Research Topics
| Nikolai AxmacherSummaryAffiliation: University of Bonn Country: Germany Publications
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Detail Information
Publications
Graded effects of social conformity on recognition memoryNikolai Axmacher
Department of Epileptology, University of Bonn, Bonn, Germany
PLoS ONE 5:e9270. 2010..These findings indicate that differential effects of social conformity on recognition of items as old and new occur in situations with an intermediate level of group pressure...- Memory formation by refinement of neural representations: the inhibition hypothesisNikolai Axmacher
Department of Epileptology, University of Bonn, Sigmund Freud Street 25, 53105 Bonn, Germany
Behav Brain Res 189:1-8. 2008..We suggest that during memory formation, the hippocampus renders neural representations more sparse by providing an inhibitory signal to the neocortex... - Interaction of working memory and long-term memory in the medial temporal lobeNikolai Axmacher
Department of Epileptology, University of Bonn, 53105 Bonn, Germany
Cereb Cortex 18:2868-78. 2008.... - Ripples in the medial temporal lobe are relevant for human memory consolidationNikolai Axmacher
Department of Epileptology, University of Bonn, Sigmund Freud Str 25, D 53105 Bonn, Germany
Brain 131:1806-17. 2008.... - Enhancement of neocortical-medial temporal EEG correlations during non-REM sleepNikolai Axmacher
Department of Epileptology, University of Bonn, 53105 Bonn, Germany
Neural Plast 2008:563028. 2008.... - Interactions between medial temporal lobe, prefrontal cortex, and inferior temporal regions during visual working memory: a combined intracranial EEG and functional magnetic resonance imaging studyNikolai Axmacher
Department of Epileptology, University of Bonn, Life and Brain Center of Academic Research, D 53105 Bonn, Germany
J Neurosci 28:7304-12. 2008..These data indicate that WM for multiple items depends on an increased strength of top-down control of activity within the IT cortex by the MTL... - Intracranial EEG correlates of expectancy and memory formation in the human hippocampus and nucleus accumbensNikolai Axmacher
Department of Epileptology, University of Bonn, 53105 Bonn, Germany
Neuron 65:541-9. 2010..These results are consistent with the hypothesis that activity in a loop involving the hippocampus and the nucleus accumbens promotes encoding of unexpected events... - Working memory-related hippocampal deactivation interferes with long-term memory formationNikolai Axmacher
Department of Epileptology, University of Bonn, D 53105 Bonn, Germany
J Neurosci 29:1052-960. 2009..However, deactivations of the hippocampus as previously observed during WM maintenance of individual items predicts failure of LTM encoding... - Interference of working memory load with long-term memory formationNikolai Axmacher
Department of Epileptology, University of Bonn, Bonn, Germany
Eur J Neurosci 29:1501-13. 2009..Taken together, these findings suggest that high WM demands interfere with LTM encoding and thus support the idea that WM and LTM processes interact in the MTL... - Memory processes during sleep: beyond the standard consolidation theoryNikolai Axmacher
Department of Epileptology, University of Bonn, Sigmund Freud Strasse 25, Bonn, Germany
Cell Mol Life Sci 66:2285-97. 2009..Here, we review the experimental evidence favoring and challenging these two views and suggest an integrative model of memory consolidation... - The specific contribution of neuroimaging versus neurophysiological data to understanding cognitionNikolai Axmacher
Department of Epileptology, University of Bonn, Bonn, Germany
Behav Brain Res 200:1-6. 2009..Taken together, we suggest that neuroscientific data contribute to the understanding of cognition by adding specific biological constraints and by extending the explanatory potential of psychological theories... - Electrophysiological signature of working and long-term memory interaction in the human hippocampusNikolai Axmacher
Department of Epileptology, University of Bonn, Sigmund Freud Str 25, D 53105 Bonn, Germany
Eur J Neurosci 31:177-88. 2010..Together, these findings indicate that multi-item WM and LTM encoding interfere within the hippocampus... - Cross-frequency coupling supports multi-item working memory in the human hippocampusNikolai Axmacher
Department of Epileptology, University of Bonn, Bonn 53105, Germany
Proc Natl Acad Sci U S A 107:3228-33. 2010..Third, we describe how the precision of cross-frequency coupling predicts individual WM performance. These data support the idea that working memory in humans depends on a neural code using phase information... - Sustained neural activity patterns during working memory in the human medial temporal lobeNikolai Axmacher
Department of Epileptology, University of Bonn, 53105 Bonn, Germany
J Neurosci 27:7807-16. 2007..Our results thus provide direct evidence for sustained neural activity patterns during working memory maintenance in the MTL, and show that these patterns depend on WM load... - The role of sleep in declarative memory consolidation--direct evidence by intracranial EEGNikolai Axmacher
Department of Epileptology, University of Bonn, 53105 Bonn, Germany
Cereb Cortex 18:500-7. 2008..These results suggest that sleep facilitates rapid processing through the hippocampus but is not necessary for information transfer into the neocortex per se... - Working memory representation in atypical language dominanceNikolai Axmacher
Department of Epileptology, University of Bonn, Bonn, Germany
Hum Brain Mapp 30:2032-43. 2009..The increased variability in right dominant subjects strongly suggests that a standard network of material-dependent WM processes exists in left dominant subjects, and that right dominant subjects use variable alternative networks... - Neuroelectric signatures of reward learning and decision-making in the human nucleus accumbensMichael X Cohen
Department of Epileptology and Center for Life and Brain, University of Bonn, Bonn, Germany
Neuropsychopharmacology 34:1649-58. 2009.... - Phase/amplitude reset and theta-gamma interaction in the human medial temporal lobe during a continuous word recognition memory taskFlorian Mormann
Department of Epileptology, University of Bonn, Germany
Hippocampus 15:890-900. 2005.... - Good vibrations: cross-frequency coupling in the human nucleus accumbens during reward processingMichael X Cohen
University of Bonn, Germany
J Cogn Neurosci 21:875-89. 2009..Gamma-alpha synchronization may reflect an electrophysiological gating mechanism in the human nucleus accumbens, and the phase differences in gamma-alpha coupling may reflect a reward information coding scheme similar to phase coding... - Sleep-dependent directional coupling between human neocortex and hippocampusTobias Wagner
Department of Epileptology, University of Bonn, Germany
Cortex 46:256-63. 2010..These results question the standard model of hippocampal-neocortical interactions and suggest that sleep-dependent consolidation is accomplished by an active retrieval of hippocampal information by the neocortex... - Rhinal-hippocampal coupling during declarative memory formation: dependence on item characteristicsJuergen Fell
Department of Epileptology, University of Bonn, Sigmund Freud Str 25, D 53105 Bonn, Germany
Neurosci Lett 407:37-41. 2006..Our data suggest, that broadband Rhinal-hippocampal coupling including the gamma range only occurs, when significant semantic associations are processed within rhinal cortex, as is the case for high-frequency words... - Activation of the caudal anterior cingulate cortex due to task-related interference in an auditory Stroop paradigmSven Haupt
Department of Epileptology, University of Bonn, Bonn, Germany
Hum Brain Mapp 30:3043-56. 2009..Taken together, we found (besides activation of regions well-known from visual Stroop tasks) activation of the very caudal and posterior part of the ACC due to task-related interference in an auditory Stroop task... - Nuclei accumbens phase synchrony predicts decision-making reversals following negative feedbackMichael X Cohen
Department of Epileptology and Center for Life and Brain and Department of Psychiatry and Psychotherapy, University of Bonn, 53105 Bonn, Germany
J Neurosci 29:7591-8. 2009..These findings suggest that a neural network including the nucleus accumbens bilaterally becomes functionally connected via theta phase synchrony to signal the need to adjust behavior... - Presurgical language fMRI in patients with drug-resistant epilepsy: effects of task performanceBernd Weber
Department of Epileptology, University of Bonn, Bonn, Germany
Epilepsia 47:880-6. 2006..To determine whether language functional magnetic resonance imaging (fMRI) before epilepsy surgery can be similarly interpreted in patients with greatly different performance levels... - Medial temporal theta/alpha power enhancement precedes successful memory encoding: evidence based on intracranial EEGJuergen Fell
Department of Epileptology, University of Bonn, D 53105 Bonn, Germany
J Neurosci 31:5392-7. 2011.... - Neuropsychological safety of nucleus accumbens deep brain stimulation for major depression: effects of 12-month stimulationChristiane Grubert
Department of Psychiatry and Psychotherapy, University Hospital, Bonn, Germany
World J Biol Psychiatry 12:516-27. 2011..However, limited information exists regarding the impact of NAcc-DBS on cognitive functioning. The aim of this study was to examine whether NAcc-DBS in patients with TRD has any cognitive effects... - Nucleus accumbens deep brain stimulation decreases ratings of depression and anxiety in treatment-resistant depressionBettina H Bewernick
Department of Psychiatry and Psychotherapy, University Hospital, 53105 Bonn, Germany
Biol Psychiatry 67:110-6. 2010..Since anhedonia is a feature of depression and there is evidence of dysfunction of the reward system, DBS to the nucleus accumbens (NAcc) might be promising... - Ventromedial prefrontal cortex activation is associated with memory formation for predictable rewardsKatharina A Bialleck
Department of Epileptology, University of Bonn, Bonn, Germany
PLoS ONE 6:e16695. 2011..Taken together, these findings show that consumption of reliably predictable rewards facilitates LTM formation and is associated with activation of the vmPFC... - Antidepressant effects, of magnetic seizure therapy and electroconvulsive therapy, in treatment-resistant depressionSarah Kayser
Department of Psychiatry and Psychotherapy, Sigmund Freud Strasse 25, University Hospital, Bonn, Germany
J Psychiatr Res 45:569-76. 2011..Thus, MST may be a potential alternative to ECT if efficacy and safety are validated in larger clinical trials... - Phase-locking within human mediotemporal lobe predicts memory formationJuergen Fell
Department of Epileptology, University of Bonn, Bonn, Germany
Neuroimage 43:410-9. 2008..Our data suggest that early mediotemporal phase adjustments constitute a relevant mechanism underlying declarative memory encoding... - Correlation between EEG rhythms during sleep: surface versus mediotemporal EEGAnnkathrin Poepel
Department of Epileptology, University of Bonn, Bonn, Germany
Neuroreport 18:837-40. 2007..In contrast, we found that within the hippocampus delta/theta power alternated in parallel with fast oscillations above 16 Hz during non-rapid-eye-movement sleep (positive correlations)... - Human neocortical and hippocampal near-DC shifts are interconnectedJuergen Fell
Department of Epileptology, University of Bonn, D 53105 Bonn, Germany
Hippocampus 17:413-9. 2007..The finding that neocortical and hippocampal near-DC shifts are interconnected may open new perspectives for the prediction and control of mediotemporal lobe seizures... - Memory formation by neuronal synchronizationNikolai Axmacher
Department of Epileptology, University of Bonn, Sigmund Freud Str 25, 53105 Bonn, Germany
Brain Res Rev 52:170-82. 2006..In summary, synchronization of neural assemblies in different frequency ranges induces specific forms of cellular plasticity during subsequent stages of memory formation... - Association between scalp hair-whorl direction and hemispheric language dominanceBernd Weber
Department of Epileptology, University of Bonn, Sigmund Freud Str 25, 53105 Bonn, Germany
Neuroimage 30:539-43. 2006..J.S., 2003. Human handedness and scalp hair-whorl direction develop from a common genetic mechanism. Genetics 1651, 269-276.] also affects cerebral language dominance... - The role of phase synchronization in memory processesJuergen Fell
Department of Epileptology, University of Bonn, Sigmund Freud Strasse 25, D 53105 Bonn, Germany
Nat Rev Neurosci 12:105-18. 2011..A deeper understanding of how phase synchronization supports the flexibility of and interaction between memory systems may yield new insights into the functions of phase synchronization in general... - From alpha to gamma: electrophysiological correlates of meditation-related states of consciousnessJuergen Fell
Department of Epileptology, University of Bonn, Sigmund Freud Str 25, D 53105 Bonn, Germany
Med Hypotheses 75:218-24. 2010..While meditation formerly has been understood to comprise mainly passive relaxation states, recent EEG findings suggest that meditation is associated with active states which involve cognitive restructuring and learning... - Deep brain stimulation to reward circuitry alleviates anhedonia in refractory major depressionThomas E Schlaepfer
Department of Psychiatry and Psychotherapy, University Hospital, Bonn, Germany
Neuropsychopharmacology 33:368-77. 2008..These preliminary findings suggest that DBS to the nucleus accumbens might be a hypothesis-guided approach for refractory major depression... - Monitoring the mind: the neurocognitive correlates of metamemoryAnne T A Do Lam
Department of Epileptology, University of Bonn, Bonn, Germany
PLoS ONE 7:e30009. 2012..Masking brain activation during predicted memory success with activation during retrieval success revealed BOLD increases of the mPFC. Our findings indicate that JOLs actually incorporate retrieval processes... - Magnetic seizure therapy of treatment-resistant depression in a patient with bipolar disorderSarah Kayser
Department of Psychiatry and Psychotherapy, University Hospital, Bonn, Germany
J ECT 25:137-40. 2009..Taken together, these results suggest that MST, compared with ECT, might have antidepressant effects and may have fewer clinical side effects... - Natural memory beyond the storage model: repression, trauma, and the construction of a personal pastNikolai Axmacher
Department of Epileptology, University of Bonn Bonn, Germany
Front Hum Neurosci 4:211. 2010..We suggest several experimental paradigms that allow for the investigation of the neural correlates of repressed memories and trauma-induced memory distortions based on a constructivist memory concept... - Inhibition of GABA release by presynaptic ionotropic GABA receptors in hippocampal CA3Nikolai Axmacher
, , Tucholskystr. 2, 10117 Berlin, Germany
Neuroreport 15:329-34. 2004..We conclude that the release of GABA from hippocampal CA3 interneurons is regulated by a negative feedback via presynaptic ionotropic GABA autoreceptors... - Intrinsic cellular currents and the temporal precision of EPSP-action potential coupling in CA1 pyramidal cellsNikolai Axmacher
INSERM EMI 0224, , UPMC, , 75013 Paris, France
J Physiol 555:713-25. 2004..The resulting inward-outward current sequences enhance the temporal precision of EPSP-spike coupling. Thus, CA1 pyramidal cells initiate action potentials with different temporal precision, depending on stimulus properties... - Presynaptic ionotropic GABA receptorsAndreas Draguhn
Institut fur Physiologie und Pathophysiologie, Universitat Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
Results Probl Cell Differ 44:69-85. 2008.... - Transmitter metabolism as a mechanism of synaptic plasticity: a modeling studyNikolai Axmacher
, , 10117 Berlin, Germany
J Neurophysiol 91:25-39. 2004..Therefore, the model allows one to decide, at a given synapse, how transmitter metabolism is linked to presynaptic function and efficacy... - Two-photon imaging of spontaneous vesicular release in acute brain slices and its modulation by presynaptic GABAA receptorsNikolai Axmacher
, , 10117 Berlin, Germany
Neuroimage 22:1014-21. 2004..Those novel methods should be well suited to study pathophysiological changes in inhibition in resections obtained from neurosurgical treatment of epilepsy patients...