impaired performance in patients with MTL lesions on tasks with short retention intervals, or no retention interval, and neuroimaging findings with similar tasks have been interpreted to mean that the MTL is sometimes needed for working memory and possibly even for visual perception itself. We present a reappraisal of this interpretation. Our main conclusion is that, if the material to be learned exceeds working memory capacity, if the material is difficult to rehearse, or if attention is diverted, performance depends on long-term memory even when the retention interval is brief. This fundamental notion is better captured by the terms subspan memory and supraspan memory than by the terms short-term memory and long-term memory. We propose methods for determining when performance on short-delay tasks must depend on long-term (supraspan) memory and suggest that MTL lesions impair performance only when immediate memory and working memory are insufficient to support performance. In neuroimaging studies, MTL activity during encoding is influenced by the memory load and correlates positively with long-term retention of the material that was presented. The most parsimonious and consistent interpretation of all the data is that subspan memoranda are supported by immediate memory and working memory and are independent of the MTL.     

False working memories? Semantic distortion in a mere 4 seconds

False memories are well-established, episodic memory phenomena: Semantically related associates are confidently and erroneously remembered as studied items. We report four experiments yielding similar effects in a working memory paradigm. Four semantically related words were retained over a brief interval. Whether or not the interval was filled with a math verification task, semantically related lures were mistakenly recognized as members of the memory set and took longer to reject than did unrelated negative probes. In a short-term recall task, semantic intrusions exceeded other errors (e.g., phonemic). Our results demonstrate false memory effects for a subspan list when a mere 4 sec was given between study and test. Such rapid semantic errors presumably result from associative processing, may be related to familiarity-based proactive interference in working memory, and are consistent with recent models that integrate short- and long-term memory processes.     

Faustian bargains: Short-term and long-term contingencies in phylogeny,ontogeny, and sociogeny

Rachlin's interpretations of self-control depend on the short-term versus the long-term consequences of behavior. Sometimes these effects support each other (typing an abstract produces a written product now and is later read by others). Sometimes they conflict (procrastination now is incompatible with finishing the abstract by deadline). We usually reserve the language of self-control for human cases where long-term consequences are chosen over short-term ones. Rachlin made this distinction salient in ontogeny, but it also applies to selection in phylogeny (Darwinian evolution) and sociogeny (behavior passed from one organism to another). Our account examines relations between short-term and long-term consequences at each level of selection. For example, sexual selection has adaptive, short-term mating consequences but may drive species to extreme specializations that jeopardize long-term survival. In sociogeny, as in the Tragedy of the Commons, group members may get immediate economic benefits from exploiting resources but exhaust those resources over the long term. Whatever the level, when short-term and long-term consequences have opposing effects, adaptive behavior may depend on whether temporally extended contingencies exert more control than more immediate benefits.     

Semantic similarity dissociates short- from long-term recency effects: Testing a neurocomputational model of list memory

The finding that recency effects can occur not only in immediate free recall (i.e., short-term recency) but also in the continuous-distractor task (ie., long-term recency) has led many theorists to reject the distinction between short- and long-term memory stores. Recently, we have argued that long-term recency effects do not undermine the concept of a short-term store, and we have presented a neurocomputational model that accounts for both short- and long-term recency and for a series of dissociations between these two effects. Here, we present a new dissociation between short- and long-term recency based on semantic similarity, which is predicted by our model. This dissociation is due to the mutual support between associated items in the short-term store, which takes place in immediate free recall and delayed free recall but not in continuous-distractor free recall.     

The anatomy of loneliness

Loneliness is a potent but little understood risk factor for broad-based morbidity and mortality. We review five social neurobehavioral mechanisms that may account for this association. The evidence suggests that different mechanisms explain short-term and long-term effects, and that the long-term effects operate through multiple pathways. Implications for the design of interventions are discussed.     

Dissociation of short- and long-term face memory: evidence from long-term recency effects in temporal lobe epilepsy

We tested whether memory deficits in temporal lobe epilepsy (TLE) are better described by a single- or dual-store memory model. To this aim, we analyzed the influence of TLE and proactive interference (PI) on immediate and 24-h long-term recency effects during face recognition in 16 healthy participants and 18 right and 21 left non-surgical TLE patients. PI in healthy participants or TLE erased the long-term recency effect, but left the immediate recency effect unaffected. Although the immediate recency effect was still visible in right TLE patients, the number of detected recency items during immediate recognition was decreased in right TLE compared to left TLE. Right TLE was also related to decreased detection of pre-recency items during delayed recognition compared to left TLE, and decreased detection of pre-recency items during immediate recognition under PI. The results show that the temporal lobes are necessary for the long-term recency effect, but not for the immediate recency effect, and thus speak for a dissociation of short- and long-term memory for faces. Right TLE is related to more severe long-term memory deficits than left TLE and is also related to additional short-term memory deficits for faces.     

Independence of long-term contextual memory and short-term perceptual hypotheses: Evidence from contextual cueing of interrupted search

Observers are able to resume an interrupted search trial faster relative to responding to a new, unseen display. This finding of rapid resumption is attributed to short-term perceptual hypotheses generated on the current look and confirmed upon subsequent looks at the same display. It has been suggested that the contents of perceptual hypotheses are similar to those of other forms of memory acquired long-term through repeated exposure to the same search displays over the course of several trials, that is, the memory supporting “contextual cueing.” In three experiments, we investigated the relationship between short-term perceptual hypotheses and long-term contextual memory. The results indicated that long-term, contextual memory of repeated displays neither affected the generation nor the confirmation of short-term perceptual hypotheses for these displays. Furthermore, the analysis of eye movements suggests that long-term memory provides an initial benefit in guiding attention to the target, whereas in subsequent looks guidance is entirely based on short-term perceptual hypotheses. Overall, the results reveal a picture of both long- and short-term memory contributing to reliable performance gains in interrupted search, while exerting their effects in an independent manner.     

Langzeitergebnisse einer Funktionellen-Magnetresonanztomographie-Studie

In a controlled functional magnetic resonance imaging (fMRI) study the effect of psychodynamic short-term psychotherapy on cerebral activation of panic disorder patients was determined. In a linguistic go-no go paradigm behavioral measures and cerebral activation to affective word stimuli with threatening, neutral and positive content were assessed pretreatment and post-treatment in 9 patients with panic disorder. 18 healthy controls were scanned twice at the same intervals. In an additional long-term follow-up after approximately 3 years post-treatment the effect of brain activation changes during treatment on the long-term outcome of core symptoms (panic-related cognition and fear of body sensations) were determined. In accordance with the hypotheses increased limbic (hippocampus and amygdala) activation accompanied by low prefrontal activation to negative words were found. At treatment termination, panic-related symptoms had improved significantly and fronto-limbic activation patterns were normalized. Reduction of activation of the limbic system during treatment was predictive of a favorable long-term outcome. The results indicate that short-term psychodynamic treatment leads to changes in fronto-limbic networks, similar to previous findings on cognitive-behavioural treatment.