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Jan Born - One of the best experts on this subject based on the ideXlab platform.
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vast amounts of encoded items nullify but do not reverse the effect of sleep on Declarative Memory
Frontiers in Psychology, 2021Co-Authors: Jan Born, Luca Kolibius, Gordon B FeldAbstract:Sleep strengthens memories by repeatedly reactivating associated neuron ensembles. Our studies show that although long-term Memory for a medium number of word-pairs (160) benefits from sleep, a large number (320) does not. This suggests an upper limit to the amount of information that has access to sleep-dependent Declarative Memory consolidation, which is possibly linked to the availability of reactivation opportunities. Due to competing processes of global forgetting that are active during sleep, we hypothesized that even larger amounts of information would enhance the proportion of information that is actively forgotten during sleep. In the present study, we aimed to induce such forgetting by challenging the sleeping brain with vast amounts of to be remembered information. For this, 80 participants learned a very large number of 640 word-pairs over the course of an entire day and then either slept or stayed awake during the night. Recall was tested after another night of regular sleep. Results revealed comparable retention rates between the sleep and wake groups. Although this null-effect can be reconciled with the concept of limited capacities available for sleep-dependent consolidation, it contradicts our hypothesis that sleep would increase forgetting compared to the wake group. Additional exploratory analyses relying on equivalence testing and Bayesian statistics reveal that there is evidence against sleep having a detrimental effect on the retention of Declarative Memory at high information loads. We argue that forgetting occurs in both wake and sleep states through different mechanisms, i.e., through increased interference and through global synaptic downscaling, respectively. Both of these processes might scale similarly with information load.
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immediate as well as delayed post learning sleep but not wakefulness enhances Declarative Memory consolidation in children
Neurobiology of Learning and Memory, 2008Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Klaus JunghannsAbstract: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.
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midlife decline in Declarative Memory consolidation is correlated with a decline in slow wave sleep
Learning & Memory, 2007Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Sylvia Fokuhl, Klaus JunghannsAbstract:Sleep architecture as well as Memory function are strongly age dependent. Slow wave sleep (SWS), in particular, decreases dramatically with increasing age, starting already beyond the age of 30. SWS normally predominates during early nocturnal sleep and is implicated in Declarative Memory consolidation. However, the consequences of changes in sleep across the life span for sleep-associated Memory consolidation have not been evaluated so far. Here, we compared Declarative Memory consolidation (for word-pair associates) during sleep in young and middle-aged healthy humans. The age groups (18–25 vs. 48–55 yr) did not differ with regard to learning performance before retention periods that covered, respectively, the first and second half of nocturnal sleep. However, after early retention sleep, where the younger subjects showed distinctly more SWS than the middle-aged (62.3 ± 3.7 min vs. 18.4 ± 7.2 min, P < 0.001), retrieval of the word pairs in the middle-aged was clearly worse than in the young (P < 0.001). In contrast, Declarative Memory retention did not differ between groups after late sleep, where retention was generally worse than after early sleep (P = 0.005). Retention of Declarative memories was the same in both age groups when sleep periods containing equal amounts of SWS were compared, i.e., across late sleep in the young and across early sleep in the middle-aged. Our results indicate a decline in sleep-associated Declarative Memory consolidation that develops already during midlife and is associated with a decrease in early nocturnal SWS.
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impaired Declarative Memory consolidation during sleep in patients with primary insomnia influence of sleep architecture and nocturnal cortisol release
Biological Psychiatry, 2006Co-Authors: Jutta Backhaus, Jan Born, Klaus Junghanns, Kornelia Hohaus, Frauke Faasch, Fritz HohagenAbstract:Background A central cognitive function of sleep is to consolidate newly acquired memories for long-term storage. Here, we investigated whether the overnight consolidation of Declarative Memory in patients with chronic sleep disturbances is impaired, owing to less slow wave sleep (SWS) and an increased cortisol release. Methods Polysomnographic recordings, serum cortisol concentrations, and overnight Memory consolidation in 16 patients with primary insomnia were compared with those of 13 healthy control subjects. Results Patients displayed distinctly less overnight consolidation of Declarative Memory ( p r = .69) but with rapid eye movement (REM) sleep in the patients ( r = .56), who had a diminished amount of SWS ( p r = −.52) and patients ( r = −.46). Conclusions Primary insomnia is associated with a diminished sleep-related consolidation of Declarative Memory. Efficient overnight consolidation of Declarative Memory is associated with high amounts of SWS and low serum cortisol levels during the early part of the night. Where SWS is decreased, REM sleep might play a partly compensatory role in the consolidation of Declarative Memory.
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Low acetylcholine during slow-wave sleep is critical for Declarative Memory consolidation
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Steffen Gais, Jan BornAbstract:The neurotransmitter acetylcholine is considered essential for proper functioning of the hippocampus-dependent Declarative Memory system, and it represents a major neuropharmacological target for the treatment of Memory deficits, such as those in Alzheimer's disease. During slow-wave sleep (SWS), however, Declarative Memory consolidation is particularly strong, while acetylcholine levels in the hippocampus drop to a minimum. Observations in rats led to the hypothesis that the low cholinergic tone during SWS is necessary for the replay of new memories in the hippocampus and their long-term storage in neocortical networks. However, this low tone should not affect nonDeclarative Memory systems. In this study, increasing central nervous cholinergic activation during SWS-rich sleep by posttrial infusion of 0.75 mg of the cholinesterase inhibitor physostigmine completely blocked SWS-related consolidation of Declarative memories for word pairs in human subjects. The treatment did not interfere with consolidation of a nonDeclarative mirror tracing task. Also, physostigmine did not alter Memory consolidation during waking, when the endogenous central nervous cholinergic tone is maximal. These findings are in line with predictions that a low cholinergic tone during SWS is essential for Declarative Memory consolidation.
Klaus Junghanns - One of the best experts on this subject based on the ideXlab platform.
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immediate as well as delayed post learning sleep but not wakefulness enhances Declarative Memory consolidation in children
Neurobiology of Learning and Memory, 2008Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Klaus JunghannsAbstract: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.
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midlife decline in Declarative Memory consolidation is correlated with a decline in slow wave sleep
Learning & Memory, 2007Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Sylvia Fokuhl, Klaus JunghannsAbstract:Sleep architecture as well as Memory function are strongly age dependent. Slow wave sleep (SWS), in particular, decreases dramatically with increasing age, starting already beyond the age of 30. SWS normally predominates during early nocturnal sleep and is implicated in Declarative Memory consolidation. However, the consequences of changes in sleep across the life span for sleep-associated Memory consolidation have not been evaluated so far. Here, we compared Declarative Memory consolidation (for word-pair associates) during sleep in young and middle-aged healthy humans. The age groups (18–25 vs. 48–55 yr) did not differ with regard to learning performance before retention periods that covered, respectively, the first and second half of nocturnal sleep. However, after early retention sleep, where the younger subjects showed distinctly more SWS than the middle-aged (62.3 ± 3.7 min vs. 18.4 ± 7.2 min, P < 0.001), retrieval of the word pairs in the middle-aged was clearly worse than in the young (P < 0.001). In contrast, Declarative Memory retention did not differ between groups after late sleep, where retention was generally worse than after early sleep (P = 0.005). Retention of Declarative memories was the same in both age groups when sleep periods containing equal amounts of SWS were compared, i.e., across late sleep in the young and across early sleep in the middle-aged. Our results indicate a decline in sleep-associated Declarative Memory consolidation that develops already during midlife and is associated with a decrease in early nocturnal SWS.
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impaired Declarative Memory consolidation during sleep in patients with primary insomnia influence of sleep architecture and nocturnal cortisol release
Biological Psychiatry, 2006Co-Authors: Jutta Backhaus, Jan Born, Klaus Junghanns, Kornelia Hohaus, Frauke Faasch, Fritz HohagenAbstract:Background A central cognitive function of sleep is to consolidate newly acquired memories for long-term storage. Here, we investigated whether the overnight consolidation of Declarative Memory in patients with chronic sleep disturbances is impaired, owing to less slow wave sleep (SWS) and an increased cortisol release. Methods Polysomnographic recordings, serum cortisol concentrations, and overnight Memory consolidation in 16 patients with primary insomnia were compared with those of 13 healthy control subjects. Results Patients displayed distinctly less overnight consolidation of Declarative Memory ( p r = .69) but with rapid eye movement (REM) sleep in the patients ( r = .56), who had a diminished amount of SWS ( p r = −.52) and patients ( r = −.46). Conclusions Primary insomnia is associated with a diminished sleep-related consolidation of Declarative Memory. Efficient overnight consolidation of Declarative Memory is associated with high amounts of SWS and low serum cortisol levels during the early part of the night. Where SWS is decreased, REM sleep might play a partly compensatory role in the consolidation of Declarative Memory.
Jutta Backhaus - One of the best experts on this subject based on the ideXlab platform.
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immediate as well as delayed post learning sleep but not wakefulness enhances Declarative Memory consolidation in children
Neurobiology of Learning and Memory, 2008Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Klaus JunghannsAbstract: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.
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midlife decline in Declarative Memory consolidation is correlated with a decline in slow wave sleep
Learning & Memory, 2007Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Sylvia Fokuhl, Klaus JunghannsAbstract:Sleep architecture as well as Memory function are strongly age dependent. Slow wave sleep (SWS), in particular, decreases dramatically with increasing age, starting already beyond the age of 30. SWS normally predominates during early nocturnal sleep and is implicated in Declarative Memory consolidation. However, the consequences of changes in sleep across the life span for sleep-associated Memory consolidation have not been evaluated so far. Here, we compared Declarative Memory consolidation (for word-pair associates) during sleep in young and middle-aged healthy humans. The age groups (18–25 vs. 48–55 yr) did not differ with regard to learning performance before retention periods that covered, respectively, the first and second half of nocturnal sleep. However, after early retention sleep, where the younger subjects showed distinctly more SWS than the middle-aged (62.3 ± 3.7 min vs. 18.4 ± 7.2 min, P < 0.001), retrieval of the word pairs in the middle-aged was clearly worse than in the young (P < 0.001). In contrast, Declarative Memory retention did not differ between groups after late sleep, where retention was generally worse than after early sleep (P = 0.005). Retention of Declarative memories was the same in both age groups when sleep periods containing equal amounts of SWS were compared, i.e., across late sleep in the young and across early sleep in the middle-aged. Our results indicate a decline in sleep-associated Declarative Memory consolidation that develops already during midlife and is associated with a decrease in early nocturnal SWS.
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impaired Declarative Memory consolidation during sleep in patients with primary insomnia influence of sleep architecture and nocturnal cortisol release
Biological Psychiatry, 2006Co-Authors: Jutta Backhaus, Jan Born, Klaus Junghanns, Kornelia Hohaus, Frauke Faasch, Fritz HohagenAbstract:Background A central cognitive function of sleep is to consolidate newly acquired memories for long-term storage. Here, we investigated whether the overnight consolidation of Declarative Memory in patients with chronic sleep disturbances is impaired, owing to less slow wave sleep (SWS) and an increased cortisol release. Methods Polysomnographic recordings, serum cortisol concentrations, and overnight Memory consolidation in 16 patients with primary insomnia were compared with those of 13 healthy control subjects. Results Patients displayed distinctly less overnight consolidation of Declarative Memory ( p r = .69) but with rapid eye movement (REM) sleep in the patients ( r = .56), who had a diminished amount of SWS ( p r = −.52) and patients ( r = −.46). Conclusions Primary insomnia is associated with a diminished sleep-related consolidation of Declarative Memory. Efficient overnight consolidation of Declarative Memory is associated with high amounts of SWS and low serum cortisol levels during the early part of the night. Where SWS is decreased, REM sleep might play a partly compensatory role in the consolidation of Declarative Memory.
Fritz Hohagen - One of the best experts on this subject based on the ideXlab platform.
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immediate as well as delayed post learning sleep but not wakefulness enhances Declarative Memory consolidation in children
Neurobiology of Learning and Memory, 2008Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Klaus JunghannsAbstract: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.
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midlife decline in Declarative Memory consolidation is correlated with a decline in slow wave sleep
Learning & Memory, 2007Co-Authors: Jutta Backhaus, Jan Born, Fritz Hohagen, Ralf Hoeckesfeld, Sylvia Fokuhl, Klaus JunghannsAbstract:Sleep architecture as well as Memory function are strongly age dependent. Slow wave sleep (SWS), in particular, decreases dramatically with increasing age, starting already beyond the age of 30. SWS normally predominates during early nocturnal sleep and is implicated in Declarative Memory consolidation. However, the consequences of changes in sleep across the life span for sleep-associated Memory consolidation have not been evaluated so far. Here, we compared Declarative Memory consolidation (for word-pair associates) during sleep in young and middle-aged healthy humans. The age groups (18–25 vs. 48–55 yr) did not differ with regard to learning performance before retention periods that covered, respectively, the first and second half of nocturnal sleep. However, after early retention sleep, where the younger subjects showed distinctly more SWS than the middle-aged (62.3 ± 3.7 min vs. 18.4 ± 7.2 min, P < 0.001), retrieval of the word pairs in the middle-aged was clearly worse than in the young (P < 0.001). In contrast, Declarative Memory retention did not differ between groups after late sleep, where retention was generally worse than after early sleep (P = 0.005). Retention of Declarative memories was the same in both age groups when sleep periods containing equal amounts of SWS were compared, i.e., across late sleep in the young and across early sleep in the middle-aged. Our results indicate a decline in sleep-associated Declarative Memory consolidation that develops already during midlife and is associated with a decrease in early nocturnal SWS.
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impaired Declarative Memory consolidation during sleep in patients with primary insomnia influence of sleep architecture and nocturnal cortisol release
Biological Psychiatry, 2006Co-Authors: Jutta Backhaus, Jan Born, Klaus Junghanns, Kornelia Hohaus, Frauke Faasch, Fritz HohagenAbstract:Background A central cognitive function of sleep is to consolidate newly acquired memories for long-term storage. Here, we investigated whether the overnight consolidation of Declarative Memory in patients with chronic sleep disturbances is impaired, owing to less slow wave sleep (SWS) and an increased cortisol release. Methods Polysomnographic recordings, serum cortisol concentrations, and overnight Memory consolidation in 16 patients with primary insomnia were compared with those of 13 healthy control subjects. Results Patients displayed distinctly less overnight consolidation of Declarative Memory ( p r = .69) but with rapid eye movement (REM) sleep in the patients ( r = .56), who had a diminished amount of SWS ( p r = −.52) and patients ( r = −.46). Conclusions Primary insomnia is associated with a diminished sleep-related consolidation of Declarative Memory. Efficient overnight consolidation of Declarative Memory is associated with high amounts of SWS and low serum cortisol levels during the early part of the night. Where SWS is decreased, REM sleep might play a partly compensatory role in the consolidation of Declarative Memory.
Guillén Fernández - One of the best experts on this subject based on the ideXlab platform.
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The rhinal cortex: 'gatekeeper' of the Declarative Memory system.
Trends in Cognitive Sciences, 2006Co-Authors: Guillén Fernández, Indira TendolkarAbstract:Almost all studies probing neural activity underlying the Declarative Memory system in humans have investigated either Memory encoding or retrieval. Here, however, we suggest integrating encoding and retrieval operations into a single operation executed by the rhinal cortex. The more familiar an item is, the less rhinal processing it requires and the less vigorously it is encoded into Memory. Given the anatomical position and the functional properties of the rhinal cortex, this operation fulfills an essential task: it optimally allocates limited encoding resources away from familiar information and towards novel information. We propose a rhinal processing stage that optimizes the Declarative Memory system by fully integrating encoding and retrieval operations into a single 'gatekeeper' operation.
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theta and gamma oscillations predict encoding and retrieval of Declarative Memory
The Journal of Neuroscience, 2006Co-Authors: Daria Osipova, Guillén Fernández, Atsuko Takashima, Robert Oostenveld, Eric Maris, Ole JensenAbstract:Although studies in animals and patients have demonstrated that brain oscillations play a role in Declarative Memory encoding and retrieval, little has been done to investigate the temporal dynamics and sources of brain activity in healthy human subjects performing such tasks. In a magnetoencephalography study using pictorial stimuli, we have now identified oscillatory activity in the gamma (60-90 Hz) and theta (4.5-8.5 Hz) band during Declarative Memory operations in healthy participants. Both theta and gamma activity was stronger for the later remembered compared with the later forgotten items (the "subsequent Memory effect"). In the retrieval session, theta and gamma activity was stronger for recognized items compared with correctly rejected new items (the "old/new effect"). The gamma activity was also stronger for recognized compared with forgotten old items (the "recognition effect"). The effects in the theta band were observed over right parietotemporal areas, whereas the sources of the effects in the gamma band were identified in Brodmann area 18/19. We propose that the theta activity is directly engaged in mnemonic operations. The increase in neuronal synchronization in the gamma band in occipital areas may result in a stronger drive to subsequent areas, thus facilitating both Memory encoding and retrieval. Alternatively, the gamma synchronization might reflect representations being reinforced by top-down activity from higher-level Memory areas. Our results provide additional insight on human Declarative Memory operations and oscillatory brain activity that complements previous electrophysiological and brain imaging studies.
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temporal and cerebellar brain regions that support both Declarative Memory formation and retrieval
Cerebral Cortex, 2004Co-Authors: Susanne Weis, Christian E Elger, Peter Klaver, Jurgen Reul, Guillén FernándezAbstract:Using event-related fMRI, we scanned young healthy subjects while they memorized real-world photographs and subsequently tried to recognize them within a series of new photographs. We confirmed that activity in the medial temporal lobe (MTL) and inferior prefrontal cortex correlates with Declarative Memory formation as defined by the subsequent Memory effect, stronger responses to subsequently remembered than forgotten items. Additionally, we confirmed that activity in specific regions within the parietal lobe, anterior prefrontal cortex, anterior cingulate and cerebellum correlate with recognition Memory as measured by the conventional old/new effect, stronger responses for recognized old items (hits) than correctly identified new items (correct rejections). To obtain a purer measure of recognition success, we introduced two recognition effects by comparing brain responses to hits and old items misclassified as new (misses). The positive recognition effect (hits > misses) revealed prefrontal, parietal and cerebellar contributions to recognition, and in line with electrophysiological findings, the negative recognition effect (hits < misses) revealed an anterior medial temporal contribution. Finally, by inclusive masking, we identified temporal and cerebellar brain areas that support both Declarative Memory formation and retrieval. For matching operations during recognition, these areas may re-use representations formed and stored locally during encoding.
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rhinal hippocampal theta coherence during Declarative Memory formation interaction with gamma synchronization
European Journal of Neuroscience, 2003Co-Authors: Juergen Fell, Peter Klaver, Hakim Elfadil, Carlo Schaller, Christian E Elger, Guillén FernándezAbstract:The hippocampus and the rhinal cortex, two substructures of the medial temporal lobe, together play a crucial role in human Declarative Memory formation. To investigate in detail the mechanism connecting these two structures transiently during Memory formation we recorded depth EEG in epilepsy patients from within the hippocampus and the rhinal cortex. During this recording, patients performed a single-trial word list-learning paradigm with a free recall Memory test following a distraction task. Rhinal-hippocampal EEG coherence and spectral power at both locations in the time interval up to 2 s after onset of word presentation were analysed in the frequency range 1-19 Hz. Successful as opposed to unsuccessful Memory formation was associated with a general rhinal-hippocampal coherence enhancement, but without alterations in spectral power. Coherence increases in the theta range were correlated with the previously reported Memory-related changes in rhinal-hippocampal gamma phase synchronization. This correlation may suggest an interaction of the two mechanisms during Declarative Memory formation. While theta coherence might be associated with slowly modulated coupling related to an encoding state, rhinal-hippocampal gamma synchronization may be more closely related to actual Memory processes by enabling fast coupling and decoupling of the two structures.
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Integrated brain activity in medial temporal and prefrontal areas predicts subsequent Memory performance: human Declarative Memory formation at the system level.
Brain research bulletin, 2001Co-Authors: Guillén Fernández, Indira TendolkarAbstract:After an era in which lesion studies have identified the Declarative Memory system and its essential anatomical structures, functional imaging and event-related potential studies have begun to delineate the neural underpinnings of Declarative Memory formation at the system level. By Memory formation, we refer to those mnemonic processes present during encoding that transform perceptual representations into enduring memories. Recent studies have revealed that distinct regions in medial temporal and prefrontal areas exhibit more neural activity during successful than unsuccessful Memory formation. We attempt to identify the nature of the processes underlying these subsequent Memory effects. Reviewed data suggest specific mnemonic operations in the medial temporal lobe that may be integrated with semantic/perceptual operations and subserving operations in the prefrontal cortex. The formation of relational and non-relational memories may be supported by distinct subregions within these two brain regions. While the medial temporal lobe may have a serial organizational structure, with a processing hierarchy, interactions between medial temporal and prefrontal areas seem to occur in a parallel and bi-directional fashion. Interacting with this system, emotionally arousing events enhance neural activity in the amygdala, which in turn may modulate processing in other brain regions responsible for Declarative Memory formation.
