scholarly journals Author response: Hippocampal pattern completion is linked to gamma power increases and alpha power decreases during recollection

2016 ◽  
Author(s):  
Bernhard P Staresina ◽  
Sebastian Michelmann ◽  
Mathilde Bonnefond ◽  
Ole Jensen ◽  
Nikolai Axmacher ◽  
...  
Keyword(s):  
Author Response ◽  
Alpha Power ◽  
Pattern Completion ◽  
Gamma Power

scholarly journals Hippocampal pattern completion is linked to gamma power increases and alpha power decreases during recollection

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Bernhard P Staresina ◽  
Sebastian Michelmann ◽  
Mathilde Bonnefond ◽  
Ole Jensen ◽  
Nikolai Axmacher ◽  
...  
Keyword(s):  
Computational Models ◽  
Memory Task ◽  
Alpha Power ◽  
Single Shot ◽  
Pattern Completion ◽  
Time Frequency ◽  
Oscillatory Dynamics ◽  
Gamma Power ◽  
Human Participants ◽  
Underlying Mechanisms

How do we retrieve vivid memories upon encountering a simple cue? Computational models suggest that this feat is accomplished by pattern completion processes involving the hippocampus. However, empirical evidence for hippocampal pattern completion and its underlying mechanisms has remained elusive. Here, we recorded direct intracranial EEG as human participants performed an associative memory task. For each study (encoding) and test (retrieval) event, we derived time-frequency resolved representational patterns in the hippocampus and compared the extent of pattern reinstatement for different mnemonic outcomes. Results show that successful associative recognition (AR) yields enhanced event-specific reinstatement of encoding patterns compared to non-associative item recognition (IR). Moreover, we found that gamma power (50–90 Hz) increases – in conjunction with alpha power (8–12 Hz) decreases not only distinguish AR from IR, but also correlate with the level of hippocampal reinstatement. These results link single-shot hippocampal pattern completion to episodic recollection and reveal how oscillatory dynamics in the gamma and alpha bands orchestrate these mnemonic processes.

scholarly journals Frontal eye field microstimulation induces task-dependent gamma oscillations in the lateral intraparietal area

2012 ◽  
Vol 108 (5) ◽  
pp. 1392-1402 ◽  
Author(s):  
Elsie Premereur ◽  
Wim Vanduffel ◽  
Pieter R. Roelfsema ◽  
Peter Janssen
Keyword(s):  
Spatial Attention ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Oculomotor Control ◽  
Saccade Target ◽  
Frontal Eye Field ◽  
Alpha Power ◽  
Lateral Intraparietal Area ◽  
Electrical Microstimulation ◽  
Gamma Power

Macaque frontal eye fields (FEF) and the lateral intraparietal area (LIP) are high-level oculomotor control centers that have been implicated in the allocation of spatial attention. Electrical microstimulation of macaque FEF elicits functional magnetic resonance imaging (fMRI) activations in area LIP, but no study has yet investigated the effect of FEF microstimulation on LIP at the single-cell or local field potential (LFP) level. We recorded spiking and LFP activity in area LIP during weak, subthreshold microstimulation of the FEF in a delayed-saccade task. FEF microstimulation caused a highly time- and frequency-specific, task-dependent increase in gamma power in retinotopically corresponding sites in LIP: FEF microstimulation produced a significant increase in LIP gamma power when a saccade target appeared and remained present in the LIP receptive field (RF), whereas less specific increases in alpha power were evoked by FEF microstimulation for saccades directed away from the RF. Stimulating FEF with weak currents had no effect on LIP spike rates or on the gamma power during memory saccades or passive fixation. These results provide the first evidence for task-dependent modulations of LFPs in LIP caused by top-down stimulation of FEF. Since the allocation and disengagement of spatial attention in visual cortex have been associated with increases in gamma and alpha power, respectively, the effects of FEF microstimulation on LIP are consistent with the known effects of spatial attention.

Cortical oscillations to measure anti-epileptic drug activity in clinical trials

2021 ◽  
Author(s):  
Andrea Biondi ◽  
Lorenzo Rocchi ◽  
Viviana Santoro ◽  
Gregory Beatch ◽  
Pierre Rossini ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Brain Activity ◽  
Systematic Evaluation ◽  
Alpha Power ◽  
Brain Oscillations ◽  
Cortical Oscillations ◽  
Anti Epileptic Drug ◽  
Beta Power ◽  
Gamma Power

Abstract The frequency analysis of electroencephalographic (EEG) activity, either spontaneous or evoked by transcranial magnetic stimulation (TMS-EEG), is a powerful tool to investigate changes in brain activity and excitability following the administration of antiepileptic drugs (AEDs). However, a systematic evaluation of the effect of AEDs on spontaneous and TMS-induced brain oscillations has not yet been provided. We studied the effects of lamotrigine, levetiracetam, and of a novel potassium channel opener (XEN1101) on TMS-induced and spontaneous brain oscillations in a group of healthy volunteers. Levetiracetam suppressed TMS-induced theta, alpha and beta power, whereas lamotrigine increased TMS-induced alpha power. XEN1101 decreased TMS-induced delta, theta and beta power. Resting-state EEG showed a decrease of theta band power after lamotrigine intake. Levetiracetam increased theta, beta and gamma power, while XEN1101 produced an increase of delta, theta, beta and gamma power. Different AEDs induce specific patterns of power changes in spontaneous and TMS-induced brain oscillations. Spontaneous and TMS-induced cortical oscillations represent a powerful tool to characterize the effect of AEDs on in vivo brain activity. Spectral fingerprints of specific AEDs should be further investigated to provide robust and objective biomarkers of biological effect in human clinical trials.

scholarly journals Oscillatory Correlates of Retrieval-induced Forgetting in Recognition Memory

2009 ◽  
Vol 21 (5) ◽  
pp. 976-990 ◽  
Author(s):  
Bernhard Spitzer ◽  
Simon Hanslmayr ◽  
Bertram Opitz ◽  
Axel Mecklinger ◽  
Karl-Heinz Bäuml
Keyword(s):  
Retrieval Practice ◽  
Time Window ◽  
Phase Locking ◽  
Memory Representation ◽  
Late Time ◽  
Alpha Power ◽  
Theta Power ◽  
Beneficial Effects ◽  
Gamma Power ◽  
Induced Forgetting

Retrieval practice on a subset of previously studied material enhances later memory for practiced material but can inhibit memory for related unpracticed material. The present study examines the effects of prior retrieval practice on evoked (ERPs) and induced (oscillatory power) measures of electrophysiological activity underlying recognition of practiced and unpracticed words. Compared to control material, recognition of unpracticed words was characterized by reduced amplitudes of the P2 ERP component and by reduced early (200–400 msec) oscillatory theta power. The reduction in P2 amplitude was associated with decreased evoked theta power but not with decreased theta phase locking (phase-locking index). Recognition of unpracticed material was further accompanied by a reduction in occipital gamma power (>250 msec). In contrast, the beneficial effects of retrieval practice on practiced words were reflected by larger parietal ERP positivity (>500 msec) and by a stronger decrease in oscillatory alpha power in a relatively late time window (>700 msec). The results suggest that the beneficial and detrimental effects of retrieval practice are mediated by different processes. In particular, they suggest that reduced theta (4–7 Hz) and gamma (60–90 Hz) power reflect the specific effects of inhibitory processes on the unpracticed material's memory representation.

scholarly journals Humans strategically shift decision bias by flexibly adjusting sensory evidence accumulation

2017 ◽  
Author(s):  
Niels A. Kloosterman ◽  
Jan Willem de Gee ◽  
Markus Werkle-Bergner ◽  
Ulman Lindenberger ◽  
Douglas D. Garrett ◽  
...  
Keyword(s):  
Cortical Excitability ◽  
Decision Criterion ◽  
Alpha Power ◽  
Internal Reference ◽  
Posterior Cortex ◽  
Decision Bias ◽  
Evidence Accumulation ◽  
Bias Drift ◽  
Gamma Power ◽  
Sensory Evidence

AbstractDecision bias is traditionally conceptualized as an internal reference against which sensory evidence is compared. Instead, we show that individuals implement decision bias by shifting the rate of sensory evidence accumulation towards a decision bound. Participants performed a target detection task while we recorded EEG. We experimentally manipulated participants’ decision criterion for reporting targets using different stimulus-response reward contingencies, inducing either a liberal or a conservative bias. Drift diffusion modeling revealed that a liberal strategy biased sensory evidence accumulation towards target-present choices. Moreover, a liberal bias resulted in stronger midfrontal pre-stimulus 2-6 Hz (theta) power and suppression of pre-stimulus 8—12 Hz (alpha) power in posterior cortex. The alpha suppression in turn mediated the output activity of visual cortex, as expressed in 59—100 Hz (gamma) power. These findings show that observers can intentionally control cortical excitability to strategically bias evidence accumulation towards the decision bound that maximizes their reward.

scholarly journals Alterations in sleep, sleep spindle, and EEG power in mGluR5 knockout mice

2020 ◽  
Vol 123 (1) ◽  
pp. 22-33 ◽  
Author(s):  
David D. Aguilar ◽  
Robert E. Strecker ◽  
Radhika Basheer ◽  
James M. McNally
Keyword(s):  
Eye Movement ◽  
Metabotropic Glutamate Receptor ◽  
Neural Oscillations ◽  
Alpha Power ◽  
Rapid Eye Movement ◽  
Sleep Spindle ◽  
Rapid Eye Movement Sleep ◽  
Metabotropic Glutamate ◽  
Gamma Power ◽  
Abnormal Sleep

The type 5 metabotropic glutamate receptor (mGluR5) represents a novel therapeutic target for schizophrenia and other disorders. Schizophrenia is associated with progressive abnormalities in cortical oscillatory processes including reduced spindles (8–15 Hz) during sleep and increased delta (0.5–4 Hz)- and gamma-band activity (30–80 Hz) during wakefulness. mGluR5 knockout (KO) mice demonstrate many schizophrenia-like behaviors, including abnormal sleep. To examine the effects of mGluR5 on the maintenance of the neocortical circuitry responsible for such neural oscillations, we analyzed sleep/wake electroencephalographic (EEG) activity of mGluR5 KO mice at baseline, after 6 h of sleep deprivation, and during a visual method of cortical entrainment (visual steady state response). We hypothesized mGluR5-KO mice would exhibit translationally relevant abnormalities in sleep and neural oscillations that mimic schizophrenia. Power spectral and spindle density analyses were performed across 24-h EEG recordings in mGluR5-KO mice and wild-type (WT) controls. Novel findings in mGluR5 KO mice include deficits in sleep spindle density, wake alpha power, and 40-Hz visual task-evoked gamma power and phase locking. Sigma power (10–15 Hz), an approximation of spindle activity, was also reduced during non-rapid eye movement sleep transitions. Our observations on abnormal sleep/wake are generally in agreement with previous reports, although we did not replicate changes in rapid eye movement sleep. The timing of these phenotypes may suggest an impaired circadian process in mGluR5 KO mice. In conclusion, EEG phenotypes in mGluR5 KO mice resemble deficits observed in patients with schizophrenia. These findings implicate mGluR5-mediated pathways in several translationally relevant phenotypes associated with schizophrenia, and suggest that agents targeting this receptor may have harmful consequences on sleep health and daily patterns of EEG power. NEW & NOTEWORTHY Metabotropic glutamate receptor type 5 (mGluR5) knockout (KO) mice show several translationally relevant abnormalities in neural oscillatory activity associated with schizophrenia. These include deficits in sleep spindle density, sigma and alpha power, and 40-Hz task-evoked gamma power. The timing of these phenotypes suggests an impaired circadian process in these mice. Previously reported rapid eye movement sleep deficits in this model were not observed. These findings suggest mGluR5-enhancing drugs may improve sleep stability and sleep spindle density, which could impact memory and cognition.

Visualization of Event-Related Changes in Brain Networks During Attention-Demanding Tasks

2020 ◽  
pp. 127-150
Author(s):  
N. P. Guhan Seshadri ◽  
B. Geethanjali ◽  
S. Muthumeenakshi ◽  
V. Bhavana ◽  
R. Vijayalakshmi
Keyword(s):  
Task Performance ◽  
Cognitive Processing ◽  
Parietal Cortex ◽  
Brain Networks ◽  
Alpha Power ◽  
Relative Power ◽  
Alpha Band ◽  
Gamma Power ◽  
Rest Time ◽  
Eeg Recordings

Attention is the primary cognitive process to induce a response to a stimulus, and maintaining the attentive state continuously for a prolonged period of time is known as sustained attention, which is vital for performing any task. This study aims at visualizing the event-related changes in brain networks during attention demanding task with the help of electroencephalography (EEG) recordings. The results showed significant increase (p<0.05) in relative theta and gamma power during task compared to rest time, whereas in alpha band the relative power was significantly higher (p<0.05) during rest when compared to task. The event-related synchronization (ERS) and event-related desynchronization (ERD) in relative theta power and relative alpha power respectively was observed particularly in the parietal cognitive processing electrodes. The study concludes that theta synchronization and alpha desynchronization noted at parietal cortex that is associated with attention resulted in improving the task performance with minimal errors.

scholarly journals Neurophysiologic Correlates of Ketamine Sedation and Anesthesia

2017 ◽  
Vol 127 (1) ◽  
pp. 58-69 ◽  
Author(s):  
Phillip E. Vlisides ◽  
Tarik Bel-Bahar ◽  
UnCheol Lee ◽  
Duan Li ◽  
Hyoungkyu Kim ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Phase Locking ◽  
Brain Regions ◽  
Alpha Power ◽  
Phase Lag ◽  
Mean Power ◽  
Healthy Human ◽  
Ketamine Anesthesia ◽  
Gamma Power ◽  
Dose Dependent

Abstract Background Previous studies have demonstrated inconsistent neurophysiologic effects of ketamine, although discrepant findings might relate to differences in doses studied, brain regions analyzed, coadministration of other anesthetic medications, and resolution of the electroencephalograph. The objective of this study was to characterize the dose-dependent effects of ketamine on cortical oscillations and functional connectivity. Methods Ten healthy human volunteers were recruited for study participation. The data were recorded using a 128-channel electroencephalograph during baseline consciousness, subanesthetic dosing (0.5 mg/kg over 40 min), anesthetic dosing (1.5 mg/kg bolus), and recovery. No other sedative or anesthetic medications were administered. Spectrograms, topomaps, and functional connectivity (weighted and directed phase lag index) were computed and analyzed. Results Frontal theta bandwidth power increased most dramatically during ketamine anesthesia (mean power ± SD, 4.25 ± 1.90 dB) compared to the baseline (0.64 ± 0.28 dB), subanesthetic (0.60 ± 0.30 dB), and recovery (0.68 ± 0.41 dB) states; P &lt; 0.001. Gamma power also increased during ketamine anesthesia. Weighted phase lag index demonstrated theta phase locking within anterior regions (0.2349 ± 0.1170, P &lt; 0.001) and between anterior and posterior regions (0.2159 ± 0.1538, P &lt; 0.01) during ketamine anesthesia. Alpha power gradually decreased with subanesthetic ketamine, and anterior-to-posterior directed connectivity was maximally reduced (0.0282 ± 0.0772) during ketamine anesthesia compared to all other states (P &lt; 0.05). Conclusions Ketamine anesthesia correlates most clearly with distinct changes in the theta bandwidth, including increased power and functional connectivity. Anterior-to-posterior connectivity in the alpha bandwidth becomes maximally depressed with anesthetic ketamine administration, suggesting a dose-dependent effect.

EP 105. The relation of prestimulus alpha power, poststimulus gamma power and perception in human somatosensory cortex

2016 ◽  
Vol 127 (9) ◽  
pp. e285-e286
Author(s):  
M.A. Wittenberg ◽  
T.J. Baumgarten ◽  
A. Schnitzler ◽  
J. Lange
Keyword(s):  
Somatosensory Cortex ◽  
Alpha Power ◽  
Gamma Power
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