Auditory memory can be object based

Identifying how memories are organized remains a fundamental issue in psychology. Previous work has shown that visual short-term memory is organized according to the object of origin, with participants being better at retrieving multiple pieces of information from the same object than from different objects. However, it is not yet clear whether similar memory structures are employed for other modalities, such as audition. Under analogous conditions in the auditory domain, we found that short-term memories for sound can also be organized according to object, with a same-object advantage being demonstrated for the retrieval of information in an auditory scene defined by two complex sounds overlapping in both space and time. Our results provide support for the notion of an auditory object, in addition to the continued identification of similar processing constraints across visual and auditory domains. The identification of modality-independent organizational principles of memory, such as object-based coding, suggests possible mechanisms by which the human processing system remembers multimodal experiences.     

Sequential learning using temporal context

The temporal context model (TCM) has been extensively applied to recall phenomena from episodic memory. Here we use the same formulation of temporal context to construct a sequential learning model called the predictive temporal context model (pTCM) to extract the generating function of a language from sequentially-presented words. In pTCM, temporal context is used to generate a prediction vector at each step of learning and these prediction vectors are in turn used to construct semantic representations of words on the fly. The semantic representation of a word is defined as the superposition of prediction vectors that occur prior to the presentation of the word in the sequence. Here we create a formal framework for pTCM and prove several useful results. We explore the effect of manipulating the parameters of the model on learning a sequence of words generated by a bi-gram generating function. In this simple case, we demonstrate that feeding back the constructed semantic representation into the temporal context during learning improves the performance of the model when trained with a finite training sequence from a language with equivalence classes among some words. We also describe , a variant of the model that is identical to pTCM at steady state. has significant computational advantages over pTCM and can improve the quality of its prediction for some training sequences.     

Scaling behavior in the temporal context model

The Temporal Context Model (TCM) postulates a distributed representation of temporal context that provides the cue for episodic recall tasks. TCM, coupled with the Luce Choice Rule for determining probability of recall, a conjunction referred to as TCMFR, is able to explain the existence of the long-term recency effect, as well as predicting the persistence of associative effects even with the inclusion of a delay between items. Here, quantitative predictions of TCMFR such as the magnitude of the delay interval is increased in continuous-distractor free recall are developed. The magnitude of the recency effect is operationally defined as the ratio of the probability of first recall (PFR) of the last list item to the PFR of the next-to-last item. Properties of associative effects are operationalized by using analogous measures derived from conditional response probability (CRP) curves. TCMFR predicts a decrease in recency with increasing delay. The rate of this decay and the qualitative pattern of change with increasing delay depend on the rate of contextual drift. For a range of values of the rate of contextual drift, TCMFR also predicts a transient increase in the recency effect as the length of the delay increases from zero. The model predicts that contiguity effects in free recall should follow a similar pattern, but that associative asymmetry, ubiquitously observed in free recall, should decay monotonically with increases in the delay interval.     

Emotion's influence on memory for spatial and temporal context

Individuals report remembering emotional items vividly. It is debated whether this report reflects enhanced memory accuracy or a bias to believe emotional memories are vivid. We hypothesized emotion would enhance memory accuracy, improving memory for contextual details. The hallmark of episodic memory is that items are remembered in a spatial and temporal context, so we examined whether an item's valence (positive, negative) or arousal (high, low) would influence its ability to be remembered with those contextual details. Across two experiments, high-arousal items were remembered with spatial and temporal context more often than low-arousal items. Item valence did not influence memory for those details, although positive high-arousal items were recognized or recalled more often than negative items. These data suggest that emotion does not just bias participants to believe they have a vivid memory; rather, the arousal elicited by an event can benefit memory for some types of contextual details.     

Emotion's influence on memory for spatial and temporal context

Individuals report remembering emotional items vividly. It is debated whether this report reflects enhanced memory accuracy or a bias to believe emotional memories are vivid. We hypothesised emotion would enhance memory accuracy, improving memory for contextual details. The hallmark of episodic memory is that items are remembered in a spatial and temporal context, so we examined whether an item's valence (positive, negative) or arousal (high, low) would influence its ability to be remembered with those contextual details. Across two experiments, high-arousal items were remembered with spatial and temporal context more often than low-arousal items. Item valence did not influence memory for those details, although positive high-arousal items were recognised or recalled more often than negative items. These data suggest that emotion does not just bias participants to believe they have a vivid memory; rather, the arousal elicited by an event can benefit memory for some types of contextual details.     

Reduced memory for the spatial and temporal context of unpleasant words

Emotional stimuli are consistently better remembered than neutral stimuli. However, the reported effects of emotional stimuli on source memory are less consistent. In four experiments, we examined spatial and temporal source memory and free recall for emotional words previously studied in an fMRI experiment. In the fMRI experiment, the unpleasant but not the pleasant words were shown to activate the amygdala. In the experiments reported here, spatial and temporal source memory were reduced for the unpleasant words compared to pleasant and neutral words. Reduced spatial memory for unpleasant words was observed across studies that varied the specific stimuli, task conditions, and incidental versus intentional encoding instructions. Free recall was enhanced for the pleasant and unpleasant words compared to neutral words. The results demonstrate reduced source memory for unpleasant words even when item recall is enhanced. Our findings are consistent with prior reports of amygdala-mediated amnestic effects evoked by unpleasant stimuli.     

A temporal ratio model of memory

A model of memory retrieval is described. The model embodies 4 main claims: (a) temporal memory--traces of items are represented in memory partly in terms of their temporal distance from the present; (b) scale-similarity--similar mechanisms govern retrieval from memory over many different timescales; (c) local distinctiveness--performance on a range of memory tasks is determined by interference from near psychological neighbors; and (d) interference-based forgetting--all memory loss is due to interference and not trace decay. The model is applied to data on free recall and serial recall. The account emphasizes qualitative similarity in the retrieval principles involved in memory performance at all timescales, contrary to models that emphasize distinctions between short-term and long-term memory.     

Perceptual continuation and depth in visual phantoms can be explained by perceptual transparency

We try to explain perceptual continuation and depth in the visual-phantom illusion in terms of perceptual transparency. Perceptual continuation of inducing gratings across the occluder in stationary phantoms could be explained with unique transparency, a notion proposed by Anderson (1997 Perception 26 419-453). This view is consistent with a number of previous reports including that of McCourt (1994 Vision Research 34 1609-1617) who criticized the stationary phantom illusion from the viewpoint of his counterphase lightness induction or grating induction, which might involve invalid transparency. Here we confirm that the photopic phantom illusion (Kitaoka et al, 1999 Perception 28 825-834) really gives in-phase lightness induction and involves bistable transparency. It is thus suggested that perceptual continuation and depth in the visual-phantom illusion depend on perceptual transparency.     

Human visual short-term memory precision can be varied at will when the number of retained items is low

It has been debated whether human visual working memory is limited by the number of items or the precision with which they are represented. In the research reported here, we show that the precision of working memory can be flexibly and willfully controlled, but only if the number of retained items is low. Electroencephalographic recordings revealed that a neural marker for visual working memory (contralateral delay activity, or CDA) that is known to increase in amplitude with the number of retained items was also affected by the precision with which items were retained. However, willfully enhanced precision increased CDA amplitude only when the number of retained items was low. These results show that both the number and the (willfully controlled) precision of retained items constrain visual working memory: People can enhance the precision of their visual working memory, but only for a few items.     

Human reconsolidation does not always occur when a memory is retrieved: the relevance of the reminder structure

Memory reconsolidation is defined as a process in which the retrieval of a previously consolidated memory returns to a labile state which is then subject to stabilization. The reminder is the event that begins with the presentation of the learned cue and triggers the labilization-reconsolidation process. Since the early formulation of the hypothesis, several controversial items have arisen concerning the conditions that define reconsolidation. It is herein proposed that two diagnostic features characterize reconsolidation, namely: the labilization of the reactivated memory and the specificity of the reminder structure. To study this proposal, subjects received two different training sessions on verbal material on Day 1 and Day 2, respectively. Finally, they were tested for the first and second acquired memories on Day 3. It is demonstrated that the human declarative memory fulfills the two requirements that define the process. First, the reactivated memory is impaired by a new learning only when it is given closely after the reminder, revealing that the memory is labilized. Second, the omission of at least one of the reminder's components prevents labilization. Therefore, results show that the new learning fails to produce an amnesic effect on the target memory either when the reminder omits the learned cue or includes the beginning of the reinforcement.     

Memantine facilitates memory consolidation and reconsolidation in the day-old chick

Memantine is a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist that has been approved for the treatment of the cognitive deficits noted in Alzheimer's disease. While there is a body of research that supports memantine's facilitative action upon memory compromise, this series of studies aimed to investigate the effects of this drug in healthy animals with intact memory functioning. A 0.1 mM dose of memantine injected immediately after a weakly aversive training event (i.e. 20% v/v methyl anthranilate) was found to enhance passive avoidance learning for this event in day-old chicks up to 24 h following training. The same dose of memantine was also observed to enhance memory for the training event when it was administered in conjunction with a reminder trial. These results suggest that memantine is capable of facilitating both memory consolidation as well as memory reconsolidation. It was concluded that memantine's mechanism may involve the short-term or intermediate memory phases of the Gibbs and Ng model of memory, and that the current findings represent enhancement of intact memory, rather than amelioration of memory compromise.     

The timing of multiple retrieval events can alter GluR1 phosphorylation and the requirement for protein synthesis in fear memory reconsolidation

Numerous studies have indicated that maintaining a fear memory after retrieval requires de novo protein synthesis. However, no study to date has examined how the temporal dynamics of repeated retrieval events affect this protein synthesis requirement. The present study varied the timing of a second retrieval of an established auditory fear memory and followed this second retrieval with infusions of the protein synthesis inhibitor anisomycin (ANI) into the basolateral amygdala. Results indicated that the memory-impairing effects of ANI were not observed when the second retrieval occurred soon after the first (within 1 h), and that the inhibitor gradually regained effectiveness as the retrieval episodes were spaced further apart. Additionally, if the second of the closely timed retrievals was omitted prior to ANI infusions, long-term memory deficits were observed, suggesting that the altered effectiveness of ANI was due specifically to the second retrieval event. Further experiments revealed that the second retrieval was not associated with a change in Zif268 protein expression but did produce a rapid and persistent dephosphorylation of GluR1 receptors at Ser845, an AMPAR trafficking site known to regulate the stability of GluR2 lacking AMPARs, which have been shown to be important in memory updating. This suggests that the precise timing of multiple CS presentations during the reconsolidation window may affect the destabilization state of the memory trace.     

The temporal dynamics of retention of a context memory: something is missing

We use a variation of contextual fear conditioning, called the context pre-exposure facilitation effect (CPFE) to study the rat's memory for context. In this paradigm, the rat is pre-exposed to a conditioning context and later returned to that context, where it is immediately shocked. The memory context is revealed by the fact that pre-exposure to the conditioning context, but not to a different context, greatly enhances conditioned fear produced by immediate shock. We report that rat's retention of the context memory is a nonmonotonic U-shaped function of the interval separating pre-exposure and immediate shock. Retention performance decays rapidly so that within 2 min of pre-exposure there is no evidence that the rat was pre-exposed to the context. Within a few hours, however, a strong CPFE was observed that persisted for at least 28 d. Two hypotheses are discussed: (1) the descending arm of the U represents a retrieval failure, and (2) the U-shaped function represents two discontinuous memory processes initiated in parallel-short-term synaptic changes that are rapidly initiated, but also decay rapidly, and long-term synaptic processes that take time to generate but can endure for days.     

The consolidation of object and context recognition memory involve different regions of the temporal lobe

These experiments investigated the involvement of several temporal lobe regions in consolidation of recognition memory. Anisomycin, a protein synthesis inhibitor, was infused into the hippocampus, perirhinal cortex, insular cortex, or basolateral amygdala of rats immediately after the sample phase of object or object-in-context recognition memory training. Anisomycin infused into perirhinal or insular cortices blocked long-term (24 h), but not short-term (90 min) object recognition memory. Infusions into the hippocampus or amygdala did not impair object recognition memory. Anisomycin infused into the hippocampus blocked long-term, but not short-term object-in-context recognition memory, whereas infusions administered into the perirhinal cortex, insular cortex, or amygdala did not affect object-in-context recognition memory. These results clearly indicate that distinct regions of the temporal lobe are differentially involved in long-term object and object-in-context recognition memory. Whereas perirhinal and insular cortices are required for consolidation of familiar objects, the hippocampus is necessary for consolidation of contextual information of recognition memory. Altogether, these results suggest that temporal lobe structures are differentially involved in recognition memory consolidation.     

Selection can be performed effectively without temporal binding,but could be even more effective with it

Experiments using spatial cues and spatial probes provide strong evidence for an attention mechanism that chooses a location and selects all information at that location. This selection process can work very quickly; so quickly that selection probably begins before segmentation and grouping. It can be implemented in a neural network simply and efficiently without temporal binding. In conjunction with this spatial attention, however, temporal binding can potentially enhance visual selection in complex scenes. First, it would allow a target object to be selected without also selecting a superimposed distractor. Second, it could maintain representations of objects after attention has moved to another object. Third, it could allow multiple parts of an object or scene to be selected, segmented, and analysed simultaneously. Thus, temporal synchrony should be more likely to appear during tasks with overlapping targets and distractors, and tasks that require that multiple objects or multipart objects be analysed and remembered simultaneously.     

Priming on perceptual implicit memory tests can be achieved through presentation of associates

Roediger and McDermott (1995) presented lists of semantic associates (e.g.,door, glass, pane, shade, ledge) to induce false recall of related, nonpresented words (e.g.,window). This study procedure was used in an attempt to determine whether associative activation of target words would be sufficient to produce priming on perceptual implicit memory tests. Priming of the nonpresented items occurred on both word stem completion and word fragment completion, but the level of priming was generally lower than for items that had been studied. Priming of the related, nonpresented words occurred on a conceptual implicit test of word association; further, the level of priming was equivalent to that of presented words.     

Who we were and who we will be: the temporal context of women's in-group stereotype content

Research has elaborated considerably on the dimensions of out-group stereotype content and on the origins and functions of different content combinations. Less attention has been given to the origins and functions of in-group stereotype content. We argue that in-group stereotypes are likely to serve different social identity functions, and thus attract different content, dependent on individual differences in in-group identification and on the temporal perspective of the perceiver. Two studies (Ns = 43 and 93) found that women's in-group stereotype content varied as a function of gender group identification and temporal perspective. When the past was primed, highly identified women generated stereotypes that emphasized the warmth (but not competence) of their group. When the future was primed, highly identified women generated stereotypes that emphasized the competence (as well as warmth) of their group. These results are discussed in terms of the use of stereotypes for social creativity versus social change.     

Emotion and false memory: How goal-irrelevance can be relevant for what people remember

Elaborating on misleading information concerning emotional events can lead people to form false memories. The present experiment compared participants’ susceptibility to false memories when they elaborated on information associated with positive versus negative emotion and pregoal versus postgoal emotion. Pregoal emotion reflects appraisals that goal attainment or failure is anticipated but has not yet occurred (e.g., hope and fear). Postgoal emotion reflects appraisals that goal attainment or failure has already occurred (e.g., happiness and devastation). Participants watched a slideshow depicting an interaction between a couple and were asked to empathise with the protagonist's feelings of hope (positive pregoal), happiness (positive postgoal), fear (negative pregoal), or devastation (negative postgoal); in control conditions, no emotion was mentioned. Participants were then asked to reflect on details of the interaction that had occurred (true) or had not occurred (false), and that were relevant or irrelevant to the protagonist's goal. Irrespective of emotional valence, participants in the pregoal conditions were more susceptible to false memories concerning goal-irrelevant details than were participants in the other conditions. These findings support the view that pregoal emotions narrow attention to information relevant to goal pursuit, increasing susceptibility to false memories for irrelevant information.