Review of the Human Brain and EEG Signals
Teodiano Freire Bastos-Filho in Introduction to Non-Invasive EEG-Based Brain–Computer Interfaces for Assistive Technologies, 2020
Beyond the interference of technical and physiological artifacts, the EEG is also affected by the electrical activity of the brain itself. The EEG of an area of interest is a mixture of unrelated signals from cortical neighboring areas that are scattered around and attenuated by the skull and scalp. This is considered a special type of artifact, in which there are no exact solutions for unmixing it from the EEG signal. This problem is known as the inverse problem that traditionally has infinite solutions, due to the nature of its variables. A particular inverse solution uses the calculation of local field potential (LFP), which is invasive recording of the electric potential in the extracellular space in brain tissue [26]. Another solution uses the distribution of cortical extracellular currents, known as cortical current density (CCD) [27].
The cortical processing of pain
Camille Chatelle, Steven Laureys in Assessing Pain and Communication in Disorders of Consciousness, 2015
Several studies have recorded local field potentials (LFPs) elicited by transient nociceptive stimuli within different areas of the brain of awake humans, using surgically implanted intracranial electrodes or subdural electrode grids (Peyron et al., 2002). These studies have demonstrated that brief thermal stimuli above the thermal activation threshold of A-delta and C fibres elicit responses in the left and right suprasylvian opercular region (Frot & Mauguiere, 1999, 2003; Frot, Rambaud, Guenot, & Mauguiere, 1999). The latency of the response coincides with the latency of the N1 and N2 waves of nociceptive ERPs. Interestingly, researchers observed a delay of approximately 15 ms between the responses elicited in the ipsilateral and contralateral hemispheres. Furthermore, the studies showed that thermal stimuli probably elicit two temporally distinct responses within the suprasylvian region: an early response originating from the parietal operculum, followed by a later response originating from the insula.
ECoG-Based BCIs
Chang S. Nam, Anton Nijholt, Fabien Lotte in Brain–Computer Interfaces Handbook, 2018
Macroscale field potentials are generated by current dipoles between cortical laminae (Nunez and Srinivasan 2006). The physiological underpinnings of the current source density (CSD) in cortical laminae that give rise to these potentials were established experimentally in the late 1970s and early 1980s (Mitzdorf 1985). These studies demonstrated that propagating action potentials in axons and axonal terminals do not contribute strongly to the CSD at spatial scales of ~50–300 μm or greater, which suggests that ECoG signals comprise dendritic synaptic current exchange (i.e., influx and efflux) that modulates the CSD. This has recently been substantiated by simultaneous in vivo recordings of the intracellular potential and local field potentials over which ECoG signals are averaged, showing tight temporal coupling that is independent of the spiking pattern of the neuron (Miller 2010; Miller et al. 2009a; Okun et al. 2009). Thus, ECoG signals can be explained by synchronous synaptic inputs from large ensembles underlying the electrode. If this synchronization/desynchronization occurs rhythmically, it can be observed as rhythmic amplitude modulations in the time series (Figure 16.3a) and as a peak in the frequency domain (Figure 16.3b) (Ritaccio et al. 2011). If the synchronization is related to a stimulus (e.g., a visual cue) or an event (e.g., movement onset), the time series may reflect a multiphasic, time-locked response, known as an “event-related potential” (ERP).
Deep brain stimulation and stereotactic-assisted brain graft injection targeting fronto-striatal circuits for Huntington’s disease: an update
Published in Expert Review of Neurotherapeutics, 2022
Thomas Kinfe, Alessandro Del Vecchio, Martin Nüssel, Yining Zhao, Andreas Stadlbauer, Michael Buchfelder
To shed light under such circumstances, Ferrea et al. applied electrophysiological measures in terms of local field potential (LFP). The first step toward the assessment and definition of specific LFP bands was performed by the Surgical Approaches Task Force of the EHDN study group, which targeted the GPi as well as the GPe. Spectral analysis was performed for alpha (8–12 Hz), beta (13–30 Hz), and gamma (30–80 Hz) bands in a subset of 2 juvenile HD patients (Westphal variant) up to 12 months after GPi or GPe-DBS. Notably, alpha and beta oscillations displayed similar characters to those detected in other movement disorders with a kinetic-rigid and dystonic phenotype responsive to pallidal DBS. These findings contrasted with the negative clinical outcome of these both juvenile HD subjects compared to the late-onset HD subgroup treated with GPi or GPe stimulation, indicating GP DBS may have limitations in efficacy in the juvenile subset of stimulated HD subjects [9,24]. Indeed, it would have been of interest to explore LFP pattern in a larger and homogenous subset of HD patients to elucidate pallidal DBS effects on neural circuits relevant for HD pathophysiology. Enhanced neuroimaging techniques (functional and structural connectivity) may support not only the highly precise placement of DBS electrodes in the target region but may allow to specifically tailor DBS waveforms on an individual level as confirmed for different other DBS targets and DBS indications using a network-related approach.
Behavior and electrophysiological effects on striatum-nigra circuit after high frequency stimulation. Relevance to Parkinson and epilepsy
Published in International Journal of Neuroscience, 2023
Igor Tchaikovsky, Marilia Marinho Lucena, Belmira-Lara da Silveira Andrade da Costa, Norberto Garcia-Cairasco, Pedro V. Carelli, Marcelo Cairrao
Microinjections were performed with 30 G cannulae and a PE10 polyethylene tubing connected to a 10 microliter Hamilton syringe, with the aid of a semi-automatic pump (Insight, Ribeirão Preto, Brazil). One minute after the end of the microinjections, local field potentials (LFP) were recorded for 10 min. For the experimental group, data were organized as follows. Block 1 (basal period). Striatum recording starts from the beginning of the experiment and before any microinjection. Block 2 (saline, recorded 20 to 30 min after basal). Striatum firing rate is recorded after bilateral microinjection of a volume of 0.2 μl (0.1 μl/min) of 0.9% saline in the SNPr. Block 3 (diazepam, recorded 40 to 50 min after basal). Recording of striatum firing rate after bilateral SNPr microinjection of diazepam with the same volume and velocity as before. The whole experimental procedure lasted about 1 h. Sham controls were anesthetized the same way, had equal brain implant of electrodes for striatum recording, and the microinjection cannulae was positioned in SNPr, but nothing was injected (sham injection). Recordings were done at equivalent times (same recording blocks).
The effects of Alzheimer's disease related striatal pathologic changes on the fractional amplitude of low-frequency fluctuations
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Yuksel Cakir
The hemodynamic model coupling synaptic activity and BOLD response presented by Friston et al. (2000) is used to make a relation between neuronal activities and the generated BOLD signal. In the literature, the fired neurons are generally considered for obtaining the BOLD signal, (Plenz and Kitai 1998; Yamanishi et al. 2013). The change in BOLD signal reflects the change in demand of energy and oxygen caused by neural activity. This neuronal activation signal must be related to all the activities of individual neuron. Considering only spiking neurons in the computation of total neuronal activity can be insufficient since the other neurons near spiking threshold will also spend energy. This assumption is consistent with the conclusions in (Logothetis and Wandell 2004) stated that there is a strong correlation between local field potentials and BOLD response. Therefore, the neuronal activity used in the computation of BOLD signal is taken as the summation of all neurons membrane potentials, not only the fired ones.
Related Knowledge Centers
- Action Potential
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