Showing papers by "Richard B. Miles published in 1984"
TL;DR: Mechanisms involved in the generation of synaptic inhibition have been investigated by making simultaneous intracellular recordings from pairs of neurones in the CA3 pyramidal cell field of guinea‐pig hippocampal slices and the recurrent nature of some hippocampal inhibition has been demonstrated by showing that activity in a single cell may initiate feed‐back i.p.s.s onto itself.
Abstract: Mechanisms involved in the generation of synaptic inhibition have been investigated by making simultaneous intracellular recordings from pairs of neurones in the CA3 pyramidal cell field of guinea-pig hippocampal slices. Inhibitory post-synaptic potentials dependent on single presynaptic action potentials (i.p.s.p.s) and mediated through monosynaptic and disynaptic connexions have been identified. The recurrent nature of some hippocampal inhibition has been demonstrated by showing that activity in a single cell may initiate feed-back i.p.s.p.s onto itself. The observation of synchronous i.p.s.p.s in recordings from two cells illustrates the divergence of synaptic contacts made by inhibitory neurones. The peak conductance change associated with an i.p.s.p. was in the range 5-9 nS and it reversed uniformly throughout its time course at membrane potentials between -73 and -80 mV. The shortest time-to-peak of synaptic potentials was approximately 3 ms and in this case the i.p.s.p. decayed with a time constant comparable to the passive membrane time constant of the post-synaptic neurone. The peak amplitude of i.p.s.p.s fluctuated in a way consistent with the quantal release of inhibitory neurotransmitter. Inhibitory neurones could fire bursts of action potentials not unlike those generated by pyramidal cells in this area. A comparison of the conductance change associated with identified i.p.s.p.s with that associated with the maximal inhibitory post-synaptic potential resulting from electrical stimulation of fibre pathways suggested that, in the slice, a pyramidal cell is innervated by up to fifteen inhibitory neurones.
183 citations
TL;DR: It is concluded that these afterdischarges depend on local neuronal interactions mediated by chemical synaptic mechanisms which may occur within a single population of as few as 1000 CA3 pyramidal cells.
183 citations
TL;DR: It is discovered that the refractory period following prolonged excitation assumed in the previous model was insufficient to allow for afterdischarge generation, and the required refractoriness was attributed to the properties of pyramidal cell axons.
48 citations
TL;DR: It remains to be determined whether neuronal properties and connectivity found to be important in this hippocampal rhythm may also play a role in the generation of other rhythmic activities in the mammalian CNS.
Abstract: Under certain circumstances large numbers of neurones in the mammalian central nervous system (CNS) can discharge simultaneously An example of such activity is recorded from a hippocampal slice in the presence of agents which block synaptic inhibition This synchronized discharge occurs spontaneously in a rhythmic fashion or may be triggered by stimulation of any afferent pathway Its generation appears to involve local circuit interactions The favourable conditions offered by an in vitro preparation have allowed the cellular events during this activity to be examined in some detail Three factors appear to be critically involved in the synchronization process Firstly, the intrinsic ability of neurones to generate bursts, secondly, the existence of powerful recurrent excitatory connections, and thirdly the absence of inhibition which normally prevents the spread of bursting activity through the recurrent connections Computer simulations show that in a sparsely connected network of bursting neurones activity initiated in a few cells may spread through recurrent connections until eventually the whole population discharges simultaneously Rhythmic discharges similar to those described here also underly various CNS functions including centrally-originating motor patterns It remains to be determined whether neuronal properties and connectivity found to be important in this hippocampal rhythm may also play a role in the generation of other rhythmic activities in the mammalian CNS
31 citations
TL;DR: In this article, the authors examined the relaxation of highly vibrationally excited HD with several collision partners using direct overtone excitation and time-resolved photoacoustic detection of the subsequent change in translational energy of the gas.
Abstract: The relaxation of highly vibrationally excited HD with several collision partners is examined using direct overtone excitation and time‐resolved photoacoustic detection of the subsequent change in translational energy of the gas. Analysis of such data for HD(v=4, 5 and 6) self‐relaxation yields vibration‐translation (V‐T) and vibration–vibration (V–V) rate constants for collisions between HD(v=1 to 6) and HD(v=0). The V‐T rate constant becomes larger than the V–V rate constant above v=4. Similarly, relaxation data for the HD(v=4 and 5)–4He systems is analyzed and the HD–4He V‐T rate constants at v=4 and v=5 are presented. The differences in the quantum number scaling of the V‐T rates for the HD–HD and HD–4He systems are discussed. Finally, the time‐resolved photoacoustic data for HD(v=4) relaxing in collisions with D2 shows the effect of the rapid, near‐resonant V–V energy transfer between HD in the v=1 through v=4 levels and D2 in v=0.
21 citations
TL;DR: In this paper, a neodymium:yttrium aluminum garnet regenerative ring amplifier seeded by multiple pulse injection is presented, which can achieve output energy up to 0.6 mJ/pulse (± 5% fluctuation).
Abstract: We report the development of a neodymium:yttrium aluminum garnet regenerative ring amplifier seeded by multiple pulse injection. This method of injection allows us to avoid the difficulties and expense of low‐power, single‐pulse selection. We observed output energy up to 0.6 mJ/pulse (±5% fluctuation). A saturable absorber in the cavity allowed compression down to 55 ps.