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Fig. 4.2 Extending an output signal
depending on how tightly it is held, suggesting that LTP might in fact require
refreshing. Certainly it is known that firmly trapped charge in solid-state systems
cannot be claimed to last more than about 5 years.
Stretched Memory Signals Using a Burst Stretcher
Short-term memory neurons are plentiful and so may be applied in places other than
explicit short-term memory. For example, they may take a neural burst and make it
longer, to aid with timing (since all signals ideally must come together at about the
same time in consciousness). Once triggered, a short-term memory neuron emits an
burst of pulses whose length depends on the chemistry of its dendrite. Figure 4.2
shows how a short-term neuron can stretch the output of a memory element based
on LTP, thus making the output signal easier to register in consciousness. This is
termed burst stretching.
A stretched signal from a memory element is reminiscent (in the author's mind)
of the output of a recursive neural circuit.
Recursive Neurons with a Circulating Pulse
Neurons could theoretically be fed back on themselves to support a circulating
pulse, forming a device that is characterized by an efficient electrical pulse that
flows indefinitely round a closed circuit until stopped by an outside signal. Since the
pulses operate between two given voltage levels, such circuits are multivibrators,
which are a type of oscillator that delivers a rectangular-shaped waveform. The
model in Fig. 4.3 is typical of a neural multivibrator. U1 is assumed sensitive to a
single pulse without a need for LTP. Depending on ancillary logic, a multivibrating
circuit may pulsate for a few milliseconds or they may pulsate indefinitely (until
power is removed).
Loop delay, which is a variable, is assumed greater than pulse width. Upon
receiving a set (S) signal, a single pulse is initiated by a weak synapse denoted
by S1. This pulse cycles back to the input via regular synapse S2, and cycles
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