Modulation Of Cortical Oscillations Research Articles

Modulation of cortical oscillations by periodic electrical stimulation is frequency-dependent

The brain oscillations play a pivotal role in transmitting and processing the information. Periodic electrical stimulation has been proposed to shape the oscillations. However, how the periodic electrical stimulation modulates the oscillatory activities remains poorly understood. To address this question, a modified cortical network by adding the brain state information (eye–open and eye–closed states) and synaptic plasticity is employed. Constraining on eye–open state and without considering the synaptic plasticity, the numerical simulation results have shown that the network responses are strong frequency–dependent and the underlying mechanism of the network oscillations has been recognized as three typical neural phenomena, that is resonance, entrainment, and nonlinear oscillation, induced by periodic stimulation with different frequencies and amplitudes. We further prove the frequency dependency of network responses through theoretical analysis. Moreover, the impacts of the brain state have been explored. It is shown that the brain state has little impact on the network oscillatory response during stimulus and generates only a very short–lasting effect. However, the introduce of the plasticity in the cortical network makes the periodic stimulation generate obvious post—stimulus effects. Even though the stimulation is removed, the cortical network can still maintain the resonance, entrainment, and nonlinear oscillatory activities. The frequency–dependent network response mechanism provides a profound understanding of neural information communication theory induced by the periodic stimulus.

Modulation of cortical oscillations using 10hz near-infrared transcranial and intranasal photobiomodulation: a randomized sham-controlled crossover study

Abstract Objective: Transcranial Photobiomodulation (tPBM) provides a safe and noninvasive brain stimulation to intervene with brain functions. Despite the large body of reported clinical and behavioral outcomes, there is still need for a fuller understanding regarding NIR penetration and mechanisms. In this study, we investigated the effect of tPBM on cortical oscillations using power spectrum analysis. Methods: Twenty five healthy volunteers (9M/16F; mean age ± SD= 68.3± 6.63 years) received 20 minutes of active tPBM using 810 nm light-emitting diodes(LEDs), pulsed at 10 Hz with 50% duty cycle. In a randomized cross-over design, all participants received four arms of stimulation: (1) active (standard montage; LEDs irradiating the 4 hubs of default mode network), (2) active (non-standard montage - rearrangement of LEDs over right temporal-occipital regions, (3) active intranasal diode only, (4) sham (standard montage). Resting state EEG data was collected 10 minutes before (pre-tPBM), and at 10 and 30 minutes after (post10-tPBM; post30-tPBM) each stimulation session. The artifact-free resting-state data were used for power spectrum analysis. Results: Our power spectrum analysis showed significant changes in most frequency bands with all active stimulations (P<0.01). However, this modulation depended on the type and the location of stimulation. Namely, in type (1), a significant increase in theta, alpha, beta and gamma both post10-tPBM and post30-tPBM. For type (2), we found a significant increase in theta post30-tPBM, and alpha both post10 and post30-tPBM. For type (3) we found a significant increase in beta and gamma post10-tPBM and post30-tPBM, prominent in the posterior channels. Type (4) showed no significant change in any frequency bands. Conclusion: Findings from this study provide novel evidence that tPBM modulates neural oscillations in a frequency and location dependent manner. This is also the first investigation to measure the significant effect of an intranasal NIR LED on brain oscillation with EEG. Keywords: tPBM, EEG, power spectrum, cortical oscillation

Targeted Stimulation of Human Orbitofrontal Networks Disrupts Outcome-Guided Behavior.

Outcome-guided behavior requires knowledge about the current value of expected outcomes. Such behavior can be isolated in the reinforcer devaluation task, which assesses the ability to infer the current value of specific rewards after devaluation. Animal lesion studies demonstrate that orbitofrontal cortex (OFC) is necessary for normal behavior in this task, but a causal role for human OFC in outcome-guided behavior has not been established. Here, we used sham-controlled, non-invasive, continuous theta-burst stimulation (cTBS) to temporarily disrupt human OFC network activity by stimulating a site in the lateral prefrontal cortex that is strongly connected to OFC prior to devaluation of food odor rewards. Subjects in the sham group appropriately avoided Pavlovian cues associated with devalued food odors. However, subjects in the stimulation group persistently chose those cues, even though devaluation of food odors themselves was unaffected by cTBS. This behavioral impairment was mirrored in changes in resting-state functional magnetic resonance imaging (rs-fMRI) activity such that subjects in the stimulation group exhibited reduced OFC network connectivity after cTBS, and the magnitude of this reduction was correlated with choices after devaluation. These findings demonstrate the feasibility of indirectly targeting the human OFC with non-invasive cTBS and indicate that OFC is specifically required for inferring the value of expected outcomes.

Effect of upright standing postures on cortical oscillation spectral power modulations

Introduction Amplitude modulation of cortical oscillations are associated to various movement parameters. Recently, theta-band cortical oscillations were shown to be involved in maintaining upright posture. However, the function of delta-, alpha-, beta-, and gamma-band cortical oscillatory components still needs to be clarified. To provide further understanding of the function of cortical oscillations in controlling balance, we investigated the effect of different upright standing postures on the modulation of cortical oscillations. Materials and methods Brain activity and ground reaction forces of 13 participants were recorded using 64 electroencephalographic electrodes and a force platform. Participants stood upright in four conditions: with regular and narrow stance widths and on firm and foam surfaces. To obtain modulation of cortical oscillations, brain activity was also recorded while sitting on a chair. Modulation of cortical oscillation spectral power and the confidence ellipse area of the center of pressure displacement were compared between stance widths and surfaces using a linear mixed model. Results Confidence ellipse area significantly increased during the narrow and the foam conditions. Delta-band synchronization significantly increased in the central region during foam and narrow conditions. In all conditions, alpha- and beta-band showed desynchronization in the central region. Additionally, alpha-band showed desynchronization in frontal and occipital regions, which was significantly greater during narrow stance conditions. Finally, gamma-band synchronization significantly increased in the right temporoparietal junction during narrow and foam conditions. Discussion/conclusion Alpha- and beta-band desynchronization as well as delta- and gamma-band synchronization and their modulations during unstable postural conditions highlight the involvement of these cortical oscillatory components in balance control.

Effects of Stimulus-Driven and Goal-Directed Attention on Prepulse Inhibition of Brain Oscillations.

Objective: Prepulse inhibition (PPI) is an operational measure of sensory gating. PPI of cortical response to a startling pulse is known to be modulated by attention. With a time-frequency analysis, we sought to determine whether goal-directed and stimulus-driven attention differentially modulate inhibition of cortical oscillations elicited by a startling pulse.Methods: An electroencephalogram (EEG) was recorded in 26 healthy controls performing an active acoustic PPI paradigm. Startling stimuli were presented alone or either 400 or 1000 ms after one of three types of visual prepulse: to-be-attended (goal-directed attention), unexpected (stimulus-driven attention) or to-be-ignored (non-focused attention). We calculated the percentage PPI for the auditory event-related spectral perturbation (ERSP) of theta (4–7 Hz), alpha (8–12 Hz), beta1 (13–20 Hz) and beta2 (20–30 Hz) oscillations and changes in inter-trial coherence (ITC), a measure of phase synchronization of electroencephalographic activity.Results: At 400 ms: (i) PPI of the ERSP of alpha, theta and beta1 oscillation was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta2 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. At 1000 ms: (i) PPI of alpha oscillations was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta1 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. The ITC values did not vary according to the type of prepulse.Conclusions: In an active PPI paradigm, stimulus-driven and goal-directed attention each have differential effects on the modulation of cortical oscillations.

Modulation of Cortical Oscillations by Low-Frequency Direct Cortical Stimulation Is State-Dependent.

Cortical oscillations play a fundamental role in organizing large-scale functional brain networks. Noninvasive brain stimulation with temporally patterned waveforms such as repetitive transcranial magnetic stimulation (rTMS) and transcranial alternating current stimulation (tACS) have been proposed to modulate these oscillations. Thus, these stimulation modalities represent promising new approaches for the treatment of psychiatric illnesses in which these oscillations are impaired. However, the mechanism by which periodic brain stimulation alters endogenous oscillation dynamics is debated and appears to depend on brain state. Here, we demonstrate with a static model and a neural oscillator model that recurrent excitation in the thalamo-cortical circuit, together with recruitment of cortico-cortical connections, can explain the enhancement of oscillations by brain stimulation as a function of brain state. We then performed concurrent invasive recording and stimulation of the human cortical surface to elucidate the response of cortical oscillations to periodic stimulation and support the findings from the computational models. We found that (1) stimulation enhanced the targeted oscillation power, (2) this enhancement outlasted stimulation, and (3) the effect of stimulation depended on behavioral state. Together, our results show successful target engagement of oscillations by periodic brain stimulation and highlight the role of nonlinear interaction between endogenous network oscillations and stimulation. These mechanistic insights will contribute to the design of adaptive, more targeted stimulation paradigms.

Modulation of Cortical Oscillations by Low-Frequency Direct Cortical Stimulation Is State-Dependent

Modulation of Cortical Oscillations by Low-Frequency Direct Cortical Stimulation Is State-Dependent

Oscillatory neural responses evoked by natural vestibular stimuli in humans.

While there have been numerous studies of the vestibular system in mammals, less is known about the brain mechanisms of vestibular processing in humans. In particular, of the studies that have been carried out in humans over the last 30 years, none has investigated how vestibular stimulation (VS) affects cortical oscillations. Here we recorded high-density electroencephalography (EEG) in healthy human subjects and a group of bilateral vestibular loss patients (BVPs) undergoing transient and constant-velocity passive whole body yaw rotations, focusing our analyses on the modulation of cortical oscillations in response to natural VS. The present approach overcame significant technical challenges associated with combining natural VS with human electrophysiology and reveals that both transient and constant-velocity VS are associated with a prominent suppression of alpha power (8-13 Hz). Alpha band suppression was localized over bilateral temporo-parietal scalp regions, and these alpha modulations were significantly smaller in BVPs. We propose that suppression of oscillations in the alpha band over temporo-parietal scalp regions reflects cortical vestibular processing, potentially comparable with alpha and mu oscillations in the visual and sensorimotor systems, respectively, opening the door to the investigation of human cortical processing under various experimental conditions during natural VS.

Long Lasting Modulation of Cortical Oscillations after Continuous Theta Burst Transcranial Magnetic Stimulation

Transcranial magnetic theta burst stimulation (TBS) differs from other high-frequency rTMS protocols because it induces plastic changes up to an hour despite lower stimulus intensity and shorter duration of stimulation. However, the effects of TBS on neuronal oscillations remain unclear. In this study, we used electroencephalography (EEG) to investigate changes of neuronal oscillations after continuous TBS (cTBS), the protocol that emulates long-term depression (LTD) form of synaptic plasticity. We randomly divided 26 healthy humans into two groups receiving either Active or Sham cTBS as control over the left primary motor cortex (M1). Post-cTBS aftereffects were assessed with behavioural measurements at rest using motor evoked potentials (MEPs) and at active state during the execution of a choice reaction time (RT) task in combination with continuous electrophysiological recordings. The cTBS-induced EEG oscillations were assessed using event-related power (ERPow), which reflected regional oscillatory activity of neural assemblies of θ (4–7.5 Hz), low α (8–9.5 Hz), µ (10–12.5 Hz), low β (13–19.5 Hz), and high β (20–30 Hz) brain rhythms. Results revealed 20-min suppression of MEPs and at least 30-min increase of ERPow modulation, suggesting that besides MEPs, EEG has the potential to provide an accurate cortical readout to assess cortical excitability and to investigate the interference of cortical oscillations in the human brain post-cTBS. We also observed a predominant modulation of β frequency band, supporting the hypothesis that cTBS acts more on cortical level. Theta oscillations were also modulated during rest implying the involvement of independent cortical theta generators over the motor network post cTBS. This work provided more insights into the underlying mechanisms of cTBS, providing a possible link between synchronised neural oscillations and LTD in humans.

Cell‐specific contribution to gamma oscillations

Gamma oscillations are a particularly prominent form of rhythmic activity occurring during wakefulness and attentive behaviour that result from synchronous activity of cortical neurons at frequencies ranging between 20 and 80 Hz. Abnormalities in these oscillations might underlie neuropsychiatric disorders such as schizophrenia (Uhlhaas et al. 2006). Therefore understanding the precise mechanisms underlying gamma oscillations – in particular the respective role of synaptic and intrinsic currents – represents a major goal in fundamental and clinical neuroscience. Gamma oscillations are prevalent in the hippocampus in vivo and they can be induced in the isolated CA3 region of the hippocampus in vitro with bath application of carbachol (Fisahn et al. 1998). They require both excitatory and inhibitory synaptic transmission. In particular, in their pioneering study Fisahn and co-workers highlighted the role of GABAergic activity by showing that prolongation of the GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) with barbiturate reduced the frequency of gamma oscillations. Models of leaky integrate-and-fire neurons suggest that synaptic recurrent feedback loops between interneurons and pyramidal cells are necessary and sufficient to explain gamma frequency oscillations (Brunel & Wang, 2003). In a recent study, gamma oscillation fluctuations in amplitude and frequency were found to be correlated with cycle-to-cycle changes in excitation and inhibition (Atallah & Scanziani, 2009). In this issue of The Journal of Physiology, Oren, Hájos and Paulsen (Oren et al. (2010) examined the relative contribution of synaptic and voltage-dependent action currents in pyramidal neurons during gamma oscillations induced with carbachol in the CA3 region of the rat hippocampus in vitro. They combined recordings of the local field potential (LFP) to monitor the oscillatory activity of the principal neurons with cell-attached recordings from subclasses of GABAergic interneurons. Changes in the oscillation amplitude were quantified by the amplitude of the wavelet transform. Oren et al. confirm in this study that inhibitory currents contribute significantly to LFP amplitude fluctuations as a consequence of an increased probability of firing in subclasses of interneurons that are responsible for perisomatic inhibition. Indeed when performing cell-attached recordings from various cell types, the authors could observe that, for a given oscillation cycle, the mean cycle amplitude was significantly higher when perisomatic (or interneuron-selective) interneurons discharged. In contrast, there was no such direct relationship between the discharge of a pyramidal cell and LFP amplitude. Therefore cycle-to-cycle variation amplitude appears to be the direct consequence of interneuron firing probability. However, the synchronized firing of pyramidal cells, which can be detected as a population spike in some cycles during gamma waves, affected the LFP. Indeed, the authors provide evidence that slow action currents, resulting from the activation of repolarisation conductances contribute in a significant manner to the early component of the LFP. Local field potentials are probably one of the oldest, least invasive and simplest ways to perform high sampling rate recordings of not only neuronal assemblies, but also the discharge activity of single neurons with the help of combined on- and offline signal processing analysis. The possibility of performing high rate recordings with almost no recording time limitation can then become an advantage in comparison with imaging techniques. Oren, Hájos and Paulsen have proven that these techniques should not yet be considered out of date since their use, in combination with other electrophysiological techniques (cell-attached and whole-cell recordings), can be useful and very informative for studying network activity and the contribution of different cell subtypes to the genesis or modulation of cortical oscillations. In this study, the firing probability of dendritic-targeting interneurons was reported not to be correlated with LFP amplitude fluctuations. This in vitro observation is in agreement with in vivo experiments showing that the discharge of these interneurons is not coupled to gamma oscillations (Tukker et al. 2007). Knowing that these interneurons exert specific inhibitory functions on EPSP integration and dendritic electrogenesis but not on action potential firing (Miles et al. 1996) leaves them free to serve distinct functions than the ‘sole’ contribution to gamma oscillations.

Influence of external input on waxing and waning of neuronal network oscillations

Introduction Experimental observations have reported modulation of cortical oscillations as phases of high synchronization (waxing) followed by periods of reduced synchronization (waning) [1-3]. Although the phenomenon is present in almost all frequency bands, it is still not understood how this is driven. Here we study whether this phenomenon can occur in a network of inhibitory (I) and excitatory (E) cells and what effect external inputs have. Methods Using NEURON, we model a network of Ne excitatory and Ni inhibitory cells such that Ne/Ni = 4. The cells have a single compartment, and include passive channels and voltage dependent Na+, K+ channels. Synaptic connections are random, projecting GABA synapses from I to I and I to E cells and AMPA synapses from E to E and E to I cells. To stimulate the network, each cell receives a baseline of current and a stream of spikes delivered at random intervals across the simulated period. from Eighteenth Annual Computational Neuroscience Meeting: CNS*2009 Berlin, Germany. 18–23 July 2009