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Emrah Duzel - One of the best experts on this subject based on the ideXlab platform.
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Neuroanatomical dissociation of encoding processes related to priming and Explicit Memory
Journal of Neuroscience, 2006Co-Authors: E Düzel, Emrah DuzelAbstract:Priming is a facilitation of cognitive processing with stimulus repetition that can occur without Explicit Memory. Whereas the functional neuroanatomy of perceptual priming at retrieval is established, encoding processes that initiate priming and Explicit Memory have not yet been anatomically separated, and we investigated them using event-related functional magnetic resonance imaging. Activations predicting later Explicit Memory occurred in the bilateral medial temporal lobe (MTL) and left prefrontal cortex (PFC). Activity predicting later priming did not occur in these areas, but rather in the bilateral extrastriate cortex, left fusiform gyrus, and bilateral inferior PFC, areas linked with stimulus identification. Surprisingly, these regions showed response reductions. Our results demonstrate that priming and Explicit Memory have distinct functional neuroanatomies at encoding, with MTL activations being specific for Explicit Memory, and suggest that priming is initiated by sharpness of neural responding in stimulus identification areas, consistent with recent electrophysiological evidence regarding priming-related neural oscillations at encoding. We tentatively suggest that this sharpened responding at encoding may set the stage for increased neural processing efficiency at retrieval, with these different neural mechanisms both leading to observed priming-related hemodynamic decreases, and argue that neural measurements at encoding, and not just at retrieval, will be critical in resolving the debate about the neural mechanisms of learning that underlie priming.
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Redefining implicit and Explicit Memory: The functional neuroanatomy of priming, remembering, and control of retrieval
P NATL ACAD SCI USA, 2005Co-Authors: Emrah DuzelAbstract:We used event-related functional MRI to study awareness of prior episodes during Memory retrieval and its relationship to the intention to retrieve memories. Participants completed cues with words from a prior list (intentional test) or with the first words that came to mind (incidental test). During both tests, Explicit Memory was separated from priming in the absence of Explicit Memory. Priming was associated with hemodynamic decreases in left fusiform gyrus and bilateral frontal and occipital brain regions; Explicit Memory was associated with bilateral parietal and temporal and left frontal increases. Retrieval intention did not change these patterns but was associated with activity in right prefrontal cortex. Our results provide firm evidence that implicit and Explicit Memory have distinct functional neuroanatomies, and that strategic control of retrieval engages brain structures distinct from those involved in both implicit and Explicit Memory. They have critical implications for theories of Memory and consciousness, which often equate consciousness with control.
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perceptual priming versus Explicit Memory dissociable neural correlates at encoding
Journal of Cognitive Neuroscience, 2002Co-Authors: Bjorn H Schott, Alan Richardsonklavehn, Hansjochen Heinze, Emrah DuzelAbstract:We addressed the hypothesis that perceptual priming and Explicit Memory have distinct neural correlates at encoding. Event-related potentials (ERPs) were recorded while participants studied visually presented words at deep versus shallow levels of processing (LOPs). The ERPs were sorted by whether or not participants later used studied words as completions to three-letter word stems in an intentional Memory test, and by whether or not they indicated that these completions were remembered from the study list. Study trials from which words were later used and not remembered (primed trials) and study trials from which words were later used and remembered (remembered trials) were compared to study trials from which words were later not used (forgotten trials), in order to measure the ERP difference associated with later Memory (DM effect). Primed trials involved an early (200–450 msec) centroparietal negative-going DM effect. Remembered trials involved a late (900–1200 msec) right frontal, positive-going DM effect regardless of LOP, as well as an earlier (600–800 msec) central, positive-going DM effect during shallow study processing only. All three DM effects differed topographically, and, in terms of their onset or duration, from the extended (600–1200 msec) fronto-central, positive-going shift for deep compared with shallow study processing. The results provide the first clear evidence that perceptual priming and Explicit Memory have distinct neural correlates at encoding, consistent with Tulving and Schacter's (1990) distinction between brain systems concerned with perceptual representation versus semantic and episodic Memory. They also shed additional light on encoding processes associated with later Explicit Memory, by suggesting that brain processes influenced by LOP set the stage for other, at least partially separable, brain processes that are more directly related to encoding success.
Daniel L. Schacter - One of the best experts on this subject based on the ideXlab platform.
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Specificity of Implicit and Explicit Memory
2017Co-Authors: Daniel L. SchacterAbstract:Specificity of Implicit and Explicit Memory Daniel L. Schacter (dls@wjh.harvard.edu) Department of Psychology, 33 Kirkland Street Cambridge, MA 02138 USA neuropsychological evidence provided by studies of amnesic patients with damage to the medial temporal lobe, and also relevant evidence from cognitive studies. I will argue that findings concerning the nature and extent of the three types of specificity have important implications for understanding the neural and cognitive underpinnings of implicit and Explicit Memory processes. Abstract Considerable research has attempted to elucidate the relation between implicit and Explicit forms of Memory. This talk focuses on the specificity of implicit and Explicit Memory: the extent to which, and sense in which, Memory performance reflects retention of specific features of a stimulus that was perceived during a study episode, the formation of a specific association between two previously presented stimuli, or a specific response that was made to a previously encountered stimulus. Cognitive, neuropsychological, and neuroimaging data will be considered that illuminate the nature and theoretical implications of the different kinds of Memory specificity. Response Specificity: Empirical and Theoretical Implications To illustrate the nature of a cognitive neuroscience approach to Memory specificity, consider recent data concerning response specificity in priming. Studies that have demonstrated response specificity in priming have been conducted with a view toward testing ideas that have been advanced to explain priming-related changes in brain activity observed in neuroimaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). In such studies, participants are scanned while they carry out a task used to assess priming, such as completing three letter word stems with the first word that comes to mind or making judgments about pictures of familiar objects. During primed scans, participants are given target items (e.g., word stems or objects) that appeared previously during the experiment; during unprimed scans, the target items did not appear previously. Virtually all studies using such procedures report decreased activity in several cortical regions during primed scans compared to unprimed scans, most consistently in areas within the frontal lobes and the extrastriate visual cortex. Wiggs and Martin (1998) argued that neural object representations are sharpened or “tuned” with repetition. By this view, when an object is presented repeatedly, the neurons that code features which are not essential for recognizing the object show decreased responding; in so doing, they weaken their connections with other neurons involved in coding the object. Thus, the network of neurons that codes the object becomes more selective, and this neural “tuning” or sharpening is linked with faster and more efficient responding. Dobbins, Schnyer, Verfaellie, & Schacter (2004) attempted to directly contrast tuning and response learning accounts with an object decision priming task that had been used in previous neuroimaging research, and yielded evidence of reductions in priming-related activation in regions of prefrontal and fusiform cortex (e.g., Koutstaal et al., 2001). Dobbins et al. modified the task so that responses either remained the same or changed across repeated trials. In the first scanning phase, pictures of common objects were either shown once or repeated three times, and subjects indicated whether each stimulus was bigger than a shoebox using a Keywords: implicit Memory; Explicit Memory; priming Introduction For the past two decades, research concerning the relation between implicit and Explicit Memory has been a major focus in cognitive science and cognitive neuroscience. A particular aspect of implicit/Explicit Memory research that has emerged as a focal point in many recent discussions of neuropsychological and neuroimaging evidence, concerns specificity of implicit and Explicit Memory: the extent to which, and sense in which, Memory performance reflects retention of specific features of a stimulus that was perceived during a study episode, the formation of a specific association between two previously presented stimuli, or a specific response that was made to a previously encountered stimulus. This issue has been explored primarily by studies concerning the phenomenon of priming, a form of implicit Memory in which there is a change in the ability to identify or produce an item as a result of a prior encounter with that item or a related item. Three types of specificity in priming and corresponding measures of Explicit Memory have been delineated: stimulus, associative, and response specificity (Schacter, Dobbins, & Schnyer, 2004). Stimulus specificity refers to the extent to which changing physical properties of a stimulus between study and test influences the magnitude of priming, including changes in perceptual modality, the identity of a stimulus (e.g., two different objects with the same name, such as two different chairs or pencils) as well as the size, orientation, and related physical features of a stimulus. Associative specificity occurs when priming is greater when associations between target items are maintained between study and test than when they are changed. Response specificity is demonstrated when priming is increased by having subjects make the same versus different responses at study and test to the same stimulus item. For each of the three types of specificity, I consider neuroimaging evidence provided by PET and fMRI studies,
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do amnesics exhibit cognitive dissonance reduction the role of Explicit Memory and attention in attitude change
Psychological Science, 2001Co-Authors: Matthew D Lieberman, Kevin N Ochsner, Daniel T Gilbert, Daniel L. SchacterAbstract:In two studies, we investigated the roles of Explicit Memory and attentional resources in the process of behavior-induced attitude change. Although most theories of attitude change (cognitive dissonance and self-perception theories) assume an important role for both mechanisms, we propose that behavior-induced attitude change can be a relatively automatic process that does not require Explicit Memory for, or consciously controlled processing of, the discrepancy between attitude and behavior. Using a free-choice paradigm, we found that both amnesics and normal participants under cognitive load showed as much attitude change as did control participants.
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Implicit and Explicit Memory for novel visual objects: Structure and function
Journal of Experimental Psychology: Learning Memory and Cognition, 1993Co-Authors: Daniel L. Schacter, Lynn A. CooperAbstract:Six experiments compared the effects of structural and functional encoding tasks on implicit and Explicit Memory for novel objects. Implicit Memory was assessed with a possible-impossible object decision test, and Explicit Memory was assessed with a yes-no recognition test. Results revealed that recognition Memory was higher after functional than after structural encoding tasks, whereas priming effects on the object decision test were unaffected by the same manipulations. The priming effects that were observed after functional encoding tasks could be attributed to structural analyses that are carried out in the course of making judgments about functional properties of novel objects. Results are consistent with the hypothesis that implicit Memory for novel objects depends on a presemantic structural description system that can operate independently of episodic Memory. Language: en
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Implicit and Explicit Memory for novel visual objects in older and younger adults.
Psychology and Aging, 1992Co-Authors: Daniel L. Schacter, Lynn A. Cooper, Michael ValdiserriAbstract:Two experiments examined effects of aging on implicit and Explicit Memory for novel visual objects. Implicit Memory was assessed with an object decision task in which subjects indicated whether briefly exposed drawings represented structurally possible or impossible objects. Explicit Memory was assessed with a yes-no recognition task. On the object decision task, old and young subjects both showed priming for previously studied possible objects and no priming for impossible objects; the magnitude of the priming effect did not differ as a function of age. By contrast, the elderly were impaired on the recognition task. Results suggest that the ability to form and retain structural descriptions of novel objects may be spared in older adults.
Ken A. Paller - One of the best experts on this subject based on the ideXlab platform.
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brain substrates of implicit and Explicit Memory the importance of concurrently acquired neural signals of both Memory types
Neuropsychologia, 2008Co-Authors: Joel L. Voss, Ken A. PallerAbstract:A comprehensive understanding of human Memory requires cognitive and neural descriptions of Memory processes along with a conception of how Memory processing drives behavioral responses and subjective experiences. One serious challenge to this endeavor is that an individual Memory process is typically operative within a mix of other contemporaneous Memory processes. This challenge is particularly disquieting in the context of implicit Memory, which, unlike Explicit Memory, transpires without the subject necessarily being aware of Memory retrieval. Neural correlates of implicit Memory and neural correlates of Explicit Memory are often investigated in different experiments using very different Memory tests and procedures. This strategy poses difficulties for elucidating the interactions between the two types of Memory process that may result in Explicit remembering, and for determining the extent to which certain neural processing events uniquely contribute to only one type of Memory. We review recent studies that have succeeded in separately assessing neural correlates of both implicit Memory and Explicit Memory within the same paradigm using event-related brain potentials (ERPs) and functional magnetic resonance imaging (fMRI), with an emphasis on studies from our laboratory. The strategies we describe provide a methodological framework for achieving valid assessments of Memory processing, and the findings support an emerging conceptualization of the distinct neurocognitive events responsible for implicit and Explicit Memory.
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neural correlates of conceptual implicit Memory and their contamination of putative neural correlates of Explicit Memory
Learning & Memory, 2007Co-Authors: Joel L. Voss, Ken A. PallerAbstract:During episodic recognition tests, meaningful stimuli such as words can engender both conscious retrieval (Explicit Memory) and facilitated access to meaning that is distinct from the awareness of remembering (conceptual implicit Memory). Neuroimaging investigations of one type of Memory are frequently subject to the confounding influence of the other type of Memory, thus posing a serious impediment to theoretical advances in this area. We used minimalist visual shapes (squiggles) to attempt to overcome this problem. Subjective ratings of squiggle meaningfulness varied idiosyncratically, and behavioral indications of conceptual implicit Memory were evident only for stimuli given higher ratings. These effects did not result from perceptual-based fluency or from Explicit remembering. Distinct event-related brain potentials were associated with conceptual implicit Memory and with Explicit Memory by virtue of contrasts based on meaningfulness ratings and Memory judgments, respectively. Frontal potentials from 300 to 500 msec after the onset of repeated squiggles varied systematically with perceived meaningfulness. Explicit Memory was held constant in this contrast, so these potentials were taken as neural correlates of conceptual implicit Memory. Such potentials can contaminate putative neural correlates of Explicit Memory, in that they are frequently attributed to the expression of Explicit Memory known as familiarity. These findings provide the first neural dissociation of these two Memory phenomena during recognition testing and underscore the necessity of taking both types of Memory into account in order to obtain valid neural correlates of specific Memory functions.
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Fluent Conceptual Processing and Explicit Memory for Faces Are Electrophysiologically Distinct
The Journal of Neuroscience, 2006Co-Authors: Joel L. Voss, Ken A. PallerAbstract:Implicit Memory and Explicit Memory are fundamentally different manifestations of Memory storage in the brain. Yet, conceptual fluency driven by previous experience could theoretically be responsible for both conceptual implicit Memory and aspects of Explicit Memory. For example, contemplating the meaning of a word might serve to speed subsequent processing of that word and also make it seem familiar. We examined electrophysiological correlates of conceptual priming with 180 celebrity faces to determine whether or not they resemble electrophysiological correlates of Explicit Memory. Celebrity faces are ideal for this purpose because they carry with them preexisting conceptual information (i.e., biographical facts) that can selectively be brought to mind such that conceptual processing can be manipulated systematically. In our experiment, exposure to biographical information associated with only one-half of the celebrities yielded conceptual priming for those faces, whereas all faces were perceptually primed. Conceptual priming was indexed by positive brain potentials over frontal regions from ∼250 to 500 ms. Explicit Memory retrieval was associated with later brain potentials over posterior regions that were strikingly similar to potentials previously associated with pure familiarity for faces (when a face seems familiar in the absence of retrieval of any specific information about previous occurrence). Furthermore, the magnitude of conceptual priming was correlated across subjects with the amplitude of frontal but not posterior potentials, whereas the opposite was true for Explicit Memory. Distinct brain processes were thus associated with conceptual priming and conscious recognition of faces, thus providing a sharper focus on the border between implicit and Explicit Memory.
Rosemary Fama - One of the best experts on this subject based on the ideXlab platform.
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thalamic volume deficit contributes to procedural and Explicit Memory impairment in hiv infection with primary alcoholism comorbidity
Brain Imaging and Behavior, 2014Co-Authors: Rosemary Fama, Margaret J Rosenbloom, Stephanie A Sassoon, Torsten Rohlfing, Adolf Pfefferbaum, Edith V SullivanAbstract:Component cognitive and motor processes contributing to diminished visuomotor procedural learning in HIV infection with comorbid chronic alcoholism (HIV+ALC) include problems with attention and Explicit Memory processes. The neural correlates associated with this constellation of cognitive and motor processes in HIV infection and alcoholism have yet to be delineated. Frontostriatal regions are affected in HIV infection, frontothalamocerebellar regions are affected in chronic alcoholism, and frontolimbic regions are likely affected in both; all three of these systems have the potential of contributing to both visuomotor procedural learning and Explicit Memory processes. Here, we examined the neural correlates of implicit Memory, Explicit Memory, attention, and motor tests in 26 HIV+ALC (5 with comorbidity for nonalcohol drug abuse/dependence) and 19 age-range matched healthy control men. Parcellated brain volumes, including cortical, subcortical, and allocortical regions, as well as cortical sulci and ventricles, were derived using the SRI24 brain atlas. Results indicated that smaller thalamic volumes were associated with poorer performance on tests of Explicit (immediate and delayed) and implicit (visuomotor procedural) Memory in HIV+ALC. By contrast, smaller hippocampal volumes were associated with lower scores on Explicit, but not implicit Memory. Multiple regression analyses revealed that volumes of both the thalamus and the hippocampus were each unique independent predictors of Explicit Memory scores. This study provides evidence of a dissociation between implicit and Explicit Memory tasks in HIV+ALC, with selective relationships observed between hippocampal volume and Explicit but not implicit Memory, and highlights the relevance of the thalamus to mnemonic processes.
Bjorn H Schott - One of the best experts on this subject based on the ideXlab platform.
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perceptual priming versus Explicit Memory dissociable neural correlates at encoding
Journal of Cognitive Neuroscience, 2002Co-Authors: Bjorn H Schott, Alan Richardsonklavehn, Hansjochen Heinze, Emrah DuzelAbstract:We addressed the hypothesis that perceptual priming and Explicit Memory have distinct neural correlates at encoding. Event-related potentials (ERPs) were recorded while participants studied visually presented words at deep versus shallow levels of processing (LOPs). The ERPs were sorted by whether or not participants later used studied words as completions to three-letter word stems in an intentional Memory test, and by whether or not they indicated that these completions were remembered from the study list. Study trials from which words were later used and not remembered (primed trials) and study trials from which words were later used and remembered (remembered trials) were compared to study trials from which words were later not used (forgotten trials), in order to measure the ERP difference associated with later Memory (DM effect). Primed trials involved an early (200–450 msec) centroparietal negative-going DM effect. Remembered trials involved a late (900–1200 msec) right frontal, positive-going DM effect regardless of LOP, as well as an earlier (600–800 msec) central, positive-going DM effect during shallow study processing only. All three DM effects differed topographically, and, in terms of their onset or duration, from the extended (600–1200 msec) fronto-central, positive-going shift for deep compared with shallow study processing. The results provide the first clear evidence that perceptual priming and Explicit Memory have distinct neural correlates at encoding, consistent with Tulving and Schacter's (1990) distinction between brain systems concerned with perceptual representation versus semantic and episodic Memory. They also shed additional light on encoding processes associated with later Explicit Memory, by suggesting that brain processes influenced by LOP set the stage for other, at least partially separable, brain processes that are more directly related to encoding success.
