Electronic Neural Models Neuromimes

Neural modeling, or computational neurobiology as it is now called, began in the early 1960s with the creation of real-time, analog, electronic models of single neurons, synapses, and spike generation. Leon Harmon at Bell Labs was one of the first workers to design an analog neural model using PNP bipolar junction transistors (BJTs) that exhibited summation, threshold (for firing), excitation, inhibition, refractoriness, and delay (van Bergeijk and Harmon, 1960). This circuit contained a...

Saltatory Conduction on Myelinated Axons

Schwann Cell Micrograph

A morphological adaptation of vertebrates that increases the spike propagation velocity on their axons is myelinization. An electron micrograph of the cross section of a myelinated axon is shown in Figure 1.2-5 from a rat sciatic nerve, x 52,000 . Where the axon is wrapped in the myelin tape, two important changes occur in the cable parameters. Because of the insulation of multiple, close-packed layers of UM, gm decreases, perhaps by a factor of 1 64. Because of the effective thickening of the...

Gravity Receptors Of The Cockroach Arenivaga Sp

Cockroach Sem

This section shows that the tricholith gravity sensors of the cockroach Arenivaga sp. are an excellent example of a small receptor array. Tricholiths have been shown to respond to the position of the cockroach with respect to the Earth's gravity vector. Only four large identi able interneurons carry spatial orientation information from the tricholith arrays to the animal's CNS where it is processed by many interneurons. Willey 1981 recorded from single, position-sensitive neurons in the...

Integral And Relaxation Pulse Frequency Modulation Models For The Spike Generator Locus

How the SGL of a spiking neuron behaves approximately as a voltage-to-frequency converter VFC , driven by a positive generator potential GP that is the spatiotemporal sum of epsps and ipsps has been described. As seen from the discussion of the HH model equations in Section 1.4, spike generation is a nonlinear process. There is a minimum GP below which a neuron will not fire, and the steady-state spike frequency is a nonlinear saturating function of the GP. To model spike generation...