The self is an expression of the genes which build and operate the brain. A self experiences an emotion in response to a stimuli which elicits a genetically-encoded neuronal function. The parameters of this neuronal reaction, its depth and degree, is determined by the genes. For instance, an individual who has a mutation in a neuronal MAO-A gene and a polymorphism in the serotonin transporter gene is likely to overreact to a negative stimuli by becoming aggressive and violent. Accordingly to Buddha, the mind is constantly changing.
Neuronal activity is continuous.
In response to stimuli, electrical activity in the form of action potentials, small electrical signals, are propagated from neuron to neuron, like flowing water. The electrical signals are passed from neuron to neuron across chemical synapses, specific regions of the neuron in which chemicals are released by one neuron and sniffed by another. Stimuli can cause synapses to change in the brain, sprouting new and strengthening existing connections. The self is existent in the sense that it is reflection of the genes. Although the genes, themselves, are permanent, the self is continually changing in response to stimuli which cause the brain to adapt.