Auditory nerve
Stanley A. Gelfand in Hearing, 2017
Let us briefly review a number of simple definitions and concepts about neural activity before we proceed. Nerve fibers elicit all-or-none electrical discharges called action potentials, which are picked up by electrodes and typically appear on recording devices as “spikes” at certain points in time (Figure 5.1). For obvious reasons, action potentials are often called spikes or spike potentials, and the discharging of a spike potential is also called firing. Similarly, the number of action potentials discharged per second is known as the firing rate or discharge rate, and the manner in which spikes are elicited over time is known as the discharge pattern or firing pattern. Figure 5.1 shows a number of idealized auditory nerve firing patterns. The rate at which a neuron fires “on its own” when there is no stimulation is called its spontaneous rate, and is illustrated in frame (a) of the figure. Activation of the neuron by a stimulus is associated with an increase in its firing rate above its spontaneous rate (frames [b] and [c]). Finally, an increase in the level of a stimulus is typically associated with an increase in the firing rate (frame [b] versus frame [c]), at least within certain limits.
Brain–Computer Interfaces (BCIs)
Teodiano Freire Bastos-Filho in Introduction to Non-Invasive EEG-Based Brain–Computer Interfaces for Assistive Technologies, 2020
Brain–computer interfaces (BCIs) are systems that use the voluntary modulation of the neural activity to transmit information that may be used for communication or control. Nowadays, the neural activity can be monitored and translated into tractable electrical signals in either of two ways: electrophysiological and hemodynamic. The former refers to the interneuronal exchange of information through electrochemical transmitters to generate ionic currents flowing across neuronal assemblies [11]. Electrophysiological activity can be noninvasively measured by electroencephalography (EEG) [9,10,12,13] and magnetoencephalography (MEG) [14] or invasively measured by electrocorticography (ECoG) [15] or intracortical neuron recording [16,17]. Hemodynamic responses are described as processes to release glucose and oxygen through the bloodstream to active neural regions, which then create a local gradient of deoxyhemoglobin and oxyhemoglobin [18]. The changes in the local ratio can be measured and quantified by means of neuroimaging methods, such as functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS). Because hemodynamic responses are triggered by electrophysiological activity, they are only indirectly related to neuronal activity. This chapter shows the results of our researches conducted with BCIs based on EEG.
Technological Evolution of Wireless Neurochemical Sensing with Fast-Scan Cyclic Voltammetry
Iniewski Krzysztof in Integrated Microsystems, 2017
Monitoring bioelectric and chemical signals provides a quantitative and reliable index of neural activity for assessing brain function. Perhaps the most widespread measurement modality for this purpose is electrophysiology, which monitors bioelectric signals. Several configurations are commonly used, including patch clamp [6], intracellular recording with a sharp microelectrode [7], and extracellular recording with saline-filled glass or metal microelectrodes [8]. In awake, behaving animals, the current state-of-the-art approach is a chronically implanted multiwire array electrode for high-density, simultaneous recording of extracellular action potentials or “units” across multiple experimental sessions [9]. Turnkey ensemble recording systems are now commercially available with hardwired (e.g., Plexon Inc.) and wireless (Triangle Biosystems Inc.) connections to the subject under investigation.
Randomised sham-controlled study of high-frequency bilateral deep transcranial magnetic stimulation (dTMS) to treat adult attention hyperactive disorder (ADHD): Negative results
Published in The World Journal of Biological Psychiatry, 2018
Yaniv Paz, Keren Friedwald, Yeheal Levkovitz, Abraham Zangen, Uri Alyagon, Uri Nitzan, Aviv Segev, Hagai Maoz, May Koubi, Yuval Bloch
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive and safe brain stimulation technique that uses brief, intense pulses of electric current delivered to a coil placed on the subject’s head in order to generate an electric field in the brain via electromagnetic induction. The induced electrical field modulates the neural transmembrane potentials and, thereby, neural activity. The effect is determined by the intensity, frequency, and number of pulses applied; the duration of the course; the coil location and, possibly, the type of coil used. In general, high-frequency (>5 Hz) rTMS promotes cortical excitability, while low-frequency (≤1 Hz) rTMS inhibits cortical excitability (Rossi et al. 2009; Lefaucheur et al. 2014). Deep TMS (dTMS) is a modification of standard TMS that enables deeper non-invasive cortical stimulation at an effective depth of approximately 3 cm depending on the coil's design and the stimulation intensity (Zangen et al. 2005). Both standard and deep-TMS directed to the prefrontal cortex are Food and Drug Administration-approved for the treatment of drug-resistant major depressive disorder and have gained worldwide attention as possible therapeutic tools for various neurological conditions (Bersani et al. 2013).
When Thinking is Doing: Responsibility for BCI-Mediated Action
Published in AJOB Neuroscience, 2020
Stephen Rainey, Hannah Maslen, Julian Savulescu
We can exercise control over our brains, and we can act neurally, and so we can establish voluntariness about some types of neural activity. This must be so for BCI training to be possible. Yet the picture gained across contexts of involuntary and voluntary neural acts presents a complex picture of neural activity. What we can see is that neural activity has various dimensions that interact in producing overt behavior, as well as other neural activity. There are dimensions of these interactions that are voluntary, and that can be acquired by training, so we can say that it can be done poorly, or done well, just as with any other acquired skill. This provides us with a basis to posit a degree of freedom of action in terms of neural activity. We appear to be partially in control of some neural states, and more like subject to others. Where this kind of control is used as a means of controlling BCIs, we may have only partial control of the actions mediated by those BCIs.
Event-related Desynchronization of Mu Rhythms During Concentric and Eccentric Contractions
Published in Journal of Motor Behavior, 2018
Joo-Hee Park, Heon-Seock Cynn, Kwang Su Cha, Kyung Hwan Kim, Hye-Seon Jeon
The ERD can also be interpreted as an electrophysiological correlate of the neural activity involved in processing sensory or cognitive information for the production of motor behavior (Pfurtscheller & Klimesch, 1989). The increase in mu rhythm ERD is commonly interpreted to result from increased cellular excitability in thalamocortical feedback loops (Steriade & Llinás, 1988). In our study, ERD amplitude decreased for both types of contractions after a great deal of repetitive practice. This result is in line with a previous study that demonstrated progressive decline during motor learning processes along with a decrease in the mu rhythm ERD (Zhuang et al., 1997). As with the results for ERD onset time, the amplitudes of both types of contractions changed significantly from phase I to phase III.
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