<P> Interneurons can be further broken down into two groups: local interneurons and relay interneurons . Local interneurons have short axons and form circuits with nearby neurons to analyze small pieces of information . Relay interneurons have long axons and connect circuits of neurons in one region of the brain with those in other regions . The interaction between interneurons allow the brain to perform complex functions such as learning, and decision - making . </P> <P> Unlike the peripheral nervous system (PNS), the central nervous system, including the brain, contains many interneurons . In the neocortex (making up about 80% of the human brain), approximately 20 - 30% of neurons are interneurons . Investigations into the molecular diversity of neurons is impeded by the inability to isolate cell populations born at different times for gene expression analysis . An effective means of identifying coetaneous interneurons is neuronal birthdating . This can be achieved using nucleoside analogs such as EdU . </P> <P> In 2008, a nomenclature for the features of GABAergic cortical interneurons was proposed, called Petilla terminology . </P> <Ul> <Li> 1a Inhibitory Neuron: Found in Lamina VII . Responsible for inhibiting antagonist motor neuron . 1a spindle afferents activate 1a inhibitory neuron . </Li> <Li> 1b Inhibitory Neuron: Found in Lamina V, VI, VII . afferent or Golgi tendon organ activates it . </Li> </Ul>

Where does an association neuron synapse with a sensory and motor neuron