Besides usual spikes employed in spiking neural P systems, we consider
"anti-spikes", which participate in spiking and forgetting rules, but also annihilate spikes
when meeting in the same neuron. This simple extension of spiking neural P systems
is shown to considerably simplify the universality proofs in this area: all rules become
of the form bc ! b0 or bc ! ¸, where b; b0 are spikes or anti-spikes. Therefore, the
regular expressions which control the spiking are the simplest possible, identifying only
a singleton. A possible variation is not to produce anti-spikes in neurons, but to consider
some "inhibitory synapses", which transform the spikes which pass along them into anti-
spikes. Also in this case, universality is rather easy to obtain, with rules of the above
simple forms.Junta de Andalucía P08 – TIC 0420
