Here we present a new model for the generation of complex calcium-bursting patterns in astrocytes, a type of brain cell recently implicated in a variety of neural functions including memory formation. The model involves two positive feedback processes, in which the key feedback species are calcium ion and glutamate. The latter is the most abundant excitatory neurotransmitter in the brain and has been shown to be involved in bidirectional communication between astrocytes and nearby neurons. The glutamate feedback process considered here is shown to be critical for the generation of complex bursting oscillations in the astrocytes and to, perhaps, code for information which may be passed from neuron to neuron via the astrocyte. These processes may be involved in memory storage and formation as well as in mechanisms which lead to dynamical diseases such as epilepsy.

As discussed in other articles in this issue, chemical emergence may have led to the appearance of life on the pre-biotic earth, but it is even more obviously clear that emergence continues in living systems, producing complex phenomena such as ordering, biorhythms and even, possibly, consciousness. The role of continuing emergence in living systems is reviewed here with special attention to the Peroxidase–Oxidase reaction and neurochemical systems. For the latter, we review the role of subnetwork dynamics in epilepsy and an intriguing new possiblity that calcium waves in fields of astrocytes in the brain may be involved in the spread of epileptic seizures.