The syntagmatic-paradigmatic shift in dichotic listening

Children at two age levels, 6 to 7 years and 9 to 10 years, listened to pairs of words presented dichotically to the left and right ear either simultaneously or in immediate succession. Their task was to report what they heard after each pair. The experimental pairs involved either syntagmatic relations (e.g., bird-fly) or paradigmatic relations (table-chair). The younger children correctly identified more syntagmatic than paradigmatic pairs (using control pairs as a base) while the older children correctly identified more paradigmatic pairs. There was no difference between associated and nonassociated pairs. The results are taken to mean that pragmatic, serial relations dominate the semantic organization of younger children and that logical, hierarchical relations make their impact later in the course of development.     

The perirhinal cortex and long-term familiarity memory

To analyse the functions of the perirhinal cortex, the activity of single neurons in the perirhinal lortex was recorded while macaques performed a delayed matching-to-sample task with up to ohree intervening stimuli. Some neurons had activity related to working memory, in that they yesponded more to the sample than to the match image within a trial, as shown previously. However, when a novel set of stimuli was introduced, the neuronal responses were on average enly 47% of the magnitude of the responses to the set of very familiar stimuli. Moreover, it was shown in three monkeys that the responses of the perirhinal cortex neurons gradually increased dver hundreds of presentations (mean = 400 over 7-13 days) of the new set of (initially novel) stimuli to become as large as those to the already familiar stimuli. Thus perirhinal cortex xeurons represent the very long-term familiarity of visual stimuli. Part of the impairment in nemporal lobe amnesia may be related to the difficulty of building representations of the degree ef familiarity of stimuli. A neural network model of how the perirhinal cortex could implement tong-term familiarity memory is proposed using Hebbian associative learning.     

The hippocampal complex and long-term memory revisited

A recent report by Cipolotti et al. demontrates that the hippocampus and perhaps the parahippocampal area are essential for retrieval of remote episodic memory and important for remote semantic memory. This report, along with other recent findings, re-opens the debate about the role of these medial temporal lobe structures, indicating that their role extends much further than traditional theory had suggested.     

The perirhinal cortex and long-term familiarity memory.

To analyse the functions of the perirhinal cortex, the activity of single neurons in the perirhinal cortex was recorded while macaques performed a delayed matching-to-sample task with up to three intervening stimuli. Some neurons had activity related to working memory, in that they responded more to the sample than to the match image within a trial, as shown previously. However, when a novel set of stimuli was introduced, the neuronal responses were on average only 47% of the magnitude of the responses to the set of very familiar stimuli. Moreover, it was shown in three monkeys that the responses of the perirhinal cortex neurons gradually increased over hundreds of presentations (mean = 400 over 7-13 days) of the new set of (initially novel) stimuli to become as large as those to the already familiar stimuli. Thus perirhinal cortex neurons represent the very long-term familiarity of visual stimuli. Part of the impairment in temporal lobe amnesia may be related to the difficulty of building representations of the degree of familiarity of stimuli. A neural network model of how the perirhinal cortex could implement long-term familiarity memory is proposed using Hebbian associative learning.     

Topographically distinct cortical activation in episodic long-term memory: The retrieval of spatial versus verbal information

Two experiments are reported to study slow potentials in the EEG during reactivation of spatial and verbal information. Subjects had to learn associations between drawings and one, two, or three mediators (locations in Experiment 1, nouns in Experiment 2). During recall, subjects had to decide whether or not two drawings were linked to each other by a common mediator. EEG was recorded during learning and recall. Both experiments were completely equivalent. Irrespective of the quality of the mediators, response time proved to be a linear function of the numbers of mediators to be recalled. Negative slow potentials that accompanied the reactivation of information during anticipation learning and cued recall had a material-specific topography: The maximum was found over the parietal cortex for spatial information and over the left frontal cortex for verbal information. Moreover, the amplitude at these scalp locations varied with the amount of the to-be-retrieved information. The results support the claim of topographically distinct cell assemblies specialized for storage and retrieval of distinct kinds of information.     

The long-term recency effect in recognition memory

Three classes of theories explain the recency effect: the modal model, single-store models, and the composite view, which integrates the two positions. None could explain the absence of a long-term recency effect in recognition memory in previous studies. We suggest that prior work did not obtain a recency effect because testing used a multiple-probe rather than a single-probe recognition procedure. Here we tested memory using a single-probe recognition procedure. Experimental conditions included an immediate test, a delayed test after a filled interval, and a continuous-distractor paradigm in which the same filled delay preceded the first word and followed every study word. The long-term recency effect in continuous-distractor recognition was equivalent to the recency effect in immediate recognition. Its absence in the delayed recognition condition demonstrated that it was not attributed to the use of a putative short-term memory store. Single-store models and the composite view can account for this novel finding.     

The neuroimaging of long-term memory encoding processes

There needs to be more crosstalk between the lesion and functional neuroimaging memory literatures. This is illustrated by a discussion of episode and fact encoding. The lesion literature suggests several hypotheses about which brain regions underlie the storage of episode and fact information, which can be explored by functional neuroimaging. These hypotheses have been underexplored because neuroimaging studies of encoding have been insufficiently hypothesis-driven and have not controlled encoding-related processes sufficiently well to allow clear interpretations of results to be made. Nevertheless, there is good evidence that certain kinds of associative encoding and/or consolidation are sufficient to activate the medial temporal lobes, and preliminary evidence that some kinds of associative priming may reduce activation of this region. It remains to be proved that attentional orienting to certain kinds of novel information activates the medial temporal lobes. Evidence is growing that the HERA model, developed from neuroimaging rather than lesion data, requires modification and that frontal cortex encoding activations are probably caused by executive processes that are important in effortful memory processing. Neuroimaging studies allow the detection of encoding-related activations in previously unexpected brain regions (e.g. parietal lobes) and, in turn, these findings can be explored with lesion studies.     

Organization and long-term memory search

A recognition RT paradigm was used to assess a number of plausible search strategies in LTM for categorized lists. List length was determined by factorially combining two, three, or five categories with two, three, or five words per category, and test items could be one of four types: (1) positive, (2) a repeated positive, (3) a related negative, or (4) an unrelated negative. It was found that RT increased linearly with category size for both positive and related negatives (about 30-40 msec/item); whereas the increase was much smaller for the unrelated negatives, especially for three and five categories (about 9 msec/item). With an increase in the number of categories, RT increased at the rate of about 40 msec/category for all three test items. A theory of .high-speed scanning for categorized material was proposed in which a serial and exhaustive search of the categories, is first undertaken. If a positive category match is found, a serial and exhaustive search within the contents of the positive category is initiated; if no category match is found, the search is simply terminated. Some evidence was presented that categories recently probed may provide for a short-circuiting of the category search.     

The representation of color and form in long-term memory

Color and form are elementary stimulus encoding dimensions that have effects on the representation of visual stimuli at early processing stages. Little is known, however, about their effects on visual long-term memory. In three experiments we investigated whether color is part of the memory representation, whether color and form are bound in the memory representation, and the effect of color context on memory performance. Experimental results suggest that color is part of the memory representation and that color and form can be represented separately in memory and accessed independently. We suggest that the binding of color and form is a deliberate strategic act that requires focal attention, not a natural consequence of processing visual stimuli. We compare our results with the predictions of two computational memory models regarding feature binding. The effect of color context was not straightforward; however, results are consistent with the encoding specificity principle.     

Media multitasking and memory: Differences in working memory and long-term memory

Increasing access to media in the 21st century has led to a rapid rise in the prevalence of media multitasking (simultaneous use of multiple media streams). Such behavior is associated with various cognitive differences, such as difficulty filtering distracting information and increased trait impulsivity. Given the rise in media multitasking by children, adolescents, and adults, a full understanding of the cognitive profile of media multitaskers is imperative. Here we investigated the relationship between chronic media multitasking and working memory (WM) and long-term memory (LTM) performance. Four key findings are reported (1) heavy media multitaskers (HMMs) exhibited lower WM performance, regardless of whether external distraction was present or absent; (2) lower performance on multiple WM tasks predicted lower LTM performance; (3) media multitasking-related differences in memory reflected differences in discriminability rather than decision bias; and (4) attentional impulsivity correlated with media multitasking behavior and reduced WM performance. These findings suggest that chronic media multitasking is associated with a wider attentional scope/higher attentional impulsivity, which may allow goal-irrelevant information to compete with goal-relevant information. As a consequence, heavy media multitaskers are able to hold fewer or less precise goal-relevant representations in WM. HMMs’ wider attentional scope, combined with their diminished WM performance, propagates forward to yield lower LTM performance. As such, chronic media multitasking is associated with a reduced ability to draw on the past—be it very recent or more remote—to inform present behavior.     

The opportunity to choose enhances long-term episodic memory

ABSTRACT

Episodic memory is typically studied under conditions that treat participants as passive agents. Here we sought to explore how actively engaging in ongoing naturalistic occurrences affects long-term episodic memory. Participants viewed 40 short movie clips that depicted a protagonist that conversed with the participants. In each clip, they were either offered the chance to (supposedly) determine the clip’s continuation (active condition), or let the computer decide for them (passive condition). Participants returned either two days or one week after the experience to undergo a true/false memory test for the clips’ details and a two-alternative recognition test for the choices made. Memory performance for both groups was superior for information and choices conveyed in the active vs. passive condition. These findings suggest that the sense of actively influencing the unfolding of events is beneficial to long-term memory of the experience at large, baring potential interventions in the fields of education and cognitive enhancement.     

The contents of long-term memory and the emergence of knowledge

Through a review of the literature, this paper proposes arguments in favour of a multimodal, dynamic, functional, and situational conception of memory. Memory is assumed to contain traces that reflect past experiences. The properties of these experiences are considered to be distributed across multiple neuronal systems, which are responsible, in particular, for sensorimotor and emotional processing. Memory is dynamic because knowledge emerges almost continuously from the activation and integration of these multimodal components. Memory is functional and situational because knowledge emerges from the subject's activity in a given situation, that is from a type of resonance between the properties of the past experiences that have shaped the neuronal networks and the properties of present experiences.     

Task-set switching and long-term memory retrieval

The authors tested the hypothesis of a close relationship between the intentional component of task-set switching ("advance reconfiguration;" R. D. Rogers & S. Monsell, 1995) and long-term memory (LTM) retrieval. Consistent with this hypothesis, switch costs are reported to be larger when the switched-to task involves high retrieval demands (i.e., retrieval of episodic information) than when it involves low retrieval demands (i.e., retrieval of semantic information). In contrast, switch costs were not affected by a primary-task difficulty manipulation unrelated to intentional retrieval demands (Experiment 2). Also, the retrieval-demand effect on switch costs was eliminated when time for advanced preparation or task cues explicitly specifying the task rules were provided (Experiment 3). Overall, results were consistent with the hypothesis that the intentional switch-cost component reflects the time demands of retrieving appropriate task rules from LTM.     

Relationship between short- and long-term memory and short- and long-term extinction

Both the acquisition and the extinction of memories leave short- and long-term mnemonic traces. Here, we show that in male Wistar rats, the short-term memory for a step-down inhibitory avoidance task (IA) is resistant to extinction, and that its expression does not influence retrieval or extinction of long-term memory. It has been known for some time that short- and long-term inhibitory avoidance memory involve separate and parallel processes. Here we show that, instead, short-term extinction of IA long-term memory is the first step towards its long-term extinction, and that this link requires functional NMDA receptors and protein synthesis in the CA1 region of the dorsal hippocampus at the time of the first CS-no US presentation.     

The posterior parietal cortex and long-term memory representation of spatial information

The hypothesis to be explored in this chapter is based on the assumption that the posterior parietal cortex (PPC) is directly involved in representing a subset of the spatial features associated with spatial information processing and plays an important role in perceptual memory as well as long-term memory encoding, consolidation, and retrieval of spatial information. After presentation of the anatomical location of the PPC in rats, the nature of PPC representation based on single spatial features, binding of visual features associated with visual spatial attention, binding of object-place associations associated with acquisition and storage of associations where one of the elements is a spatial component, and binding of ideothetic and allothetic information in long-term memory is discussed. Additional evidence for a PPC role in mediation of spatial information in long-term storage is offered. Finally, the relationship between the PPC and the hippocampus from a systems and dynamic point view is presented.     

Positional uncertainty in long-term memory

Long-term memory for position was examined from the perspective of an immediate memory framework, the perturbation model of Estes (Estes, 1972; Lee & Estes, 1977, 1981). First, a simple version of the perturbation model is shown to provide a reasonable fit of previously reported long-term data (Nairne, 1990b), even though the perturbation idea was developed to explain the phenomena of immediate retention. Second, new results are reported that extend the application to multiple dimensions. Long-term memories for list and within-list position appear to mimic the classic patterns of immediate retention, in that both show bow-shaped serial position curves and error generalization gradients that are roughly symmetrical around the true serial position.     

Creation of visual long-term memory

Currently, it is not known by which mechanisms novel visual representations are stored in long-term memory (LTM). Here we report evidence that visual working memory (WM) plays an important role in the formation of visual LTM. By varying exposure times and perceptual difficulty of the stimuli, we find that the rate-limiting factor constraining storage in LTM is the amount of information that can be simultaneously kept in WM, whereas the time needed to store this information into LTM is constant irrespective of the size of the WM content. These results support the hypothesis that visual WM serves as a gate for the storage of information into LTM.