Clues Revealed by Ketamine
Scott Mendelson in Herbal Treatment of Major Depression, 2019
The simplified version of neuronal activity is that neurotransmitters activate receptors on the surface membranes of neurons in the brain and turn those cells on or off like light switches. In fact, the activations of surface receptors by neurotransmitters are only the starting places of long and complicated cascades of intracellular activity. Receptor activation triggers enzymes. One enzyme affects another, then another, with the results being altered by what other enzymes may have interacted inside the neuron microseconds before. The end results of those various biochemical cascades are what drive and direct neurons to express genes; synthesize proteins; repair themselves; utilize energy; make neurotransmitters and receptors; and maintain the critical dendritic processes through which they communicate with each other.
Neuropeptide Regulation of Ion Channels and Food Intake
Tian-Le Xu, Long-Jun Wu in Nonclassical Ion Channels in the Nervous System, 2021
Ion channels tightly control the neuronal activity through transmembrane ion flux for depolarization or hyperpolarization. Changes in the protein structure of ion channels can drastically change how the neuron responds to extracellular signals such as neuropeptides. For instance, dysfunctional KATP channels, possibly from high-fat diets, would be unable to close under elevated glucose levels, resulting in constitutively active inhibition of the anorexigenic POMC neurons, leading to the development of obesity (Parton et al. 2007). Mutations in KATP channels are also associated with congenital diabetes and hyperinsulinism (Tinker et al. 2018). Tonically elevated PIP3, a signaling molecule naturally activated by insulin, acts as a sexually dimorphic inhibitor of POMC neurons via stimulation of KATP channels. Female mice have a larger weight gain than males when PIP3 is perpetually elevated (Plum et al. 2006). Kir6.2 is a key pore-forming subunit of KATP channels (Miki et al. 2001). The defective Kir6.2 prevents ATP blockade of KATP channels, which results in increased food intake and obesity due to loss of glucose sensitivity of Kir6.2-expressing hypothalamic neurons (Sohn 2013; Miki et al. 2001). Kir6.2 knockout mice also showed a blunted hypothalamic response to glucose loading and elevated hypothalamic NPY expression accompanied by hyperphagia, while they are resistant to obesity (Park et al. 2011).
The Biology of Dream Formation
Milton Kramer in The Dream Experience, 2013
There has been an intense interest in brain activity (functioning) with the development of new techniques that can assess neuronal activity in various areas of the brain, functional MRIs, and relating the results correlatively to functions of the mind. Mental health professionals have gotten caught up in this biological fervor and see brain function and psychological experience as increasingly closely related. They have embraced the concept of the mind/brain to express this unification of the psychological and biological aspects of brain function. This is an effort to bridge the chasm that Descartes introduced some 500 years ago in his discussion of what came to be called the mind-body problem. Why this view, mind/brain, has been so vigorously and, I believe, unreflectively embraced by mental health professionals is part of the biological hegemony in present day mental health research and practice.
Inter-organ regulation by the brain in Drosophila development and physiology
Published in Journal of Neurogenetics, 2023
Sunggyu Yoon, Mingyu Shin, Jiwon Shim
The brain is composed of two specialized cell types: glial cells that maintain, nourish, and protect neurons and neurons that transmit electrochemical signals to induce neuronal activity (Jessen, 2004; Tsodyks & Gilbert, 2004; von Bartheld et al., 2016). It has been extensively reported that neuroactivity in the brain determines mental or behavioral characteristics. As a well-known example, dopaminergic neurons found in the substantia nigra pars compacta play a critical role in controlling mood, reward, and stress response, and serotonin neurons located in the raphe nuclei of the brainstem control emotional conditions, such as depression, anxiety, and sadness (Berger et al., 2009; Chinta & Andersen, 2005; Meneses & Liy-Salmeron, 2012). With the view that obvious consequences of neuronal function are changes in animal behavior, previous research in neurobiology has largely focused on animals’ external, emotional, and behavioral phenotypes.
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).
Studying complex brain dynamics using Drosophila
Published in Journal of Neurogenetics, 2020
Sophie Aimon, Ilona C. Grunwald Kadow
More complex models can also be developed (Breakspear, 2017). Neuronal type specificities can be incorporated thanks to their detailed associated knowledge in Drosophila. If necessary, all neurons of the same type can be grouped together (i.e. neural mass model) for simplicity. Neuronal activity can be modeled using spikes or continuous quantities such as spike rate for spiking neurons, and using membrane voltage for the many fly neurons that are actually non-spiking. When oscillations are present inside regions, they can be captured using mechanistic models (Kass et al., 2018), and interactions between regions can be modeled as oscillators coupled through anatomical connections (i.e. Kuramoto model (Schmidt, LaFleur, de Reus, van den Berg, & van den Heuvel, 2015)). This will help understand for example how patterns of inter-regional synchrony lead to effective information paths opening and closing.
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