2025

Terlau, J., Ethofer, S., Naros, G., Fonken, Y., Lin, J. J., Knight, R. T., & Helfrich, R. F. (2025). Conjunctive population coding integrates sensory evidence to guide adaptive behavior. Proceedings of the National Academy of Sciences. (DOI)

Boroujeni, K. B., Helfrich, R. F., Fiebelkorn, I. C., Bentley, N., Brunner, P., Lin, J. J., Knight, R. T., & Kastner, S. High frequency bursts facilitate fast communication for human spatial attention. Nature Neuroscience. (PDF) (DOI)

Heidiri, L. F., Ethofer, S., Naros, G., van Schalkwijk, F. J., & Helfrich, R. F. (2025). Aperiodic activity reflects pathologic waveform shapes in focal epilepsy. Journal of Neuroscience. (DOI)

Terlau, J., Martini, J., & Helfrich, R. F. (2025). Structure in noise: Recurrent connectivity shapes neural variability to balance perceptual and cognitive demands in the human brain. Neuron. (DOI)

Raposo, I., Fiebelkorn, I. C., Lin, J. J., Parvizi, J., Kastner, S., Knight, R. T., Breska, A., & Helfrich, R. F. Human attention-guided visual perception is governed by rhythmic oscillations and aperiodic timescales. PLoS Biology. (PDF) (DOI)

Helfrich, R. F. Orchestrating prefrontal cognitive control: The thalamus in command. Neuron. (PDF) (DOI)

Cross, Z. R., Helfrich, R. F., Corcoran, A. W., Dede, A. J., Kohler, M. J., Coussens, S. W., Zou-Williams, L., Schlesewsky, G., Gaskell, G. M., Knight, R. T., & Bornkessel-Schlesewsky, I. Slow oscillation–spindle coupling predicts sequence-based language learning. Journal of Neuroscience. (PDF) (DOI)

Machetanz, K., Weinbrenner, E., Wuttke, T. V., Ethofer, S., Helfrich, R. F., Kegele, J., Lauxmann, S., Alber, M., Rona, S., Tatagiba, M., Lerche, H., Honegger, G., & Naros, G. Connectome-based disentangling of epilepsy networks from insular stereoelectroencephalographic leads. Frontiers in Neurology. (PDF) (DOI)

2024

Lendner, J. D., & Helfrich, R. F. Defining slow wave sleep without slow waves. Trends in Neurosciences. (PDF) (DOI)

Lendner, J. D., Lin, J. J., Larsson, P. G., & Helfrich, R. F. Multiple intrinsic timescales govern distinct brain states in human sleep. Journal of Neuroscience. (PDF) (DOI)

Hahn, M. A., Lendner, J. D., Anwander, M., Slama, K. S., Knight, R. T., Lin, J. J., & Helfrich, R. F. A tradeoff between efficiency and robustness in the hippocampal-neocortical memory network during human and rodent sleep. Progress in Neurobiology. (PDF) (DOI)

Kopf, M., Martini, J., Stier, C., Ethofer, S., Braun, C., Hegner, Y. L., Focke, N. K., Marquetand, J. & Helfrich, R. F. Aperiodic activity indexes neural hyperexcitability in generalized epilepsy. eNeuro. (PDF) (DOI)

Weber, J., Solbakk, A. K., Blenkmann, A. O., Llorens, A., Funderud, I., Leske, S., Larson, P. G., Ivanovic, J., Knight, R. T., Endestad, T. & Helfrich, R. F. Ramping dynamics and theta oscillations reflect dissociable signatures during rule-guided human behavior. Nature Communications. (PDF) (DOI)

2023

Raposo, I., Szczepanski, S. M., Haaland, K., Endestad, T., Solbakk, A. K., Knight, R. T., & Helfrich, R. F. Periodic neglect after frontoparietal lesions provides causal evidence for rhythmic attention sampling. Current Biology. (PDF) (DOI)

Helfrich, R. F., & Knight, R. T. Neural recordings and time series analyses. The Sage Handbook of Cognitive and Systems Neuroscience. (PDF)

Lendner, J. D., & Helfrich, R. F. How can I run sleep and anesthesia studies with intracranial EEG?. Intracranial EEG for Cognitive Neuroscience. (PDF) (DOI)

Lendner, J. D., Niethard, N., Mander, B. A., van Schalkwijk, F. J., Schuh-Hofer, S., Schmidt, H., Knight, R. T., Born, J., Walker, M. P., Lin, J. J., & Helfrich, R. F. Human REM sleep recalibrates neural activity in support of memory formation. Science Advances. (PDF) (DOI)

Weber, J., Iwama, G., Solbakk, A. K., Blenkmann, A. O., Larsson, P. G., Ivanovic, J., Knight, R. T., Endestad, T., & Helfrich, R. F. Subspace partitioning in the human prefrontal cortex resolves cognitive interference. Proceedings of the National Academy of Sciences. (PDF) (DOI)

2022

van Schalkwijk, F. J., Weber, J., Hahn, M. A., Lendner, J. D., Inostroza, M., Lin, J. J., & Helfrich, R. F. An evolutionary conserved division-of-labor between hippocampal and neocortical sharp-wave ripples organizes information transfer during sleep. Progress in Neurobiology. (PDF) (DOI)

Helfrich, R. F., Knight, R. T., & D’Esposito, M. Methods to study human memory. The Oxford Handbook of Human Memory. (PDF)

Helfrich, R. F., & R. T. Knight. Making memories last: How sleep promotes neuroplasticity. Changing Brains: Essays on Neuroplasticity in Honor of Helen J. Neville. (PDF) (DOI)

Helfrich, R. F. Human intracranial cognitive neurophysiology. Electrophysiological Recording Techniques, Neuromethods. (PDF) (DOI)

Hahn, M. A., Bothe, K., Heib, D., Schabus, M., Helfrich, R. F., & Hoedlmoser, K. Slow oscillation–spindle coupling strength predicts real-life gross-motor learning in adolescents and adults. eLife. (PDF) (DOI)

2021

Helfrich, R. F., Lendner, J. D., & Knight, R. T. Aperiodic sleep networks promote memory consolidation. Trends in Cognitive Sciences. (PDF) (DOI)

Kam, J. W., Helfrich, R. F., Solbakk, A. K., Endestad, T., Larsson, P. G., Lin, J. J., & Knight, R. T. Top–down attentional modulation in human frontal cortex: Differential engagement during external and internal attention. Cerebral Cortex. (PDF) (DOI)

2020

Lendner, J. D., Helfrich, R. F., Mander, B. A., Romundstad, L., Lin, J. J., Walker, M. P., Larsson, P.G., & Knight, R. T. An electrophysiological marker of arousal level in humans. eLife. (PDF) (DOI)

Hahn, M. A., Heib, D., Schabus, M., Hoedlmoser, K., & Helfrich, R. F. Slow oscillation-spindle coupling predicts enhanced memory formation from childhood to adolescence. eLife. (PDF) (DOI)

2019

Helfrich, R. F., & Knight, R. T. Cognitive neurophysiology: Event-related potentials. Handbook of Clinical Neurology. (PDF) (DOI)

Helfrich, R. F., & Knight, R. T. Cognitive neurophysiology of the prefrontal cortex. Handbook of Clinical Neurology. (PDF) (DOI)

Winer, J. R., Mander, B. A., Helfrich, R. F., Maass, A., Harrison, T. M., Baker, S. L., Knight, R. T., Jagust, W., & Walker, M. P. Sleep as a potential biomarker of tau and β-amyloid burden in the human brain. Journal of Neuroscience. (PDF) (DOI)

Helfrich, R. F., Breska, A., & Knight, R. T. Neural entrainment and network resonance in support of top-down guided attention. Current Opinion in Psychology. (PDF) (DOI)

Helfrich, R. F., Lendner, J. D., Mander, B. A., Guillen, H., Paff, M., Mnatsakanyan, L., Vadera, S., Walker, M., Lin, J. J., & Knight, R. T. Bidirectional prefrontal-hippocampal dynamics organize information transfer during sleep in humans. Nature Communications. (PDF) (DOI)

2018

Helfrich, R. F., Fiebelkorn, I. C., Szczepanski, S. M., Lin, J. J., Parvizi, J., Knight, R. T., & Kastner, S. Neural mechanisms of sustained attention are rhythmic. Neuron. (PDF) (DOI)

Helfrich, R. F., Mander, B. A., Jagust, W. J., Knight, R. T., & Walker, M. P. Old brains come uncoupled in sleep: Slow wave-spindle synchrony, brain atrophy, and forgetting. Neuron. (PDF) (DOI)

Helfrich, R. F. The rhythmic nature of visual perception. Journal of Neurophysiology. (PDF) (DOI)

2017

Helfrich, R. F., Huang, M., Wilson, G., & Knight, R. T. Prefrontal cortex modulates posterior alpha oscillations during top-down guided visual perception. Proceedings of the National Academy of Sciences. (PDF) (DOI)

Slama, S. K., & Helfrich, R. F. How does expectation shape object-based attentional selection?. Journal of Neuroscience. (PDF) (DOI)

2016

Helfrich, R. F., & Knight, R. T. Oscillatory dynamics of prefrontal cognitive control. Trends in Cognitive Sciences. (PDF) (DOI)

Helfrich, R. F., Herrmann, C. S., Engel, A. K., & Schneider, T. R. Different coupling modes mediate cortical cross-frequency interactions. Neuroimage. (PDF) (DOI)

Helfrich, R. F., Knepper, H., Nolte, G., Sengelmann, M., König, P., Schneider, T. R., & Engel, A. K. Spectral fingerprints of large‐scale cortical dynamics during ambiguous motion perception. Human Brain Mapping. (PDF) (DOI)

Herrmann, C. S., Strüber, D., Helfrich, R. F., & Engel, A. K. EEG oscillations: From correlation to causality. International Journal of Psychophysiology. (PDF) (DOI)

2014

Helfrich, R. F., Schneider, T. R., Rach, S., Trautmann-Lengsfeld, S. A., Engel, A. K., & Herrmann, C. S. Entrainment of brain oscillations by transcranial alternating current stimulation. Current Biology. (PDF) (DOI)

Helfrich, R. F., Knepper, H., Nolte, G., Strüber, D., Rach, S., Herrmann, C. S., Schneider, T., & Engel, A. K. Selective modulation of interhemispheric functional connectivity by HD-tACS shapes perception. PLoS Biology. (PDF) (DOI)

2013

Helfrich, R. F., & Schneider, T. R. Modulation of cortical network activity by transcranial alternating current stimulation. Journal of Neuroscience. (PDF) (DOI)

Helfrich, R. F., Becker, H. G., & Haarmeier, T. Processing of coherent visual motion in topographically organized visual areas in human cerebral cortex. Brain Topography. (PDF) (DOI)

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