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Review of the Human Brain and EEG Signals
Published in Teodiano Freire Bastos-Filho, Introduction to Non-Invasive EEG-Based Brain–Computer Interfaces for Assistive Technologies, 2020
Alessandro Botti Benevides, Alan Silva da Paz Floriano, Mario Sarcinelli-Filho, Teodiano Freire Bastos-Filho
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].
Functional Neuroimaging of the Central Auditory System
Published in Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm, Advances in Audiology and Hearing Science, 2020
David L. McPherson, Richard Harris, David Sorensen
It should be noted that BOLD has a reasonable correlation with local field potentials (see Section 10.2.6). A common misinterpretation is the response curves of the BOLD response and the curves for action potential (AP). The visual similarity is coincidental and not relational.
The cortical processing of pain
Published in Camille Chatelle, Steven Laureys, 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.
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).
Thalamic neuromodulation in epilepsy: A primer for emerging circuit-based therapies
Published in Expert Review of Neurotherapeutics, 2023
Bryan Zheng, David D. Liu, Brian B Theyel, Hael Abdulrazeq, Anna R. Kimata, Peter M Lauro, Wael F. Asaad
Reliable neurophysiologic biomarkers for detection of the myriad seizure types and networks have thus far remained elusive[232,233]. In comparison, the study of chronic local field potential (LFP) recordings for closed-loop DBS in Parkinson’s disease (PD) has recently expanded dramatically and could potentially serve as a model paradigm[234]. Specifically, the study of LFPs in the context of PD has yielded information about what types of signals (e.g. beta-band synchronization) are most likely to be useful as control signals for closed-loop control of PD symptoms[235–238]. Analogously, neuromodulation devices for epilepsy with chronic recording ability may likewise allow us to examine LFPs for neural signatures of seizures and perhaps even their impending onset, to more effectively avert them[239,240]. Given the heterogeneity of seizure networks across individuals, these signatures may even be patient-specific, thus arguing for the importance of personalized closed-loop therapies.
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.