A R Gardner-Medwin

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1. Potential changes evoked by stimulation of the perforant path have been recorded in the dentate area of the hippocampal formation in chronically prepared unanaesthetized rabbits.2. Components attributed to excitatory synaptic current flow and to action potentials in the granule cell population were distinguishable, with characteristics largely the same(More)
Equations are derived for potassium (K+) dynamics in simplified models of brain tissue. These describe K+ movement in extracellular space, transfer of K+ associated with current flow through cells (the so-called spatial buffer mechanism) and equilibration between extracellular space and cytoplasm. Numerical calculations show that the principal data on K+(More)
It is commonly assumeda, 7,9 that the solution to the diffusion equation with point source, derived from the equivalent heat problem s , describes ion migration in the brain. We show both theoretically and experimentally that the above solution must be generalized for iontophoresis of ions which are confined to the extracellular space of the brain. We(More)
The flux of K+ produced by electric current across the pia-arachnoid surface of the neocortex of anaesthetized rats has been studied with K+-selective electrodes in a cup at the surface and with flame photometry. The potential differences developed across three regions of the rat brain (neocortex, cerebellum, hippocampus) have been measured as [K+] was(More)
Work with ion-selective microelectrodes on the retina of the honeybee drone has shown that potassium is released from photoreceptors during activity and enters glial cells. Measurements of the extracellular voltage gradients indicate that, in this preparation, currents flowing through the glial cells in the 'spatial buffer' pattern account for a large(More)
Ion-selective micro-electrodes have been used to measure K+ and Ca2+ activity changes in extracellular space beneath the surface of the neocortex and cerebellar cortex during current flow across the tissue surface in anaesthetized rats. Inward currents produced decreases of [K+]o and outward currents produced increases, with insignificant changes in(More)
Magnetic fields were measured with SQUID magnetometry outside the skull of anaesthetised rabbits during initiation and propagation of spreading depression (SD) in the cortex. Slowly changing fields (up to 1.4 pT) were observed during the propagation phase, from 4-8.5 min after initiation of SD with KCl application, with maxima at about 6 min. The peak(More)
1. The electrical responses produced by stimulation at the surface of the cerebellar cortex have been studied in anaesthetized cats.2. The propagation of the underlying activity is attributed to parallel fibres, but the mode of generation of the potential changes is less certain.3. The threshold for a second response is up to 40% lower following a(More)
1. The early receptor potential of the isolated retina of the frog has the following properties:(a) It is unaffected by reversing the direction of incidence of the light, and by soaking the retina in isotonic solutions of salts containing neither sodium nor chloride.(b) Soaking the retina in solutions containing high concentrations of salts or glycerol(More)