What, if anything, is the medial temporal lobe, and how can the amygdala be part of it if there is no such thing?

Should the medial temporal lobe (MTL) of primates--which includes allocortical structures such as the hippocampus, neocortical structures such as the parahippocampal cortex, and nuclear structures such as the basolateral amygdala--be considered a single "thing"? According to the prevailing view, here termed the reification theory, the answer is yes. According to this theory, the MTL functions as an amalgamated entity that provides the neuronal mechanisms for declarative memory; the greater the damage to the MTL or any of its components, the greater the deleterious effects on declarative memory. A countervailing view, here called the balkanization theory, holds that the various components of the MTL process and store different kinds of information. According to this theory, damage to each part of the MTL causes a unique set of behavioral deficits-some involving memory, others involving perception, and yet others involving response selection. The empirical neuropsychological evidence favors the balkanization theory, as do some new concepts in theoretical neuroanatomy.     

Childhood amnesia and distinctions between forms of memory: A comment on Wood, Brown, and Felton

Recently, Wood and his colleagues (1989) presented a case of childhood amnesia as evidence against the distinction between declarative and procedural memory that has sometimes been applied to human amnesia. Their argument was based on the observation that their patient showed some progress in school over the years, i.e., acquired some declarative knowledge, despite severely impaired day-to-day memory ability. We briefly review their case, together with a carefully studied second case of childhood amnesia not mentioned by Wood et al. Their argument is wrong in several ways. First, the utility of the declarative/procedural distinction for amnesia, or the utility of any other distinction between memory systems, depends on whether or not one kind of memory is impaired selectively, not on the severity of the impairment. In particular there is no requirement that one kind of memory be totally absent. Second, they have not provided the data necessary to support their argument; namely, data showing that the amount of declarative knowledge accumulated during years in school was better than would have been expected given the capacity for moment-to-moment or day-to-day memory. Indeed, the patient's moment-to-moment memory ability is better than represented, and the patient's progress in school was abnormally slow. Third, it is not clear that academic achievement scores provide a direct measure of declarative memory abilities (skill learning and recovery of function may also have contributed). We conclude that the evidence from childhood amnesia is fully consistent with the proposal that amnesia reflects a selective impairment in the formation of long-term declarative memory.     

Perirhinal cortical contributions to object perception

The traditional theory of the medial temporal lobe (MTL) memory system asserts that the primate MTL (hippocampus, perirhinal, entorhinal and parahippocampal cortices) is exclusively involved in consolidating declarative memories. However, several recent reports have directly challenged this dogma by arguing that MTL structures also contribute to perception. Controversy remains as many of the behavioural tasks used have confounded memory with perception. We review the evidence here and highlight new studies in humans and macaques that indicate a perceptual role for MTL in the absence of such confounds. We argue that the challenge to MTL memory system theory is substantiated and that the implications are considerable, namely that most psychologists and neuroscientists have held a fundamentally flawed view of how memory is implemented in the brain.     

Immediate as well as delayed post learning sleep but not wakefulness enhances declarative memory consolidation in children

While there is mounting evidence for the importance of sleep for declarative memory consolidation in adults, so far this issue has not been investigated in children despite considerable differences in sleep duration and sleep architecture between children and adults. Here, 27 children (aged between 9 and 12yr) were examined on two conditions: on the Sleep-Wake condition, subjects learned word pairs in the evening and delayed recall was tested first in the next morning after sleep and then again in the following evening after daytime wakefulness. On the Wake-Sleep condition, learning took place in the morning and delayed recall was tested in the evening of the same day and again in the next morning after sleep. In both conditions retention of declarative memory was significantly increased only after an interval of sleep that either followed immediately after learning (as in the Sleep-Wake condition) or that followed after daytime wakefulness (as in the Wake-Sleep condition), respectively. The results support the hypothesis that sleep plays an active role in declarative memory consolidation even if delayed and further show for the first time the importance of sleep for declarative memory consolidation during childhood.     

The explicit and implicit dance in psychoanalytic change

How the implicit/non-declarative and explicit/declarative cognitive domains interact is centrally important in the consideration of effecting change within the psychoanalytic arena. Stern et al. (1998) declare that long-lasting change occurs in the domain of implicit relational knowledge. In the view of this author, the implicit and explicit domains are intricately intertwined in an interactive dance within a psychoanalytic process. The author views that a spirit of inquiry (Lichtenberg, Lachmann & Fosshage 2002) serves as the foundation of the psychoanalytic process. Analyst and patient strive to explore, understand and communicate and, thereby, create a 'spirit' of interaction that contributes, through gradual incremental learning, to new implicit relational knowledge. This spirit, as part of the implicit relational interaction, is a cornerstone of the analytic relationship. The 'inquiry' more directly brings explicit/declarative processing to the foreground in the joint attempt to explore and understand. The spirit of inquiry in the psychoanalytic arena highlights both the autobiographical scenarios of the explicit memory system and the mental models of the implicit memory system as each contributes to a sense of self, other, and self with other. This process facilitates the extrication and suspension of the old models, so that new models based on current relational experience can be gradually integrated into both memory systems for lasting change.     

Overcoming interference: an fMRI investigation of pattern separation in the medial temporal lobe

The medial temporal lobe (MTL) supports the formation and retrieval of long-term declarative memories, or memories for facts and everyday events. One challenge posed for this type of memory stems from the highly overlapping nature of common episodes. Within cognitive psychology, it is widely accepted that interference between information learned at different times is a major limitation on memory. In spite of several decades of intense research in the fields of interference theory and the neurobiological underpinnings of declarative memory, there is little direct evidence bearing on how the MTL resolves this interference to form accurate memories of everyday facts and events. Computational models of MTL function have proposed a mechanism in which the MTL, specifically the hippocampus, performs pattern separation, whereby overlapping representations are made less similar. However, there is little evidence bearing on how this process is carried out in the intact human MTL. Using high-resolution fMRI, we conducted a set of experiments that taxed behavioral pattern separation by using highly similar, interfering stimuli in a modified continuous recognition task. Regions within the parahippocampal gyrus demonstrated activity consistent with a "recall to reject" strategy. In contrast and critical to performing the task, activity within the hippocampus distinguished between correctly identified true stimulus repetitions, correctly rejected presentations of similar lure stimuli, and false alarms to similar lures. These data support the computational models' assertion that the hippocampus plays a key role in pattern separation.     

儿童情景记忆绑定加工:研究范式、发展特点及影响因素

个体需要将亲身经历的核心事实信息及其发生的时间、空间等背景信息绑定起来形成情景记忆，绑定加工能力的发展是儿童情景记忆发展的基础。目前，儿童情景记忆绑定加工研究的主要范式有要素绑定范式和配对关联学习范式。绑定加工在儿童期的发展表现出项目-空间绑定记忆优于项目-时间绑定记忆，复杂任务的绑定加工水平较低的特点。儿童情景记忆绑定加工的发展依赖于编码和提取能力的发展、执行功能认知灵活性的提高以及内侧颞叶和前额叶皮层的发育。未来可以对情景记忆绑定加工的发展开展纵向研究、采用VR技术提高绑定加工研究的生态效度、加强对情景记忆绑定加工神经机制的探讨等。     

Memory for reward location is enhanced even though acetylcholine efflux within the amygdala is impaired in rats with damage to the diencephalon produced by thiamine deficiency

Sleep facilitates declarative memory processing. However, we know little about whether sleep plays a role in the processing of a fundamental feature of declarative memory, relational memory – the flexible representation of items not directly learned prior to sleep. Thirty-one healthy participants first learned at 12 pm two sets of face–object photograph pairs (direct associative memory), in which the objects in each pair were common to both lists, but paired with two different faces. Participants either were given approximately 90 min to have a NREM-only daytime nap (n = 14) or an equivalent waking period (n = 17). At 4:30 pm, participants who napped demonstrated significantly better retention of direct associative memory, as well as better performance on a surprise task assessing their relational memory, in which participants had to associate the two faces previously paired with the same object during learning. Particularly noteworthy, relational memory performance was correlated with the amount of NREM sleep during the nap, with only slow-wave sleep predicting relational memory performance. Sleep stage data did not correlate with direct associative memory retention. These results suggest an active role for sleep in facilitating multiple processes that are not limited to the mere strengthening of rote memories, but also the binding of items that were not directly learned together, reorganizing them for flexible use at a later time.     

The role of medial temporal lobe in item recognition and source recollection of emotional stimuli

Recent neuroimaging results suggest that distinct regions within the medial temporal lobe (MTL) may differentially support the episodic encoding of item and relational information for nonemotional stimuli (for a review, see Davachi, 2006). The present study was designed to assess whether these findings generalize to emotional stimuli. Behaviorally, we found that emotion reduced item recognition accuracy but did not reliably affect relational memory. fMRI analyses revealed that neutral and emotional words elicited distinct activation patterns within MTL regions predictive of subsequent memory. Consistent with previous findings for neutral words, hippocampal activation predicted later relational memory, whereas activation in the perirhinal cortex predicted successful item recognition. However, for emotional words, activation in the amygdala, hippocampus, and posterior parahippocampal cortex predicted item recognition only. These data suggest that MTL regions differentially support encoding of neutral and emotional stimuli.     

The contribution of the human medial temporal lobe to perception: Bridging the gap between animal and human studies

The medial temporal lobe (MTL) has been considered traditionally to subserve declarative memory processes only. Recent studies in nonhuman primates suggest, however, that the MTL may also be critical to higher order perceptual processes, with the hippocampus and perirhinal cortex being involved in scene and object perception, respectively. The current article reviews the human neuropsychological literature to determine whether there is any evidence to suggest that these same views may apply to the human MTL. Although the majority of existing studies report intact perception following MTL damage in human amnesics, there have been recent studies that suggest that when scene and object perception are assessed systematically, signifi-cant impairments in perception become apparent. These findings have important implications for current mnemonic theories of human MTL function and our understanding of human amnesia as a result of MTL lesions.     

The perceptual-mnemonic/feature conjunction model of perirhinal cortex function.

The perirhinal cortex was once thought to be "silent cortex", virtually ignored by researchers interested in the neurobiology of learning and memory. Following studies of brain damage associated with cases of amnesia, perirhinal cortex is now widely regarded as part of a "medial temporal lobe (MTL) memory system". This system is thought to be more or less functionally homogeneous, having a special role in declarative memory, and making little or no contribution to other functions such as perception. In the present article, we summarize an alternative view. First, we propose that components of the putative MTL system such as the hippocampus and perirhinal cortex have distinct and dissociable functions. Second, we provide evidence that the perirhinal cortex has a role in visual discrimination. In addition, we propose a specific role for perirhinal cortex in visual discrimination: the contribution of complex conjunctive representations to the solution of visual discrimination problems with a high degree of "feature ambiguity". These proposals constitute a new view of perirhinal cortex function, one that does not assume strict modularity of function in the occipito-temporal visual stream, but replaces this idea with the notion of a hierarchical representational continuum.     

The contribution of the human medial temporal lobe to perception: bridging the gap between animal and human studies.

The medial temporal lobe (MTL) has been considered traditionally to subserve declarative memory processes only. Recent studies in nonhuman primates suggest, however, that the MTL may also be critical to higher order perceptual processes, with the hippocampus and perirhinal cortex being involved in scene and object perception, respectively. The current article reviews the human neuropsychological literature to determine whether there is any evidence to suggest that these same views may apply to the human MTL. Although the majority of existing studies report intact perception following MTL damage in human amnesics, there have been recent studies that suggest that when scene and object perception are assessed systematically, significant impairments in perception become apparent. These findings have important implications for current mnemonic theories of human MTL function and our understanding of human amnesia as a result of MTL lesions.     

The temporal context model in spatial navigation and relational learning: toward a common explanation of medial temporal lobe function across domains

The medial temporal lobe (MTL) has been studied extensively at all levels of analysis, yet its function remains unclear. Theory regarding the cognitive function of the MTL has centered along 3 themes. Different authors have emphasized the role of the MTL in episodic recall, spatial navigation, or relational memory. Starting with the temporal context model (M. W. Howard & M. J. Kahana, 2002a), a distributed memory model that has been applied to benchmark data from episodic recall tasks, the authors propose that the entorhinal cortex supports a gradually changing representation of temporal context and the hippocampus proper enables retrieval of these contextual states. Simulation studies show this hypothesis explains the firing of place cells in the entorhinal cortex and the behavioral effects of hippocampal lesion in relational memory tasks. These results constitute a first step toward a unified computational theory of MTL function that integrates neurophysiological, neuropsychological, and cognitive findings.     

Cognitive procedural learning in early Alzheimer's disease: impaired processes and compensatory mechanisms

Introduction. The aim of this study was to study cognitive procedural learning in early Alzheimer's disease (AD). Methods. Cognitive procedural learning was assessed using the Tower of Hanoi (TH) task. In order to take account of possible interactions between different systems during cognitive procedural learning, we also measured non‐verbal intellectual functions, working memory, and declarative memory. Results. Our results showed an apparent preservation of cognitive procedural learning in AD and a deleterious effect of the disease on verbal intelligence and declarative memory. Correlational analyses revealed a difference between AD patients and control participants in the type of processing they applied to the task. Conclusion. The non‐involvement of declarative memory would appear to be partly responsible for a slowdown in the cognitive procedural dynamics of AD patients. As the AD patients were unable to use their declarative memory, they were still in a problem‐solving mode at the end of the learning protocol and had to implement higher order cognitive processes (i.e., compensatory mechanisms) to perform the procedural task.     

The perceptual-mnemonic/feature conjunction model of perirhinal cortex function

The perirhinal cortex was once thought to be “silent cortex”, virtually ignored by researchers interested in the neurobiology of learning and memory. Following studies of brain damage associated with cases of amnesia, perirhinal cortex is now widely regarded as part of a “medial temporal lobe (MTL) memory system”. This system is thought to be more or less functionally homogeneous, having a special role in declarative memory, and making little or no contribution to other functions such as perception. In the present article, we summarize an alternative view. First, we propose that components of the putative MTL system such as the hippocampus and perirhinal cortex have distinct and dissociable functions. Second, we provide evidence that the perirhinal cortex has a role in visual discrimination. In addition, we propose a specific role for perirhinal cortex in visual discrimination: the contribution of complex conjunctive representations to the solution of visual discrimination problems with a high degree of “feature ambiguity”. These proposals constitute a new view of perirhinal cortex function, one that does not assume strict modularity of function in the occipito-temporal visual stream, but replaces this idea with the notion of a hierarchical representational continuum.     

The Explicit and Implicit Domains in Psychoanalytic Change

New research findings of the development and organization of the mind, brain, and behavior bolster the ongoing relational- or intersubjective-field paradigmatic revision of psychoanalytic theory. A multisystems view of learning, memory, and knowledge provide us with a more complex picture of information processing that has fundamental implications for a psychoanalytic theory of therapeutic action.

If the implicit and explicit learning/memory systems are viewed as parallel processes, not easily translatable from one to the other, then new implicit relational experience carries considerably more power as compared to explicit/declarative processing in changing and establishing new implicit mental models. When these cognitive processing systems are viewed as more closely interconnected with a developmental emphasis on connecting them through language, then exploratory/interpretive work becomes more central. REM, dream, infant, and cognitive research evidence suggests that imagistic symbolic capacity exists at birth. Learning and remembering using imagistic symbolic processing could suggest a more easily translatable connection with later developed verbal symbolic processing and a closer, although varied, interconnection between implicit and explicit (symbolic) memory systems.

Explicit attitudes are more directly modifiable through an explicit/declarative focus. Implicit mental models, it is proposed, are variably modifiable through two different change processes: (1) accommodation or transformation of expectancies through new implicit procedural experience (not requiring explicit focus) and (2) diminished activation and increased capacity to deactivate implicit mental models through explicit/declarative processing and the establishment of contrasting implicit models through new implicit procedural experience.     

Dissociable contributions within the medial temporal lobe to encoding of object-location associations

The crucial role of the medial temporal lobe (MTL) in episodic memory is well established. Although there is little doubt that its anatomical subregions-the hippocampus, peri-, entorhinal and parahippocampal cortex (PHC)-contribute differentially to mnemonic processes, their specific functions in episodic memory are under debate. Data from animal, human lesion, and neuroimaging studies suggest somewhat contradictory perspectives on this functional specialization: a general participation in declarative memory, an exclusive involvement in associative mnemonic processes, and a specific contribution to spatial memory are reported for the hippocampus, adjacent cortices, and the PHC. A functional lateralization in humans dependent on the verbalizability of the material is also discussed herein. To further elucidate the differential contributions of the various MTL subregions to encoding, we employed an object-location association memory paradigm. The memory for each of the studied associations was tested twice: by the object, and by the location serving as retrieval cue. The memory accuracy in response to both cue types was also assessed parametrically. Brain activity during encoding which leads to different degrees of subsequent memory accuracy under the two retrieval conditions was compared. We found the bilateral posterior PHC to participate in encoding of both the object associated with a location and the location associated with an object. In contrast, activity in an area in the left anterior PHC and the right anterior MTL was only correlated with the memory for the location associated with an object.     

Contributions of the medial temporal lobe to declarative memory retrieval: manipulating the amount of contextual retrieval

We investigated how the hippocampus and its adjacent mediotemporal structures contribute to contextual and noncontextual declarative memory retrieval by manipulating the amount of contextual information across two levels of the same contextual dimension in a source memory task. A first analysis identified medial temporal lobe (MTL) substructures mediating either contextual or noncontextual retrieval. A linearly weighted analysis elucidated which MTL substructures show a gradually increasing neural activity, depending on the amount of contextual information retrieved. A hippocampal engagement was found during both levels of source memory but not during item memory retrieval. The anterior MTL including the perirhinal cortex was only engaged during item memory retrieval by an activity decrease. Only the posterior parahippocampal cortex showed an activation increasing with the amount of contextual information retrieved. If one assumes a roughly linear relationship between the blood-oxygenation level-dependent (BOLD) signal and the associated cognitive process, our results suggest that the posterior parahippocampal cortex is involved in contextual retrieval on the basis of memory strength while the hippocampus processes representations of item-context binding. The anterior MTL including perirhinal cortex seems to be particularly engaged in familiarity-based item recognition. If one assumes departure from linearity, however, our results can also be explained by one-dimensional modulation of memory strength.     

Content-specific source encoding in the human medial temporal lobe

Although the medial temporal lobe (MTL) is known to be essential for episodic encoding, the contributions of individual MTL subregions remain unclear. Data from recognition memory studies have provided evidence that the hippocampus supports relational encoding important for later episodic recollection, whereas the perirhinal cortex has been linked with encoding that supports later item familiarity. However, extant data also strongly implicate the perirhinal cortex in object processing and encoding, suggesting that perirhinal processes may contribute to later episodic recollection of object source details. To investigate this possibility, encoding activation in MTL subregions was analyzed on the basis of subsequent memory outcome while participants processed novel scenes paired with 1 of 6 repeating objects. Specifically, encoding activation correlating with later successful scene recognition memory was evaluated against that of source recollection for the object paired with the scene during encoding. In contrast to studies reporting a link between perirhinal cortex and item familiarity, it was found that encoding activation in the right perirhinal cortex correlates with successful recollection of the paired object. Furthermore, other MTL subregions also exhibited content-specific source encoding patterns of activation, suggesting that MTL subsequent memory effects are sensitive to stimulus category.     

Longitudinal study of declarative and procedural memory in primary school‐aged children

This study examined the development of declarative and procedural memory longitudinally in primary school‐aged children. At present, although there is a general consensus that age‐related improvements during this period can be found for declarative memory, there are conflicting data on the developmental trajectory of the procedural memory system. At Time 1 children aged around 5½ years were presented with measures of declarative and procedural memory. The tasks were then administered 12 months later. Performance on the declarative memory task was found to improve at a faster rate in comparison to the procedural memory task. The findings of the study support the view that multiple memory systems reach functional maturity at different points in development.