Gamma frequency activity (30-150 Hz) is induced in cognitive tasks and is thought to reflect underlying neural processes. Gamma frequency activity can be recorded directly from the human brain using intracranial electrodes implanted in patients undergoing treatment for drug-resistant epilepsy. Previous studies have independently explored narrowband oscillations in the local field potential and broadband power increases. It is not clear, however, which processes contribute to human brain gamma frequency activity, or their dynamics and roles during memory processing. Here a large dataset of intracranial recordings obtained during encoding of words from 101 patients was used to detect, characterize and compare induced gamma frequency activity events. Individual bursts of gamma frequency activity were isolated in the time-frequency domain to determine their spectral features, including peak frequency, amplitude, frequency span, and duration. We found two distinct types of gamma frequency activity events that showed either narrowband or broadband frequency spans revealing characteristic spectral properties. Narrowband events, the predominant type, were induced by word presentations following an initial induction of broadband events, which were temporally separated and selectively correlated with evoked response potentials, suggesting that they reflect different neural activities and play different roles during memory encoding. The two gamma frequency activity types were differentially modulated during encoding of subsequently recalled and forgotten words. In conclusion, we found evidence for two distinct activity types induced in the gamma frequency range during cognitive processing. Separating these two gamma frequency activity components contributes to the current understanding of electrophysiological biomarkers, and may prove useful for emerging neurotechnologies targeting, mapping and modulating distinct neurophysiological processes in normal and epileptogenic brain.

Columbia University Department of Neurology New York NY USA

Czech Institute of Informatics Robotics and Cybernetics Czech Technical University Prague Czech Republic

Dartmouth Hitchcock Medical Center Department of Neurology Lebanon NH USA

Emory University Department of Neurosurgery Atlanta GA USA

Mayo Clinic Department of Neurology Mayo Systems Electrophysiology Laboratory Rochester MN USA

Mayo Clinic Department of Physiology and Biomedical Engineering Rochester MN USA

Thomas Jefferson University Hospital Department of Neurology Philadelphia PN USA

Thomas Jefferson University Hospital Department of Radiology Philadelphia PN USA

University of Pennsylvania Department of Psychology Philadelphia PN USA

University of Pennsylvania Hospital Department of Radiology Philadelphia PN USA

University of Texas Southwestern Medical Center Department of Neurosurgery Dallas TX USA

Citace poskytuje Crossref.org

Prefrontal electrophysiological biomarkers and mechanism-based drug effects in a rat model of alcohol addiction

High frequency oscillations in human memory and cognition: a neurophysiological substrate of engrams?

Phase-Amplitude Coupling Localizes Pathologic Brain with Aid of Behavioral Staging in Sleep

Intracranial electrophysiological recordings from the human brain during memory tasks with pupillometry

Leveraging electrophysiologic correlates of word encoding to map seizure onset zone in focal epilepsy: Task-dependent changes in epileptiform activity, spectral features, and functional connectivity

High frequency oscillations in epileptic and non-epileptic human hippocampus during a cognitive task

Unsupervised machine-learning classification of electrophysiologically active electrodes during human cognitive task performance

Human Verbal Memory Encoding Is Hierarchically Distributed in a Continuous Processing Stream

Pupil size reflects successful encoding and recall of memory in humans

Electrical Stimulation Modulates High γ Activity and Human Memory Performance

Progress and Remaining Challenges in the Application of High Frequency Oscillations as Biomarkers of Epileptic Brain