Synaptic Self: How Our Brains Become Who We Are

by Joseph E. LeDoux

GABA inhibition prevents much from happening in response, and if the sound is repeated without consequence, the cells quickly stop responding. But if the sound is followed by a shock, the weak preexisting response is greatly amplified following the rules of Hebbian plasticity: the shock activates the postsynaptic cell while the sound is causing the presynaptic terminals to release glutamate. During the activation, calcium enters the postsynaptic cell, and then a host of intracellular chemical reactions, involving kinases and transcription factors, activate genes, inducing them to make proteins that then stabilize the relation between the presynaptic and postsynaptic neuron. As a result of conditioning, the sound acquires the ability to elicit strong excitation in the amygdala, making it a more potent stimulus for activating amygdala circuits after conditioning than it was before.

Quick overview of conditioned response via neuronal change