Showing papers by "Endel Tulving published in 1994"

Hemispheric encoding/retrieval asymmetry in episodic memory: positron emission tomography findings

Abstract: Data are reviewed from positron emission tomography studies of encoding and retrieval processes in episodic memory. These data suggest a hemispheric encoding/retrieval asymmetry model of prefrontal involvement in encoding and retrieval of episodic memory. According to this model, the left and right prefrontal lobes are part of an extensive neuronal network that subserves episodic remembering, but the two prefrontal hemispheres play different roles. Left prefrontal cortical regions are differentially more involved in retrieval of information from semantic memory and in simultaneously encoding novel aspects of the retrieved information into episodic memory. Right prefrontal cortical regions, on the other hand, are differentially more involved in episodic memory retrieval.

Memory Systems 1994

Abstract: Current thinking on memory systems of 1994, D.L. Schacter, E. Tulving multiple memory systems - what and why - an update, L. Nadel variations in synaptic plasticity and types of memory in corticohippocampal networks, G. Lynch, R. Granger hippocampal function and interference, M.L. Shapiro, D.S. Olton the memory coherence problem - configured associations and the hippocampal system, J.W. Rudy, R.J. Sutherland the hippocampal system and declarative memory in humans and animals - experimental analysis and historical origins, H. Eichenbaum declarative and non-declarative memory - multiple brain systems supporting learning and memory, L.R. Squire priming and multiple memory systems - perceptual mechanisms of implicit memory, D.L. Schacter memory and working with memory - evaluation of a component process model and comparisons with other models, M. Moscovitch binding complex memories - the role of reactivation and the hippocampus, M.K. Johnson, B.L. Chalfonte working interface - the interface between memory and cognition, A. Baddeley cognitive binding, J. Metcalfe, W.E. Mencl, G.W Cottrell.

Neuroanatomical correlates of encoding in episodic memory: levels of processing effect

Abstract: Cognitive studies of memory processes demonstrate that memory for stimuli is a function of how they are encoded; stimuli processed semantically are better remembered than those processed in a perceptual or shallow fashion. This study investigates the neural correlates of this cognitive phenomenon. Twelve subjects performed two different cognitive tasks on a series of visually presented nouns. In one task, subjects detected the presence or absence of the letter a; in the other, subjects categorized each noun as living or nonliving. Positron emission tomography (PET) scans using 15O-labeled water were obtained during both tasks. Subjects showed substantially better recognition memory for nouns seen in the living/nonliving task, compared to nouns seen in the a-checking task. Comparison of the PET images between the two cognitive tasks revealed a significant activation in the left inferior prefrontal cortex (Brodmann's areas 45, 46, 47, and 10) in the semantic task as compared to the perceptual task. We propose that memory processes are subserved by a wide neurocognitive network and that encoding processes involve preferential activation of the structures in the left inferior prefrontal cortex.

Neuroanatomical correlates of retrieval in episodic memory: auditory sentence recognition

Abstract: This study used positron emission tomography (PET) to investigate the neuroanatomical correlates of remembering previously experienced events. Twelve young healthy adults listened to "old" meaningful sentences which they had studied 24 hr previously. As a control task the subjects listened to comparable "new" sentences that they had never heard before. Regional cerebral blood flow associated with each task was measured by PET scans using 15O-labeled water. Comparison (old-sentence task minus new-sentence task) of the PET images revealed an extended strip of increased blood flow in the right dorsolateral prefrontal cortex (Brodmann's areas 10, 46, and 9) and the anterior portion of area 6. Other principal regions of increased blood flow were situated around the left anterior cingulate sulcus and bilaterally in the parietal lobes (areas 7 and 40). Major decreases in blood flow were situated bilaterally in the temporal lobes (areas 21, 22, 41, and 42). A high proportion of activity changes seemed to be located in the depths of cortical sulci. Increases in blood flow are seen as reflecting the operations of a widely distributed neuronal network involving prefrontal and parietal cortical regions that subserves the conscious recollection of previously experienced events. Decreases in blood flow in the temporal auditory areas are interpreted as reflecting auditory priming. The prevalence of sulcal blood-flow changes may reflect extensive cortical gyrification; it may also indicate that memory-related processes rely on the densely packed neuropil of sulcal regions.

Novelty encoding networks in the human brain: positron emission tomography data

Abstract: DATA from positron emission tomography (PET) studies showed novelty activations—higher regional cerebral blood flow associated with perceiving novel rather than familiar stimuli. Regions in the right 'expanded' limbic system—hippocampal formation, parahippocampal gyrus, retrosplenial cortex, thalamu

Priming and multiple memory systems: Perceptual mechanisms of implict memory

Abstract: Research examining the relation between explicit and implicit forms of memory has generated a great deal of evidence concerning the issue of multiple memory systems. This article focuses on an extensively studied implicit memory phenomenon, known as direct or repetition priming, and examines the hypothesis that priming effects on various tasks reflect the operation of a perceptual representation system (PRS)a class of cortically based subsystems that operate at a presemantic level and support non conscious expressions of memory. Three PRS subsystems are examined: visual word form, structural description, and auditory word form. Pertinent cognitive, neuropsychological, and neurobiological evidence is reviewed, alternative classificatory schemes are discussed, and important conceptual and terminological issues are considered.

The role of the left prefrontal cortex in verbal processing : semantic processing or willed action ?

Abstract: This study was designed to test the various proposed explanations (semantic processing, willed action, production of a spoken response) for the unilateral activation of the left prefrontal cortex noted in PET studies of verbal processing. Twenty subjects underwent 15O-water PET scans while undertaking a lexical task (detecting the letter 'a' in visually presented words) and a semantic task (categorizing nouns into living/non-living). The semantic task resulted in a significant unilateral left dorsolateral prefrontal activation. This finding suggests that the left inferior prefrontal cortex is the anatomical region involved in 'working with meaning', and that the activation does not reflect willed action, is not task-specific and is not attributable to the requirements of a spoken response.

Reducing retroactive interference: an interference analysis.

Abstract: In 4 experiments on retroactive interference (RI), we varied paired-associate learning lists that produced either appreciable or negligible forgetting. When the category of the stimulus word predicted its response word category, and the response was relatively unique within its category, learning was extremely rapid, and negative transfer and RI were negligible. The more the competing primed items in the predicted response category, the slower the learning and the greater the RI. If cues and responses were unrelated, learning was very slow, and RI was appreciable. Thus, predictive relations that help stimuli retrieve unique responses greatly alter forgetting in RI paradigms. This research returns to a fundamental question in the psychology of memory: Why do people forget things they have once learned? One of the oldest, most widely accepted theories of forgetting is associative interference, that people forget some target material because it is interfered with by other material in memory. Traditionally, the principles of associative interference have best been laid bare by studying learning and retention of paired associates, where, in successive lists, subjects learn different responses to the same cues—the so-called A-B, A-C paradigm. The second-learned response, C, is alleged to compete with successful recall of the first-learned response, B. The A-C association supposedly intrudes or wins out in competition with the requested A-B association (for reviews, see Keppel, 1968; Postman, 1961; Postman & Underwood, 1973).

Cognitive processes and cerebral cortical fundi: findings from positron-emission tomography studies.

Abstract: Positron-emission tomography (PET) studies of regional cerebral blood flow have provided evidence relevant to localization of cognitive functions. The critical loci identified in these studies are typically described in terms of macroanatomically labeled cortical and subcortical regions. We report the results of a meta-analysis of localization of changes in blood flow, based on nearly 1000 cerebral cortical peaks of activity obtained from groups of subjects in 30 PET studies. The results showed that, on average, 47% of these peaks were localized within the fundus regions of cortical sulci. This is an unexpectedly high proportion because fundal regions compose < 8% of the cortical mantle. Further analysis suggested a coarse correlation between the extent of fundal activation observed in different studies and the estimated cognitive complexity of the tasks used in the studies. These findings are potentially interesting because (i) the preponderance of fundal activation has implications for the interpretation of the PET data, (ii) they suggest that cortical sulcal and fundal regions may play a distinctive role in higher cognitive processing, or (iii) both of the above.