• Hossein Hassanpoor added an answer:
    Do hippocampal astrocytes have any effect on spatial memory formation and retrieval? If yes how?
    According the effects of astrocyte in synaptic plasticity and neural function, it's not out of mind that astrocyte may play an important roles in formation and retrieval of spatial memory. But I’m looking for the related mechanism(s).I'll be appreciate who help me to finding my answer.
    Hossein Hassanpoor · Amirkabir University of Technology

    Dear Shivendra

    Thanks a lot. I had it before. That is a nice paper. please see my paper too and let me know your comments about it.

    "Mechanisms of hippocampal astrocytes mediation of spatial memory and theta rhythm by gliotransmitters and growth factors"

  • Javad Mirnajafi-Zadeh added an answer:
    What is the role of Donnan membrane equilibrium in generation of resting membrane potential (RMP)?
    I am a bit confused after reading about Donnan membrane equilibrium. In neurons, we have semi permeable membrane and a mixture of permeable and impermeable charged ions/molecules, that could lead to steady state. The asymmetric ionic gradient as well as permeability leads to the driving force/voltage across the membrane. Then, role of Na+K+ATPase is to maintain the steady state level and balance the leak of Na+ and K+ (specialty due to action potential, leak or co-transporters). My question is if we block Na+K+ATPase pump, what would be the resting membrane potential of a NEURON? will it be ZERO? Of course, we have some permeability for Na+ and CL-. What is the more dominating factor to generate RMP? is it Donnan membrane equilibrium or Na+K+ATPase pump ? Thank you
    Javad Mirnajafi-Zadeh · Tarbiat Modares University
    I think you could get your response with a lot of interesting mentioned responses. However, for simplicity consider that there are 3 factors in determining the RMP: 1-the most important is difference in membrane permeability to different ions (you can guess the effect of chenges in permeability of each ion by the Goldman equation). 2- Donnan effect which can change the diffusion of anions and cations inside and outside the cell. Usually it can produce a -17 mV changes in RMP. 3- Na-K ATPase pump which have a Max effect of 10-15% in some (not all of the cells). If you like to understand the Donnan effect very precisely, I highly recommend you to study the following reference: Kutchai HC, Ion equilibria and resting membrane potential. In Physiology (Fifth Edition), Berne RM, Levy MN, Koeppen BM, Stanton BA (Eds), Mosby, 2004, pp. 22-30. Please note that in more recent edition of this book, these parts have been deleted, so please try to find the 5th edition of this book. I'm sure you will enjoy its study specially pages 24-26.
  • Felix Scholkmann asked a question:
    BEyond the Hodgkin-Huxley model of nerve pulse propagation
    On the action potential as a propagating density pulse and the role of anesthetics Thomas Heimburg, Andrew D. Jackson Abstract: The Hodgkin-Huxley model of nerve pulse propagation relies on ion currents through specific resistors called ion channels. We discuss a number of classical thermodynamic findings on nerves that are not contained in this classical theory. Particularly striking is the finding of reversible heat changes, thickness and phase changes of the membrane during the action potential. Data on various nerves rather suggest that a reversible density pulse accompanies the action potential of nerves. Here, we attempted to explain these phenomena by propagating solitons that depend on the presence of cooperative phase transitions in the nerve membrane. These transitions are, however, strongly influenced by the presence of anesthetics. Therefore, the thermodynamic theory of nerve pulses suggests a explanation for the famous Meyer-Overton rule that states that the critical anesthetic dose is linearly related to the solubility of the drug in the membranes. The thermodynamics of general anesthesia Authors: Thomas Heimburg, Andrew D. Jackson Abstract: It is known that the action of general anesthetics is proportional to their partition coefficient in lipid membranes (Meyer-Overton rule). This solubility is, however, directly related to the depression of the temperature of the melting transition found close to body temperature in biomembranes. We propose a thermodynamic extension of the Meyer-Overton rule which is based on free energy changes in the system and thus automatically incorporates the effects of melting point depression. This model provides a quantitative explanation of the pressure reversal of anesthesia. Further, it explains why inflammation and the addition of divalent cations reduce the effectiveness of anesthesia.
  • Felix Scholkmann asked a question:
    Long-term memory in brain magnetite
    Banaclocha MA, Bókkon I, Banaclocha HM. (2009) Long-term memory in brain magnetite. Medical Hypotheses. DOI:10.1016/j.mehy.2009.09.024 Abstract: Despite theoretical and experimental efforts to model neuronal networks, the origin of cerebral cognitive functions and memory formation are still unknown. Recently, we have proposed that in addition to chemical and electrical signals, the cellular components of the neocortex (especially neurons and astrocytes) may communicate with each other through magnetic signals generated by themselves. This magnetic communication would be the ground of short-term memory. In the present paper, we propose that brain magnetite may be a component of the mechanisms, conserved during evolution, to detect and transduce magnetic fields generated inside the cerebral neocortex. Specifically, we propose a possible role for magnetite nanoparticles, distributed through neuronal and astroglial membranes, in perception, transduction and storage of information that arrives to the neocortex.
  • Felix Scholkmann asked a question:
    A redox molecular hypothesis on visual mental imagery
    Bokkon, I. & D’Angiulli, A. Emergence and transmission of visual awareness through optical coding in the brain: A redox molecular hypothesis on visual mental imagery. Bioscience Hypotheses 2009 2: 226-232 Abstract: Does the primary visual cortex mediate consciousness for higher-level stages of information processing by providing an outlet for mental imagery? Evidence based on neural electrical activity is inconclusive as reflected in the ‘‘imagery debate’’ in cognitive science. Neural information and activity, however, also depend on regulated biophoton (optical) signaling. During encoding and retrieval of visual information, regulated electrical (redox) signals of neurons are converted into synchronized biophoton signals by bioluminescent radical processes. That is, visual information may be represented by regulated biophotons of mitochondrial networks in retinotopically organized cytochrome oxidase-rich neural networks within early visual areas. Therefore, we hypothesize that regulated biophotons can generate intrinsic optical representations in the primary visual cortex and then propagate variably degraded versions along cytochrome oxidase pathways during both perception and imagery. Testing this hypothesis requires to establish a methodology for measurement of in vivo and/or in vitro increases of biophoton emission in humans’ brain during phosphene inductions by transcranial magnetic stimulation and to compare the decrease in phosphene thresholds during transcranial magnetic stimulation and imagery. Our hypothesis provides a molecular mechanism for the visual buffer and for imagery as the prevalent communication mode (through optical signaling) within the brain. If confirmed empirically, this hypothesis could resolve the imagery debate and the underlying issue of continuity between perception and abstract thought.
  • Felix Scholkmann asked a question:
    Biophotons as neural communication signals
    Yan Sun, Chao Wang and Jiapei Dai. Biophotons as neural communication signals demonstrated by in situ biophoton autography. Photochem. Photobiol. Sci., 2010, DOI: 10.1039/b9pp00125e Abstract: Cell to cell communication by biophotons has been demonstrated in plants, bacteria, animal neutrophil granulocytes and kidney cells. Whether such signal communication exists in neural cells is unclear. By developing a new biophoton detection method, called in situ biophoton autography (IBA), we have investigated biophotonic activities in rat spinal nerve roots in vitro. We found that different spectral light stimulation (infrared, red, yellow, blue, green and white) at one end of the spinal sensory or motor nerve roots resulted in a significant increase in the biophotonic activity at the other end. Such effects could be significantly inhibited by procaine (a regional anaesthetic for neural conduction block) or classic metabolic inhibitors, suggesting that light stimulation can generate biophotons that conduct along the neural fibers, probably as neural communication signals. The mechanism of biophotonic conduction along neural fibers may be mediated by protein–protein biophotonic interactions. This study may provide a better understanding of the fundamental mechanisms of neural communication, the functions of the nervous system, such as vision, learning and memory, as well as the mechanisms of human neurological diseases.

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Neurobiophysics is the study of the structure and function of the nervous system from the perspectiv

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