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 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A variety of cardiovascular and cerebrovascular diseases are associated with alterations in cholesterol levels and metabolism. Moreover, convincing evidence shows that high cholesterol diet can lead to learning and memory impairments. On the other hand, a significant body of research has also demonstrated that learning is improved by elevated dietary cholesterol. Despite these conflicting findings, it is clear that cholesterol plays an important role in these cognitive properties. However, it remains unclear how this blood-brain barrier (BBB)-impenetrable molecule affects the brain and under what circumstances it provides either detrimental or beneficial effects to learning and memory. The aim of this study was to characterize the effects of 5% cholesterol diet on six-month-old inbred Brown Norway rats. More important, we sought to examine the role that cholesterol can play when repeated anesthesia and intravenous infusion disrupts cognitive function. This present study supports previous work showing that enriched cholesterol diet leads to significant alterations in neuroinflammation and BBB disruption. Following repeated anesthesia and intravenous infusion of saline we observe that animals under normal diet conditions exhibit significant deficiencies in spatial learning and cholinergic neuron populations compared to animals under enriched cholesterol diet, which do not show such deficiencies. These findings indicate that cholesterol diet can protect against or counteract anesthesia/infusion-induced cognitive deficits. Ultimately, these results suggest that cholesterol homeostasis serves an important functional role in the brain and that altering this homeostasis can either exert positive or negative effects on cognitive properties.
Neurobiol Learn Mem 2013 Nov
PMID:Cholesterol diet counteracts repeated anesthesia/infusion-induced cognitive deficits in male Brown Norway rats. 2397 49

A statistical procedure that separates storage from retrieval was used to study the acoustic similarity effect as a function of retention interval in the Brown-Peterson paradigm. Both storage and retrieval components showed reliable and independent changes with retention interval, but only the storage component was affected by acoustic similarity. Hence, acoustic similarity affects trace durability and retrieval plays no essential role in the similarity effect. This finding is inconsistent with the address hypothesis (cf. Baddeley, 1968). It is argued that acoustic similarity induces subjects to encode the target item in a confused fashion, particularly in regard to order information.
Mem Cognit 1977 Sep
PMID:Storage-retrieval analysis of acoustic similarity. 2420 21

The purpose of this study was to examine the significance of Brown and McNeill's (1966) findings regarding the "tip of the tongue" (TOT) phenomenon, A modified version of their procedure was used with 56 Ss. Although their findings that Ss in a TOT state can detect parts and properties of the missing word were generally replicated, a division of the TOT state into a variety of substates showed correct detection rate to vary greatly, depending on the substate involved. In addition, correct detection of partial information was demonstrated even when S declared he had no knowledge of the selected word (don't know). It was suggested that a distinction be made between information detection based on knowledge of the characteristics common to the class of items of which the target is a member ("class detection") and detection based on knowledge of characteristics specific to the target in question ("differential detection"). Both class and differential detection were found to obtain in TOT states as well as in the don't know state. Some theoretical and methodological implications were suggested.
Mem Cognit 1974 Jul
PMID:What does a person in a "TOT" state know that a person in a "don't know" state doesn't know. 2420 33

The notion that difficult initial retrieval facilitates subsequent recall was tested in a situation similar to Brown and McNeill's (1966) tip-of-the-tongue (TOT) paradigm. After 50 trials, Ss were unexpectedly asked to recall all the target words. It was found that words retrieved with difficulty in the definition session were relatively well recalled in the final test. Further analyses revealed that the critical factor for good recall was the presence of a TOT state, or a strong feeling of knowing the word, during initial retrieval. An explanation in terms of activation of the word's attributes was suggested.
Mem Cognit 1973 Sep
PMID:Retrieval difficulty and subsequent recall. 2421 47

This paper presents the results of a series of experiments using the release from proactive inhibition technique for identifying the salient encoding attributes of words. The technique uses the Brown-Peterson paradigm, but, after three trials on words of one class, a fourth trial is given with words of another class. The power of the class encoding is inferred from the extent of gain (release from PI) found on the shift trial. The studies reported show a high degree of effectiveness for semantic variables; practically no effectiveness for grammatical variables; a moderate amount for physical variables (i.e., figure-ground shift); and varying amounts for other shifts such as word frequency, imagery, language of the presentation to bilingual Ss. Some evidence is also given for the occurrence of simultaneous multiple encoding.
Mem Cognit 1973 Dec
PMID:Some characteristics of word encoding. 2421 46

Previous research suggests the prelimbic (PL) cortex is involved in expression of conditioned fear (Burgos-Robles, Vidal-Gonzalez, & Quirk, 2009; Corcoran & Quirk, 2007). However, there is a long history of research in the appetitive domain which implicates this region in using higher-order cues to modulate a behavioural response (Birrell & Brown, 2000; Floresco, Block, & Tse, 2008; Marquis, Killcross, & Haddon, 2007; Sharpe & Killcross, 2014). For example, the PL cortex is necessary to allow animals to use contextual cues to disambiguate response conflict in ambiguous circumstances (Marquis et al., 2007). Using an ABA fear renewal procedure, we assessed the role of the PL cortex in using contextual cues to modulate a response towards a conditioned stimulus (CS) in an aversive setting. We found that pre-training lesions of the PL cortex did not impact on the expression or extinction of conditioned fear. Rather, they selectively abolished renewal. Functional inactivation of the PL cortex during extinction did not disrupt the subsequent renewal of conditioned fear or the ability of animals to exhibit fear towards a CS during the extinction session. However, PL inactivation during the renewal test session disrupted the ability of animals to demonstrate a reinstatement of responding in the renewal context. An analysis of orienting responses showed that renewal deficits were accompanied by a lack of change in attentional responding towards the CS. These data suggest the PL cortex uses contextual cues to modulate both a behavioural and an attentional response during aversive procedures. We argue that the role of the PL cortex in the expression of conditioned fear is to use higher-order information to modulate responding towards predictive cues in ambiguous circumstance.
Neurobiol Learn Mem 2015 Feb
PMID:The prelimbic cortex uses contextual cues to modulate responding towards predictive stimuli during fear renewal. 2546 11

In a recent empirical study, Starns, Hicks, Brown, and Martin (Memory & Cognition, 36, 1-8 2008) collected source judgments for old items that participants had claimed to be new and found residual source discriminability depending on the old-new response bias. The authors interpreted their finding as evidence in favor of the bivariate signal-detection model, but against the two-high-threshold model of item/source memory. According to the latter, NEW responses only follow from the state of old-new uncertainty for which no source discrimination is possible, and the probability of entering this state is independent of the old-new response bias. However, when missed old items were presented for source discrimination, the participants could infer that the items had been previously studied. To test whether this implicit feedback led to second retrieval attempts and thus to source memory for presumably unrecognized items, we replicated Starns et al.'s (Memory & Cognition, 36, 1-8 2008) finding and compared their procedure to a procedure without such feedback. Our results challenge the conclusion to abandon discrete processing in source memory; source memory for unrecognized items is probably an artifact of the procedure, by which implicit feedback prompts participants to reconsider their recognition judgment when asked to rate the source of old items in the absence of item memory.
Mem Cognit 2016 Jan
PMID:No source memory for unrecognized items when implicit feedback is avoided. 2637 31

The causal role of verbal rehearsal in working memory has recently been called into question. For example, the SOB-CS (Serial Order in a Box-Complex Span) model assumes that there is no maintenance process for the strengthening of items in working memory, but instead a process of removal of distractors that are involuntarily encoded and create interference with memory items. In the present study, we tested the idea that verbal working memory performance can be accounted for without assuming a causal role of the verbal rehearsal process. We demonstrate in two experiments using a complex span task and a Brown-Peterson paradigm that increasing the number of repetitions of the same distractor (the syllable ba that was read aloud at each of its occurrences on screen) has a detrimental effect on the concurrent maintenance of consonants whereas the maintenance of spatial locations remains unaffected. A detailed analysis of the tasks demonstrates that accounting for this effect within the SOB-CS model requires a series of unwarranted assumptions leading to undesirable further predictions contradicted by available experimental evidence. We argue that the hypothesis of a maintenance mechanism based on verbal rehearsal that is impeded by concurrent articulation still provides the simplest and most compelling account of our results.
Mem Cognit 2016 Feb
PMID:Working memory still needs verbal rehearsal. 2644 77

In a series of four experiments, we explored what conditions are sufficient to produce a phonological similarity facilitation effect in working memory span tasks. By using the same set of memoranda, but differing the secondary-task requirements across experiments, we showed that a phonological similarity facilitation effect is dependent upon the semantic relationship between the memoranda and the secondary-task stimuli, and is robust to changes in the representation, ordering, and pool size of the secondary-task stimuli. These findings are consistent with interference accounts of memory (Brown, Neath, & Chater, Psychological Review, 114, 539-576, 2007; Oberauer, Lewandowsky, Farrell, Jarrold, & Greaves, Psychonomic Bulletin & Review, 19, 779-819, 2012), whereby rhyming stimuli provide a form of categorical similarity that allows distractors to be excluded from retrieval at recall.
Mem Cognit 2016 08
PMID:Phonological similarity in working memory span tasks. 2704 10

We tested the list homogeneity effect in reading aloud (e.g., Lupker, Brown, & Colombo, 1997) using a megastudy paradigm. In each of two conditions, we used 25 blocks of 100 trials. In the random condition, words were selected randomly for each block, whereas in the experimental condition, words were blocked by difficulty (e.g., easy words together, etc.), but the order of the blocks was randomized. We predicted that standard factors (e.g., frequency) would be more predictive of reaction times (RTs) in the blocked than in the random condition, because the range of RTs across the experiment would increase in the blocked condition. Indeed, we found that the standard deviations and ranges of RTs were larger in the blocked than in the random condition. In addition, an examination of items at the difficulty extremes (i.e., very easy vs. very difficult) demonstrated a response bias. In regression analyses, a predictor set of seven sublexical, lexical, and semantic variables accounted for 2.8% more RT variance (and 2.6% more zRT variance) in the blocked than in the random condition. These results indicate that response deadlines apply to megastudies of reading aloud, and that the influence of predictors may be underestimated in megastudies when item presentation is randomized. In addition, the CDP++ model accounted for 0.8% more variance in RTs (1.2% in zRTs) in the blocked than in the random condition. Thus, computational models may have more predictive power on item sets blocked by difficulty than on those presented in random order. The results also indicate that models of word processing need to accommodate response criterion shifts.
Mem Cognit 2017 05
PMID:Participants shift response deadlines based on list difficulty during reading-aloud megastudies. 2821 Oct 25


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