Cholinergic modulation of the hippocampus during encoding and retrieval

The present experiments were aimed at determining whether acetylcholine (ACh) plays a role in encoding and retrieval of spatial information using a modified Hebb-Williams maze. In addition, the present experiments tested two computational models of hippocampal function during encoding and retrieval using a maze sensitive to hippocampal disruption. Thirty male, Long-Evans rats served as subjects. Chronic cannulae were implanted bilaterally into the CA3 (n=26) and CA1 (n=5) subregions of the hippocampus. Rats were tested using a modified Hebb-Williams maze. In the first experiment, rats were injected with either saline or scopolamine hydrobromide 10 min before testing for each day. The number of errors made per day per group was used as the measure of learning. Encoding was assessed by the average number of errors made on the first five trials of Day 1 compared to the last five trials of Day 1, whereas the average number of errors made on the first five trials of Day 2 compared to the last five trials of Day I was used to assess retrieval. No deficit was found for the saline group. The scopolamine group showed a deficit in encoding, but not retrieval. In the second experiment, rats were injected with either saline or physostigmine 10 min before testing each day. In contrast to the scopolamine groups, the physostigmine group showed a deficit in retrieval, but not encoding. To test whether the retrieval deficit was due to a disruption in storage or gaining access to the information two groups of rats received either saline on Day 1 and physostigmine on Day 2 or physostigmine on Day 1 and saline on Day 2. In addition, one group received physostigmine immediately after testing on Day 1. Data indicate that physostigmine causes a disruption of retrieval by means of a disruption in consolidation process. In conclusion, the cholinergic antagonist, scopolamine, disrupts encoding in both CA3 and CA1 subregions of the hippocampus. Furthermore, the cholinesterase inhibitor, physostigmine, boosts ACh action during a time when cholinergic levels need to decline for proper consolidation.     

Inhibition of endogenous carbon monoxide production induces transient retention losses in the day-old chick when trained using a single trial passive avoidance learning task

Carbon monoxide (CO) is most often thought of as an exogenous toxin rather than as a possible endogenous nootrope. However, a limited number of studies have suggested that CO is necessary in memory processing for at least some tasks. While nitric oxide (NO) and CO are known activators of guanylyl cyclase (GC), only the effect of NO on GC has been extensively investigated as a mechanism underlying memory processing. The aim of the present study was to determine if inhibition of CO production would have an effect on memory processing. Using chicks trained on a single trial passive avoidance task, inhibition of CO production using zinc (II) deuteroporphyrin IX 2,4-bis ethylene glycol (ZnBG; 5 microM) resulted in two transient retention losses occurring at around 40 and 130 min post-training. The timing of these transient retention losses was similar to those observed following inhibition of GC, using the same species and task in a previous study. This supports the notion that CO is necessary in memory processing for this task and may act through a GC-dependent mechanism. As ZnBG also directly inhibits GC or nitric oxide synthase (NOS) at high concentrations, a second experiment was carried-out to confirm the specificity of ZnBG for heme oxygenase (HO) at the concentration used. The action of ZnBG was challenged with the HO agonist hemin (100 microM) and the transient deficits were abolished. This confirmed that the action of ZnBG on memory was through a CO-related mechanism rather than directly on GC or NOS. In this way the specificity of ZnBG (5 microM) for HO could be confirmed. The results support a role for endogenous CO in memory processing, possibly through activation of GC. In addition, the transient retention losses observed following administration of ZnBG suggest that CO may be necessary for memory retrieval and not formation as previously thought.     

Learning related modulation of functional retrieval networks in man

The medial temporal lobe has been implicated in studies of episodic memory tasks involving spatio-temporal context and object-location conjunctions. We have previously demonstrated that an increased level of practice in a free-recall task parallels a decrease in the functional activity of several brain regions, including the medial temporal lobe, the prefrontal, the anterior cingulate, the anterior insular, and the posterior parietal cortices, that in concert demonstrate a move from elaborate controlled processing towards a higher degree of automaticity. Here we report data from two experiments that extend these initial observations. We used a similar experimental approach but probed for effects of retrieval paradigms and stimulus material. In the first experiment we investigated practice related changes during recognition of object-location conjunctions and in the second during free-recall of pseudo-words. Learning in a neural network is a dynamic consequence of information processing and network plasticity. The present and previous PET results indicate that practice can induce a learning related functional restructuring of information processing. Different adaptive processes likely subserve the functional re-organisation observed. These may in part be related to different demands for attentional and working memory processing. It appears that the role(s) of the prefrontal cortex and the medial temporal lobe in memory retrieval are complex, perhaps reflecting several different interacting processes or cognitive components. We suggest that an integrative interactive perspective on the role of the prefrontal and medial temporal lobe is necessary for an understanding of the processing significance of these regions in learning and memory. It appears necessary to develop elaborated and explicit computational models for prefrontal and medial temporal functions in order to derive detailed empirical predictions, and in combination with an efficient use and development of functional neuroimaging approaches, to further the understanding of the processing significance of these regions in memory.     

复述、提取抑制与有意遗忘的实验研究

有意遗忘是关于记忆研究的另一种实验范式,对于在实验中出现的要求遗忘的学习项目的记忆成绩差于要求记忆的项目的结果,目前主人存在着两种理论解释：基于编码的理论和基于提取抑制的理论。该实验运用单字提示方式,采用控制较为严密的补笔测验方法和加入所谓的“无关项”,对有意遗忘的心理过程进行进一步的探讨,实验表明：在单了提示方式下,被试在进行有意遗忘的过程中,既对记忆项进行了有意的复述又对遗忘项产生了提取抑制。     

Non-monotonic relationships between emotional arousal and memory for color and location

Recent research points to the decreased diagnostic value of subjective retrieval experience for memory accuracy for emotional stimuli. While for neutral stimuli rich recollective experiences are associated with better context memory than merely familiar memories this association appears questionable for emotional stimuli. The present research tested the implicit assumption that the effect of emotional arousal on memory is monotonic, that is, steadily increasing (or decreasing) with increasing arousal. In two experiments emotional arousal was manipulated in three steps using emotional pictures and subjective retrieval experience as well as context memory were assessed. The results show an inverted U-shape relationship between arousal and recognition memory but for context memory and retrieval experience the relationship was more complex. For frame colour, context memory decreased linearly while for spatial location it followed the inverted U-shape function. The complex, non-monotonic relationships between arousal and memory are discussed as possible explanations for earlier divergent findings.     

Cumulative and non-cumulative semantic interference in object naming: Evidence from blocked and continuous manipulations of semantic context

Experiments involving blocked and continuous manipulations of the semantic naming context demonstrate that, when speakers name several taxonomically related objects in close succession, they display persistent interference effects. A review of studies using the blocked paradigm shows that, unlike the continuous paradigm, it typically does not induce cumulative interference effects in healthy speakers. This contrasts with the simulation results obtained from a model of semantic context effects recently put forward by Oppenheim and colleagues [Oppenheim, G. M., Dell, G. S., & Schwartz, M. F. (2010). The dark side of incremental learning: A model of cumulative semantic interference during lexical access in speech production. Cognition, 114, 227--262], which generates cumulative effects in both paradigms. We propose that the effects are non-cumulative in the blocked paradigm, because it allows participants to bias top-down the levels of activation of lexical-semantic representations, thereby curtailing the accumulating interference. Indeed, prior research has shown that the interference effects in the blocked paradigm are exacerbated when participants carry out a concurrent digit-retention task, loading on working memory and reducing their capacity to exert a top-down bias. In Experiment 1, combining the continuous paradigm with a digit-retention task, we demonstrate that this does not exacerbate cumulative context effects, corroborating the selective role of working memory and the associated top-down biasing mechanism in the blocked paradigm. A review of neuropsychological and neuroimaging studies demonstrates that left inferior frontal regions may play a critical role in controlling semantic interference top-down. We discuss the implications of these findings for language production research and for models of lexical-semantic encoding.     

Effects of Item Difficulty on the Retrieval of Solutions during Cognitive Skill Acquisition: Age Differences

ABSTRACT

In cognitive skill learning, shifts to better strategies for obtaining solutions often occur while associations between problems and solutions are being strengthened. In two skill learning experiments, we examined the effects of item difficulty on the retrieval of solutions and the learning of problem–solution associations in younger and older adults. The results of both experiments demonstrated an ‘easy effect’ in both younger and older adults, such that the retrieval of solutions as well recognition memory for problems was best for the easier items. In addition, a ‘hard effect’ was found in younger adults, but not in older adults, whereby the retrieval of solutions as well as recognition memory for problems was better for harder items than for medium-difficulty items. The finding that increased computational demands at the item level delayed item memorization and the retrieval of solutions in older adults but not younger adults is consistent with a general-resources account of age-related differences in skill learning.     

The real trouble with intentionality

I argue that the project of naturalizing intentionality is misconceived. Intentionality should not be considered as a challenge to our naturalistic world-view, but rather as something which gives rise to a logical problem: how to save the principle of indiscernibility of identicals from apparent counterexamples arising from intensional discourse.     

What’s ours is yours: recall of history for lesser-known countries is guided by one’s own national history

ABSTRACT

The present studies examine how people recall history. Sometimes, certain national histories are well known and sometimes they are not. We propose that, under certain circumstances, culturally distinctive representations of typical national histories can be used to guide recall, particularly in cases where the history is not well known. We focus on three national samples with varied levels of knowledge about each history: Great Britain, India, and the United States. In Study 1, we establish typical historical event templates for each nation consisting of events that a large proportion of participants from each sample identify as important in a typical nation’s history. We examine points of divergence between the different groups’ typical event templates and the valences of these events. In Study 2, we test and find that, in conditions of less knowledge, participants tend to refer to particular historical events that coincide with events unique to their own group’s typical history. In Study 3, we demonstrate that this effect can be found even when a group possesses a reasonable amount of knowledge about the target country. We conclude by discussing the implications in relation to how such a retrieval strategy might inform interpretations of events in the present.     

Iterated Non‐Refutation: Robert Lockie on Relativism 1

Abstract

I argue that an experience’s sensuous elements play an ineliminable role in our being intentionally directed upon an entity through perception. More specifically, I argue that whenever we appreciate a sensuous element in experience, we appreciate an intrinsic and irreducibly phenomenal aspect of experience that I call phenomenal presence – an aspect of experience that I show is central to its presentational character – and that the appreciation of phenomenal presence is necessary for perceptual intentionality. If an experience is to possess intentionality, the experience itself must make an entity available as an object of perceptually-based singular beliefs and the experiencing subject, by virtue of undergoing the experience, must in some sense be able to appreciate that it has done so. Phenomenal presence is necessary for perceptual intentionality because it plays an ineliminable role in making an entity available to its subject in this way.